毒物学资料的缺乏成为制约我国污染土壤中Cr生态风险评价及土壤环境质量标准修订的主要瓶颈。本研究选取了我国7种不同性质土壤,分别以蚯蚓生物量、小白菜生物量和微生物基质诱导呼吸(SIR)为毒性测试终点,基于Log-logistic剂量-效应关系及低剂量刺激效应函数模型对不同土壤中铬的毒性阈值(EC_x)进行了测定,在此基础上,对不同性质土壤中Cr的毒性阈值进行了预测。研究结果表明:不同性质土壤中Cr对蚯蚓、小白菜、土壤微生物毒性均随着土壤Cr含量的增加而表现出明显抑制效应,剂量-效应关系呈现明显的S型曲线;不同性质土壤中,基于微生物(SIR)、蚯蚓、小白菜毒性测试的EC₁₀分别为22.1~53.7、65.0~137.2和82.1~220.2 mg/kg,EC₅₀分别为50.3~103.7、103.9~369.0和159.9~441.9 mg/kg;不同物种Cr毒性阈值由大到小顺序为小白菜>蚯蚓>土壤微生物,土壤微生物对Cr毒性最为敏感;在土壤Cr低含量(<112 mg/kg)条件下,3种测试物种对Cr毒性表现出明显的低剂量刺激效应,其中,蚯蚓在不同性质土壤中最大刺激效应为102%~108%,小白菜为105%~112%,相对来说,土壤中Cr对微生物的低剂量刺激效应较小,最大刺激效应为104%;pH、黏土含量和土壤阳离子交换量(CEC)可以较好预测不同性质土壤中Cr的毒性阈值。研究结果对土壤中Cr的生态风险评价及土壤中Cr环境质量标准制、修订提供了科学依据。

The lack of toxicology data is the main factor hindering the ecological risk assessment of Cr contamination in soils and the revision of soil environmental quality standards in China. In this study, we conduct toxicology tests on seven soil types (with different soil properties) in China, using earthworm biomass, cabbage biomass, and microbial matrix induced respiration (SIR) as measurement endpoints. We determined the effective concentration (EC_x) values under different soil types based on the Log-logistic dose-effect relationship and low-dose stimulus effect function model. On this basis we developed predictive models for estimating toxicity thresholds of Cr under different soil properties. Chromium toxicity in earthworms, Chinese cabbage, and soil microorganisms under different soil types showed significant inhibitory effect with increased soil Cr concentrations, and the dose-response (D-R) relationship was clearly sigmoid in shape. Under different soil types, the EC₁₀ values for soil microorganisms (SIR), earthworms, and Chinese cabbage ranged between 22.1-53.7, 65.0-137.2, and 82.1-220.2 mg/kg, respectively, and the EC₅₀ values between 50.3-103.7, 103.9-369.0, and 159.9-441.9 mg/kg, respectively. The Cr toxicity thresholds for the tested species, from high to low, followed the order of Chinese cabbage>earthworms>soil microorganisms, with soil microorganisms being the most sensitive to Cr toxicity. Under low Cr concentrations (<112 mg/kg), the tested species showed significant hormesis effects, among which earthworms had a maximum hormesis between 102%-108% under different soil types, and Chinese cabbage between 105%-112%, while soil microorganisms showed relatively small effect at 104%. Chromium toxicity thresholds under different soil types can be well predicted based on soil pH and clay/CEC contents. The research results provide a scientific basis for the ecological risk assessment of Cr in soils and for the formulation and revision of environmental quality standards for Cr in soils.