土壤Mehlich-3可浸提态镍对大麦根伸长的毒性

本研究选择我国具有代表性的11种外源添加镍（水溶性镍盐）污染土壤样品，在模拟田间人工降水（淋洗和非淋洗）处理后，研究了Mehlich-3单次或连续3次浸提态镍对大麦根伸长的毒性.结果发现：结合重要影响因素土壤pH值，Mehlich-3可浸提态镍和外源添加镍具有显著相关关系；基于Mehlich-3可浸提态镍的植物毒性阈值也显著受土壤性质影响（半抑制浓度可相差38倍以上）.通过回归分析发现土壤性质对Mehlich-3浸提镍的生物毒性的影响与Mehlich-3浸提次数有关，主要影响因子分别是铁铝锰氧化物和粘粒含量（单次浸提）或土壤pH值和有机质（3次浸提）.研究建立了基于可浸提态镍对大麦根伸长的毒性阈值预测模型.研究结果证明了重金属的化学浸提态代替全量作为风险评价标准的可行性，为提高土壤中镍的生态风险评估的准确性和科学性提供支撑.

Toxicity thresholds based on Mehlich-3 extractable nickel to barley root elongation

After water-soluble nickel salt (NiCl₂) was spiked to 11representative Chinese soil samples, the spiked soil samples were incubated and treated with or without artificial rainwater leaching in order to simulate field conditions. The toxicity of these soil samples to barley root elongation was studied by a bioassay method, and the extractability of the added Ni in the soils was evaluated using single or sequential three Mehlich-3extractions. The results showed that the extractability of Ni added to soil was affected by soil pH, and Mehlich-3extractable Ni is as a function of total added Ni in soils and soil pH significantly. The phytotoxicity thresholds based on Mehlich-3extractable Ni were significantly affected by soil properties. In other words, the effective concentration causing 50% inhibition based on Mehlich-3extractable Ni varied with ≥ 38-fold difference among soils. Regression analysis indicated that the soil citrate dithionate extractable Fe, Al and Mn, and clay content in soils were the most important factors to affect the phytotoxicity based on single Mehlich-3extractable Ni, and that soil pH and organic content were the most important factors to affect the phytotoxicity based on sequential three Mehlich-3extractable Ni. The influence of soil properties on the phytotoxicity based on Mehlich-3extractable Ni was associated with the number of extraction times. Finally, the predictive models for phytotoxicity thresholds based on Mehlich-3extractable Ni to barley root elongation were developed. The results indicated that the extractable Ni in soil can be used as criteria in order to improve the accuracy and scientificity of Ni ecological risk assessment in soil.