科研之友
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摘要
There is still no consensus over the specific effects of metal-based nanoparticles when compared with the conventional metal salts. Here, the accumulation and toxicity of ZnO-NPs and ZnCl2 in Enchytraeus crypticus over time (1-14 d) were investigated using a sand-solution exposure medium and applying a toxicokinetics and toxicodynamics approach. For both Zn forms, body Zn concentration in the organisms was dependent on both the exposure concentration and exposure time, with equilibrium being reached after 7-14 days of exposure. Generally, the uptake and elimination rate constants (K-u and K-e1) were smaller for ZnO-NPs (5.74-12.6 mg kg(-1)d(-1) and 0.17-0.39 d(-1)) than for ZnCl2 (8.32-40.1 mg kg(-1)d(-1) and 0.31-2.05 d(-1)), suggesting that ionic Zn was more accessible for E. crypticus than nanoparticulate Zn. Based on external exposure concentrations, LC50s for ZnO-NPs and ZnCl2 decreased with time from 123 to 67 Zn mg L-1 and from 86 to 62 Zn mg L-1, reaching an almost similar ultimate value within 14d. LC50s based on body Zn concentrations were almost constant over time (except for 1 d) for both ZnO-NPs and ZnCl2, with overall LC50(body) of Zn being 1720 and 1306 mg kg(-1) dry body weight, respectively, Body Zn concentration, which considers all available pathways, was a good predictor of dynamic toxicity of ZnCl2, but not for ZnO-NPs. This may be attributed to the specific internal distribution and detoxification mechanisms of ZnO-NPs. The particles from ZnO-NPs dominated the accumulation (>75%) and toxicity (similar to 100%). Our results suggest that dynamic aspects should be taken into account when assessing and comparing NPs and metals uptake and consequent patterns of toxicity.
