Lead toxicity thresholds in 17 Chinese soils based on substrate-induced nitrification assay.
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 >2515mg/kg soil for leached soil and 130 to >2490mg/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 pH 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.
Agro-Environmental Protection Institute, Ministry of Agriculture, Tianjin 300191, China; Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
Ji
J
Li
Agro-Environmental Protection Institute, Ministry of Agriculture, Tianjin 300191, China. Electronic address: hyz@rcees.ac.cn.
Yizong
Y
Huang
Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
Ying
Y
Hu
Shangrao Normal University, Shangrao 334000, China.
Shulan
S
Jin
Agro-Environmental Protection Institute, Ministry of Agriculture, Tianjin 300191, China.
Qiongli
Q
Bao
Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
Fei
F
Wang
Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
Meng
M
Xiang
Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
Huiting
H
Xie
D001681:Biological Assay; D002681:China; D004784:Environmental Monitoring / Q000379:methods* / Q000592:standards; D007854:Lead / Q000032:analysis* / Q000592:standards; D058465:Nitrification; D012987:Soil / Q000737:chemistry*; D012989:Soil Pollutants / Q000032:analysis* / Q000592:standards
D012987:Soil; D012989:Soil Pollutants; D007854:Lead
Leaching; Nitrification assay; Pb toxicity; Risk assessment