土壤外源铬的作物毒性响应及富集差异研究

为了研究土壤外源铬（Cr）对不同作物毒性和有效性的差异，本研究选用生菜、小麦和玉米作为受试植物，分别采用K₂CrO₄溶液和某化工厂Cr污染土壤作为土壤外源Cr污染来源开展了作物根伸长实验和田间试验。结果表明：两种外源Cr处理土壤中，小麦根伸长的EC₁₀和EC₅₀值（10%和50%效应浓度）分别为生菜相应值的2.22~2.35倍和1.45~1.87倍，说明生菜对土壤Cr污染更为敏感。外源添加化工厂Cr污染土壤的处理中EC₁₀值大约为外源添加K₂CrO₄处理土壤中的14~15倍，而对于EC₅₀值该倍数为4~5倍。田间试验中，与对照处理相比，两种外源Cr处理均显著增加了土壤中乙二胺四乙酸提取态Cr（EDTA-Cr）含量。生菜-小麦-玉米轮作过程中，在生菜种植的3个月内，土壤中EDTA-Cr含量下降迅速，不同外源Cr处理中下降了75.2%~89.4%。在小麦和玉米种植期间，EDTA-Cr含量下降速率变慢，到玉米收获后EDTA-Cr含量共下降了89.0%~94.9%，并且外源添加K₂CrO₄处理的土壤中EDTA-Cr含量的下降速率高于添加化工厂Cr污染土壤的处理。三种作物可食用部分Cr含量均低于国家食品安全标准，但生菜对Cr的富集显著大于小麦和玉米的。

Toxicity response and difference in accumulation of exogenous soil chromium in crops

To study the differences in the toxicity and bioavailability of exogenous chromium(Cr) to lettuce, wheat, and corn, a K₂CrO₄ solution and Cr-contaminated soil from a chemical plant were used to conduct root elongation and field experiments. The results showed that in soils treated with the two different sources of Cr, the EC₁₀ and EC₅₀ values of Cr for wheat were 2.22-2.35 times and 1.45-1.87 times those of lettuce, respectively, with root elongation as the evaluation endpoint, indicating that lettuce was more sensitive to soil Cr pollution than wheat. The EC₁₀ values in the treatments spiked with Cr-contaminated soil from the chemical plant approximately 14-15 times those treated with K₂CrO₄ solution, while the multiples were 4-5 for EC₅₀ values. In the field experiments, both sources of Cr treatments significantly increased the ethylene diamine tetraacetic acid extractable Cr(EDTA-Cr) content in the soil compared with the control treatments. During the lettuce-wheat-corn rotation, the EDTA-Cr content in the soil decreased sharply within three months of lettuce growing, with a decrease of 75.2%-89.4% in different treatments. During the subsequent time of planting wheat and corn, the EDTA-Cr content decreased slowly, decreasing by 89.0%-94.9% overall by the time the corn was harvested, and the decrease rates in the soil treated with K₂CrO₄ solution were higher than those treated with Cr-contaminated soil from the chemical plant. The Cr content in the edible parts of the three crops was lower than the permitted limits specified in the National Food Safety Standard, but the accumulation of Cr in lettuce was significantly greater than those in wheat and corn.