Toxicokinetics may help assessing the risk of metal-contaminated soils by quantifying the development of internal metal concentrations in organisms over time. This study assessed the toxicokinetics in Enchytraeus crypticus of non-essential (Pb and Cd) and essential elements (Zn and Cu) in metal-contaminated field soils from a mining area, containing 3.49–24.3 mg Cd/kg dry soil, 433–1416 mg Pb/kg dry soil, 15.7–44.9 mg Cu/kg dry soil and 1718–6050 mg Zn/kg dry soil. Three different uptake-elimination patterns in E. crypticus were found. Both essential elements (Zn and Cu) showed fast increasing internal concentrations reaching equilibrium within 2 d in the uptake phase, without hardly any elimination after transfer to clean soil. The non-essential Cd showed a slow linear accumulation and excretion with body concentrations not reaching steady state within 21 d. Internal Pb concentrations, however, reached equilibrium within 7 d in the uptake phase. Longer exposure times in ecotoxicological tests, therefore, are required for elements like Cd. Porewater pH and dissolved organic carbon (DOC) levels were the dominant factors controlling Cd uptake from the test soils. The 21-d body Cd and Pb concentrations were best explained from 0.01 M CaCl2-extractable soil concentrations. Steady-state Cu and Zn body concentrations were independent of soil exposure concentrations. Bioaccumulation factors (BAF) were low for Pb (<0.1 kgsoil/kgworm), but high for Cd at 1.78–24.3 kgsoil/kgworm, suggesting a potential risk of Cd biomagnification in the terrestrial food chain of the mining area ecosystem.
Bibliographical noteFunding Information:
This study was supported by the China Postdoctoral Science Foundation (No. 2019TQ0325 ), Guangdong Basic and Applied Basic Research Foundation (No. 2019A1515110496 ), Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou) (No. GML2019ZD0408 ), R&D program of Guangdong Provincial Department of Science and Technology (No. 2018B030324003 ) and R&D program of Bureau of Science and Information Technology of Guangzhou Municipality (No. 201903010022 ).
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- Bioaccumulation kinetics
- Elimination kinetics
- Essential and non-essential metals
- Mining soils