土壤中水溶性铜对西红柿的毒害影响因素及预测模型

该文选取17种具有代表性的中国土壤,研究了土壤孔隙水以及0.01mol/LCaCl2浸提态Cu对西红柿生长的毒害,结果发现对于土壤孔隙水中Cu对西红柿生物量10%抑制的毒性阈值(EC10)和50%抑制的毒性阈值(EC50),在17个非淋洗土壤中变化范围分别为0.06～1.47和0.17～3.42mg/L,淋洗土壤变化范围分别为0.05～2.24和0.13～4.37mg/L,最大值与最小值相差为23～41倍;0.01mol/LCaCl2提取态Cu的EC10和EC50,在非淋洗土壤变化范围分别为0.18～2.64和0.57～6.14mg/kg,淋洗土壤变化范围分别为0.18～1.28和0.61～7.11mg/kg,相差从6.9～14.4倍,表明土壤溶液性质影响水溶性Cu对西红柿的毒性阈值。同时,发现土壤孔隙水中Ca2+、溶解性有机碳是影响孔隙水中Cu对西红柿生长毒性的主要因子。当进一步考虑土壤溶液的重要因子(溶解性有机碳、土壤溶液pH值、电导率、全硫含量、Ca2+、Mg2+、K+、Na+),发现基于水溶性Cu的毒性阈值和土壤溶液性质的多元回归系数变化范围为0.75～0.99,说明利用土壤溶液性质能较好的预测土壤中水溶性Cu对西红柿的毒性阈值。该研究可为土壤水溶性Cu的风险评估提供参考。

Influence of soil solution properties and predicting model on soil soluble copper toxicity to tomato shoot

Abstract: Metal bioavailability and toxicity is not only determined by its speciation and contents, but also by the soil water chemistry. In the present study, bioassays of tomato shoot were performed in 17 Chinese soils to evaluate the phytotoxicity of soluble copper (Cu) toxicity based on soil pore water and 0.01 M CaCl2 extraction. The selected soils, which represented the major soil types and properties in China, were spiked with soluble Cu chloride. Sub-samples of the spiked soil were leached by artificial rainwater to simulate the field conditions and the toxicity was compared with that in unleached soils. When considering the toxicity thresholds for Cu in soil pore water, it was found that the effective concentrations that caused 10% root growth inhibition (EC10) and 50% inhibition (EC50) varied widely from 0.06 to 1.47 mg/L and from 0.17 to 3.42 mg/L in 17 unleached soils and from 0.05 to 2.24 mg/L, from 0.13 to 4.37 mg/L in leached soils, representing 23 to 41.1 folds differences. Similarly, the toxicity thresholds for Cu extracted by 0.01 M CaCl2 showed that the EC10 and EC50 values for unleached or leached soils also varied considerably from 0.18 to 2.64 mg/L and from 0.57 to 6.14 mg/L in unleached soils and from 0.18 to 1.28 mg/L, from 0.61 to 7.11 mg/L in leached soils, representing 6.9 to 14.4 fold differences. However, leaching did not significantly decrease soluble Cu toxicity thresholds in most soils. These results indicated that the toxicity thresholds of soluble Cu variations were influenced by soil solution properties in a wide range of soils. Meanwhile, the relationships were developed between soil solution properties and phytotoxicity threshold values for copper in a wide range of soils. The multiple regression results showed that Ca2+ and dissolved organic carbon (DOC) were the two most important factors affecting the extent of Cu toxicity in soil pore water on tomato shoot in leached and unleached soils, respectively, and meanwhile they were positively related to the toxicity thresholds. Single Ca2+ was found to explain 64% and 31% of the variance in soluble Cu toxicity threshold EC10 and EC50, respectively, in pore water across unleached soils. For leached soils, single DOC was found to explain 48% and 56% of the variance of EC10 and EC50. Soil solution pH was not the most important factor controlling the soluble Cu toxicity, while it could improve the prediction of the model to some extent, with the toxicity thresholds in pore water increasing as pH increased. When incorporating these parameters (DOC, pH, electrical conductivity (EC), S, Ca2+, Mg2+, K+ and Na+) into the regression models, together with corresponding toxicity thresholds for soluble Cu, the coefficient of determination (r2) for EC10 or EC50 ranged from 0.75 to 0.99 in leached and unleached soil. This implied that the soluble Cu toxicity on tomato shoot could be better estimated by soil pore water chemistry. These quantitative relationships between soluble Cu toxicity and soil solution properties can contribute to the development of a soluble Cu toxicity risk assessment of the terrestrial environment in China.