RESUMO
Ten field soils with various properties were added with Pb at 8 levels, and treated with or without leaching using simulated rain to test the Pb toxicity threshold (EC10, EC50) according to the ISO 11269-1 root elongation toxicity testing method. The leaching factors of Pb toxicity to barley root elongation were determined and the predicted models of Pb toxicity thresholds in soils with various properties were developed. The results indicated that the determined toxicity threshold (EC10, EC50) of Pb varied significantly (P<0.01) among the soils, and the EC10 and EC50 of Pb to barley in the soils ranged from 300-4130 mg . kg-1 and 55-633 mg . kg-1, respectively. The Pb toxicity decreased sharply after leaching treatment. The determined leaching factors (LF) ranged from 0.96-1.96 (LFEC50) and 1.03-1.81 (LFEC10) respectively, and the obvious effect was observed for the Pb toxicity decreasing in the soils with pH<6.81. The predicted models for Pb toxicity thresholds in soils were developed based on main soil properties (soil pH, organic carbon content and cation exchange capacity), and the determined Pb toxicity thresholds (ECx, x = 10,50) in soils fell in the range of mean values with ± 2 standard error (SD) prediction interval for the leached and unleached soils except for the red soil of Jiangxi Province, which indicated that the models based on the main soil properties could well predict the Pb toxicity in soils with various soil properties.
