Landfill leachate: An invisible threat to soil quality of temperate Himalayas

Shayesta Islam; Haleema Bano; Asif Aziz Malik; Fahad Alotaibi

doi:10.1371/journal.pone.0314006

. 2024 Nov 19;19(11):e0314006. doi: 10.1371/journal.pone.0314006

Landfill leachate: An invisible threat to soil quality of temperate Himalayas

Shayesta Islam ^1,^#, Haleema Bano ^1,^#, Asif Aziz Malik ^2,^*, Fahad Alotaibi ³

Editor: Susmita Lahiri (Ganguly)⁴

PMCID: PMC11575778 PMID: 39561139

Abstract

Landfills are the most affordable and popular method for managing waste in many parts of the world, However, in most developing nations, including India, the infiltration of hazardous materials from improperly managed dumping site continues to be a significant environmental problem. Around the world, leachate is a significant point source of contamination in numerous environmental media, including soil, groundwater, and surface water. Soil is an important asset as it is the key factor for food production and has tremendous significance in achieving sustainable development goals (SDGs). The contaminants from soil enter into food chain and ultimately reach humans. So in order to prevent the adverse effects of toxic elements on humans, there is need to maintain the soil quality and to prevent deterioration. Keeping in view the consequences of unscientific management of waste, the goal of the experiment was to determine how landfill leachate from Achan landfill affected the soil quality in the temperate Himalayas. All four seasons of the year, viz Spring, Summer, Autumn, and Winter, at four sites viz, Center of dumping site, inside, Outside and Control were monitored. Among sites center was found to have maximum value of EC (3.04 dS/m), Moisture content (42.51%), N (285.43 mg/kg), P (70.07 mg/kg), K (265.71 mg/kg), Ca (957.67 mg/kg), Mg(402.42 mg/kg), Zn (2.02 mg/kg), Fe (10.56 mg/kg), Cu (2.07 mg/kg), Mn (10.73 mg/kg), Pb (85.02 mg/kg), Cd (4.50 mg/kg), Ni (29.04 mg/kg), Cr (23.37 mg/kg), As (14.10 mg/kg). While as the lowest value of all parameters was reported at control site. From the study it is recommended that the waste generated is mostly organic (65–75%), thus can be segregated and treated at source. The waste can be treated at source using microbial consortium technology in order to transform the waste in to wealth in a sustainable way and to prevent the deterioration of soil quality.

Introduction

Soil ecosystems are the foundation for food production and are crucial for achieving sustainable development goals (SDGs), so are regarded as significant environmental assets [1]. It supports or carries out a variety of tasks, such as biomass production, storing, filtering, and changing a wide variety of materials, including water and nutrients [2]. The majority of the carbon (C) and nutrient elements that support life are generated by soils, which also act as a repository for them [3]. Soils are also the pedestal that plants rely on to remain upright. They also serve as the habitat for a vast biodiversity and biomass of soil organisms [4]. Soils hold the water that plants and soil creatures need to exist and thrive, and they restrict the pace of water movement, limiting erosion and soil loss [5]. It has been reported that improving soil health through various amendments like biochar application improves soil physicochemical properties and enzymatic activities [6]. But this valuable asset is currently under serious threat due to generation of excessive quantity of waste due to rapid population growth and urbanization. According to the reports of world bank, the world wide generation of municipal solid waste in 2018 was 1.3 billion tons per year and is expected to reach approximately 2.2 billion tons by 2025 [7]. Kashmir Valley is also grappling with significant challenges stemming from increasing waste generation. Srinagar city alone produces 0.526 kg of waste per capita per day, with Anantnag following at 0.479 kg, Ganderbal at 0.400 kg, and Budgam at 0.397 kg respectively. The total annual waste generated across these districts amounts to 57,199.99 Metric Tonnes (MT), with Srinagar producing the highest at 236,732.75 MT and Budgam the lowest at 42,840.00 MT [8]. This enormous amount of waste can pose great challenge especially to low- and middle-income countries and developing nations.

The immense volume of waste generated from various sources ultimately finds its way to landfills, with Srinagar city in the Kashmir Valley being no exception. Here, all the waste produced across the city is disposed of at the Achan landfill site, the sole dumping ground for Srinagar. This site, located in the northern part of the city, between the coordinates 34° 09′ N “latitude” and 74° 79′ E “longitude”, lies approximately 5–6 kilometers from the city’s center. Before 1985, Srinagar produced minimal waste, free from the burden of plastic. Back then, the Srinagar Municipal Corporation (SMC) disposed of the city’s waste either in the Noorbagh grounds or along the banks of the river Jhelum. However, with the advent of stricter environmental policies, the Government of Jammu and Kashmir, following state cabinet approval, transferred around 30.35 hectares (75 acres) of state land to the SMC for waste disposal at Achan [9]. By 1986, this site became the primary location for the open dumping of municipal solid waste. For many years, vast amounts of refuse were deposited here without consideration for the environmental consequences. Achan remained the sole dumping ground for Srinagar until 2008 [10], with waste from 518 collection points across the city being transported to this location [9]. Once a thriving wetland, home to vibrant birds and lush vegetation, Achan has since become a source of pollution, contaminating water bodies, air, and soil. The nearby population has also been affected, suffering from various diseases. The waste deposited at the site undergoes biodegradation through a combination of physical, chemical, and biological processes, leading to the production of leachate—a dark brown liquid with a foul odor. This leachate contains dissolved organic and inorganic compounds, nutrients, suspended particles, heavy metals, and hazardous chemicals. When left untreated and uncontrolled, it poses a serious threat to natural and agricultural ecosystems, significantly degrading soil quality due to its high concentrations of nutrients, heavy metals, and soluble salts [11,12].

Contaminated soil affects ecosystems and human, plant and animal health in a number of ways [13]. The acidic leachate formed due to production of organic acids liberated by the degradation of waste, leads to the acidic surroundings that destroys micro-organisms, which are helpful in improving the composition of the soil. Furthermore contaminated soil has the potential to alter agricultural metabolism and diminish crop yields by forcing trees and crops to absorb soil pollutants [14]. In addition to this, contaminated soils with high nitrogen and phosphorus levels will leach into waterways, leading in death of aquatic organisms by diminishing the amount of dissolved oxygen [15]. The metals in leachate are common environmental pollutants that are non-biodegradable, can deplete available soil resources, and have a negative impact on plant growth and yield [16,17].

Keeping in view the far reaching consequences of landfill leachate and contaminated soil and need for global attention on improving or restoring soil health, it is imperative to evaluate the affect of leachate on soil physico chemical properties for proper management strategy to prevent soil degradation and alleviate the threats posed by the expansion of waste. Understanding and estimating the quality of leachate-impacted soils can establish an opportunity to judge the sustainability of land management and land-use systems. In this context, the present study aimed to evaluate the influence of landfill leachate from Srinagar’s Achan dump on soil physico-chemical parameters across different seasons and sites.

Study area

The study was conducted at the Achan landfill, located in Srinagar city, Jammu and Kashmir UT, at an elevation of 1600 meters above mean sea level. The landfill’s coordinates range between 74°41’ 6’’ and 74°57’ 27’’ East Longitude and 33° 59’ 14’’ and 34°12’ 37’’ North Latitude, as shown in Fig 1.

Spanning an area of 30.35 hectares (75 acres), the landfill is situated amidst residential settlements and water bodies, directly impacting the lives of residents in nine villages: Saidapora, Shonglipora, Waganpora, Sangam, Braywar, Danmar, Guzerbal, Noorshah Colony, and Bagh-i-Lal Pandith. Every day, the Srinagar Municipal Corporation (SMC) disposes of 450 metric tonnes in this site. Waste generation is projected to surge to 1,723 metric tonnes per day by 2035. Currently, 62% of the total waste produced daily in Srinagar consists of organic material, with 7% being plastic waste [18]. Approximately 65–70% of Srinagar’s municipal solid waste is collected through door-to-door methods and street bin systems, and then transported to the Achan landfill. However, the remaining 30–35% is illegally discarded into depressions, river embankments, open spaces, or is burned locally by individuals and Safai Karamcharis. This not only causes a public nuisance but also creates breeding grounds for various diseases [19]. Due to inadequate waste management and improper handling, large heaps of waste have accumulated at the site, emitting a foul odor that disturbs nearby residents. During the rainy season, leachate from the waste seeps into the soil, altering its physico-chemical properties and rendering the surrounding land unsuitable for agriculture.

Materials and methods

Soil samples were collected from the Achan dumpsite in Srinagar throughout all four seasons of 2022—spring, summer, autumn, and winter—following proper authorization from the Srinagar Municipal Corporation, headquartered at Kara Nagar, Srinagar, Jammu and Kashmir. Four distinct sampling sites were chosen: the center of the dumpsite, inside the dumpsite (four cardinal points within), outside the dumpsite (four cardinal points outside), and a control site located at the Shalimar campus of SKUAST Kashmir. These sites were selected to assess the impact of leachate produced from the waste on soil properties at varying distances from the dumping points. Three replicates were collected from each site.

Samples were taken solely from the soil, as leachate was directly seeping into the ground. The soil was collected in separate moisture cans to preserve its moisture content. Once collected, the samples were air-dried in the shade, then ground and sieved through a 2mm mesh before analyzing various physico-chemical parameters. Soil moisture content was determined using the gravimetric method by Prihar and Sandhu [20], while soil pH and electrical conductivity were measured using the potentiometric method with a pH meter and an electrical conductivity meter [21]. Nitrogen content was determined via the potassium permanganate method [22], and the available phosphorus was measured using the spectrophotometric method by Olsen et al. [23]. The Jackson method [21] was used to quantify available potassium, while calcium and magnesium levels were assessed using the Versenate method, as outlined by Chesin and Yein [24]. Heavy metal concentrations were determined using the DTPA extraction process and an atomic absorption spectrophotometer (AAS), following the method of Lindsay and Norwell [25].

Statistical analysis

The data in the table are given as an interactive mean of sites and seasons in accordance with the usual technique outlined by Gomez and Gomez [26]. Two-way ANOVA (analysis of variance) was performed at a 5% level of significance to test for differences across sites and seasons. In the univariate statistical pairwise comparison between all the samples comparing the means of two populations that are seasons and sites in our situations, analysis of variance with post hoc testing (Duncan’s multiple range test) is performed [27]. The significance is shown by the various letters, and vice versa [27].

Results

pH determines the acidity or alkalinity of soil solutions and refers to the soil’s hydrogen ion content. In our study among seasons maximum mean pH was recorded in winter (6.6), followed by spring (6.5), autumn (6.4) and minimum was recorded in summer season (6.3). Among sites maximum mean pH was recorded in control (6.7), outside (6.6), inside (6.3) and minimum (6.2) was recorded at center as depicted in Table 1. The pH values varied significantly between summer, autumn, and winter, but there was no significant difference between spring and autumn. Additionally, the pH values at different locations—inside, outside, and control—were significantly different, though there was no significant difference between the center and inside locations. During this study mean EC of dumpsite soil was found to deviate from 0.27 dS/m to 3.43 dS/m. Maximum mean value of EC among seasons was recorded in summer (1.81 dS/m), spring (1.66 dS/m), autumn (1.48 dS/m) and minimum was recorded in winter (1.35 dS/m). Among sites maximum mean value of EC was recorded at center (3.04 dS/m), followed by inside (2.01 dS/m), outside (0.86 dS/m) and minimum was recorded at control (0.40 dS/m). The EC values during spring, summer, autumn and winter were significantly different. In addition to this EC values at all sites were significantly different. In this study, the mean moisture content values ranged from 12.87% to 48.42%. Moisture content was recorded maximum in winter (36.95%) among seasons, followed by spring (32.48%), autumn (29.34%) and minimum was recorded in summer (25.23%). Among sites mean maximum moisture content was recorded at center (42.51%), followed by inside (34.07%), outside (28.83%) and minimum was recorded at control site (18.58%). The moisture content values between all seasons were significantly different, in addition this, the moisture content values between all sites were also significantly different.

Table 1. Seasonal and site wise variation in pH, EC (dS/m) and moisture content (%) of soil.

Parameters	Seasons	Sites				Mean	C.D (P≤0.05)
Parameters	Seasons	Center	Inside	Outside	(Control)	Mean	C.D (P≤0.05)
pH	Spring	6.3±0.05^fgh	6.4±0.09^efg	6.6±0.06^bc	6.8±0.10^ab	6.5 ^b	Sites: 0.12 Seasons: 0.12 Sites × Seasons: 0.24
	Summer	6.1±0.05^h	6.2±0.11^gh	6.4±0.06^cdef	6.5±0.14^bcde	6.3 ^c
	Autumn	6.2±0.35^gh	6.3±0.09^fgh	6.5±0.04b^cd	6.7±0.18^ab	6.4 ^b
	Winter	6.4±0.21^defg	6.5±0.13^cdef	6.7±0.05^ab	6.9±0.15^a	6.6 ^a
	Mean	6.2 ^c	6.3 ^c	6.6 ^b	6.7 ^a
EC	Spring	3.16±0.28^ab	2.12±0.23^cd	0.95±0.24^ef	0.41±0.10^gh	1.66 ^ab	Sites: 0.21 Seasons: 0.21 Sites× Seasons:0.42
	Summer	3.43±0.25^a	2.23±0.29^c	1.06±0.24^e	0.55±0.22^fgh	1.818 ^a
	Autumn	2.84±0.21^b	1.96±0.19^cd	0.79±0.20^efg	0.35±0.13^h	1.485 ^bc
	Winter	2.74±0.26^b	1.74±0.51^d	0.66±0.25^efgh	0.27±0.06^h	1.35 ^c
	Mean	3.04 ^a	2.01 ^b	0.86 ^c	0.40 ^d
Moisture content (%)	Spring	43.34±1.01^b	36.48±0.87^d	29.44±0.47^g	20.67±1.01^j	32.48 ^b	Sites:1.797 Seasons: 1.797 Sites× Seasons:3.594
	Summer	36.87±0.99^d	26.65±0.99^h	24.55±0.97ⁱ	12.87±0.69^l	25.23 ^d
	Autumn	41.43±1.01^c	31.37±1.03^f	28.09±0.99^gh	16.48±1.01^k	29.34 ^c
	Winter	48.42±1.01^a	41.79±1.02^bc	33.27±1.00^e	24.32±1.01ⁱ	36.95 ^a
	Mean	42.51 ^a	34.07 ^b	28.83 ^c	18.58 ^d
Standard limits (ICAR manual)	pH Acidic < 6.0 Normal to saline (6.0–8.5) Tending to became alkaline (8.9–9.0) Alkaline ˃ 9.0		EC Low <1.0 dS/m Medium (1.0–3.0 dS/m) High ˃ 3.0 dS/m			Moisture content Low (3–10%) Medium (20–40%) High ˃ 40%

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Mean N concentration in soils of the experimental site ranged from 110.67 to 320.49 (mg/kg). The concentration of N was maximum at center of dumping site (285.43 mg/kg), followed by inside (266.73 mg/kg), outside (241.61 mg/kg) and least (131.26 mg/kg) was reported at control site during all the seasons. Among seasons the maximum N concentration was observed during summer season (264.11 mg/kg), followed by spring season (244.93 mg/kg), autumn season (221.85 mg/kg) and least (194.14 mg/kg) was observed in winter season as depicted in Table 2. Additionally, the mean values of N between sites change significantly, and the mean values of N between all seasons were significantly different.

Table 2. Seasonal and site wise variation in N, P and K (mg/Kg) of soil.

Parameters	Seasons	Sites				Mean	C.D (P≤0.05)
Parameters	Seasons	Center	Inside	Outside	Control	Mean	C.D (P≤0.05)
N	Spring	300.33±2.43^c	283.40±2.74^d	256.73±2.06^e	139.27±3.13^k	244.93 ^b	Sites: 4.700 Seasons: 4.700 Sites × Seasons: 9.401
	Summer	320.49±1.80^a	307.15±0.65^b	282.34±1.95^d	146.47±1.16^j	264.11 ^a
	Autumn	280.41±1.79^d	252.50±2.19^f	225.85±2.08^h	128.64±2.07^l	221.85 ^c
	Winter	240.51±2.04^g	223.86±1.52^h	201.54±1.32ⁱ	110.67±2.24^m	194.14 ^d
	Mean	285.43 ^a	266.73 ^b	241.61 ^c	131.26 ^d
P	Spring	71.29±1.12 ^c	57.42±0.89^e	43.95±1.71^h	25.39±1.08^k	49.51 ^b	Sites: 2.017 Seasons: 2.017 Sites × Seasons: 4.034
	Summer	87.36±0.85^a	73.44±1.87^b	54.68±1.24^f	28.45±2.01^l	60.98 ^a
	Autumn	63.35±1.04^d	48.60±1.24^g	36.06±1.23^j	19.42±0.95^m	41.86 ^c
	Winter	58.29±1.02^e	41.01±41.01ⁱ	29.94±0.54^k	15.38±1.08ⁿ	36.15 ^d
	Mean	70.07 ^a	55.12 ^b	41.16 ^c	22.16 ^d
K	Spring	275.70±0.38^b	251.77±0.97^d	237.70±1.08^e	125.35±1.03^l	222.63 ^b	Sites: 6.887 Seasons: 6.887 Sites × Seasons:13.774
	Summer	301.28±1.03^a	273.33±1.05^c	251.77±1.63^d	132.41±1.12^k	239.70 ^a
	Autumn	253.38±1.12^d	234.29±0.90^f	218.64±1.12^h	110.35±0.94^m	204.14 ^c
	Winter	232.49±1.07^g	210.03±1.03ⁱ	195.28±0.95j	96.54±1.11ⁿ	183.58 ^d
	Mean	265.71 ^a	242.35 ^b	225.85 ^c	116.16 ^d
Standard Limits (ICAR manual)		N Low<107.1 mg/kg Medium (107.1–214.2 mg/kg) High ˃214.2 mg/kg		P Low < 13.2mg/kg Medium (13.2–33 mg/kg) High ˃ 33 mg/kg		K Low < 49.10 mg/kg Medium (49.10–125 mg/kg) High ˃ 125 mg/kg

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N: Nitrogen, P: Phosphorus, K: Potassium.

Soil phosphorus content at the experimental site ranged from 15.38 to 87.36 mg/kg. The highest mean P level was found at the center of the dumping site (70.07 mg/kg), followed by the inside (55.12 mg/kg) and outside (41.16 mg/kg) locations, with the lowest at the control site (22.16 mg/kg), as shown in Table 2. Seasonally, the highest mean phosphorus content was observed during the summer (60.98 mg/kg), followed by spring (49.51 mg/kg), autumn (41.85 mg/kg), and the lowest during winter (36.15 mg/kg). Additionally, there are considerable differences in the mean values of P between locations and the mean values of P throughout all seasons.

Soil potassium levels ranged from 96.54 to 301.28 mg/kg. Among seasons maximum mean potassium (239.70 mg/kg) was recorded in summer season followed by spring (222.63 mg/kg), autumn (204.14 mg/kg) and minimum (183.58 mg/kg) was recorded in winter season. Among sites mean maximum value of potassium was recorded in center (265.71 mg/kg), followed by inside (242.35 mg/kg), outside (225.85 mg/kg) and minimum (116.16 mg/kg) was recorded at control site as depicted in Table 2. Additionally, there are considerable differences in the mean values of K between sites as well as the mean values of K across all seasons.

During the present study, mean Ca concentration ranged from 668.33 to 984.39 (mg/Kg). Mean maximum concentration of Calcium among seasons was recorded in summer season (913.52 mg/kg), followed by spring (893.44 mg/kg), autumn (856.92) and minimum was recorded in winter (826.58). Among sites mean maximum concentration of calcium was recorded in center (957.67 mg/kg), inside (941.24 mg/kg), outside (876.38 mg/kg) and minimum (712.91 mg/kg) was recorded at control. The mean values of Ca between all seasons were significantly different; furthermore the mean values of Ca between sites also vary significantly.

During the present study the mean Mg concentration ranged from 280.82 to 418.61 (mg/Kg). Magnesium concentration was recorded maximum (385.09 mg/kg) during summer season, followed by spring (374.66 mg/kg), autumn (357.80 mg/kg) and minimum (349.58 mg/kg) was recorded in winter. Among sites maximum mean concentration of magnesium was recorded in center (402.42 mg/kg), followed by inside (396.72 mg/kg), outside (368.48 mg/kg) and minimum (299.49 mg/kg) was recorded at control site as depicted in Table 3. Additionally, there are considerable differences in the mean levels of Mg between locations as well as the mean values of Mg across all seasons.

Table 3. Seasonal and site wise variation in Ca and Mg (mg/kg) of soil.

Parameters	Seasons	Sites				Mean	C.D (P≤0.05)
Parameters	Seasons	Center	Inside	Outside	Control	Mean	C.D (P≤0.05)
Ca	Spring	982.31±0.96^c	965.34±0.97^d	893.60±0.99ⁱ	723.50±0.94ⁿ	893.44 ^b	Sites:1.809 Seasons:1.809 Sites × Seasons:3.618
	Summer	997.74±1.13^a	984.39±0.90^b	913.43±0.93^g	758.51±0.88^m	913.52 ^a
	Autumn	940.40±1.06^e	925.85±0.73^f	860.11±0.94^l	701.31±1.10°	856.92 ^c
	Winter	910.25±0.96^h	889.40±1.08^j	838.37±1.04^k	668.33±0.95^p	826.58 ^d
	Mean	957.67 ^a	941.24 ^b	876.38 ^c	712.91 ^d
Mg	Spring	412.86±0.71^b	405.61±1.35^c	376.28±0.81^g	303.89±1.25^l	374.66 ^b	Sites:3.873 Seasons:3.873 Sites × Seasons:7.745
	Summer	419.24±0.97^a	418.61±0.93^a	383.85±1.02^f	318.66±1.21^k	385.09 ^a
	Autumn	395.12±0.77^d	388.99±0.90^e	352.50±1.27^j	294.61±1.13^m	357.80 ^c
	Winter	382.47±0.95^f	373.67±0.94^h	361.38±1.03ⁱ	280.82±1.17ⁿ	349.58 ^d
	Mean	402.42 ^a	396.72 ^b	368.48 ^c	299.49 ^d
Standard limits (ICAR manual)		Ca Low< 500 mg/kg Medium (500–2500 mg/kg) High ˃ 2500 mg/kg			Mg Sandy soils (51–250 mg/kg) Clayey soils (101–500 mg/kg)

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Ca: Calcium, Mg: Magnesium.

Zinc (Zn) concentration in the soil in the current study ranged from 0.75 to 3.57 (mg/Kg). Among seasons maximum mean concentration of Zn (2.89 mg/kg) was recorded in winter season, followed by autumn (2.54 mg/kg), spring (1.75 mg/kg) and minimum was recorded in summer (1.53 mg/kg). Among sites maximum mean concentration of Zn was recorded at center (2.92 mg/kg), followed by inside (2.50 mg/kg), outside (2.03 mg/kg) and minimum (1.27 mg/kg) was recorded at control. The mean values of Zn between spring, summer and autumn were significantly different, while as no significant difference was reported between autumn and winter. However the mean values of all sites were significantly different. The mean maximum Fe in the current study ranged from 1.51 to 12.51 (mg/Kg). For iron (Fe) maximum mean concentration among seasons was recorded in winter (8.78 mg/kg), followed by autumn (8.26 mg/kg), spring (5.48 mg/kg) and minimum (4.65 mg/kg) was recorded in summer, while as among sites maximum mean concentration was recorded at center (10.56 mg/kg), followed by inside (6.52 mg/kg), outside (6.37 mg/kg) and minimum (3.71 mg/kg) was recorded at control. The mean values of Fe between all seasons were significantly different. Among sites the values of Fe were significantly different between center, inside and control, however no significant difference was reported between inside and outside dumpsite. Mean concentration of Cu ranged from 0.17 to 2.72 (mg/Kg). Copper (Cu) was recorded maximum among seasons in winter (2.11 mg/kg), followed by autumn (1.97 mg/kg), spring (1.19 mg/kg) and minimum was recorded in summer (0.88 mg/kg). Among sites maximum mean concentration of Cu was recorded in center (2.07 mg/kg), followed by inside (1.80 mg/kg), outside (1.74 mg/kg) and minimum was recorded at control (0.54 mg/kg). The mean values of Cu were significantly different throughout all seasons, and it was also observed that these differences were significant between sites.

Mean Manganese (Mn) concentration of soils ranged from 4.54 to 11.83 (mg/Kg) shown in Table 4. Manganese was recorded maximum in winter (8.92 mg/kg), followed by autumn (8.38 mg/kg), spring (7.62 mg/kg) and minimum was recorded in summer (7.24 mg/kg). Among sites maximum mean concentration was recorded at center (10.73 mg/kg), followed by inside (9.34 mg/kg), outside (7.42 mg/kg) and minimum was recorded at control (4.68 mg/kg) as depicted in Table 4. The mean Mn values also varied significantly between different locations and across all seasons.

Table 4. Seasonal and site wise variation in micronutrients, viz Zn, Fe, Cu and Mn (mg/kg) of soil.

Parameters	Seasons	Sites				Mean	C.D (P≤0.05)
Parameters	Seasons	Center	Inside	Outside	Control	Mean	C.D (P≤0.05)
Zn	Spring	2.39±0.14^de	2.01±0.31^ef	1.55±0.33^gh	1.07±0.28^ij	1.75 ^b	Sites:0.212 Seasons:0.212 Sites × Seasons:0.424
	Summer	2.34±0.52^de	1.76±0.01^fg	1.30±0.04^hi	0.75±0.32^j	1.53 ^c
	Autumn	3.36±0.21^ab	2.99±0.09^bc	2.53±0.17^d	1.27±0.12^hi	2.54 ^a
	Winter	3.57±0.29^a	3.26±0.15^ab	2.74±0.24^cd	1.98±0.24^ef	2.89 ^a
	Mean	2.92 ^a	2.50 ^b	2.03 ^c	1.27 ^d
Fe	Spring	9.25±0.29^b	5.21±0.15^f	5.14±0.32^f	2.31±0.14^h	5.48 ^c	Sites:0.250 Seasons:0.250 Sites × Seasons:0.50
	Summer	8.45±0.21^c	4.41±0.24^g	4.24±0.23^g	1.51±0.18ⁱ	4.65 ^d
	Autumn	12.05±0.17^a	8.01±0.27^cd	7.85±0.11^d	5.13±0.19^f	8.26 ^b
	Winter	12.51±0.89^a	8.46±0.15^c	8.27±0.18^cd	5.88±0.06^e	8.78 ^a
	Mean	10.56 ^a	6.52 ^b	6.37 ^b	3.71 ^c
Cu	Spring	1.62±0.24^d	1.36±0.09^e	1.29±0.13^e	0.49±0.12^h	1.19 ^c	Sites:0.117 Seasons:0.117 Sites × Seasons: 0.235
	Summer	1.33±0.11^e	1.04±0.08^f	0.99±0.11^f	0.17±0.06ⁱ	0.88 ^d
	Autumn	2.61±0.24^ab	2.33±0.15^c	2.28±0.18^c	0.65±0.05^gh	1.97 ^b
	Winter	2.72±0.06^a	2.46±0.07^bc	2.39±0.19^bc	0.87±0.10^fg	2.11 ^a
	Mean	2.07 ^a	1.80 ^b	1.74 ^b	0.54 ^c
Mn	Spring	10.21±0.63^cd	8.79±0.25^f	6.89±0.39ⁱ	4.58±0.17^j	7.62 ^c	Sites: 0.212 Seasons: 0.212 Sites × Seasons: 0.425
	Summer	9.73±0.04^e	8.32±0.28^g	6.47±0.08ⁱ	4.54±0.05^j	7.24 ^d
	Autumn	11.18±0.23^b	9.83±0.11d^e	7.81±0.39^h	4.69±0.06^j	8.38 ^b
	Winter	11.83±0.06^a	10.42±0.09^c	8.53±0.21^fg	4.92±0.05^j	8.92 ^a
	Mean	10.73 ^a	9.34 ^b	7.42 ^c	4.68 ^d
Standard limits (ICAR manual)	Zn Low < 0.5 mg/kg Medium (1–3 mg/kg) High ˃ 5 mg/kg		Fe Low < 2 mg/kg Medium (4 -6mg/kg) High ˃ 10 mg/kg		Cu Low < 0.1 mg/kg Medium (0.3–0.8mg/kg) High ˃ 3 mg/kg		Mn Low< 0.5 mg/kg Medium (1.2–3.5 mg/kg) High ˃ 6 mg/kg

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Zn: Zinc, Fe: Iron, Cu: Copper, Mn: Manganese.

In the present study the concentration of lead (Pb) ranged from 0.98 mg/kg to 98.3 mg/kg. The mean maximum concentration of lead (Pb) among seasons was recorded in summer (72.1 mg/kg), followed by autumn (68.5 mg/kg), spring (59.08 mg/kg) and minimum was recorded in winter (35.9 mg/kg) while as among sites maximum mean concentration of Pb was recorded at center (85.02 mg/kg), followed by inside (76.02 mg/kg), outside (68.72 mg/kg) and minimum (5.90 mg/kg) was recorded at control. Additionally to the fact that the mean Pb values between sites varied greatly, these mean values of Pb between seasons varied significantly as well. The concentration of cadmium Cd ranged from 0.06mg/kg to 5.89 mg/kg. Cadmium (Cd) was recorded maximum in summer season (4.46 mg/kg), followed by autumn (3.80 mg/kg), spring (3.22 mg/kg) and minimum (1.57 mg/kg) was recorded in winter and among maximum mean concentration of Cd was recorded at center (4.56 mg/kg), followed by inside (4.26 mg/kg), outside (4.08 mg/kg) and minimum was recorded at control (0.15 mg/kg). Among the sites, the mean cadmium values were significantly different between the center and control, and inside and control; however, no significant difference was reported between outside and control. The concentration of nickel (Ni) ranged from 0.65mg/kg to 42.10 mg/kg. Ni was recorded maximum in summer (29.70 mg/kg), followed by autumn (22.23 mg/kg), spring (17.01 mg/kg) and minimum was recorded in winter (9.30 mg/kg). In case of sites it was recorded maximum at center (29.04 mg/kg), followed by inside (25.86 mg/kg), outside (21.88 mg/kg) and minimum (1.47 mg/kg) was recorded at control as depicted in Table 5. The mean values of Ni between seasons as well as sites differ significantly. The concentration of chromium (Cr) ranged from 2.31 mg/kg to 30.40 mg/kg. Among seasons max concentration (22.41 mg/kg) was reported during summer season followed by autumn (19.67 mg/kg), spring (15.37 mg/kg) and min during winter (9.88 mg/kg). Among sites maximum concentration (23.37 mg/kg) was reported at center of dumpsite, followed by inside (21.12 mg/kg), outside (18.61 mg/kg) and minimum was reported at control site (4.23 mg/kg). The mean values of Cr between seasons were reported to be significantly different. Among sites the mean values of Cr between inside, outside, control were significantly different; however no significant difference in mean values of Cr was reported between center and inside. The value of Arsenic (As) ranged from 0.23 mg/kg to 18.50 mg/kg. Among seasons max concentration (12.63 mg/kg) was reported during summer season followed by autumn (9.86 mg/kg), spring (8.04 mg/kg) and min during winter (5.63 mg/kg). Among sites maximum concentration (14.10 mg/kg) was reported at center of dumpsite, followed by inside (11.53 mg/kg), outside (9.87 mg/kg) and minimum was reported at control site (0.66 mg/kg) as depicted in Table 6. The mean values of As between seasons were significantly different. In addition to this the mean values of As between all sites was also reported to be significantly different. Furthermore the correlation between the recorded paramaters is depicted in Table 7.

Table 5. Seasonal and site wise variation in Pb, Cd and Ni (mg/Kg) of soil.

Parameters	Seasons	Sites				Mean		C.D (P≤0.05)
Parameters	Seasons	Center	Inside	Outside	Control	Mean		C.D (P≤0.05)
Pb	Spring	89.1±3.34^b	76.4±1.62^c	65.8±2.44^d	5.03±0.58^hi	59.08 ^c		Sites: 1.799 Seasons: 1.799 Sites × Seasons: 3.557
	Summer	98.3±4.05^a	92.5±2.53^ab	87.4±2.25^b	10.2±1.22^h	72.1 ^a
	Autumn	96.8±1.69^a	88.6±2.09^b	81.4±1.56^c	7.4±0.90^h	68.5 ^b
	Winter	55.9±1.41^e	46.6±2.00^f	40.3±1.83^g	0.98±0.07ⁱ	35.9 ^d
	Mean	85.02 ^a	76.02 ^b	68.72 ^c	5.90 ^d
Cd	Spring	4.69±1.08^a	4.12±1.00^ab	3.98±0.85^ab	0.12±0.02^cd	3.22 ^b		Sites: 1.10 Seasons:1.10 Sites × Seasons: 2.20
	Summer	6.11±1.28^a	5.89±0.76^a	5.61±0.66^a	0.25±0.08^cd	4.46 ^a
	Autumn	5.11±1.23^a	5.01±0.50^a	4.89±1.28^a	0.19±0.03^cd	3.80 ^ab
	Winter	2.34±0.57^bc	2.02±0.43^bcd	1.87±0.52^bcd	0.06±0.32^d	1.57 ^c
	Mean	4.56 ^a	4.26 ^a	4.08 ^a	0.15 ^b
Ni	Spring	26.20±1.02^de	22.50±2.15^ef	18.30±1.45^fg	1.06±0.24ⁱ	17.01 ^c		Sites: 2.047 Seasons: 2.047 Sites × Seasons:4.093
	Summer	42.10±3.02^a	38.70±4.33^ab	35.70±2.80^bc	2.32±0.46ⁱ	29.70 ^a
	Autumn	32.40±2.11^c	29.80±3.51^cd	24.90±1.96^de	1.85±0.19ⁱ	22.23 ^b
	Winter	15.47±2.17^g	12.46±1.64^gh	8.65±1.10^h	0.65±0.18ⁱ	9.30 ^d
	Mean	29.04 ^a	25.86 ^b	21.88 ^c	1.47 ^d
Permissible value of soil (mg/kg) Pb = 85; Cd = 0.8; Ni = 35				Permissible value of plant Pb = 2; Cd = 0.02; Ni = 10			Permissible value of water Pb = 0.05; Cd = 0.005; Ni = 0.07

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Pb: Lead, Cd: Cadmium, Ni: Nickel.

Table 6. Seasonal and site wise variation in Cr, and As (mg/Kg) of soil.

Parameters	Seasons	Sites				Mean		C.D (P≤0.05)
Parameters	Seasons	Center	Inside	Outside	Control	Mean		C.D (P≤0.05)
Cr	Spring	21.80±1.52^cd	19.60±1.62^de	16.70±1.49^ef	3.41±0.63ⁱ	15.37 ^c		Sites: 1.43 Seasons: 1.43 Sites × Seasons: 2.86
	Summer	30.40±3.25^a	27.60±1.58^ab	25.30±2.01^bc	6.34±0.72^hi	22.41 ^a
	Autumn	26.10±1.21^abc	24.90±1.95^bc	22.80±2.52^cd	4.89±1.03ⁱ	19.67 ^b
	Winter	15.20±1.47^ef	12.40±1.54^fg	9.64±0.41^gh	2.31±0.26ⁱ	9.88 ^d
	Mean	23.37 ^a	21.12 ^a	18.61 ^b	4.23 ^c
As	Spring	13.40±1.12^bcd	9.65±0.65^ef	8.67±0.42^ef	0.45±0.07^h	8.04 ^c		Sites: 1.31 Seasons: 1.31 Sites × Seasons:2.62
	Summer	18.50±1.47^a	16.30±1.76^ab	14.60±1.45^bc	1.12±0.12^h	12.63 ^a
	Autumn	15.30±1.58^bc	12.70±1.26^cd	10.60±1.15^de	0.86±0.05^h	9.86 ^b
	Winter	9.21±0.79^ef	7.48±0.68^fg	5.62±1.10^g	0.23±0.07^h	5.63 ^d
	Mean	14.10 ^a	11.53 ^b	9.87 ^c	0.66 ^d
Permissible value of soil (mg/kg) Cr = 100; As = 20				Permissible value of plant (mg/kg) Cr = 1.30 As = 0.05			Permissible value of Water (mg/kg) Cr: 0.05 As: 0.05

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Cr: Chromium, As: Arsenic.

Table 7. Correlation between various physico–chemical paramaters of soil.

	pH	EC	MC	N	P	K	Ca	Mg	Zn	Fe	Cu	Mn	Pb	Cd	Ni	Cr	As
pH	1
EC	-0.86	1
MC	-0.48	0.78	1
N	-0.87	0.81	0.61	1
P	-0.92	0.92	0.60	0.93	1
K	-0.86	0.82	0.65	0.99	0.92	1
Ca	-0.88	0.84	0.67	0.98	0.92	0.98	1
Mg	-0.87	0.84	0.67	0.98	0.92	0.98	0.99	1
Zn	-0.36	0.57	0.85	0.37	0.34	0.43	0.45	0.45	1
Fe	-0.39	0.64	0.86	0.40	0.41	0.46	0.45	0.45	0.93	1
Cu	-0.33	0.46	0.80	0.39	0.28	0.46	0.47	0.46	0.95	0.88	1
Mn	-0.68	0.84	0.93	0.71	0.69	0.75	0.78	0.78	0.88	0.86	0.85	1
Pb	-0.87	0.75	0.56	0.95	0.86	0.95	0.93	0.92	0.43	0.46	0.48	0.70	1
Cd	-0.84	0.67	0.43	0.93	0.83	0.92	0.89	0.87	0.31	0.33	0.36	0.57	0.98	1
Ni	-0.89	0.71	0.41	0.92	0.88	0.91	0.87	0.86	0.29	0.33	0.30	0.57	0.95	0.98	1
Cr	-0.90	0.73	0.45	0.93	0.87	0.92	0.90	0.88	0.35	0.38	0.38	0.62	0.98	0.98	0.98	1
As	-0.90	0.79	0.54	0.95	0.91	0.95	0.92	0.91	0.41	0.45	0.42	0.69	0.97	0.96	0.98	0.98	1

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Discussion

Soil pH determines the acidity or alkalinity of soil solutions and refers to the soil’s hydrogen ion content. Natural soil typically has a pH between 7 and 8.5, although this range can vary based on biological activity, temperature, and municipal waste disposal practices [28]. Soil pH influences the availability of essential plant nutrients and the concentration of toxic elements, thereby affecting plant growth [29]. As it impacts the availability of all nutrients in the soil it has a direct effect on the survival and development of plants. In this, study pH of dumpsite soils ranged from 6.1 to 6.9 throughout study period. The mean pH values ranged from slightly acidic to neutral, which may be due to the decomposition of organic matter leading to the formation of organic acids. However, the pH increased with increase in distance from dumpsite which may be attributed to release of less organic acids away from dumpsite. Further, the lowest pH value reported during summer season may be attributed to more degradation of organic matter leading to increase in production of organic acids because of increased microbial activity and favorable temperature and moisture conditions during summer season as compared to winter season as depicted in Fig 2.

Fig 2 — S1 is spring, S2 is summer, S3 is autumn and S4 is winter, while as C1 is center, C2 is inside, C3 is outside and C4 is Control.

The pH value of control site (Shalimar) soil was higher than the other three sites during all the seasons, this may be due to presence of less organic matter and hence less microbial activity. The slightly acidic pH of the soils at three other sites suggests that solid waste contributed to soil acidity, leading to a decrease in the availability of essential plant nutrients such as phosphorus and molybdenum, while increasing the availability of toxic elements, particularly aluminum and manganese [30]. Electrical conductivity is an indirect measurement that is correlated with a number of the physical and chemical characteristics of soil. EC is affected by moisture content that soil particles hold. The total quantity of anions and cations determines electrical conductivity. It also depends on the primary salts in the soil solution, which have a negative impact on the qualities of the soil [31]. The optimal EC is crop specific, and depends on environmental conditions [32]. In general, higher EC hinders nutrient uptake by increasing the osmotic pressure of the nutrient solution, and the increased discharged of nutrients into the environment, resulting in environmental pollution. Lower EC may severely affect plant health and yield [33,34]. In the current study, maximum mean value of EC was reported at center of dumping site, which may be due to increased concentration of cations and anions within the dumpsite soil [35] and minimum was reported at control site. Among seasons maximum mean EC value was reported during summer season, which may be due to increase in degradation of salts and release of large number of cations and anions favoured by temperature and minimum was reported during winter due to decrease in degradation of organic matter as shown in Table 1 and Fig 3.

Fig 3 — S1 is spring, S2 is summer, S3 is autumn and S4 is winter, while as C1 is center, C2 is inside, C3 is outside and C4 is Control.

The electrical conductivity of the soil samples collected within the dumpsite was high compared to the soil sample collected from the control site. Moisture content refers to the amount of water soil can hold. Most soil samples from municipal solid waste have moisture content ranging from 15% to 40% [31]. The highest mean moisture content was observed at the center of the dumping site, which may be because dumpsite soil retains more moisture due to the natural ground being covered by municipal solid waste, which has high moisture content and prevents soil moisture from evaporating directly [36]. The mean moisture content of soil decreased with the increase of the distance from the dumpsite. This higher moisture content in the dumpsite soil may be associated with the presence of high organic matter which has capacity to hold more water [37]. This excess amount of water suffocates plant roots by reducing the amount of oxygen available to them. Without enough oxygen, roots are not able to absorb nutrients and water effectively, which in turn inhibits the growth of plants. The moisture content was high during winter season which may be attributed to the high precipitation rate during winter. Nitrogen (N) is the most important ingredient that plants take up from the soil. In the present study, the concentration of N was maximum at center of dumping site during all the seasons as shown in Table 2. The samples within the dumpsite have high N concentration than the samples away from dumpsite, which may be attributed to abundant amount of the putrescible waste (biowaste, kitchen waste) [38]. The maximum N concentration observed during summer season may be due to increase in reaction rate because of high temperature. Additionally, the high levels of organic matter present in dump soil may be responsible for the high N content [39]. It has been reported that application of N significantly increases tuber yield and other yielding components in Colocasia [40]. Although N is a necessary component for the synthesis of proteins and amino acids, a high concentration of nitrogen in the tissues can be hazardous to the plant’s physiological and phonological responses [41]. The movement of leachate from municipal solid waste (MSW) disposal site can increase the phosphorus (P) content in soil at dumpsites. In the current study the highest mean P level was found at the center of the dumping site. e which may be attributed to the large quantities of organic waste, paper and cardboard, textiles, and plastics [42]. Seasonally, the highest mean phosphorus content was observed during the summer (and the lowest during winter. The concentration of P was higher in the soil samples of the dumping site than the controlled site. This may be explained by the fact that organic matter in waste contains sizable amounts of P, and that orthophosphate is released into the soil solution during mineralization. Additionally, humic substances and organic acids can be absorbed into soil surfaces, leading to depletion in ability of P adsorption by obstructing sites for the formation of complexes with Al, Fe, and Ca. Inorganic and organic products are also produced during the partial decomposition of organic waste [43]. Potassium readily dissolves in water; however, it remains largely intact in undisturbed soils. After being released from decomposing organic matter, potassium quickly and strongly binds to clay particles [31]. In this study the highest concentration of potassium was found at the center of the dumping site, likely due to the decomposition of a substantial amount of kitchen waste. Conversely, the lowest concentration was observed at the control site, where there was less organic waste as given in Table 2. Among seasons, maximum K content reported during summer may be due to high decomposition rate of kitchen waste and less leaching and minimum content of it reported during winter may be due to high leaching losses by precipitation. Similar results were obtained by Deshmukh and Aher [28]. Despite the fact that K controls stomatal opening and shutting, cell enlargement, and other critical physiological activities. Numerous research have examined importance of potassium on plant growth, however high K concentrations in soil solutions restrict magnesium uptake, leading to magnesium deficiency in plants [44]. Calcium (Ca) is crucial element in figuring out the soil’s physical and chemical properties, especially its structure and pH. Clay platelets in soil colloids (caused by calcium ions) bind or aggregate to produce crumbs or peds. Frequent correlation has been reported between pH and exchangeable calcium levels in soil. For example in the pH range of 7.0 to 8.5, Ca is accessible, while as low Exchangeable calcium levels were reported in acidic pH [31]. In the current study maximum Ca content reported during summer may be because of degradation of calcium rich waste such as bones and eggshells present in the kitchen waste and minimum was reported during winter, which may be because of low rate of degradation of waste. Among sites, maximum Ca content reported at center of dumping site may be attributed to the clayey nature of soils of dumpsite as shown in Table 3. Magnesium (Mg) is found in both relatively soluble forms and ionic form, Mg²⁺, which is attached to the soil colloidal complex. It has been reported that magnesium levels in acidic soils, especially sandy soils, are frequently low, while as neutral soils usually contain more exchangeable magnesium [31]. In this investigation among sites maximum Mg concentration reported at center of dumping site may be because of its less mobility due to presence of high organic waste and clayey nature of soil [45] and minimum at control site may be because of the presence of less organic matter as given in Table 3. Among seasons maximum Mg concentration reported during summer season may be beca use of less leaching and high rate of decomposition of organic waste and minimum during winter may be attributed to high leaching loss due to the high positive water balance [45]. An excessive amount of magnesium in the soil inhibits plant growth because it reduces the ability of roots to reduce TTC (2, 3, 5-Triphenyl Tetrazolium chloride) through the inhibition of the dehydrogenase enzyme linked to the respiratory systems [46].

Micronutrients are essential for sustaining the fertility of the soil and crop productivity. Compared to macronutrients, micronutrients are required in smaller amounts. Even if the supply of macronutrients is balanced and high yielding varieties are cultivated, lack of micronutrients will prevent maximum yield from being achieved [47]. In this study, the presence of Zn element in both naturally occurring materials, such as yard wastes and food wastes, as well as man-made materials like pigments, inks, metals, and plastics may account for the highest mean Zn value at the centre of the dumping site, while the lowest mean Zn value was reported at the control site, as shown in Table 4. Furthermore micronutrients are more tightly bonded to the soil at high pH than at low pH, the highest mean Zn concentration during the winter season may be attributed to low pH, whereas the lowest mean Zn concentration during the summer season may be attributed to high pH [48]. Although Zn serves as a nutrient for plants, but is hazardous to them in larger amounts. Zn toxicity in plants results in growth inhibition, a reduction in biomass production, competition for nutrients, inactivation of enzymes, removal of vital components from functional locations, chlorosis, and, in certain situations, blockage of Fe translocation [49].

Ferric oxide (Fe₂O₃), also known as hematite, is the most prevalent form of Iron (Fe) in soils. It is exceedingly insoluble and gives soil its red colour. Commonly, the oxide form is hydrated [50]. In this study the maximum mean Fe concentration recorded at the centre of the dumping site may be attributed to the presence of organic matter in soils, as organic matter rich soils contain Fe in the reduced state (Fe²⁺) or is adsorbed on the surface of soil particle [50]. The maximum iron concentration reported during winter season depicted in Table 4 may be attributed to low pH, because with increase in pH, ferrous ion (Fe²⁺) gets converted to ferric ion (Fe³⁺). Low solubility in solution makes the ferric ion (Fe³⁺) compounds less bioavailable, and a minimum concentration was recorded during the summer [51]. The root cells and plasma membrane are damaged by the extra iron ions, which results in oxidative stress and increased formation of reactive oxygen species (ROS). Root cells may die as a result of ROS harming cellular components such lipids, proteins, and DNA [52]. Furthermore it, can also affect the uptake of other essential elements, such as phosphorus and zinc, by competing with the transporters that facilitate their uptake by the roots. This interference can lead to nutrient imbalances, reduced growth, and overall plant health [53].

Compared to other trace metals, copper (Cu) has extremely little mobility because it is firmly adsorbed onto soil particles. Due to this reduced mobility, Cu has a tendency to concentrate on soil particles. Leaching of Cu occurs when the amount of Cu in the soil exceeds the capacity of the soil type to hold the copper ions. The pH, cation exchange capacity, organic matter content, and presence of iron, manganese, and aluminium oxides all affect how much Cu is present in soils. The amount of water in the soil affects the ability of the soil to store copper through biotic and abiotic oxidation-reduction reactions [31]. Among sites mean maximum concentration reported at center of dumping site may be due to the higher stability constants of Cu complexes with organic matter and minimum was reported at control site as shown in Table 4. Among seasons, maximum Cu concentration reported during winter season may be because of low pH, as at low pH Cu compounds are more soluble and minimum concentration of Cu reported during summer may be because of high pH, as high pH results in precipitation of copper (Ⅱ) hydroxide (Cu (OH)₂) and Copper(Ⅰ) hydroxide (CuOH) [54]. All phases of plant growth are affected by high Cu concentration toxicity, which has considerable detrimental impacts on morphology, physiological function, and molecular level [55]. Additionally, too much copper in the soil inhibits the activity of -amylase and invertase isoenzymes, which limits the ability of many plant species to break down reserve food supplies like starch and sucrose [56]. Maximum concentration of Mn reported at center of dumping site may be due to decomposition of plants and animals waste as well as animal excrement [57]. The lowest concentration of Mn was reported at control site as given in Table 4. The highest Mn concentration observed during the winter season, is likely due to a decrease in soil pH. At low pH, trace elements are typically more soluble because of high desorption and low adsorption [31]. Conversely, the lowest Mn concentration was reported during the summer, which may be attributed to increased adsorption [58]. Manganese is essential for terrestrial plants, but excessive accumulation in leaves can cause toxicity and reduce crop yield.

Heavy metals are significant pollutants that enter in to environment through various channels, including landfill leachate, solid waste, and wastewater. According to Radfard et al. [59] and Kusin et al. [60], heavy metals in leachate contaminate soil and subsurface water supplies. As these contaminants move up the food chain, they impact human health and cause various ailments. Leachate is a critical source of pollution, releasing chemicals into soil and water sources, and its toxicity to human cells highlights its environmental impact [61]. In the current study among seasons max mean concentration of Pb was reported during summer season and min during winter. Among sites maximum concentration was reported at center of dumpsite and minimum was reported at control site. The values of Pb are higher than permissible limit (85mg/kg) at center during spring, summer and autumn, inside during summer and autumn and outside during summer season as depicted in Table 5 and Fig 4.

Fig 4 — S1 is spring, S2 is summer, S3 is autumn and S4 is winter, while as C1 is center, C2 is inside, C3 is outside and C4 is Control.

Lead-acid batteries used in automobiles, rechargeable nickel-cadmium batteries, consumer electronics, glass, ceramics, and plastic products including PVC resins are sources of Pb in landfill leachate. Other sources of lead include soldered cans, pigments, brass and bronze products, rubber goods, spent motor oil, and wine bottle wrappers made of lead foil. Among seasons max concentration of Cd was reported during summer season and min during winter. Among sites maximum concentration was reported at center of dumpsite, and minimum was reported at control site. Cadmium (Cd) levels at all sites exceeded the permissible limit of 0.8 mg/kg across all seasons as depicted in Table 5 and Fig 5.

Fig 5 — S1 is spring, S2 is summer, S3 is autumn and S4 is winter, while as C1 is center, C2 is inside, C3 is outside and C4 is Control.

The sources of cadmium in waste include nickel-cadmium batteries, pigments, stabilizers in plastics (primarily PVC), consumer electronics (notably the steel chassis of vintage TVs and radios that were cadmium-plated to prevent corrosion), antique appliances with cadmium-plated parts, textile dyes and paints, glass and ceramics, and pigments used in non-newspaper printing inks. Cadmium is one of the most ecotoxic metals, causing detrimental effects on soil health, plant metabolism, and the health of humans and animals [62]. Even at very low concentrations, chronic exposure to cadmium can lead to anemia, anosmia, cardiovascular diseases, and renal problems [63]. Ni was reported maximum during summer season and min during winter. Among sites maximum concentration was reported at center of dumpsite and minimum was reported at control site as depicted in Table 5 and Fig 6.

Fig 6 — S1 is spring, S2 is summer, S3 is autumn and S4 is winter, while as C1 is center, C2 is inside, C3 is outside and C4 is Control.

The values of Ni were higher than the permissible limits (35 mg/kg) during summer season at all sites. The values were lower than the permissible limits during other seasons. The sources of Ni are lead cadmium batteries, electroplating materials, clinical wastes [64]. Because nickel is non-biodegradable and has the potential to accumulate in the food web, it is responsible for a number of health issues in humans, including allergic skin, headache, vertigo, nausea, vomiting, insomnia, and irritability [64,65]. Among seasons max concentration of Cr was reported during summer season and min during winter. Among sites maximum concentration was reported at center of dumpsite, and minimum was reported at control site as depicted in Table 6 and Fig 7.

Fig 7 — S1 is spring, S2 is summer, S3 is autumn and S4 is winter, while as C1 is center, C2 is inside, C3 is outside and C4 is Control.

The sources of Cr are electroplating and Cr containing wastes. The concentration of Cr was less than permissible value at all sites. The sorption properties of the soil, such as its clay, iron oxide, and organic matter contents, influence the mobility of Cr. Surface runoff can carry chromium to surface waters in both its soluble and precipitated forms. Chromium compounds, both soluble and unadsorbable, can seep into groundwater from the soil. As soil pH rises, Cr (VI) has a greater propensity to leach. However, the majority of Cr discharged into natural rivers is particle associated and eventually deposits into the sediment [66]. Human allergic dermatitis and chromium are related [67]. The value of Arsenic (As) ranged from 0.23 mg/kg to 18.50 mg/kg. Among seasons max concentration was reported during summer season and min during winter. Among sites maximum concentration was reported at center of dumpsite, and minimum was reported at control site as depicted in Table 6 and Fig 8.

Fig 8 — S1 is spring, S2 is summer, S3 is autumn and S4 is winter, while as C1 is center, C2 is inside, C3 is outside and C4 is Control.

The permissible limit of As in soil is 20 mg/kg. The concentration of heavy metals, specifically Pb, Cd, Ni, Cr, and As, is higher during the summer than other seasons. The leaching of heavy metals is also higher during the summer because temperature influences it; as the temperature rises, the leaching of heavy metals also increases. However, the minimum concentration of heavy metals during winter season might be attributed to runoff effect during winter season which facilitates the leaching of heavy metals from soil and contributes to the dilution of soil solution during winter season.

Heavy metal toxicity in plants severely hampers nutrient and water uptake, while intensifying oxidative damage, ultimately stunting plant growth. Cadmium (Cd) has been shown to interact with plants at the physio-biochemical level, leading to reduced growth. Cd toxicity disrupts nutrient and water absorption, heightens oxidative stress, and impairs plant metabolism, and negatively impacts plant morphology and physiology [68]. Similarly, chromium (Cr) toxicity inhibits seed germination, slows plant growth, impairs enzymatic activities, and disrupts the photosynthetic machinery, leading to oxidative imbalances [69,70]. Lead (Pb) toxicity has been found to inhibit ATP production, elevate reactive oxygen species (ROS) levels, and cause DNA damage. It significantly affects germination, root elongation, plant growth, chlorophyll synthesis, and disturbs transcriptome sequencing [71]. Nickel (Ni) toxicity reduces seed germination, root and shoot development, biomass accumulation, and overall yield. It also causes chlorosis, necrosis, and disrupts physiological processes like photosynthesis and transpiration, while inducing oxidative stress. The threat posed by Ni increases with its concentration in the environment, particularly in soils [72]. Arsenic (As) exposure adversely affects plants at both biochemical and molecular levels, inhibiting key physiological processes such as overall growth, photosynthetic efficiency, and biomass production. Arsenic induces oxidative stress by increasing ROS production or reducing their elimination, leading to damage of lipids, proteins, and nucleic acids. It interferes with metabolic pathways, either by acting as a competitive inhibitor of phosphate (Pi) or by disrupting enzyme activities. Additionally, As inhibits seed germination, root and shoot development, and other critical early-stage processes during seedling growth [73].

Available management strategy for remediation of soil health

Soil is very important asset for plant and human health, so the need of hour is to maintain the soil quality and prevent its degradation. The waste generated from various sources like houses, restaurants, agricultural fields, orchards is mostly organic (65–75%), which is diverted to landfill in huge amounts on daily basis can be segregated at source and then converted into compost. The compost generated can then be used to ameliorate the nutrient status of soil quality as well as to enhance the plant growth and development. Furthermore the compost generated will replace the chemical fertilizers used. The plan of utilization of microbial consortium technology for degradation of waste is depicted in flow chart given in Fig 9.

Conclusion

The soil plays a crucial role in controlling the flow of pollutants into the food chain. Population growth is causing waste generation to grow rapidly as well. Landfills have been a popular choice for residue dumping for the past 20 years. Our investigation has shown that, regardless of the time of year or the distance from the waste site, landfills seriously degrade the soil quality of nearby communities. pH was more acidic during the summer season and at center of the dumping site due to an increase in the production of organic acids, while as it was less acidic during the winter season and away from the dump site. The acidic pH results in a decrease in the availability of essential elements viz, N.P and K, however, it results in an increase in the availability of toxic heavy metals viz, Pb, Cd, Ni, Cr, As. The heavy metals were reported to be maximum during the summer season at all sites and minimum during the winter season. Among sites the heavy metals were maximum and decreased with increase in distance from the landfill. Our findings led to the conclusion that there is a need for global attention on improving or restoring soil health. Assessment of soil health indicators is expected to enhance our understanding of the factors underlying processes that contribute to sustainable agriculture. The leachate must be treated before disposal and that landfills must have adequate lining. Before disposing of rubbish, segregate non-biodegradable items like polythene and plastic bags since they take roughly 500 years to degrade. Biodegradable garbage must be handled using ecologically friendly techniques like anaerobic digestion and composting. The garbage that needs to be landfilled should only be non-biodegradable, inert, or unsuitable for recycling. MSW must not be combined with biomedical waste. Media should be used to inform people about trash management. The organic waste ought to be isolated at the point of generation and turned into compost using microbial processes.

Supporting information

S1 Data

(XLSX)

pone.0314006.s001.xlsx^{(16.6KB, xlsx)}

Acknowledgments

The authors acknowledge the support of SKUAST Kashmir and Division of Environmental sciences in carrying out the research.

Data Availability

All relevant data are within the manuscript and its Supporting Information files.

Funding Statement

Funder: Fahad Naseer Alotaibi, Assistant professor- Department of Soil Science, College of Food and Agriculture Sciences, King Saud University, P.O.Box 2460, Riyadh, Saudi Arabia. Project Number: RSPD2024R889 “In addition to funding the funder has a role in preparation and modification of manuscript”.

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PONE-D-24-19939Landfill leachate: an invisible threat to soil quality of temperate HimalayasPLOS ONE

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The Gateway to Astronaut Photography of Earth (public domain): http://eol.jsc.nasa.gov/sseop/clickmap/

Maps at the CIA (public domain): https://www.cia.gov/library/publications/the-world-factbook/index.html and https://www.cia.gov/library/publications/cia-maps-publications/index.html

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7. Please review your reference list to ensure that it is complete and correct. If you have cited papers that have been retracted, please include the rationale for doing so in the manuscript text, or remove these references and replace them with relevant current references. Any changes to the reference list should be mentioned in the rebuttal letter that accompanies your revised manuscript. If you need to cite a retracted article, indicate the article’s retracted status in the References list and also include a citation and full reference for the retraction notice.

[Note: HTML markup is below. Please do not edit.]

Reviewers' comments:

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Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: Yes

**********

2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: Yes

**********

3. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: Yes

**********

4. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

**********

5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: Comments

I have read the exhaustive article on “Landfill leachate: an invisible threat to soil quality of temperate Himalayas”. In this article, the authors thoroughly document previous literature. However, it is necessary to cite the following research articles in the introduction and methodology sections before publishing.

1. DOI: 10.1007/s11104-023-06016-4

2. DOI: 10.3390/microorganisms10102078

3. DOI: 10.4236/ojss.2018.82007

Reviewer #2: PAPER PRESENTS NOVEL WORK HOWEVER IT REQUIRES MINOR EDITING IN INTRODUCTION AND DISCUSSION

Landfills are the most affordable and popular method for managing waste in many

parts of the world, However, in most developing nations, including India, the infiltration

of hazardous materials from improperly managed dumping sites continues to be a

significant environmental problem. Around the world, leachate is a significant point

source of contamination in numerous environmental media, including soil,

groundwater, and surface water.

**********

6. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

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Reviewer #1: No

Reviewer #2: Yes: Owais Ali Wani

**********

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Attachment

Submitted filename: Landfill Comments.docx

pone.0314006.s002.docx^{(13.6KB, docx)}

PLoS One. 2024 Nov 19;19(11):e0314006. doi: 10.1371/journal.pone.0314006.r002

Author response to Decision Letter 0

21 Jul 2024

Rebuttal

1. Please ensure that your manuscript meets PLOS ONE's style requirements, including those for file naming.

Response: Formatted my manuscript as per PLOS ONE templates attached (Title, author affiliations and main body).

Response: I have included the full name of authority that permitted for visit to the study site in my Methods section.

3. We note that your Data Availability Statement is currently as follows: [All relevant data are within the manuscript and its Supporting Information files.]

For example, authors should submit the following data:

- The values behind the means, standard deviations and other measures reported;

- The values used to build graphs;

- The points extracted from images for analysis.

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Response: The raw data of results of this study has been attached as separate file “Supplementary data”. There are no ethical or legal restrictions in sharing the data.

Response: The ORCID iD of the corresponding author has been validated in Editorial Manager.

Response: The ethical statement was earlier in acknowledgement section. Now I have moved to Methods section.

We require you to either (1) present written permission from the copyright holder to publish these figures specifically under the CC BY 4.0 license, or (2) remove the figures from your submission:

a. You may seek permission from the original copyright holder of Figure 1 to publish the content specifically under the CC BY 4.0 license.

We recommend that you contact the original copyright holder with the Content Permission Form (http://journals.plos.org/ plosone/s/file?id=7c09/content-permission-form.pdf) and the following text: “I request permission for the open-access journal PLOS ONE to publish XXX under the Creative Commons Attribution License (CCAL) CC BY 4.0 (http://creativecommons.org/licenses/by/4.0/). Please be aware that this license allows unrestricted use and distribution, even commercially, by third parties. Please reply and provide explicit written permission to publish XXX under a CC BY license and complete the attached form.”

Please upload the completed Content Permission Form or other proof of granted permissions as an "Other" file with your submission.

The following resources for replacing copyrighted map figures may be helpful:

USGS National Map Viewer (public domain): http://viewer.nationalmap.gov/viewer/

The Gateway to Astronaut Photography of Earth (public domain): http://eol.jsc.nasa.gov/sseop/clickmap/

Maps at the CIA (public domain): https://www.cia.gov/library/publications/the-world-factbook/index.html and https://www.cia.gov/library/publications/cia-maps-publications/index.html

NASA Earth Observatory (public domain): http://earthobservatory.nasa.gov/ Landsat: http://landsat.visibleearth.nasa.gov/

USGS EROS (Earth Resources Observatory and Science (EROS) Center) (public domain): http://eros.usgs.gov/# Natural Earth (public domain): http://www.naturalearthdata.com/

Response: I have revised map as per suggestions and have used resources from the sources which don’t have copyright issues.

Response: I have reviewed the reference list as per the journal requirements. Few reference including 22, 24, 25, 26, 27, 33, 34, 35, 40, 41, 51. The reference Hochmuth, 2017 has been replaced by Lucena and Apaolaza, 2017.

5. Review Comments to the Author

Reviewer #1: Comments

1. DOI: 10.1007/s11104-023-06016-4

Response: Cited from line number 52-54, reference no 6.

2. DOI: 10.3390/microorganisms10102078

Response: Cited from line number 63-64, reference no 10.

3. DOI: 10.4236/ojss.2018.82007

Response: Cited from line number 250-251, reference no 41.

Reviewer #2:

PAPER PRESENTS NOVEL WORK HOWEVER IT REQUIRES MINOR EDITING IN INTRODUCTION AND DISCUSSION Landfills are the most affordable and popular method for managing waste in many parts of the world, However, in most developing nations, including India, the infiltration of hazardous materials from improperly managed dumping sites continues to be a significant environmental problem. Around the world, leachate is a significant point source of contamination in numerous environmental media, including soil, groundwater, and surface water.

Response: Done as per suggestions

Response: Uploaded all the figure files in PACE.

Attachment

Submitted filename: Response to reviewers.docx

pone.0314006.s003.docx^{(17.2KB, docx)}

PLoS One. doi: 10.1371/journal.pone.0314006.r003

Decision Letter 1

Susmita Lahiri (Ganguly)

23 Aug 2024

PONE-D-24-19939R1Landfill leachate: an invisible threat to soil quality of temperate HimalayasPLOS ONE

Dear Dr. Malik,

Please submit your revised manuscript by Oct 07 2024 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

Please include the following items when submitting your revised manuscript:

A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'.
A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'.
An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'.

We look forward to receiving your revised manuscript.

Kind regards,

Susmita Lahiri (Ganguly)

Academic Editor

PLOS ONE

Journal Requirements:

Please review your reference list to ensure that it is complete and correct. If you have cited papers that have been retracted, please include the rationale for doing so in the manuscript text, or remove these references and replace them with relevant current references. Any changes to the reference list should be mentioned in the rebuttal letter that accompanies your revised manuscript. If you need to cite a retracted article, indicate the article’s retracted status in the References list and also include a citation and full reference for the retraction notice.

[Note: HTML markup is below. Please do not edit.]

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #2: All comments have been addressed

Reviewer #3: All comments have been addressed

Reviewer #4: All comments have been addressed

Reviewer #5: All comments have been addressed

Reviewer #6: (No Response)

**********

2. Is the manuscript technically sound, and do the data support the conclusions?

Reviewer #2: Yes

Reviewer #3: Yes

Reviewer #4: Yes

Reviewer #5: Yes

Reviewer #6: Yes

**********

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #2: Yes

Reviewer #3: Yes

Reviewer #4: Yes

Reviewer #5: Yes

Reviewer #6: Yes

**********

4. Have the authors made all data underlying the findings in their manuscript fully available?

Reviewer #2: Yes

Reviewer #3: Yes

Reviewer #4: Yes

Reviewer #5: Yes

Reviewer #6: Yes

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English?

Reviewer #2: Yes

Reviewer #3: Yes

Reviewer #4: Yes

Reviewer #5: Yes

Reviewer #6: Yes

**********

6. Review Comments to the Author

Reviewer #2: (No Response)

Reviewer #3: Dear Authors,

The subject of the study is interesting and topical, with scientific and practical importance.

The authors took into account the recommendations of the reviewers and made the necessary corrections.

The article has been considerably improved.

The following aspects are brought to the attention of the authors.

1.Article structure

Page 13, row 101

“Study area:”

Page 14

“Methodology:”

It is recommended to check and revise the structure of chapters (chapter titles), according to the one recommended in the Submission Guidelines, PLOS ONE.

e.g.

“Manuscript Organization”

“Materials and Methods”

2.Writing ionic forms

Page 27, row 348

“Mg2+” instead of “Mg2+”

"2+" as index

Page 30, row 402

“Fe2O3” instead of “Fe2O3”

Page 31, row 404

“Fe2+” instead of “Fe++”

"2+" as index

row 409

“Fe3+” instead of “Fe3+”

"3+" as index

It is recommended to use the Word Equation Editor to write the ionic forms correctly

3.Presentation of the Figures

Figure 14 is presented on page 41

Until figure 14, no other figure is presented in the content of the article.

References are made to the other figures, but they are presented at the end, starting with page 53.

Please check and revise, if necessary, according to the Submission Guidelines, PLOS ONE

4. References

Please check the References chapter, and revise, if necessary, according to the Submission Guidelines, PLOS ONE

Reviewer #4: PLOS ONE- Landfill leachate: an invisible threat to soil quality of temperate Himalayas

Manuscript Number: PONE-D-24-19939R1

Overall comments

� The manuscript is informative. I am very positive about the manuscript, but it still requires additional work and minor editing before being considered for publication.

� Please ensure that your manuscript meets PLOS ONE's style requirements. The paper needs a total revision; especially the results section and the discussion section should be separate.

� Please review your reference list to ensure that it is complete and correct. Please follow the references style of plos journal formet. Provide DOI no. of the references and try to add recent references. For example ‘Amoakwah E, Arthur E, Frimpong KA, Islam KR. Biochar Amendment Influences Tropical Soil Carbon and Nitrogen Lability. Journal of Soil Science and Plant Nutrition. 2021; 21: 3567–3579. http://dx.doi. org/10.1007/s42729-021-00628-4’’

Specific comments

1. Please check no. of words in Abstract, not exceed 300 words according to journal style. Please ensure that your manuscript meets PLOS ONE's style requirements

2. Please insert the title of the figure or table just below the text. Please ensure that your manuscript meets PLOS ONE's style requirements

3. It would be better to separate the results section and the discussion section. Please check the PLOS ONE's style.

4. Rewrite the discussion section.

5. Please follow the reference style of PLOS ONE's style. Provide DOI no. of the references and try to add recent references. Please review your reference list to ensure that it is complete and correct. For example ‘’Amoakwah E, Arthur E, Frimpong KA, Islam KR. Biochar Amendment Influences Tropical Soil Carbon and Nitrogen Lability. Journal of Soil Science and Plant Nutrition. 2021; 21: 3567–3579. http://dx.doi. org/10.1007/s42729-021-00628-4’’

6. Please check the front style of headline, sub-headline and text front. Please check the PLOS ONE's style.

7. If possible try to reduce no of figures. No. of fig 14 is too high.

8. Please check line no. 58. Remove double full stop.

9. Please check line no. 84. Close bracket

10. Please check line no. 90. Check the space

11. Please check line no. 108. Remove bracket

12. Please check line no. 121. Edit space

13. Please check line no. 121, 150, 121. Edit space

14. Please check line no. 312, 314, 352, and 354 and so on. Why are the numbers bold?

15. Please check Table 3, column 8. Some words are overlapped

16. Please check line no. 474, 476,506. Please check the line spacing

17. Please provide declaration, consent for publication and conflict of interest from the manuscript and add in a separate file to PLOS ONE's online system. Only Acknowledgement and Author contributions would be attached with the article.

18. Please ensure that your manuscript meets PLOS ONE's style requirements.

Reviewer #5: A brief study on "Landfill leachate: an invisible threat to soil quality of temperate

Himalayas" has been conducted by the authors. The major concern is the content of toxic elements like Pb, Cd, Ni, As and Cr in the leachate. This will help the environmentalist and planner of the region for sustainable development goals for the locality.

Please mention the safe limit of all the parameters studied in this work for soil just like Pb, Cd, Ni, As and Cr.

Reviewer #6: 1. Abstract: Grammatical correction is required in lines- 15, 19, 29, 30, 33-36, 41. Punctuation correction is required in lines-30, 34.

2. Introduction: Too much narration on soil health in the introduction section (lines 54-64) while less description of the keywords -landfill and leachate. An individual paragraph on Achan landfill and leachate could be helpful for better understanding and reading. Coordination of the paragraphs in the introduction section is suggested. Grammatical and punctuation correction is required in all through the introduction section (lines- 45-47, 52,54,58, 60-68, 81, 82).

3. Study area: No indication of the area in the sampling site. Precise information about the sampling site is needed. Grammatical and punctuation correction is required in the study area section- 108,112,113

4. Methodology: No indication of year of sampling. Why sampling was done in those locations? Are those sites the leachate outflow sites? Authors analyzed only soils. But analysis of both soil and leachate would give a clear understanding about the impact of landfill leachate on soil quality. Grammatical and punctuation correction is required in the methodology section (lines- 120-122, 140)

5. Result and discussion: I suggest to establish a relationship among pH, EC and element concentration.

**********

7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #2: No

Reviewer #3: No

Reviewer #4: Yes: Dr. Rakhi Rani Sarker

Senior Scientific Officer

Soil Science Division

Bangladesh Institute of Nuclear Agriculture,

Mymensingh-2202, Bangladesh

E-mail: rrssarker@gmail.com

Reviewer #5: No

Reviewer #6: Yes: Prof. Dr. Md. Rafiqul Islam

**********

Attachment

Submitted filename: PONE-D-24-19939_R1_reviewer_revised.pdf

pone.0314006.s004.pdf^{(4.1MB, pdf)}

PLoS One. 2024 Nov 19;19(11):e0314006. doi: 10.1371/journal.pone.0314006.r004

Author response to Decision Letter 1

18 Sep 2024

Review Comments to the Author Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #2: (No Response)

Reviewer #3:

Dear Authors,

The subject of the study is interesting and topical, with scientific and practical importance. The authors took into account the recommendations of the reviewers and made the necessary corrections. The article has been considerably improved.

The following aspects are brought to the attention of the authors.

1.Article structure

Page 13, row 101

“Study area:”

Page 14

“Methodology:”

It is recommended to check and revise the structure of chapters (chapter titles), according to the one recommended in the Submission Guidelines, PLOS ONE.

e.g.

“Manuscript Organization”

“Materials and Methods”

Response: All the chapter titles and subtitles have been revised according to the guidelines of PLOS ONE

2.Writing ionic forms

Page 27, row 348

“Mg2+” instead of “Mg2+”

"2+" as index

Page 30, row 402

“Fe2O3” instead of “Fe2O3”

Page 31, row 404

“Fe2+” instead of “Fe++”

"2+" as index

row 409

“Fe3+” instead of “Fe3+”

"3+" as index

It is recommended to use the Word Equation Editor to write the ionic forms correctly

Response: All the corrections suggested have been made and word equation editor has been used to write ionic forms.

3. Presentation of the Figures

Figure 14 is presented on page 41

Until figure 14, no other figure is presented in the content of the article.

References are made to the other figures, but they are presented at the end, starting with page 53.

Please check and revise, if necessary, according to the Submission Guidelines, PLOS ONE

Response: According to submission guidelines of PLOS ONE, figures are not to be included in the main manuscript file, figures are to be prepared as individual file. The Fig 14 has now also been removed from main manuscript. The captions of all figures have been inserted in the text of manuscript immediately after the paragraph in which it is cited.

4. References Please check the References chapter, and revise, if necessary, according to the Submission Guidelines, PLOS ONE

Response: References have been revised according to submission guidelines

Reviewer #4: PLOS ONE- Landfill leachate: an invisible threat to soil quality of temperate Himalayas

Manuscript Number: PONE-D-24-19939R1

Overall comments �

The manuscript is informative. I am very positive about the manuscript, but it still requires additional work and minor editing before being considered for publication.

Please ensure that your manuscript meets PLOS ONE's style requirements. The paper needs a total revision; especially the results section and the discussion section should be separate.

Response: Separated result and discussion section

Please review your reference list to ensure that it is complete and correct. Please follow the references style of plos journal formet. Provide DOI no. of the references and try to add recent references. For example ‘Amoakwah E, Arthur E, Frimpong KA, Islam KR. Biochar Amendment Influences Tropical Soil Carbon and Nitrogen Lability. Journal of Soil Science and Plant Nutrition. 2021; 21: 3567– 3579. http://dx.doi. org/10.1007/s42729-021-00628-4’’

Response: Revised reference section according to journal guidelines

Specific comments

1. Please check no. of words in Abstract, not exceed 300 words according to journal style. Please ensure that your manuscript meets PLOS ONE's style requirements

Response: Abstract has been reduced to 300 words only

2. Please insert the title of the figure or table just below the text. Please ensure that your manuscript meets PLOS ONE's style requirements

Response: Title of figures and tables have been inserted in the text as per journal guidelines.

3. It would be better to separate the results section and the discussion section. Please check the PLOS ONE's style.

Response: Separated results and discussion section.

4. Rewrite the discussion section.

Response: Modified the discussion section

5. Please follow the reference style of PLOS ONE's style. Provide DOI no. of the references and try to add recent references. Please review your reference list to ensure that it is complete and correct. For example ‘’Amoakwah E, Arthur E, Frimpong KA, Islam KR. Biochar Amendment Influences Tropical Soil Carbon and Nitrogen Lability. Journal of Soil Science and Plant Nutrition. 2021; 21: 3567– 3579. http://dx.doi. org/10.1007/s42729-021-00628-4’’

Response: Revised reference section as per journal guidelines

6. Please check the front style of headline, sub-headline and text front. Please check the PLOS ONE's style.

Response: Followed PLOS one font style for each section.

7. If possible try to reduce no of figures. No. of fig 14 is too high.

Response: Reduced the number of figures to 9

8. Please check line no. 58. Remove double full stop.

Response: Done

9. Please check line no. 84. Close bracket

Response: Done

10. Please check line no. 90. Check the space

Response: Done

11. Please check line no. 108. Remove bracket

Response: Done

12. Please check line no. 121. Edit space

Response: Done

13. Please check line no. 121, 150, 121. Edit space

Response: Done

14. Please check line no. 312, 314, 352, and 354 and so on. Why are the numbers bold?

Response: Done

15. Please check Table 3, column 8. Some words are overlapped

Response: The line numbers have been overlapped with the table values, corrected

16. Please check line no. 474, 476,506. Please check the line spacing

Response: Done

Response: Done as per suggestion

18. Please ensure that your manuscript meets PLOS ONE's style requirements.

Response: Modified as per journal guidelines

Reviewer #5: A brief study on "Landfill leachate: an invisible threat to soil quality of temperate Himalayas" has been conducted by the authors. The major concern is the content of toxic elements like Pb, Cd, Ni, As and Cr in the leachate. This will help the environmentalist and planner of the region for sustainable development goals for the locality. Please mention the safe limit of all the parameters studied in this work for soil just like Pb, Cd, Ni, As and Cr.

Response: Safe limits for all paramaters have been incorporated

Reviewer #6:

1. Abstract: Grammatical correction is required in lines- 15, 19, 29, 30, 33-36, 41. Punctuation correction is required in lines-30, 34.

Response: Corrected

2. Introduction: Too much narration on soil health in the introduction section (lines 54-64) while less description of the keywords - landfill and leachate. An individual paragraph on Achan landfill and leachate could be helpful for better understanding and reading. Coordination of the paragraphs in the introduction section is suggested. Grammatical and punctuation correction is required in all through the introduction section (lines- 45-47, 52,54,58, 60-68, 81, 82).

Response: Line numbers from 54-64 have been removed from the manuscript. Separate paragraph on Achan landfill and leachate have been added. Grammatical and punctuation errors have been corrected.

Response: Area under landfill have been added and corrections are made.

Response: Mentioned year of sampling and reasons for soil sampling, Grammatical and punctuation correction done

5. Result and discussion: I suggest to establish a relationship among pH, EC and element concentration.

Response: Incorporated correlation table in results section (Table 7)

Response: Done

Attachment

Submitted filename: Response to reviewers (Sec Rev).docx

pone.0314006.s005.docx^{(17.1KB, docx)}

PLoS One. doi: 10.1371/journal.pone.0314006.r005

Decision Letter 2

Susmita Lahiri (Ganguly)

29 Oct 2024

PONE-D-24-19939R2Landfill leachate: an invisible threat to soil quality of temperate HimalayasPLOS ONE

Dear Dr. Malik,

Please submit your revised manuscript by Dec 13 2024 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

Please include the following items when submitting your revised manuscript:

A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'.
A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'.
An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'.

We look forward to receiving your revised manuscript.

Kind regards,

Susmita Lahiri (Ganguly)

Academic Editor

PLOS ONE

Journal Requirements:

[Note: HTML markup is below. Please do not edit.]

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

Reviewer #3: All comments have been addressed

Reviewer #6: All comments have been addressed

**********

2. Is the manuscript technically sound, and do the data support the conclusions?

Reviewer #3: Yes

Reviewer #6: Yes

**********

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #3: Yes

Reviewer #6: Yes

**********

4. Have the authors made all data underlying the findings in their manuscript fully available?

Reviewer #3: Yes

Reviewer #6: Yes

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English?

Reviewer #3: Yes

Reviewer #6: Yes

**********

6. Review Comments to the Author

Reviewer #3: Dear Authors,

The subject of the study is interesting and topical, with scientific and practical importance.

The authors took into account the recommendations of the reviewers and made the necessary corrections.

The article has been considerably improved.

The following minor aspects are brought to the attention of the authors.

Space between the bibliographic source number and the previous word

e.g.

"Gomez [16]."

Central positioning of all values in the table columns.

e.g.

Table 1

Space between the value and the unit of measure

e.g.

"0.98 mg/kg"

Some suggestions were made in the article.

Reviewer #6: The authors have revised the manuscript as per my comments and suggestions. Now the manuscript has become sound scientifically.

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PLoS One. 2024 Nov 19;19(11):e0314006. doi: 10.1371/journal.pone.0314006.r006

Author response to Decision Letter 2

30 Oct 2024

6. Review Comments to the Author

Reviewer #3: Dear Authors,

The subject of the study is interesting and topical, with scientific and practical importance.

The authors took into account the recommendations of the reviewers and made the necessary corrections.

The article has been considerably improved.

The following minor aspects are brought to the attention of the authors.

Space between the bibliographic source number and the previous word

e.g.

"Gomez [16]."

Reply: Corrected

Central positioning of all values in the table columns.

e.g.

Table 1

Reply: Done

Space between the value and the unit of measure

e.g.

"0.98 mg/kg"

Reply: Done

Some suggestions were made in the article.

Reply: Incorporated all suggestions

Reviewer #6: The authors have revised the manuscript as per my comments and suggestions. Now the manuscript has become sound scientifically.

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PLoS One. doi: 10.1371/journal.pone.0314006.r007

Decision Letter 3

Susmita Lahiri (Ganguly)

5 Nov 2024

Landfill leachate: an invisible threat to soil quality of temperate Himalayas

PONE-D-24-19939R3

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PLoS One. doi: 10.1371/journal.pone.0314006.r008

Acceptance letter

Susmita Lahiri (Ganguly)

8 Nov 2024

PONE-D-24-19939R3

PLOS ONE

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S1 Data

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pone.0314006.s002.docx^{(13.6KB, docx)}

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pone.0314006.s007.docx^{(11.5KB, docx)}

Data Availability Statement

All relevant data are within the manuscript and its Supporting Information files.

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PERMALINK

Landfill leachate: An invisible threat to soil quality of temperate Himalayas

Shayesta Islam

Haleema Bano

Asif Aziz Malik

Fahad Alotaibi

Roles

Abstract

Introduction

Study area

Fig 1. Map of study area (Map prepared by USGS).

Materials and methods

Statistical analysis

Results

Table 1. Seasonal and site wise variation in pH, EC (dS/m) and moisture content (%) of soil.

Table 2. Seasonal and site wise variation in N, P and K (mg/Kg) of soil.

Table 3. Seasonal and site wise variation in Ca and Mg (mg/kg) of soil.

Table 4. Seasonal and site wise variation in micronutrients, viz Zn, Fe, Cu and Mn (mg/kg) of soil.

Table 5. Seasonal and site wise variation in Pb, Cd and Ni (mg/Kg) of soil.

Table 6. Seasonal and site wise variation in Cr, and As (mg/Kg) of soil.

Table 7. Correlation between various physico–chemical paramaters of soil.

Discussion

Fig 2. Graphical representation of pH among different sites and seasons.

Fig 3. Graphical representation of EC (dS/m) among different sites and seasons.

Fig 4. Graphical representation of Pb (mg/kg) among different sites and seasons.

Fig 5. Graphical representation of Cd (mg/kg) among different sites and seasons.

Fig 6. Graphical representation of Ni (mg/kg) among different sites and seasons.

Fig 7. Graphical representation of Cr (mg/kg) among different sites and seasons.

Fig 8. Graphical representation of As (mg/kg) among different sites and seasons.

Available management strategy for remediation of soil health

Fig 9. Flow chat depicting management strategy for waste.

Conclusion

Supporting information

Acknowledgments

Data Availability

Funding Statement

References

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Susmita Lahiri (Ganguly)

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Susmita Lahiri (Ganguly)

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Acceptance letter

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Associated Data

Supplementary Materials

Data Availability Statement

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