Heavy metals in reservoirs: pollution characteristics, remediation technologies, and future prospects

Song Cui; Chao Ma; Fuxiang Zhang; Zhaoyang Jia; Fengyang Pan; Dingwen Zhang; Hongliang Jia; Jingwei Wang; Zulin Zhang; Rupert Hough; Song Cui; Chao Ma; Fuxiang Zhang; Zhaoyang Jia; Fengyang Pan; Dingwen Zhang; Hongliang Jia; Jingwei Wang; Zulin Zhang; Rupert Hough

doi:10.48130/aee-0025-0003

Figures (5) Tables (4)

Figure 1.
Framework diagram of the entire process of heavy metal pollution research and control in reservoirs.
Figure 2.
Schematic diagram of multi-source input of HM pollution in reservoirs.
Figure 3.
Sources, migration processes, and biogeochemical cycles of HM in the reservoir environment.
Figure 4.
Schematic diagram of the full-chain technical architecture for smart water environment management.
Figure 5.
The four HMs remediation methods introduced in this section are as follows: (a) Illustrates biochar modification approaches, including chemical modification and physical modification; (b) represents in situ capping technology; (c) stands for the Floating Phytoremediation System, also known as the Biological Floating Island; (d) denotes the electrochemical remediation method.

Model name	Formula	Parameter annotation	Application scenario
Potential ecological risk index (PERI)	E_ri = T_ri× Cⁱ/$ C_b^{i} $	T_ri: Toxicity coefficient; Cⁱ/$ C_b^{i} $: pollutant concentration/background value	Sediment ecological risk assessment
Comprehensive potential ecological risk index (RI)	RI = ∑$ E_r^{i} $	$ E_r^{i} $: Ecological risk index for single pollutant	Ecological risk assessment of multi-pollutant synergy
Bioaccumulation factor (BAF)	BAF = C_biota / C_water	C_biota: HM concentration in fish/shellfish C_water: Aqueous concentration	Assessment of enrichment effects in aquatic organisms
	C_water	Fish/shellfish C_water: Aqueous concentration	enrichment effects in aquatic organisms
Target hazard quotient (THQ)	$ THQ=\dfrac{EF\,\times \,ED\, \times \,FIR\,\times\, C}{RfD\,\times \,BW\,\times\, AT} $	EF: Exposure frequency (d/year); FIR: Ingestion rate (g/day); RfD: Reference dose (mg/kg·d); ED: Exposure duration (years); BW: Body weight (kg); AT: Averaging time (d)	Health risk assessment of drinking water/aquatic products
Lifetime cancer risk (LCR)	LCR = SF × ADD	SF: Slope factor (mg/kg·d) ADD: Average daily intake (based on water concentration and ingestion), (mg/kg·d)	Long-term risk assessment of carcinogenic HMs

Table 1.

Common risk assessment models and applications in reservoir-HMs research N

Material	Preparation process	HMs	Performance indicators	Features/applications	Ref.
Fe₃O₄-CS	Plant extract	Pb²⁺	Pb²⁺: 98.39%	Cyclic stability: after three cycles, the adsorption capacity retention rates were 95.81%, 70.65%, 50.50%, and 42.75%, respectively	[152]
		Cu²⁺	Cu²⁺: 75.52%
		Cd²⁺	Cd²⁺: 51.54%
		Ni²⁺	Ni²⁺: 45.34
Lignin hybrid NPs	Chemical cross-linking method	Pb²⁺	Pb²⁺: 150.33 mg/g	Reaches equilibrium within 30 s, suitable for actual reservoir water treatment	[153]
Lignin hybrid NPs	Chemical cross-linking method	Cu²⁺	Cu²⁺: 70.69 mg/g		[153]
Fe₃O₄/SiO₂	Rosemary extract	As³⁺	As³⁺: 49 mg/g	Biological-nano synergistic system achieves simultaneous oxidation and removal of As³⁺	[154]
rGO/Ag NPs	Green tea reduction	Pb²⁺	Pb²⁺: 84.2%	In actual AMD treatment, the Pb²⁺ removal rate increased from 46.4% to 63.2% after five cycles (due to the in situ formation of iron oxide)	[155]
nFeS@GS	Geobacter biohybrid	Cu²⁺	Cu²⁺: 87.9%	The recovery rate of heavy metals after sodium citrate desorption is > 90.7%, which is suitable for acidic mine wastewater	[156]
		Pb²⁺	Pb²⁺: 96.2%
		Cd²⁺	Cd²⁺: 95.1%
Fly ash-nZVI/Ni	Waste-derived	Cr⁶⁺	Cr⁶⁺: 48.31 mg/g	The removal rate of Cr⁶⁺, Cu²⁺, etc. in actual industrial wastewater is > 87%	[157]
Fly ash-nZVI/Ni	Waste-derived	Cu²⁺	Cu²⁺: 147.06 mg/g		[157]
MNPs-WSP	Walnut shell coprecipitation	Cd²⁺	Cd²⁺: 1.43 mg/g	Recovery rates of 85%–98%, suitable for various water sources such as tap water and groundwater	[158]

Table 2.

Examples of nanotechnology in remediating HM-contaminated water bodies

Method	Agricultural waste adsorbent	Adsorption capacity/removal efficiency	Ref.
NaOH treatment	Rice straw	Cd²⁺ removal: 61.5%	[167]
NaOH treatment	Rice straw	Zn²⁺ removal: 52.9%	[167]
H₂SO₄	Rice husk	Zn²⁺ maximum adsorption capacities: 19.38 mg/g	[168]
H₂SO₄	Rice husk	Hg²⁺ maximum adsorption capacities: 384.62 mg/g	[168]
Tetraethylenepentamine (TEPA)	Ramie fiber	Cu²⁺ maximum adsorption capacities: 0.587 mmol/g	[169]
Grinding & drying	Walnut shell	Cr⁶⁺ maximum adsorption capacities: 16.73~40.99 mg/g	[170]
NaOH + citric acid	Peanut shell	Cu²⁺ removal: 31%	[171]
NaOH + epichlorohydrin + N, N-dimethylformamide + TETA	Pomelo peel	Cr⁶⁺ maximum adsorption capacities: 193.17 mg/g	[172]
NaOH + TEMPO + NaBr + NaClO	Luffa sponge	Pb²⁺ maximum adsorption capacities: 96.6 mg/g	[173]
NaOH treatment	Watermelon rind	Cu²⁺ removal: 99.53%	[174]
Brine sediment	Sawdust	Zn: 5.59 mg/g	[175]
Brine sediment	Sawdust	Cu 4.33 mg/g	[175]
Boiling in HCl	Coffee grounds	Pb: 61.6 mg/g	[176]
Grinding & drying	Pine cone	Cr⁶⁺ removal: 90.84%	[177]
Grinding & drying	Apple pomace (AP) & beetroot residue (BR)	Max Pb adsorption: 31.7 mg/g (AP), 79.8 mg/g (BR)	[178]
Grinding & drying	Crab shell	Pb removal > 97%	[179]
Grinding & drying	Crab shell	Cd removal > 90%	[179]
TEPA + BCTTC Modification	Metasequoia sawdust (MS)	Pb²⁺ removal: 24.0%	[180]
TEPA + BCTTC Modification	Metasequoia sawdust (MS)	Cd²⁺ removal: 93.2%	[180]
Cyclopropylene chloride cross-linked polyethylene imine (PEI) and coconut shell carbon (CSC)	Sugarcane bagasse, corn cob, peanut shell, coconut shell carbon (CSC)	Complete removal (100%) of Cr⁶⁺, Cu²⁺, Pb²⁺, Cd²⁺ in 10 min	[181]
Polydopamine (PDA) functionalization	Juncus effusus (JE) fiber	Cr⁶⁺ maximum adsorption capacities: 145.8 mg/g	[182]

Table 3.

Comparative performance of agricultural waste-derived adsorbents for HM removal: methods, materials, and efficiency

Species	Remediation site	Remediation effect	Target part	Ref.
Eichhornia crassipes	Textile wastewater, mining wastewater	Textile wastewater: Cr: 94.78%, Zn: 96.88%, Mining wastewater: Fe: 70.5%, Cr: 69.1%	Roots	[185]
Black algae	Nutrient solution	Cu²⁺: 61.4%	Leaves	[186]
Cattail and vetiver	Mensin gold bibiani Limited mining soil	Hg: > 80%, As: > 80%, Cu: > 80%, Zn: > 80%	Roots	[187]
Arundo donax and Phragmites australis	Cartagena-La Unión mining area, Spain	Phragmites australis: Pb: 480 mg/kg	Stems and leaves	[188]
Arundo donax and Phragmites australis	Cartagena-La Unión mining area, Spain	Arundo donax: Zn: 406 mg/kg	Stems and leaves	[188]
Apium nodiflorum	Nestos river, Greece	The maximum daily removal capacity: Cd: 0.208 kg, Cr: 0.45 kg, Cu: 0.368 kg, Pb: 0.113 kg, Mn: 0.425 kg, As: 0.312 kg, Ni: 0.398 kg, Hg: 0.116 kg, Zn: 0.357 kg, Sn: 0.197 kg	Whole plant	[189]
Chlorella vulgaris	Copper mine tailings water, northern Chile	Cu: 64.7%, Mo: 99.9%	Cell surface (adsorption) and intracellular (absorption)	[190]
Pistia stratiotes	Steel mill wastewater	Cd: 82.8%, Cu: 78.6%, Pb: 73%	Roots	[191]
Salvinia natans	Electroplating plant wastewater	Zn: 84.8%, Cu: 73.8%, Ni: 56.8%, Cr: 41.4%	Leaves	[192]
Azolla	Polluted water bodies	Al³⁺: 96%, Fe³⁺: 92%, Au³⁺: 100%	Whole plant	[193]
Lythrum salicaria L	Aquatic systems	pH: 7 and Ni²⁺: 10 mg/L, Roots: 3,737.8 mg/kg, Stems: 697 mg/kg, Leaves: 418.4 mg/kg	Roots, stems and leaves	[194]
Stachys inflata	Bama Pb-zinc mining area	AMF + PGPR + earthworms: Pb availability increased: 25 mg/kg, Zn availability increased: 102 mg/kg	Whole plant	[195]
Lemna gibba	Hayatabad Industrial Estate (HIE) wastewater	Cd: 95%, Cu: 93%, Pb: 82%, Ni: 88%, Cr: 92%	Roots and shoots	[196]
Nymphaea aurora	Hydroponic experiment	pH: 5.5, Cd: 140 mg/g, Cd: 140 mg/g	Shoots and leaves	[197]

Table 4.

Phytoremediation performance of various plant and algal species for HM removal from contaminated aquatic systems