Lead toxicity thresholds in 17 Chinese soils based on substrate-induced nitrification assay
Author(s): Ji Li, Yizong Huang, Ying Hu, Shulan Jin, Qiongli Bao, Fei Wang, Meng Xiang, Huiting Xie, Agro-Environmental Protection Institute, Ministry of Agriculture, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Shangrao Normal University
Pages: 131-140
Year: 2016 Issue: 6
Journal: Journal of Environmental Sciences
Keyword: Pb toxicity; Leaching; Nitrification assay; Risk assessment;
Abstract: The influence of soil properties on toxicity threshold values for Pb toward soil microbial processes is poorly recognized. The impact of leaching on the Pb threshold has not been assessed systematically. Lead toxicity was screened in 17 Chinese soils using a substrate-induced nitrification(SIN) assay under both leached and unleached conditions.The effective concentration of added Pb causing 50% inhibition(EC50) ranged from 185 to> 2515 mg/kg soil for leached soil and 130 to > 2490 mg/kg soil for unleached soil. These results represented > 13- and > 19-fold variations among leached and unleached soils,respectively. Leaching significantly reduced Pb toxicity for 70% of both alkaline and acidic soils tested, with an average leaching factor of 3.0. Soil p H and CEC were the two most useful predictors of Pb toxicity in soils, explaining over 90% of variance in the unleached EC50 value. The relationships established in the present study predicted Pb toxicity within a factor of two of measured values. These relationships between Pb toxicity and soil properties could be used to establish site-specific guidance on Pb toxicity thresholds.
Pages: 131-140
Year: 2016 Issue: 6
Journal: Journal of Environmental Sciences
Keyword: Pb toxicity; Leaching; Nitrification assay; Risk assessment;
Abstract: The influence of soil properties on toxicity threshold values for Pb toward soil microbial processes is poorly recognized. The impact of leaching on the Pb threshold has not been assessed systematically. Lead toxicity was screened in 17 Chinese soils using a substrate-induced nitrification(SIN) assay under both leached and unleached conditions.The effective concentration of added Pb causing 50% inhibition(EC50) ranged from 185 to> 2515 mg/kg soil for leached soil and 130 to > 2490 mg/kg soil for unleached soil. These results represented > 13- and > 19-fold variations among leached and unleached soils,respectively. Leaching significantly reduced Pb toxicity for 70% of both alkaline and acidic soils tested, with an average leaching factor of 3.0. Soil p H and CEC were the two most useful predictors of Pb toxicity in soils, explaining over 90% of variance in the unleached EC50 value. The relationships established in the present study predicted Pb toxicity within a factor of two of measured values. These relationships between Pb toxicity and soil properties could be used to establish site-specific guidance on Pb toxicity thresholds.
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