Ecological toxicity (ECx) of Pb and its prediction models in Chinese soils with different physiochemical properties.

The lack of toxicological data becomes the main bottleneck of ecological risk assessment of lead (Pb) in Chinese soils. The present study assessed Pb toxicity on three underground test endpoints (barley root elongation, earthworm avoidance response, and substrate-induced respiration (SIR) of microorganism) in 10 different soils. Hormetic dose-response induced by Pb was >118 % for earthworm avoidance response. EC10 and EC50 (the effective concentrations of Pb that inhibit 10 % or 50 % of endpoint bioactivity and also represents the toxicity threshold of Pb) after leaching increased by 0.32-8.73 times, and 1.02-3.75 times, respectively. Leaching factor (LF) prediction models indicated pH and cation exchange capacity (CEC) were the vital predictors for LF10 and LF50, explaining 60.6 % and 73.1 % of variations, respectively. SIR was one sensitive test endpoint for Pb toxicity, with the lowest of EC10 and EC50 values (from 373.7 to 1008.5 mg·kg-1, and from 837.1 to 2869.0 mg·kg-1, respectively). The best prediction models between ECx and soil properties is LogEC50 = 1.324Log(pH) + 0.423Log(CEC) + 1.742 (R2 = 0.761, p < 0.01). The results displayed significant implications for deriving ECx of Pb, and provided a scientific basis for soil ecological risk assessment of Pb.