Micronutrients and contaminants in the grazing and agricultural soils of Kashmir Valley, India

Abstract

Soil plays a critical role in determining the food nutrition at the base of the food chain, which makes it essential for food safety. This study demonstrates how micronutrient deficiencies and pollution from hazardous elements may affect crop productivity as well as human and animal health. In the Kashmir valley’s Bandipora-Ganderbal region, 200 top soils were examined to ascertain the toxicity risks and trace element deficiencies. With mean values of 44,759 ± 6072, 120 ± 23, 114 ± 18, 89 ± 22, 44 ± 8, 33 ± 7, 23 ± 4, 19 ± 4, and 11 ± 5 respectively, the concentrations (mg kg⁻¹) vary from Fe: 31,326 to 77,420, Cr: 59 to 228, V: 79 to 235, Zn: 30 to 174, Ni: 18 to 79, Cu: 10 to 59, Pb: 15 to 55, Co: 10 to 38 and As: 1 to 36. A portion of the study area has hazardous levels of As, Cr, Ni, and V and is deficient in Cu, Ni, and Zn for agricultural production. Micronutrient deficiencies are associated to carbonate rock topography, while pollution symptoms are linked to areas with human footprints. Weak correlations for As, Pb, and Zn and significant correlations for Fe, Co, Cr, Cu, Ni, and V indicate anthropogenic and geogenic origins, respectively. For Co, Cr, Cu, Ni, and V, the enrichment factor is minimum; for As, Pb, and Zn, it is moderate. The soil pollution indices for Cu, Pb, and Zn are low, while those for As, Co, Cr, Ni, and V are moderate. The integrated toxic risk index was evaluated in order to gain a better understanding of the toxicity in the research region. The values ranged from 3.80 to 10.64, with 5% of samples having no risk, 63.5% having low risk, and 31.5% having moderate risk. Compared to forest, grazing areas, and waste land sites, areas used for agriculture, habitation, and hydroelectric projects are more contaminated. The main causes of pollution are pesticides, fertilizers, construction, and vehicle emissions. The study’s main conclusions about As, Cr, Ni, and V pollution and deficiencies in Cu, Ni, and Zn in soils may help policymakers improve soil health for higher crop yields and a healthier lifestyle.

Introduction

The growing global population is posing a major threat to adequate food production. Healthy soils are essential for productive farming. For plants and animals to develop, the soil must have adequate levels of major and minor nutrients in addition to minute amounts of elements that are toxic at high concentrations^1–3. The Commission of European Communities states that soil is a natural resource that must be preserved because it is extremely crucial to ecosystems and humanity¹. The composition of parent rock, climate and land use all affect soil chemistry^4,5. The chemical makeup of a soil can be categorised as lithogenic or anthropogenic. The availability of elements in the immediate environment is revealed through soil chemistry. Local geology, which determines the natural geochemistry, and human activity, which discharges materials into the environment, both affect their availability^6–8.

The distribution of chemical elements has two main components: baseline levels, the concentration ranges expected without pollution from anthropogenic activities, and anomalous levels, values outside the range of baseline concentrations, typically produced by human activities. Reference levels serve as a representation of the borders between baseline and anomalies, and they must be adjusted locally because they change based on local geology⁹. Local areas are not suitable for large-scale national element maps¹⁰, as the distinctive characteristics of the parent materials may result in natural enrichments or the absence of elements that are not considered on a general scale. For this reason, in several countries, maps are now being created at the local scale¹¹. Regional geochemical maps are a helpful tool for identifying local baselines and geochemical anomalies that are either naturally occurring or caused by humans. Understanding the region’s soils is made easier with the aid of this knowledge, which is also a useful tool for organising and regulating soil use, particularly in agricultural applications⁹.

Micronutrients are equally crucial for balanced crop growth as macronutrients¹². Micronutrients, such as boron (B), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), zinc (Zn), chlorine (Cl), sodium (Na), cobalt (Co), nickel (Ni), silicon (Si), vanadium (V), and selenium (Se), positively affect plant growth. Almost every cellular and metabolic process in plants is influenced by micronutrients¹³. Plants produce less biomass as a result of any key micronutrient being deficient¹⁴. Micronutrient deficiencies cause poor health around the world, including crop, livestock, and human death¹⁵. Excessive abundance of essential nutrients, lead (Pb), mercury (Hg), cadmium (Cd), arsenic (As), and aluminium (Al) are hazardous to biota. Because of the chemistry of parent rocks, very high concentrations of toxic elements may occur naturally. However, because of anthropogenic pollution, soil concentrations of hazardous components frequently exceed background values of natural concentration, especially in industrialised areas¹⁶. High levels of hazardous elements in soil can cause plants to absorb too much toxic elements, increasing exposure of toxic elements at a higher levels of the food chain¹⁷. As the concentration of heavy metals increases up the food chain, they can bioaccumulate in higher trophic levels^18–20. As a result, when heavy metals enter the food chain, they can have a wide range of harmful effects on organisms, such as immune system impairment, cancer, neurological issues, developmental disorders, and organ damage¹⁶.

As a baseline research for soil management and health needs in the districts of Bandipora and Ganderbal, this work represents a component of the first multi-element geochemical mapping of surface sediments in the Kashmir valley (Fig. 1). The major goals of this study are to assess and look into the biological benefits of micronutrients, the risks of hazardous elements, and their regional distributions. The agricultural belt of Kashmir serves as the study area and is home to some of the most important water features in the region. This study’s primary goal was to determine likely chemical element sources, distributions, and concentrations while also explaining the existence of odd amounts.

Fig. 1.

Study area location map falling in toposheet 43 J/11 and portion of 43 J/12. On the left side of the figure is the outline map of India, at centre is the land-use land-cover map of Kashmir valley⁸¹ and on the right side is where the sample spots are located.

Materials and methods

Description of the study area

The study region covers an area of around 800 km², in the Bandipora-Ganderbal districts of the Kashmir valley, between latitudes 34°10′N to 34°30′N and longitudes 74°30′E to 74°45′E (Fig. 1). The terrain of the research region is mountainous in the north and east, and is mostly plain across the remaining portion of the study area (Figs. 1 and 2). The main wetlands are Wular, Manasbal, Haigam, Tulmul, and Naugam, and the key rivers are Jhelum, Sindh, Erin, Madhumati, and Ningli²¹. The study region’s extreme northern side is primarily composed of siltstone, shale, arenite, and slate; strata of basalt and limestone can be seen in the northern, north-eastern, and southwest portions; Quaternary sediments can be found in the southern, south-westerly, and southeast areas²¹. The Valley of Kashmir may fall within the Dfb category of Koppen’s climatic classification, which has humid, severe, and harsh winters and brief, pleasant summers²². Information regarding the soils in the study area is essentially non-existent. According to an analysis of the soil dataset based on the global soil map, immature soils are found on mountain slopes and higher reaches where low temperatures slow down weathering as elevation increases. A thick soil cover is limited to the bottoms and terraces of the Kashmir Valley²³. The FAO-UNESCO soil standard²⁴ has identified two distinct soil types in the research area (Fig. 3). The valley floor is dominated by eutric cambisols, whereas the mountain slopes and high altitude regions are covered in lithosols²⁵. Among the most productive soils on Earth are the temperate zone’s Eutric Cambisols, whereas lithosols—also referred to as skeletal soils—are shallow, rocky soils composed of partially²⁵ weathered rock fragments.

Fig. 2.

Geological map of the Kashmir Valley⁸² on left side and detailed geology of the study area falling in toposheet no. 43 J/11 and part of 43 J/12¹⁹ on right side of the figure.

Fig. 3.

Soil types of the study area⁸³.

Sampling and geochemical analysis

In compliance with standard operating procedure⁹ of the Geological Survey of India (GSI), sediments were collected at regular intervals on a 2 × 2 km grid pattern. First, second, and third order streams yielded fine sediments (− 120 micron). When there were no streams in the grids, slope wash samples were collected. After being collected in polythene bags and regularly tagged, the samples were transported to the field camp for further analysis. The materials were ground up and dried in the camp before being sent to the GSI chemical laboratory in Lucknow, India, for chemical analysis.

For chemical analysis, five-gram powdered samples were spread out in a 40 mm diameter aluminium cup over AR Grade boric acid powder (H₃BO₃). A hydraulic press pellet machine was then used to press the powder into a homogenous pressed pellet at a pressure of 20 tonnes. X-ray fluorescence (XRF) equipment (PANalytical MagiX 2424 WD) was utilised to examine major and trace elements, as well as micronutrients and toxic elements. The major element detection limit was 0.1%, and the trace element detection limit was 1.00 mg/L. Each batch of 10 samples was followed by an evaluation of duplicate samples for repeatability and reproducibility. Using standard reference material (GBW-07312) with known element concentrations, accuracy was assessed following each batch of 20 samples. The measurement accuracy is 3% and precision is 5%^9,26,27.

Data treatment

To perform calculations using the data, Microsoft Excel was employed. Multivariate statistical analyses ascertained relationships among the components⁸. The free Origin-Pro 2016 tool (URL link: http://www.originlab.com) was utilised to create spatial distribution maps, bivariate plots, Pearson’s correlation matrix, and hierarchical cluster analysis. The concentrations of toxic elements and micronutrients important for agriculture, the environment, and food safety can be measured using the following indices.

The Enrichment Factor (EF) represents the enrichment of a specific element in sediments relative to its natural background values. The EF was estimated using the equation presented by²⁸.

1

Where Cx represents the concentration of the element “x”. Elemental background concentrations are determined using data from subsurface sediments collected at a depth of 50 cm below the surface (Table 1). Fe was chosen as the normalizing element since it is predominantly derived from natural weathering processes of bed rocks, and it has been successfully used to normalize toxic element pollution in sediments²⁹. Klerks and Levinton³⁰ define EF as levels of enrichment above the background value, ranging from minimum (EF < 2), moderate (EF = 2–5), significant (EF = 5–20), very high (EF = 20–40), and extremely high (EF > 40). Aluminium is also widely used as a normalizing element in enrichment factor³¹.

Table 1.

Descriptive statistics for the elements examined in samples of top soil and subsoil (subsoils taken from 100 cm below the surface for background value purposes). Values for global agricultural soil³⁶ and European union toxic risk³³ are provided for comparison.

(mg kg−1)			Fe	As	Co	Cr	Cu	Ni	Pb	V	Zn
Present study	Top soil (N = 200)	Average	44,759	11	19	120	33	44	23	114	89
		Minimum	31,326	1	10	59	10	18	15	79	30
		Maximum	77,420	36	38	228	59	79	55	235	174
		Standard deviation	6072	5	4	23	7	8	4	18	22
	Subsoil (N = 10)	Average	42,667	14	18	105	30	44	22	110	73
		Minimum	33,735	6	13	65	20	32	19	88	43
		Maximum	48,815	22	22	109	41	58	26	121	93
		Standard deviation	4531	5	3	21	7	9	2	11	17
References	World agriculture soil (Alloway, 2005)	Average	38,000	6	8	54	19	20	32	58	64
		Minimum	5000	1	0	1	1	0	3	18	17
		Maximum	50,000	95	70	1300	205	450	189	115	125
	Risk levels (MEF, 2007)	Threshold	–	5	20	100	100	50	60	100	200
		Lower guideline	–	50	100	200	150	100	200	150	250
		Higher guideline	–	100	250	300	200	150	750	250	400

To find single element contamination indices, the Soil Pollution Index (SPI), a simple and well-known pollution evaluation tool³², was utilised. SPI was computed using the following formula:

2

Where P_P is the allowable level of pollutants and S_P is the pollutant content in the soil under investigation. The regulations specified in the Finnish legislation for contaminated soil by the Ministry of the Environment, Finland³³, were applied to set permissible values of potentially toxic elements for soil (Table 2). Finnish standards closely correspond to the average values of the various national systems that the European Union adopted³⁴ and the degree of each heavy metal present was categorised as low contamination (SPI ≤ 1), moderate contamination (1 < SPI ≤ 3) or high contamination (SPI > 3)³².

Table 2.

Classification of top soil samples for the soil health in relation to the presence of the elements analysed is defined according to the values of world agriculture soil³⁶ and European union³³.

Element (mg kg−1) (N = 200)	Top soil samples from this study, no. (%) of samples
	Deficiency	Normal	Toxicity
As	0 (0%)	14 (7%)	186 (93%)
Co	0 (0%)	142 (71%)	58 (29%)
Cr	0 (0%)	24 (12%)	176 (88%)
Cu	5 (3%)	195 (97%)	0 (0%)
Ni	4 (3%)	161 (80%)	35 (17%)
Pb	2 (1%)	198 (99%)	0 (0%)
V	0 (0%)	37 (19%)	163 (81%)
Zn	16 (8%)	184 (92% )	0 (0%)

Calculating toxic levels of elements might underestimate toxicity since they do not consider the threshold effect level (TEL) and probable-effects-levels (PEL). Toxic risk index (TRI³⁵) considers the TEL and PEL of toxic elements in sediments to assess the biological risks. The individual toxic risk index (TRIi) is calculated by using the following equation:

3

Where Cⁱ_s is the surface sediment metal concentration, and Cⁱ_TEL, and Cⁱ_PEL are the TEL and PEL of the potential toxic elements respectively. TEL for As = 5.9, Cr = 37.3, Cu = 35.7, Ni = 18, Pb = 35, Zn = 123 and PEL for As = 17, Cr = 90, Cu = 197, Ni = 36, Pb = 91.3, Zn = 315³⁵. The sum of individual TRIi of metals is the potential toxicity risk index (ΣTRI) for the sediments and is calculated by using the following equation:

4

The toxicity classification based on integrated toxic risk index (ΣTRI, Eq. 4) provide a better picture of toxicity risks. Based on the ƩTRI (Eq. 4) the toxic risks may be categorised as no toxic risk (< 5), low toxic risk (5–10), moderate toxic risk (10–20) and high toxic risk (> 20).

Results

A statistical summary of the micronutrient and toxic element concentration in topsoil (N = 200) and subsoil (N = 10) samples in the study area and their comparison with the values reported for world agriculture soil³⁶ and European soils adopted from the Ministry of the Environment, Finland³³ is shown in Table 1. The concentrations of Fe, As, Co, Cr, Cu, Ni, Pb, V and Zn in the top soils are in the ranges of 31,326 to 77,420 mg kg⁻¹ with a mean of 44,759 ± 6072 mg kg⁻¹, 1.4 to 36.4 mg kg⁻¹ with a mean of 11.5 ± 5 mg kg⁻¹, 10 to 38 mg kg⁻¹ with a mean of 19.1 ± 4.4 mg kg⁻¹, 59 to 228 mg kg⁻¹ with a mean of 120.1 ± 23.2 mg kg⁻¹, 10 to 59 mg kg⁻¹ with a mean of 32.7 ± 7.2 mg kg⁻¹, 18 to 79 mg kg⁻¹ with a mean of 43.6 ± 8.4 mg kg⁻¹, 15 to 55 mg kg⁻¹ with a mean of 23.3 ± 3.7 mg kg⁻¹, 79 to 235 mg kg⁻¹ with a mean of 114.4 ± 18.2 mg kg⁻¹ and 30 to 174 mg kg⁻¹ with a mean of 89.4 ± 21.6 mg kg⁻¹. The concentrations of Fe, As, Co, Cr, Cu, Ni, Pb, V and Zn in the sub soils are in the ranges of 33,735 to 48,815 mg kg⁻¹ with a mean of 42,667 ± 4531 mg kg⁻¹, 6 to 22 mg kg⁻¹ with a mean of 14 ± 5 mg kg⁻¹, 13 to 22 mg kg⁻¹ with a mean of 17.8 ± 2.5 mg kg⁻¹, 65 to 109 mg kg⁻¹ with a mean of 105 ± 21.4 mg kg⁻¹, 20 to 41 mg kg⁻¹ with a mean of 30 ± 6.6 mg kg⁻¹, 32 to 58 mg kg⁻¹ with a mean of 44 ± 8.9 mg kg⁻¹, 19 to 26 mg kg⁻¹ with a mean of 22 ± 2 mg kg⁻¹, 88 to 121 mg kg⁻¹ with a mean of 110 ± 11 mg kg⁻¹ and 43 to 93 mg kg⁻¹ with a mean of 73 ± 17 mg kg⁻¹ (Figs. 4 and 5). In top soil samples the order of concentration of investigated elements follows a trend as Fe > V > Cr > Zn > Ni > Cu > Pb > Co > As.

Fig. 4.

The concentration (mg/kg) of the elements under investigation in the top soil (left) and subsoil (right) samples is shown in box plots.

Fig. 5.

Spatial distribution of (a) As, (b) Co, (c) Cr, (d) Cu, (e) Ni, (f) Pb, (g) V, and (h) Zn, (all elements are in mg/kg). Black line in each panel indicates the world agriculture soil average values.

Discussion

Regional distribution characteristics of micronutrients and toxic elements

Cobalt, Cr, Cu, Ni, and V exhibit similar distribution patterns (Fig. 5), with the study areas northwest having the highest values and the southeast having the lowest levels. As, Pb, or Zn show no similarities with one another or with elements that share the same distribution pattern. The local geology of the region (Fig. 2) and the pattern of Fe, Co, Cr, Cu, Ni, and V (Fig. 5) show a positive association suggesting similar geogenic sources²¹. The high-altitude, uninhabited mountains that make up the northwest of the research zone provide support to the view that Co, Cr, Cu, Ni, and V have natural sources there²¹. Higher concentrations of Fe, Co, Cr, Cu, Ni, and V are found in soils on basalt compared to soils developed on carbonates. High levels of arsenic in quaternary soils and close to large towns point to human activity³⁷ and pesticides rich³⁸ in arsenic as anthropogenic sources. Elevated levels of lead have been found in the vicinity of the Kishan Ganga hydroelectric project, which implies that construction-related activities are the likely human cause²¹. Zinc concentrations in low-lying quaternary soils, where apples and rice are heavily farmed, indicate that anthropogenic sources of zinc may include pesticides and fertilisers enriched with zinc³⁹.

To determine the deficiency, normal range, and toxicity of the studied elements, micronutrients and toxic elements in the top soils of the investigated area (Table 2) are compared with values of world agriculture soil³⁶ and European Union³³. For 14 (7%) of the samples, arsenic is within safe levels; but for 186 (93%), it is beyond toxicity threshold values, indicating that arsenic contamination in the area requires attention. Arsenic is frequently found in fertilisers such as rock phosphate and triple super phosphate⁴⁰ and insecticides such as Paris Green, lead arsenate, and Agent Blue⁴¹. These pesticides are widely used in rice and apple farms in the study area to boost crop yields²¹. For 142 (71%) of the samples, cobalt is within safe ranges; for 58 (29%) of the samples, it is above toxicity threshold values, indicating cobalt pollution in the area requires concern. For 24 (12%) samples, chromium is within safe levels; for 176 (88%) samples, chromium is over the threshold values, indicating chromium contamination in the area requires attention. Attention may be needed to address the copper deficiency in the region, as evidenced by the fact that 5 (3%) samples have low copper levels, 195 (97%) samples have acceptable standards, and no sample has copper levels over the threshold. Concerns about nickel deficiency and contamination in the area need to be addressed. Of the samples tested, 4 (3%) had low levels of nickel, 161 (80%) have acceptable limits, and 35 (17%) have high levels of nickel. Lead is within acceptable levels in 198 (99%) samples, and it is not over threshold values in any samples, indicating that lead in the region is not in need of any care. For 37 (19%) samples, the vanadium content is below acceptable limits; however, for 163 (81%), the vanadium content is over the threshold values, indicating that vanadium contamination in the area requires attention. Zinc insufficiency in the region requires care as evidenced by the 16 (8%) samples that are deficient, the 184 (92%) samples that are within allowable levels, and the zero samples that are above the threshold values. No sample had deficiencies in micronutrients Co, Cr, or V, however numerous samples have deficiencies in micronutrients Cu, Ni, and Zn. Conversely, numerous samples exhibit toxicity indicators for the hazardous elements As and Pb as well as the micronutrient Ni. A negative impact on agricultural productivity as well as human and animal health might result from both the toxicity and inadequacy of the elements under investigation.

Multivariate statistics to trace the origins of elements

To determine the origins and behaviour of the elements under study, the Pearson’s correlation matrix (PCM, Table 3), hierarchical cluster analysis (HCA, Fig. 6), and enrichment factor (EF, Fig. 7) are employed^26,27. The EF is used to differentiate between natural and man-made sources of elements. Anthropogenic sources are indicated by an EF value larger than 2, whereas geogenic sources are often indicated by a value close to 1⁴². Anthropogenic factors have been suggested for lead (EF: 0.38 to 2.25), zinc (EF: 0.39 to 2.15), and arsenic (EF: 0.09 to 2.52). Geogenic sources are suggested for nickel (EF 0.43 to 1.21), chromium (EF 0.50 to 1.60), cobalt (EF 0.66 to 1.34), vanadium (EF 0.83 to 1.28), and copper (EF 0.45 to 1.63). Fe, V, Co, Cu, Cr, and Ni have similar origins or chemical behaviours, whereas Zn, As, and Pb have different sources or chemical behaviours, according to the cluster analysis dendrogram (Fig. 6). The elements in the first group are close to one another (0.0 to 0.4), whereas the elements in the second group are farther apart (0.5 to 0.9). This observation is further supported by the correlation matrix (Table 3). Fe, V, Co, Cu, Cr, and Ni have high positive correlations with one another, but As, Zn, and Pb have negative to weak positive correlations (− 0.04 to 0.35). According to the first group of elements, the origins of As, Zn, and Pb are different, while those of Fe, V, Co, Cu, and Cr are comparable. Aagrochemicals, construction, and automobile emissions appear to be the anthropogenic sources of toxic elements, while basalts are considered to be the most likely geogenic source of micronutrients. Insecticides and phosphate fertilisers, which are commonly used in farming activities in the research area, contain As^40,41. Fertilisers, fungicides, disposal of metals, and industrial wastes containing Zn can all contribute to Zn poisoning in agricultural farms⁴³. Air pollution, sewage sludge, insecticides, and fertilisers can all cause Pb toxicity in agricultural farms⁴⁴ Understanding the detrimental impacts of As, Zn, and Pb on health is necessary due to their long-term persistence in nature.

Table 3.

P-values and Pearson’s correlation matrix for the hazardous and micronutrient elements found in the top soil samples; bold values denote a strong correlation between different variables.

(mg kg−1)		Fe	As	Co	Cr	Cu	Ni	Pb	V	Zn
Fe	Pearson Corr.	1.00
	p-value	–
As	Pearson Corr.	0.07	1.00
	p-value	0.31	–
Co	Pearson Corr.	0.85	− 0.04	1.00
	p-value	0.00	0.60	–
Cr	Pearson Corr.	0.64	0.00	0.62	1.00
	p-value	0.00	0.98	0.00	–
Cu	Pearson Corr.	0.69	0.01	0.65	0.51	1.00
	p-value	0.00	0.88	0.00	0.00	–
Ni	Pearson Corr.	0.68	0.12	0.59	0.76	0.68	1.00
	p-value	0.00	0.10	0.00	0.00	0.00	–
Pb	Pearson Corr.	0.08	0.13	0.07	0.08	0.15	0.25	1.00
	p-value	0.28	0.07	0.29	0.27	0.04	0.00	–
V	Pearson Corr.	0.91	0.07	0.81	0.58	0.54	0.52	− 0.07	1.00
	p-value	0.00	0.36	0.00	0.00	0.00	0.00	0.33	–
Zn	Pearson Corr.	0.35	− 0.08	0.31	0.28	0.51	0.33	0.21	0.22	1.00
	p-value	0.00	0.24	0.00	0.00	0.00	0.00	0.00	0.00	–

Fig. 6.

Dendrogram for the micronutrient and hazardous elements present in the top soil samples.

Fig. 7.

Box plots showing the micronutrient and hazardous element enrichment factor (EF) in the top soil samples in the Bandipora-Ganderbal research region.

In summary, polluted soil provides a route for contaminants to reach the food chain and endanger human health⁴⁵. By putting dangerous chemicals into the plants, which people eat and which can lead to diseases like cancer, organ damage, and developmental disorders, this can have a big effect on crop uptake⁴⁶. Additionally, it can reduce agricultural productivity and growth by interfering with the plants’ nutrient uptake⁴⁶.

Soil toxicity and their impacts on soils, crops and biota health

The individual soil pollution index (SPI) for each element investigated (Fig. 8) in this study indicates a variety of contamination levels: low to high for As (1 to > 3); low to moderate for Co, Cr, Ni, and V (1 to 3); and low for Cu, Pb, and Zn (< 1). The soil toxicity of Co, Cr, Ni, and V is deemed mild even if their sources are geogenic. Arsenic is the main contaminating element and has an anthropogenic origin. However, for the soils under study, anthropogenic Pb and Zn have low toxicity levels. The order of the SPI is As > Cr > V > Co > Ni > Pb > Zn > Cu.

Fig. 8.

Box plots representing the soil pollution index (SPI) for each hazardous element and micronutrient in the top soil samples from the Bandipora-Ganderbal research area.

A regional distribution map (Fig. 9A) and a cumulative frequency plot (Fig. 9B) display the soil toxicity categorization based on the integrated toxic risk index (ΣTRI, Eq. 4). When considering all hazardous elements together, the range of ΣTRI values is 3.80 to 10.64, indicating no to considerable harmful risk. In terms of toxic risk, 5.5% of samples have no danger, 63.5% have low risk, and 31.5% have moderate risk. Samples from Bandipora Town, agricultural farms, basaltic terrain, and Kishan Ganga Hydroelectric project provide a moderate risk of toxicity. There are no hazardous concerns associated with samples on carbonate terrain soils. Naturally lacking in micronutrients, soils formed on carbonate rocks are neglected by agricultural practices in the region. However, because basalt soils naturally contain a high concentration of micronutrients, over use of fertilizers and pesticides is enhancing their content and turning the soils hazardous. Anthropogenic activities enhance hazardous materials in large human habitation regions and hydropower stations. The research area’s northwestern side and the farming areas have the most hazardous soils, whereas the south eastern side has the least toxic soils. Geographically, the Bandipora district’s northern and western regions have the highest toxic risks, whereas the Ganderbal district’s eastern and south-eastern regions have the lowest toxic risks.

Fig. 9.

The integrated toxic risk index (ƩTRI) in the study region’s spatial distribution heat map (A) and frequency distribution plot (B) show the samples’ distribution among the various toxic risk index categories.

The results of this investigation indicate toxicity in As, Co, Cr, Ni, and V for several of the soil samples, with values above the threshold³³ (Tables 1 and 2). Insecticides, fertilisers, and dust can all introduce toxins into agricultural soils and lower agricultural production⁴⁷. Toxic elements are extremely harmful to human health since they have a negative impact on food, water quality, soil fertility, and the possibility of entering the human food chain⁴⁸.

Due to its extreme toxicity and carcinogenic properties, arsenic contamination affects human health, agriculture, and the environment globally⁴⁹. Plant health is impacted by arsenic even at very low exposure levels and it is believed that plants and other living things do not require arsenic⁵⁰. Arsenic enters the environment from anthropogenic activities including mining, toxic wood preservatives, excessive pesticide and fertilizer use in agriculture, and irrigation with As-contaminated groundwater^26,27. In the research area, significant doses of arsenic-rich pesticides are sprayed on apple-growing agricultural areas in the Bandipora district to ensure good harvests, so this area is where arsenic pollution is most common. It is necessary to replace hazardous chemical pesticides with safe biological ones and implement sustainable farming practices.

In small amounts, cobalt is an essential trace metal and is a part of vitamin B12. Cobalt, when at hazardous and inadequate amounts, adversely affects the physiochemical processes of plants⁵¹. Reduced biomass, poor nutrient absorption, and low protein content are all observed in plants with high cobalt levels⁵². It is increasingly important to monitor Co level in the plant, soil, and human systems. Both human activity and the weathering of rocks can release cobalt into the environment. Burning fossil fuels, applying cobalt-containing sludge, and using phosphate fertilisers are the main human sources of cobalt pollution. Reduced lung function, interstitial lung disease, wheezing, respiratory tract hyperplasia, pulmonary fibrosis, cardiac function, and allergic dermatitis are just a few of the health issues that cobalt toxicity can cause in both humans and animals⁵³. The cobalt content of soils in the research area is elevated by large dosages of cobalt-rich phosphate fertilisers and fossil fuel emissions from agricultural machinery used in apple and rice fields. The lower Co levels found in carbonate soils compared to basaltic soils point to weathering of basalts as a geogenic source of cobalt contamination. To stop additional cobalt poisoning in the study region, cobalt-rich phosphate fertilisers may be substituted with cobalt-free fertilisers. Clean fuel must be used in farm machinery to reduce emissions.

Chromium, the second most common metal contaminant in soil, is extremely dangerous to the ecosystem and is not required for plant metabolism⁵⁴. The International Agency for Research on Cancer lists Cr as the leading carcinogen, which raises grave implications for human health⁵⁵. Cr toxicity has a major impact on our sustainable agriculture and food security because it impacts most important crops for agriculture⁵⁶. There are a number of sources of chromium in soil, including contamination from human activities such as the use of chromium-containing fertilisers and pesticides, incorrect handling of industrial waste, and burning of fossil fuels⁵⁵. The research area’s soils have higher levels of Cr due to the use of substantial amounts of fertilisers and pesticides, emissions from burning fossil fuels, and waste disposal. The weathering of basalts is suggested to be a geogenic source of Cr contamination by the lower Cr levels detected in carbonate soils when compared to basaltic soils. In order to prevent more cases of Cr poisoning in the research area, cobalt-free alternatives to pesticides and fertilisers containing Cr may be used instead, and clean fuels must be utilised in farm machinery to lower emissions.

Nickel toxicity damages soil fertility, which could soon result in less crop yield. It also causes chlorosis, necrosis, and oxidative damage in plants⁵⁷. Although its usefulness as a trace element for both humans and animals has not yet been shown, its toxicity has a number of negative health consequences on people, including allergies, kidney and cardiovascular disorders, lung and nose cancer, and lung fibrosis⁵⁸. Environmental pollution from nickel may be due to industry, the use of liquid and solid fuels, as well as municipal and industrial waste⁵⁹. The soils in the research region contain higher amounts of nickel due to emissions from burning fuels and agricultural waste. Because carbonate soils have lower Ni levels than basaltic soils, geogenic sources of Ni contamination could be basalt weathering. The research area may employ waste disposal practices and clean fuels machines to prevent further instances of Ni poisoning.

Vanadium (V) is one of the toxic elements with the most extensive distribution in nature⁶⁰. A significantly elevated level of V results in the destabilization of plant physiological balance, slowing down the growth of biomass which significantly reduces yield⁶¹. The high mobility of V from soil to plants directly affects humans and animals. Vanadium toxicity may cause lung damage, neurotoxicity in brain cells, gastrointestinal problems, skin and eye irritation and cardiovascular diseases in humans⁶². Vanadium is released to the environment by weathering of rocks, volcanic emissions, steels and ceramic waste, and the combustion of coal and petroleum crude oils⁶³. Vanadium concentrations in the soil are higher in the research region’s major settlement areas—the Bandipora district headquarters and a number of smaller towns and villages—than in farming areas. This suggests fuel burning and trash disposal of are primary human sources of V contamination. A combination of geogenic and human sources of V is indicated by the lower V levels found in carbonate soils and the moderate V levels observed in basaltic soils. The research region may reduce emissions from automobiles and factories and implement scientific waste disposal methods to prevent additional incidents of V poisoning.

Because it impacts the entire ecosystem, environmental toxicity is a global concern⁶⁴. Pollutants from geological and human sources are cycling through the ecosystem, farmlands, vegetation, animals, and eventually humans via the food chain⁶⁵. The majority of hazardous element incidents in the research region are caused by local geology, small-scale industrial units, automotive emissions, construction activities related to hydropower projects, inadequate waste management, and agricultural practices. We can prevent further degradation of the delicate ecology of the Bandipora-Ganderbal areas of Kashmir Himalayas by reducing, recycling, and repairing natural and anthropogenic resource products, adhering to organic farming practices, and adopting clean energy alternatives to fossil fuel combustion using solar, wind, water and biogas energy⁶⁴.

The impact of micronutrient deficiencies on crops, soils, human and animal health, and the climate

Micronutrients are nutrients that the human body requires in trace levels⁶⁶. Humans need micronutrients for a wide range of physiological processes; they are essential for the synthesis of hormones, enzymes, and other chemicals that control immune and reproductive system function as well as growth and development⁶⁷. More than two billion people globally suffer from one or more micronutrient deficiencies, which continue to be a serious public health concern in many nations⁶⁸. The current global burden of disease is mostly attributed to micronutrient deficiencies, which have tremendous financial and human implications and disproportionately affect the poor, particularly women and children⁶⁹. The confluence of poor nutrition, poor health, and poverty has a multiplier effect on population overall wellbeing and also contributes significantly to downward trends in nutritional security and increased poverty⁷⁰. This makes correcting micronutrient deficits a significant concern for the scientific community as a whole.

Some soil samples in this study have inadequacies in Cu, Ni, Pb and Zn (Table 2). Zimdahl and Hassett⁷¹ reported no evidence that Pb is essential for the growth of any plant species, so there are no Pb deficits in the soils of the examined area. But deficiencies in Cu, Ni, and Zn in agricultural soils affect plant development and human and animal health. Reduced agricultural yields may result from soil micronutrient deficits, which affect plant growth.

Cu has a remarkable capacity to interact chemically with both organic and mineral soil constituents. In agronomic practice, copper levels in soils are crucial⁷². Cu shortage in soils will affect plant productivity and nutrition because Cu is important for many physiological processes in plants as well as disease resistance⁷³. Cu is not only a component of many distinct plant enzymes and required for the operation of numerous particular enzymes, but it is also a significant component of blood proteins that are vital for the animal body’s regular physiological processes⁷⁴. The Ganderbal district, located in the southeast of the research region, has carbonate rocks that produced the soils. These rocks are deficient in copper (Cu), which may be the reason for low plant yields and negative effects on people and animals.

Ni is the latest element to be included in the list of essential micronutrients to plants. The first evidence of its essentiality was verified in soybean plants under controlled conditions of Ni depletion, when these plants accumulated toxic concentrations of urea in leaflet tips⁵⁷. The evidence that Ni is an essential plant micronutrient was confirmed four years later, when after three successive generations of growing barley plants in Ni-depleted controlled conditions, these plants failed to produce viable grains⁷⁵. Ni is a component of urease and hydrogenase required by legumes that transport N from roots to tops. The low plant yields and negative effects on people and animals may be caused by the lack of Ni in the carbonate rocks that produced the soils in the Ganderbal district, which is located in the southeast of the research region.

Zinc is essential for both plant and animal growth and reproduction⁷⁶. Plants with reduced zinc levels tend to produce lower crop yields and, in most cases, lower-quality agricultural products. Low zinc levels affect several essential physiological processes that depend on zinc, therefore inadequate growth is bad for the health of the plant¹⁴. Zinc deficiency is linked to poor nutrition quality in humans and animals, and soils lacking in zinc make the condition worse. Globally, there is often a zinc deficit in soil-crop systems, particularly on calcareous, alkaline, degraded, and land-leveled soils⁷⁶. Soils on carbonate rocks in the Ganderbal district, southeast of the research area, may suffer from zinc deficiency, plant yields may be reduced, and human and animal health may suffer.

The absence of several micronutrients in agricultural soils worldwide are among the reasons for low crop yield, decreasing nutritional quality of agricultural food, and malnutrition and diseases in humans and animals⁷⁷. A plant will grow abnormally or stunted and its subsequent development, particularly its metabolic cycles, will be disrupted if the availability of an essential trace element is insufficient. The Ganderbal district in the Kashmir valley’s soils are deficient in several micronutrients, which limits crop productivity, health of people and animals, and the local economy. Cu, Ni, and Zn, the deficient micronutrients, can be applied singly or in combination with compost, biochar, and organic manures^19,20. Crushed, quickly responding basaltic rocks can be added to croplands to improve soil nutrition, boost crop yield, strengthen defences against pests and diseases, and rebuild soil structure through biogeochemical soil improvement⁷⁸. In the micronutrient-poor soils in the carbonate terrain of the study area, Panjal Trap basalt powders²¹ can be used to supplement in areas where uptake of micronutrients is excessive due to intense farming and enrich micronutrient-rich soils developed on carbonate rocks. By reducing CO₂ sources to the atmosphere from energy generation as soon as possible, and by implementing measures that actively remove CO₂ from the environment, future climate change and soil fertility difficulties caused by multi micronutrient deficiencies could be reduced⁷⁸.

Recommendations and need for further investigation

Water bodies, soils, vegetation, human and animal health, and agricultural productivity will all be impacted by toxic elements (As, Cr, Ni, and V) and micronutrient deficiencies (Cu, Ni, and Zn). To prevent harming the ecosystem, care must be taken while using agrochemicals containing potentially hazardous chemicals. Synthetic agrochemicals should be replaced with natural farming practices²⁰. To help solve the nutritional shortage, encourage a healthy lifestyle, and increase agricultural output, nutrient-poor soils can be treated using fertilisers fortified with micronutrients. To improve nutrient-poor soils and manage waste disposal difficulties, locally available and less expensive compost, egg shell meal, and bone meal are advised^20,79,80. Given the region’s reliance on agriculture and the dangers of soil pollution, this study is important for both the environment and public health. The results are crucial for directing policies related to food safety and soil management. In order to gain a comprehensive understanding of the effects of harmful and inadequate elements, in-depth research investigations on soil, water, plant, humans, and animal samples may be conducted in the future.

Conclusion

This study illustrates the spatial distribution, inadequacy, and toxic hazards of micronutrients and potentially hazardous elements in the top soils of the Bandipora-Ganderbal area of the Kashmir valley. Trace element concentrations (mg/kg) exhibit the following trend: Fe > V > Cr > Zn > Ni > Cu > Pb > Co > As. Numerous samples are deficient in micronutrients (Cu, Ni, and Zn), rendering the soils unsuitable for increased crop productivity and animal and human nutrition. The major geological borders exhibit large variations in micronutrient concentrations, with soils over carbonate terrain having lower levels than those over basaltic terrain. For crop productivity and the health of the biota, As, Co, Cr, Ni, and V are excessive and unsafe in a number of samples from the study area. The lower enrichment factors (< 2) for V, Co, Cu, Cr, and Ni indicate geogenic sources, while the moderate enrichment factors (> 2) for As, Pb, and Zn suggest anthropogenic sources. These findings are further corroborated by cluster analysis and correlation matrix. Arsenic has a high soil pollution index; Co, Cr, Ni, and V have a moderate index; Cu, Pb, and Zn have a low index. The integrated toxic risk index (ƩTRI) is zero for 5% of samples, low for 63.5% of samples, and high for 31.5% of samples. Farm lands, habitation, and hydroelectric project site occupy more contaminated regions than forest, grazing areas, and waste land locations. Pesticides, fertilisers, the building sector, and vehicular emissions are the primary sources of pollution. Policymakers, environmentalists, and agricultural specialists can find great assistance in creating management and control plans from the study’s main conclusions about soil contamination and trace element deficiencies.

Author contributions

Methodology, Validation, Review and Editing are done by Ishfaq Ahmad Mir. Ishfaq Ahmad Mir read and approved the final manuscript.

Funding

The Ministry of Mines, Government of India, provided funding for this work under the NGCM FSP of 2014–2015.

Data availability

Data is provided with the manuscript in the Tables and Figures file. Additional data will be provided on request. Ishfaq Ahmad Mir should be contacted if someone wants to request the data from this study.

Declarations

Competing interests

The authors declare no competing interests.