镉砷在线蚓中的毒物-毒效动力学过程及定量模拟

The dynamic accumulation and toxicity processes of a heavy metal(Cd)and metalloid(As)in terrestrial organisms were ex- plored. In this study, laboratory experiments and a modeling approach were both applied to quantitatively describe the toxicokinetic and tox- icodynamic processes of Cd and As in the soil organism Enchytraeus crypticus. The results showed that the accumulation of Cd and As in E. crypticus increased with increasing exposure concentration and time, and equilibrium was reached after a certain exposure period. The max- imum body concentrations of Cd and As during the exposure period were 459.60 mg·kg^-1 and 32.91 mg·kg^-1, respectively. The estimated overall uptake rate constant (Ku)of Cd(1.761 mg·kg^-1·d^-1)was greater than that of As(0.102 mg·kg^-1·d^-1), while the elimination rate con- stant (Ke)of Cd(0.015 d^-1)was smaller than that of As(0.287 d^-1). Based on the external exposure concentrations, the median lethal con- centration(LC50)for Cd and As decreased over time and reached equilibrium after 7 d of exposure, and the ultimate LC50(LC50∞)of Cd (0.314 mmol·L^-1)was smaller than that of As(1.253 mmol·L^-1). When based on the body concentrations, the LC50inter was calculated, with an almost constant LC50inter of As, while the LC50inter of Cd increased over time. The overall LC50interCd (468.80 mg·kg^-1·d^-1)was significantly higher than LC50interAs (26.65 mg·kg^-1·d^-1). Overall, the accumulation and toxicity of Cd and As were both time-dependent. The accumula- tion capacity of Cd in E. crypticus was greater than that of As. The toxicity of Cd was higher than that of As when based on the external con- centration, while the accumulated As in the organism showed a stronger toxic effect. There was a good correlation between the dynamic tox- icity and the body concentration of As(R² = 0.75), but not for Cd(R² = 0.57), thereby suggesting that the accumulated Cd inside the organ- ism cannot well represent the bioavailable fraction that causes toxicity. This study emphasizes the importance of considering the exposure time and bioavailability of metals for risk assessments in the future.