Table 5.

Detailed study focused on candidate waste by-products.

Lab or field	Waste by-product amendments used	Description of tested medium and site	Targeted metals	Successful amendment(s) or blend(s) (final application rate)	Maximum Metal reduction/change	Maximum plant success (post- treatment)	Findings	References
L	Phosphogypsum (pH = 3.8)	Contaminated soil (central Spain); pH = 5.45	Arsenic (As), cadmium (Cd), and thallium (Tl)	SF2 = 1% (adds 25.5 kg calcium [Ca])	As: 26% more retained (pretest: 616.2 mg/kg)	Not presented	Enhanced immobilization, particularly for As and Cd and Tl to a lesser extent. Presence of Cd may favor As adsorption due to formation of aluminum (Al) hydroxy polymers or reprecipitation of new carbonate minerals	[169,170]
	Sugar foam (SF) (pH = 9.3)				Cd: 49% more retained (pretest: 568.4 mg/kg)
					Tl: 42% more retained (pretest: 693.2 mg/kg)
F	Sewage sludge (SS)/paper mill (PM) residues/aluminum plant sludge blend; pH = 8–10	Acid mine soils at the depleted copper mine (northwest Spain); pH = 3.3	Chromium (Cr), copper (Cu), nickel (Ni), lead (Pb), and zinc (Zn)	SS/PM residues (forest and sludge field site: 297 metric tons/hectare (ha) of SS + PM)	Cr: 41% of 130 mg/kg	Increase bacterial and fungal abundance and microbial functions	Addition of the sludges and residues recovered bacterial and fungal abundance; however, the high Cu and Cr concentrations still negatively impacted microorganism activity and plant recovery. Activity of the acid phosphatase may have been negatively affected due to the feedback inhibition by inorganic phosphate usually found in SS. Sites treated with sludges decreased the specific activity of all enzymes involved in carbon (C) and nitrogen (N) cycle indicating that their microbial community is characterized by higher C and N use efficiency than unamended soil	[54]
					Cu: 90% of 644 mg/kg
					Ni: 69% of 14.64 mg/kg
					Pb: 43% of 21,99 mg/kg
					Zn: 4% of 113 mg/kg
L	Lime-stabilized biosolids (pH = 12.3), rock phosphate (pH = 7), and anaerobic biosolids (pH = 7.1)	Contaminated soil from Zn and Pb milling and smelting operations in Oklahoma; pH = 6.4–6.88	Cd, Pb, and Zn	Lime-stabilized biosolids (LSB) 100 g/kg soil	Post-90 days	LSB significantly reduced the concentration of Cd and Zn in lettuce	The largest reductions in metal extractability and phytoavailability were realized using LSB; however, this ability was lost when soil was acidified to pH <6	[89]
					Phytotoxic Zn: 86% of 1,188 mg/kg
					Cd: No values given
					Zn: No values given
F	Agricultural limestone (pH = 7.3), mineral rock phosphate (pH = 6.84–7.11), and diammonium phosphate (DAP) (pH = 7.45–8.02)	Surface soil (<20 cm) with elevated residual metal concentrations from an inoperative smelter site in northeastern Oklahoma; pH = 6.97	Cd, Pb, and Zn	DAP 10 g/kg soil	Post-6 months	Not presented	DAP was the most effective treatment for immobilizing heavy metals	[82]
					Cd: 94.6%
					Pb: 98.9%
					Zn: 95.8%
L	Alperujo compost biochar	Contaminated soil (top 10 cm; <2 mm fraction) from sporadically vegetated part of the La Mina Monica mine site area, Spain	As, Cd, Cu, Pb, and Zn	Compost (C) 10 v/v	(BC) Reduction in pore water:	(C) Germination success increase 55%	The greatest reduction of metal concentrations in pore water was achieved by biochar; however, application of both alperujo compost and biochar increased the potential for As leaching. Compost increased plant growth, and compost and biochar together decreased toxicity the most	[147]
				Biochar (BC) 10% v/v	As: 80% (increased mobilization)	(C) Root length increase 52%
				C+BC 5% v/v each	Cd: 98% of ~130 μg/L	(C + BC) Toxicity decrease ~50%
					Cu: 98% of ~1,150 μg/L
					Pb: 95% of ~95 μg/L
					Zn: 95% of ~7,500 μg/L
F	Hydroxylapatite (pH = 7.3)	Sediments (top 20 cm; <2 mm fraction) were contaminated due to past and present non-ferrous metal processing and smelting activities; pH = 7	Zn, Cd, Cu, Pb, and As	TBS, 5% DW	Cd: 81% of 0.64 mg/kg	Species richness reduction:	The incorporation of TBS into the metal-contaminated sediment decreased the extractable fraction of Cd and Zn. In contrast, the hydroxyapatite did not decrease Cd and Zn extractability. TBS was effective in Cd and Zn immobilization, did not cause any nutrient imbalance or sediment ecotoxicity, and improved the bacterial activity	[171]
	Thomas Basic Slag (TBS) (pH = 7.7)				Cu: 42% of 0.12 mg/kg	Before = 21
						After = 14
						33% reduction
F	Biochar–wheat straw (pH = 10.4)	Rice paddy topsoil contaminated by emissions from a metallurgical smelter; pH = 5.36	Cd and Pb	Biochar (40 t/ha)	Post-2 years	Cd% reduction shoot: 27.0–75.0%	By-product successfully used to increase pH, total organic carbon (TOC), and decreased extractable Cd over a 3-year period. Cd was reduced in rice plant tissues, while Pb reduction was found only in roots. Analysis indicated that Cd and Pb had bonded with mineral phases of Al, iron (Fe), and phosphorous (P) on and around the inside of the biochar particles. Immobilization of Cd and Pb also occurred to cation exchange on the porous C structure of the biochar particles	[172]
					Cd: 46% of 2.72 mg/kg	Cd% reduction root: 29.1–57.8%
					Pb: 35% of 63.44 mg/kg	Cd% reduction rice plant uptake: 27.5–67.33%
						Pb% reduction rice plant uptake: 27%–69%
F	Biochar–wheat straw (pH = 10.4)	Contaminated rice paddy topsoil pH ranged from 5.01 to 6.31	Cd	Wood biochar (40 tons/ha)	Cd: 92% reduction reported for Cd (pretreatment range 0.31–3.13 mg/kg)	Rice grain Cd% reduction: 42–48%	Reduced Cd uptake by rice and immobilized Cd and Pb	[173]
F	Phosphate via fish bones (pH not reported)	Soil-contaminated from former chemical distribution facility and metals scrap yard (U.S. Superfund site); pH = not reported	Pb	Not presented	Not presented	Not presented	Immobilization of Pb achieved through the precipitation of pyromorphite (a mineral consisting of a chloride and phosphate of Pb)	[174]
F	Biosolids, agricultural lime, sugar beet lime, lime kiln dust (LKD); pH = 6.39	Fluvially deposited mine tailing sediment (Colorado); pH = 4.9–5.3	Zn and Pb	Biosolids (BS) + LKD	(LKD + BS): Zn: 99% of 970 mg/kg	Post: (LKD + BS) 95% cover	Soil pH increased and extractable metals decreased in lower soil horizons. Plant response in the field study was disappointing. Use of LKD + BS showed lush growth after an initial period of no growth. Response to in situ amendments may vary across large-scale restoration efforts	[55]
				LKD only	(LKD): Cd: 100% of 7.5 mg/kg
				Each added to lime equivalent of 224 mg/ha CaCO3
L	Fresh alperujo (pH = 5.43); sugar beet lime (pH = 9.04); composted biosolids (pH = 6.93)	Trace element polluted soil near a mine (acidic and alkaline soils tested); pH = 4–7	Cd, Cu, Mn, and Zn	Alperujo separate applications of about 30,000 kg/ha	Soil A	Pre: –	Alperujo stimulated biological activity; both alperujo and sugar beet lime effectively immobilized metals	[148]
					Cd: 0% of 0.4 mg/kg	Post: increase in microbial biomass
					Cu: 57% of 3.5 mg/kg	% reduction:–
					Mn: 20% of 200 mg/kg
					Zn: 6% of 75 mg/kg
F	Seashell grit (pH = 6.47) (compared and in combination with biosolids, natural zeolite, and iron-activated zeolite)	Degraded topsoil surrounding copper smelter (Puchuncaví Valley, central Chile); pH = 6.3	Cu, Zn, and As	Seashell grit (SG: 0.5 tons/ha) + Fe-activated zeolite (AZ: 1 ton/ha)	Post-14 weeks:	Rye grass post (SG, AZ, Z, and B): biomass/root cover 125–280% higher than reference soil	Eliminated phytotoxicity and bioaccumulation in plant tissues; reduced Cu and Zn, but not As solubilization in pore water	[56]
					SG only:
				Seashell grit only (SG: 0.5 tons/ha)	Zn: 98% of 6.36 mg/kg
				Note: Inclusion of biosolids had no apparent effect on metal reduction	SG + AZ:
					Cu: 89% of 4.81 mg/kg
					As: 1.5% of 38.2 mg/kg
L	Individual applications of vermicompost, sugarcane filter cake, palm kernel pie (compared to and in combination with lime, phosphate rock, and zeolite); pH range = 5.3–6.5	Supernatant of amendment solutions from Cd-contaminated soils; pH = not reported	Cd	Vermicompost, sugarcane filter cake, palm kernel pie, zeolite, and lime	Best performance for adsorption was from both liming agents (lime and also the zeolite)	Not presented	Increased precipitation of Cd most successfully via liming agents (lime and zeolite)	[60]
				All amendments 0.25 g of soil amendment and 25 mL of a synthetic Cd solution containing 0, 1.12, 5.62, 11.24, 16.86, 33.72, or 84.30 mg/L Cd
F/L	Phosphoric acid	Contaminated hardrock mining site soils	Pb	Not presented	Not presented	Post-18 months:	Phosphate amendments resulted in overall bioavailability reduction	[175]
						Bioavailability reduction:
						Pig 29%
						Rat 40%
						Human 69%
						In vitro (pH 1.5) 18%
						In vitro (pH 2.5) 69%
F	Limestone	Contaminated hardrock mining site soils at Palmerton, PA “Revival Field”; pH = 6.25	Cd and Zn	Biosolids compost application rate not presented	Post-5 years	Not presented	Biosolids compost resulted in a reduction of Cd- and Zn-extractable soil concentrations	[175]
					diethylenetriamine pentaacetate (DTPA)–extractable reduction
	Biosolids compost				Cd 16.8% from 83.1 mg/kg
					Zn 7.8% from 4940 mg/kg
L	Individual applications of biochar–wood (pH = 10.9), crushed oyster shell (pH = 8.11), blast furnace slag (pH = 9.83), and fluidized-bed crystallized calcium (pH = 9.44)	Alluvial Cd-contaminated topsoil (0–20 cm), from illegal discharge of industrial wastewater (northern Taiwan); pH = 4.42	Cd	Crushed oyster shell (OS)	Post-90 days	58% reduction of Cd in rice shoots	Cd mobility and bioavailability reduced by all amendments	[69]
				(Soil + 4% OS)	Cd: 35% reduction of 3.85 mg/kg
L	Red mud (pH = 11.12)	Sandy clay loam (top 30 cm, <2 mm fraction) from abandoned mining site of Baccu Locci (Villaputzu, Italy); pH = 6.84	As (Cd, Cu, Pb, and Zn)	3% w/w amorphous Al hydroxide (Al-OH)	As Al-OH ~65%	Plant growth	The adsorbed As fraction did not change in red mud-treated soil compared to control but decreased significantly in Fe-rich water and Fe2O3 soils (~27% reduction), and Al-OH soil (~65%). Plant growth, estimated by shoot dry weight, was significantly influenced by the amendments, and Al-OH was the best treatment followed by Fe-WTR	[176]
	Hematite					Al-OH 2.5 and 3 times > control
	Fe-rich water					Fe-WTR 1.8–2.5 > control
	treatment residual (pH = 7.78)
	Amorphous Al hydroxide
L	Cyclonic ash (norbergite) commercial Na-silicates	Soil (<2 mm fraction) contaminated by metal smelters in Flanders, Belgium; pH = 6.3	Cd	Na silicate + cyclonic ash (CA + SIL) 5% CA +1% SIL	Zn 98% of 410 mg/kg	Post-28 days:	All tested amendments reduced Ca(NO3)2− extractable soil metal concentrations and reduced metal uptake in Agrostis capillaris seedlings. Cyclonic ash appeared efficient in both reducing oxidative stress in beans and Zn, Cu, and Pb uptake in grasses	[177]
					Cd 95% of 5.6 mg/kg	Agrostis capillaris uptake reduction
					Cu 88% of 5.2 mg/kg	Zn 93% of 5330 mg/kg DW
					Pb 96% of 4.7 mg/kg	Cd 86% of 31.5 mg/kg DW
						Cu 60% of 81.6 mg/kg DW
						Pb 82% of 72 mg/kg DW
L	Marble sludge (pH = 8.5), compost (pH = 8.7), and bayferrox (pH = 7.6)	Contaminated soil (top 20 cm, <2 mm fraction) from the El Arteal mining district (Almeria, SE Spain)	As, Cd, Cu, Pb, and Zn	Marble sludge (MS) at 4 and 8% (w/w), compost (CM) at 2 and 6% (w/w), and synthetic Fe oxides (BF) at 1 and 3% (w/w)	(MS) Zn, Cd, Pb >90%	Highest root elongation index (reduction of toxicity to lettuce)	Amendments that raised the pH, especially MS, effectively diminished soluble heavy-metal concentrations; however, these amendments increased As concentration in lixiviates, encouraging the risk of the As dispersion. The amendment that fixed As, iron oxide, was not effective in diminishing soluble heavy-metal concentrations	[178]
					Cu 50–60%	MS (8%) + CM (2%)
					(BF) As 66% from 0.03 mg/L	Soils treated with Bayferrox, alone or mixed with MS or compost, were the most phytotoxic
L/F	Red mud (pH = 10.2)	Contaminated soils (top 23 cm, <2 mm fraction) adjacent to a decommissioned Zn/Pb smelter at Avonmouth in the United Kingdom; pH = 4.7	Pb, Zn, Cd, and Cu	Red mud 5%	Post-21 months	Post-21 months	Field: Application of lime or red mud amendments had no significant effect on total metal concentrations in soil pot experiments. However, the 5% red mud treatment increased Cr concentrations from 45 mg/kg up to 135 mg/kg due to Cr in red mud	[78]
					Cu, Zn, Cd, Cu – no reduction	average Festuca rubra yield 4,400% increase of 0.2 t/ha
					Pot: reduction in pore water
					Pb 84% of 4.58 mg/L
					Zn 7% of 2.5 mg/L		Post: Red mud alone decreased uptake of Pb in Festuca rubra
					Cd 95% of 6.11 mg/L
					Cu 37% of 2.58 mg/L
					Ni 97% of 0.3 mg/L
L/F	Fly ash (pH = 13) and steel slag (pH = 13)	Soil (top 15 cm; <2 mm fraction) from paddy field in Shangba, China, contaminated by Dabao Mountain sulfide mining; pH = 4	Cd, Zn, Pb, and Cu	Fly ash (FA40) 40 g/kg, steel slag (SS6) 6 g/kg, and steel slag (SS3) 3 g/kg	Post	Decrease of metal contents in leaf to stem ratio	The experiment indicated that the application of fly ash and steel slag increased soil pH from 4.0 to 5.0–6.4, decreased the phytoavailability of heavy metals by at least 60%, and further suppressed metal uptake by rice	[179]
					(FA40)	(FA40) Cd 0.13
					Cd: 99% of 7.3 μg/kg	(SS3) Zn: 0.19
					Zn: >99% of 6.7 μg/kg	(SS3) Cu 0.40
					Pb: >99% of 57 μg/kg	(SS6) Pb 0.29
					(SS6)
					Cu: 89% of 6.3 μg/kg
L	CaCO3	Soil (top 14 cm, <2 mm fraction) contaminated by Zn industries in Prayon (Liège province, eastern part of Belgium); pH = 5.8	Cd, Pb, and Zn	25 g mass of CaCO3 (C) and iron grit (IG) to 500 g of contaminated soil and 250 g of washed sand	Reduction in flow-weighted mean concentrations	Bone meal reduced Pb concentrations in white lupin shoots by 74%	Cd and Zn leaching was reduced by all amendments mainly due to alkalinity increase. Pb leaching was strongly affected by DOC release. Therefore, bonemeal and manure treatments, which highly increased DOC concentrations in leachates, increased the flow-weighted mean Pb concentrations by 2.3 and 16 times, respectively. While iron grit induced strong Cd and Pb leaching reductions, this amendment doubled Cd and Pb concentrations in shoots of white lupin. Conversely, the addition of bone meal reduced Pb concentrations in shoots by 74%, probably because of organo-Pb complexes. Overall, the addition of CaCO3 offered the best compromise, as it successfully reduced both the leaching and the phytoavailability of the three considered metals	[180]
	Iron grit, fly ash, manure, bentonite, and bone meal				(C) Cd 88.3% from 98 μg/L
					(C) Zn 98.5% from 2875 μg/L
					(IG) Pb 83% from 15 μg/L
L	Food waste compost (60% food waste and 40% sawdust) (pH = 7.76), market compost (50% food waste, 10% agricultural waste, 10% manure, and 30% lime), and zeolite (pH = 8.44)	Weathered tailings from abandoned mine site in South Korea; pH = 3.03	Zn, Mn, Cr, Fe, Cd, and Al	Mixed with 200 g tailings:	Post-4 weeks:	Not presented	Both organic and inorganic materials were successful for increasing pH and metal immobilization, except in the case of As, where leaching potential increased up to 158%. With the exception of Market compost and Zeolite (MCZ), amendments increased leachability of Pb up to 43%	[181]
					Reduction in metal leaching potential
				(MCZ) Market compost (50 g) + Zeolite (12.5 g)	Zn (MCZ) 91%
					Mn (MCZ) 76%
				(Z) Zeolite (12.5 g)	Cr (Z) 53%
					Fe (MCZ) 44%
					Cd (MCZ) 43%
					Al (MCZ) 24%
L	Limestone waste, red mud, and furnace slag	Mine area soil (Korea); pH = 4.58	As, Cd, Pb, and Zn	Limestone (LS), red mud (RM), and furnace slag (FS) applied to soils at 5% w/w	As (RM): 77% of 0.13 mg/kg	Bioaccessible fraction reduction in lettuce:	Fe-rich industrial by-products proved highly effective at stabilizing As and heavy metals, decreasing the levels of extractable contaminants. As a result, a corresponding reduction in the concentrations of these contaminants occurred in plant (lettuce). In addition, the reduction in extractable As and metals led to increases in microbial activity	[182]
					Cd (RM): 98% of 0.959 mg/kg	As (FS) 46%
				LS + RM and LS + FS at 2% w/w ratio	Pb (LS): 99% of 1.25 mg/kg	Pb (RM) 44%
					Zn (LS+RM): ≤100% of 27.79 mg/kg
L	Zero valent iron limestone (pH = 9.50), acid mine drainage treatment sludge (pH = 8.21), bone mill (pH = 6.69), and bottom ash (pH = 9.23)	Topsoil (<20 cm depth, <2 mm fraction) from contaminated sites in the Suseong gold mining area, Chungnam Province, Korea	Cd, Pb, and Zn	2% (w/w); limestone (LS); bottom ash (BA)	Post – 40 days	BM lettuce shoot yield increase reduction in lettuce shoots	Ls and Ba were most successful in reducing metal extractability. With the exception of the BM treatment, lettuce shoot yields did not differ significantly among treatments. However, BA increases Cd concentrations in lettuce shoots compared to untreated soil	[183]
					(LS) Ca(NO3)[2 extractability reduction	Cd (BA) ~69%
					Cd 19.30%	Pb (BA) ~61%
					Pb 37.43%	Zn (BA) ~58%
					Zn 52.21%
					(BA) DTPA extractability reduction
					Cd 35%
					Pb 38%
					Zn 25%
L	Bone mill (pH = 8.91), bottom ash (pH = 9.23), furnace slag (pH = 10.57), red mud (pH = 11.32), and plant species (Miscanthus sinensis and Pteridium aquilinum)	Mine tailings from the Suseong Pb/Zn mining area in Chungnam Province, Korea; pH = 7.64	Cd, Cu, Pb, and Zn	Red mud 2% (w/w) and P. aquilinum (fern)	Post-90 days reduction in porewater	P. aquilinum planted tailings	The most significant reduction in heavy metal concentrations in pore water was observed in the RM-amended tailings for both plant species. In contrast, the BM application increased the concentrations of all metals evaluated in pore-water samples	[184]
					Cd 99%	Decrease of bioavailability:
					Cu 99%	Pb 34%	Furnace slag and M. sinensis reduced CaCl2-extractable heavy metals by 56–91%. Red mud and P. aquilinum treatment was the most effective at decreasing bioaccessible Pb, reducing it to 34% of the total Pb
					Pb 98%	Mobility factor decrease:
					Zn 99%	Cd 79–96%
						Pb 77–91%
						Zn 77–96%
N/A	1. Zeolite	1. Mine soils	1. Zn, Pb, Cu, and Cd	1. 0.5–5% by weight	1. Labile and easily available fractions 42–72%	1. –	Nanomaterials with high potentials for mine soil reclamation include zeolites, nZVI, iron oxide nanoparticles, phosphate-based nanoparticles, iron sulfide nanoparticles, and C nanotubes	[185]
	2. Zeolite	2. Contaminated soil	2. Hg	2. 1–5% (g/g)	2. –	2. Plant uptake (rye and alfalfa) 58% in roots and 86% in shoots
	3. Zeolite	3. Soil near Zn–Pb smelter	3. Cd, Pb, and Zn	3. 2.5–5%	3. –	3. Substantially enhanced maize and oat growth and decreased metal in plant tissue
	4. Nanoscale Zero-valent iron particles (nZVI)	4. –	4. CrVI+	4. –	4. Reduction of Cr + 6 to Cr + 3 97.5%	4. –
	5. nZVI	5. Cd-spiked soil	5. Cd	5. 0.01% (g/g)	5. –	5. Rice seeds <10% and leaves <20%
	6. Iron phosphate (vivianite) nanoparticles	6. Contaminated soil	6. Pb	6. 0.61–3.0 mg/g soil as PO4−3	6. TCLP leachable 85–95%	6. Bioaccessible fraction 31–47%
	7. Synthesized apatite nanoparticles	7. Pb-laden soil from a shoot range	7. Pb	7. 2 mL solution to 1 g soil	7. TCLP leachable ~56%	7. –
L	Coarse zeolite (pH = 9.5), fine zeolite (pH = 8.6), flue gas desulfurization (FGD) (pH = 11.2), fly ash (pH = 7.6), and biosolids (pH = 7.8)	Loamy-skeletal, mixed, mesic typic udorthents soil (top 10 cm; <2 mm fraction) with elevated Be and Cd concentrations from coal strip mining (Ohio); pH = 3–4	Study targeted vegetative growth of soil with elevated levels of Be and Cd, which inhibits seed germination and root uptake of Ca and Mg and also degrades some proteins and enzymes	FGD 10%	Post-35 days	Pre: –	Application of FGD at 10% by weight increased soil pH from 3.1 to 5.0 and from 4.2 to 7.0, enhancing germination and rate of shoot elongation of lettuce; however, biosolids significantly enhanced soil aggregate stability and saturated water-holding capacity	[36]
					Be: FGD reduced Be levels	Post: FGD exhibited the best remediation result among all the amendment materials, promoting the shoot growth to 9.6 cm
					Cd: Not presented	% Reduction: –
					Al: 97% of 8 mg/L
L	Water treatment sludges (WTS) (pH = 7.2 and 6.3), red muds (pH = 10.7 and 12.2), and red gypsum (pH = 7.1)	Agricultural grassland soils (top 20 cm) contaminated by 19th century Cu and As mining at Devon Great Consols Mine, Devon, UK; pH = 4.6	As and Cu	Water treatment sludges (WTS-A) 2% (w/w)	Reduction in pore water	Pre: –	WTS was the most effective amendment in terms of enhancing plant and microbial growth, decreasing metal and As mobility, and diminishing bioaccessible As. Rye grass and lettuce grown in WTS had the largest shoot biomass	[124]
					Cu: 44% of 998 μg/L	Post: Rye grass and lettuce grown in WTS had the largest shoot biomass
					As: 75% of 1,795 μg/L	% Reduction: –
L	Granulated blast furnace slag (GBFS)	Typical soil found in the Ostrobothnia region of Northern Finland	As, Cd, Cr, Cu, Ni, Pb, vanadium (V), and Zn	MI: GBFS 0.15, FA 0.15, PMS 0.30, GLD 0.10, L 0.30	Residual fraction (not bioavailable):		Results for the use of GBFS with pulp and paper residues seem encouraging regarding the replacement of commercial fertilizers. However, with the use of converter steel slag, elevated total concentrations of Cr and V were detected. However, 46.0% of the total concentration of V occurred in the easily reduced fraction indicating potential bioavailability	[186]
	GSS-Converter steel slag			MII: GSS 0.15, FA 0.15, PMS 0.30, GLD 0.10, L 0.30	As (MII) 61.7%
	FA-Fly ash (P&P)				Cr (MI) 84.6%
	GLD-Green liquor dregs (P&P)			According to the liming effect value of commercial ground limestone, which is 38% (Ca-equivalents, d.w.), 1.03 and 1.06 tons of Matrices I and II respectively would be needed to replace 1 ton of limestone	Ni (MI or MII) 53%
	PMS-Paper mill sludge				Pb (MII) 90.3%
	L-Lime waste				Cu (MI) 84.6%
L	Nano-Fe/CaO	Mica/fibrolite soils (<2 mm fraction) from Okayama prefecture, Japan	As, Cd, Cr, and Pb	Soil: Nano ratio	Decrease in metal surface amounts on soil surface	Not presented	The addition of nano-Fe/Ca/CaO immobilized 95–99% of heavy metals, versus 65–80% by simple grinding. Nano-Fe/Ca/CaO treatment reduced the concentration of leachates heavy metals to values lower than the Japan soil elution standard regulatory threshold of 0.01 mg/L for As, Cd, and Pb; and 0.05 mg/L for Cr	[187]
	Nano-Fe/Ca/CaO			Soil: Nano-Fe/CaO (2/5) 10:1	Cr 99%
	Nano-Fe/Ca/CaO/PO4			Soil:Nano-Fe/Ca/CaO (2/2/5) 10:1	As 100%
				Soil:Nano-Fe/Ca/CaO/PO4 (10:0.5:0.5 (NaH2PO4))	Cd 99.4%
					Pb 99.7%
L/F	Steel shot (pH = 8.5), beringite (pH = 11), and municipal compost	Fine-grained spoil (top 0.3 m) of the former gold mine of Jales, Portugal; pH = 4.1	As, Pb, Cd, and Zn	CBSS: Compost (5%) + Steelshot (1%) + Beringite (5%)	Post–443 days	When compared with the results of 1998, Holcus lanatus shoot growth in amended spoils increased 4–6 fold, depending on amendments. CBSS amendments decreased As plant uptake. Similar results were obtained for Cd and Zn	Over a 443-day period following spoil treatment, CBSS treatment decreased leached Cd, Zn, and Pb amounts and achieved the lowest increase in As leaching. Short-term plant experiments showed a better restoration of the vegetation cover from CBSS than compost alone	[109]
					Leachate reduction:
					As: 661%
					Pb: 15%
					Zn: 0.2%
					Cd: 0.08%
L	P-spiked Linz–Donawitz (LD) slag	Sandy Cu-contaminated soil (<2 mm fraction) from a former wood preservation site; pH = 5.7	Cu	0% (T1), 1% (T2), 2% (T3), and 4% (T4) per air-dried soil weight	Not presented	Post-2 weeks	All incorporation rates of LD slag increased the root and shoot dry weight yields compared to the untreated soil. Foliar Cu, Zn, and Cr concentrations of beans decreased with the LD slag incorporation rate	[188]
						T2 highest bean growth and foliar Ca concentration, foliar Cu reduction below upper critical value, prevent excessive soil electrical conductivity and Zn deficiency
L	Cyclonic ashes (Beringite) (pH = 9.5)	Soils in the southern Netherlands contaminated from Zn smelter emissions; pH = 5.2–5.8	Cd and Zn	Cyclonic ashes (CA) 25%	Zn reduction in solution <100% of 9 μmol/L	Not presented	Initially, Zn decreases in all treatments, but only the CA treatment shows a continuous decrease to almost zero	[189]
	Synthetic zeolites (pH = 10.1)
L	Olive-mill compost (pH = 8.8) and fresh pig slurry (pH = 7.8)	Loamy sand mine spoil soil (top 10 cm; <2 mm fraction) from the mining area of La Unión-Cartagena, Spain; pH = 3.5	As, Pb, and Zn	First application:	Reduction in pore water:	Pre: –	Addition of compost and pig slurry in combination with hydrated lime reduced the high metal mobility in soil, increased soluble nutrients concentrations, and allowed the growth of rye grass (Lolium perenne) in the soil. However, plant metal uptake increased	[190]
				Compost 60 t/ha	5-cm depth	Pb post – 1st harvest: 500 mg/kg
					Pb: 94% of 2.67 mg/L	Pb post – 2nd harvest: 1,500 mg/kg
				Second application (2 weeks later, combined with 15.5 t/ha of hydrated lime):	Zn: 85% of 3,296 mg/L	% Reduction: 67%
				Compost 30 t/ha
					12-cm depth
					Pb: 40% of 1.98 mg/L
					Zn: 62% of 3,100 mg/L
F	Biosolids compost (pH = 6.9), leonardite (pH = 6.08), and sugar beet lime (SBL) (pH = 0.04)	Topsoil (top 15 cm; <2 mm fraction) contaminated by mine tailing spillage along the Guadiamar River (Spain); pH = 3.52	Cu	Leonardite (LE)	Complexing capacity (CC) of humic acids from waste by-products (mol/kg)	Not presented	Biosolids slightly more effective in reducing bioavailable Cu(II); Cu precipitated as a hydroxide with pH increase	[191]
				SBL	Pre: –
				Unamended soil (S)	Post (LES2) 1.44 ± 0.04
					%Reduction: –
				BS 30 t/ha/y
				BIS2 − Soil + BS (2 years)
				BIS4 − Soil + BS (4 years)
				Soil + LE 25 t/ha/y
				SBL 10 t/ha/y
				LES2 − Soil + LE + SBL (2 years)
				LES4 − Soil + LE + SBL (4 years)
L	Sepiolite	Soil (top 20 cm, <4 mm fraction) from agricultural fields in Jilin, China. The soils were artificially polluted with Cd (CdCO3): 1.25, 2.5, and 5 mg/k); pH = 7.76	Cd, Zn	Sepiolite (S) applied to soils at 0, 0.5, 1, 3, and 5%	Post: –	Cd uptake by spinach	Sepiolite addition not only decreased Cd absorption in spinach and increased safety for edible vegetables, but it also improved the quality of Cd-contaminated soil. Results showed that the sepiolite treatments significantly increased soil pH, resulting in a decrease in the available form of Cd in soil. Concentrations in the edible parts of spinach at 1% sepiolite treatment were lower than MPC for vegetables at 1.25 mg/kg Cd concentration and met MPC at 5% sepiolite treatment under higher Cd concentrations of 2.5 and 5 mg/kg	[192]
					Extractable Cd decrease:	28–63.7% from 1.25 mg/kg
					9.8–44.6% from 1.25 mg/kg	29.4–67.8% from 2.5 mg/kg
					14–33.5% from 2.5 mg/kg	17.2–72.1% from 5 mg/kg
					15.1–22.5% from 5 mg/kg
	Apatite (pH = 7.8) and slovakite (pH = 8.7)	Contaminated loamy soil (top 30 cm, <2 mm fraction) from an old lead and zinc smelter site in Arnoldstein, Austria; pH = 6	Pb, Zn, Cu, and Cd	Slovakite 5% (w/w) (S5)	Post-1 month	Phytoavailability reduction (DTPA extraction)	Apatite and slovakite amendments were both successful in lowering the potential bioavailability of metals, slovakite being more effective at the same weight share with the soil	[43]
				Apatite 5% (W/W) (A5)	Apatite (5%) Switch from carbonate and Fe and Mn oxide-bound fractions to less mobile and available chemical forms bound to soil organic component by factors of Pb 1.6, Zn 1.5, and Cd 3.4	Pb (S5) 54%
						Zn (S5) 55%
						Cu (S5) 19%
						Cd (A5) 52%
L	Tourmaline	Soil (top 20 cm (<2 mm fraction) from the bank of the Dagu Drainage River in Tianjin, northern China; pH = 7.45	Cd, Cu, Pb, and Zn	5% (w/w)	Post-3 months	Post-3 months	Results indicated that tourmaline could decrease the available heavy metal content and transform heavy metals into less toxic forms. Tourmaline increased the maximum dry matter and total chlorophyll content of lettuce and decreased the Cd and Cu content in lettuce shoots	[193]
					DTPA-extractable reduction	Lettuce plant growth 109.11%
					Cd 20.41% from 0.49 ± 0.01 mg/kg	Chlorophyll 31.76%
					Cu 19.20% from 8.02 ± 0.43 mg/kg	Lettuce shoots
						Cd reduction 49.01%
						Cu reduction 30.90%
F	Individual and mixed applications of fly ash, spent mushroom substrate, silkworm excrement, and limestone mine waste (pH ranged from 6.86 to 9.62)	Topsoil (<20 cm) contaminated by pyrite mine tailing spillage (China); pH = 5.62	Cd	Fly ash (FA): 5%	FA 5% (Cd): 39.9% reduction reported	% reduction in bioavailable Cd:	Decreased Cd mobility, bioavailability, and leachability. Cd immobilized as carbonates, Fe–Mn oxides, and fraction bound with OM. Mixed amendment applications more effective than individual amendments; when applied alone, limestone and fly ash were most effective	[193]
						Root (FA) 35.5%
						Shoot (FA) 46.9%
						Bean (FA) 46.6%
	Limestone, rock phosphate, palygorskite, and Ca Mg phosphate (CMP)	Calcareous urban soil (pH = 8.22)	Pb, Cd, Cu, and Zn	2% phosphate (RP), palygorskite (PG), and CMP	Reductions in metal leaching	Not presented	Palygorskite and CMP were generally quite efficient in reducing the availability of metal, while rock phosphate was only efficient in acidic soil. The effects of rock phosphate in reducing metal availability in the calcareous soil were the least efficient	[194]
		Acidic urban soil (pH = 4.63)			Calcareous soil
					Cd (CMP) 75.93%
					Cu (PG) 60.64%
					Pb (CMP) 74.12%
					Zn (PG) 64.38%
					Acidic soil
					Cd (RP) 79.06%
					Cu (PG) 49.64%
					Pb (RP) 69.44%
					Zn (PG) 43.77%
F	Limestone (pH = 9.13), sepiolite (pH = 5.54), hydroxyapatite (pH = 8.21), and zeolite (pH = 10.61)	Soil (top 20 cm) contaminated from mining and smelting in the Shuikoushan Mine Zone in Hengyang City, southern Hunan Province, China; pH = 5.41	Pb, Cd, Cu, and Zn	Combined amendments: Limestone + sepiolite (LS)		Post-4 months	Concentrations of Pb, Cd, Cu, and Zn in brown rice were decreased by 10.6–31.8%,16.7–25.5%, 11.5–22.1%, and 11.7–16.3%, respectively, as a result of 0.2–0.8% addition of LS, and decreased by 5.1–40.8%, 16.7–20.0%, 8.1–16.2%, and 13.3–21.7%, respectively, as a result of 0.2–0.8% addition of HZ	[195]
				Hydroxyapatite + zeolite (HZ)		The rice cultivar “II You93”
				0.2, 0.4, and 0.8% (w/w)