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| Influence of soil solution properties on the transformation of Zn forms and its toxicity threshold to soil microbes as determined by substrated induced nitrification |
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Abstract 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% forlog(EC50), log(EC10) and p(Zn2+) respectively.
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Received: 14 February 2014
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