土壤溶液性质对Zn的形态变化及其微生物毒性的影响

摘要

采集了我国具有代表性的12种不同性质土壤,利用基础诱导硝化(SIN)方法测定了不同土壤中锌的微生物毒性阈值,同时利用850离子色谱仪与WHAM6.0模型,测定了溶液不同阴离子组成及自由Zn2+含量,建立了基于不同土壤性质与溶液离子的土壤中Zn毒性预测模型.结果表明,基于SIN测定的不同土壤Zn微生物毒性阈值在不同土壤间有显著差异,其中EC50从196mg/kg至1310mg/kg；EC10值从48mg/kg增加至682mg/kg,不同土壤EC50与EC10的最大值与最小值的比例分别达到了6.68及14.3倍,表明土壤性质对Zn的微生物毒性有非常显著的影响；基于SIN的Zn的毒性阈值ECx(x=10,50)与溶液自由Zn2+浓度的负对数p(Zn2+)间呈正相关关系,表明随着土壤溶液中自由Zn2+值的升高,Zn的毒性逐渐增加.土壤pH值、OC、CEC、F-、Cl-、Ca2+及Mg2+与Zn的毒性阈值ECx(x=10,50)及p(Zn2+)呈正相关关系,其中土壤pH值为最重要的影响因子,偏相关系数均达到极显著水平(P<0.01),其次为OC、CEC及F-,ECx与溶液中NO3-, SO42-呈负相关关系.基于不同主控因子的土壤中Zn毒性阈值(ECx)及P(Zn2+)的预测模型表明,pH值、OC、CEC、F-四个变量因子分别解释了log(EC50)、log(EC10)及p(Zn2+)预测模型变异的89.9%、81.2%和92.3%.%Twelve different samples, representing soils in China, were selected for this experiment on toxicity of Zn to soil microbes as determined by substrated induced nitrification (SIN), meanwhile, the predicted models for Zn toxicity to microbes and free Zn2+in soil solutions were developed based on soil properties and soil solution anions determined by ion chromatograph (850) and WHAM model (6.0). The results showed that the toxicity thresholds of Zn to soil microbes as determined by SIN varied significantly among the soils. The half inhibition of Zn concentration to soil microbes (EC50) ranged from 196 mg/kg to 1310 mg/kg with nearly 6.68-fold variation and the 10%inhibition of Zn concentration to soil microbes (EC10) ranged from 48 mg/kg to 682 mg/kg with a variation of 14.3-fold, indicating the significant influences of soil properties on the toxicity of Zn to microbes. A positive correlation between the toxicity thresholds of Zn (ECx, x=10,50) and the negative logarithm of free Zn2+[p(Zn2+)] in solution were observed, which indicated that the Zn toxicity increased with the concentration of free Zn2+in soil solution. Similarly, the positive correlations between the toxicity thresholds of Zn (ECx, x=10,50) and the pH value, organic carbon (OC), cation exchangeable capacity (CEC) in soils, F-,Cl-,Ca2+and Mg2+etc in soil solution were also observed in this study. The result showed that pH value was the most significant factor with significant partial correlation coefficient (P<0.01), followed by OC、CEC and F-, while negative correlations were observed between the toxicity thresholds of Zn (ECx, x=10,50) and the NO3-, SO42-in solution. The prediction model for Zn toxicity and p(Zn2+) indicated that the pH, OC, CEC and F-could accurately predict Zn toxicity and p(Zn2+) in soil solution with variation coefficients of 89.9%, 81.2% and 92.3% for log(EC50), log(EC10) and p(Zn2+) respectively.