College of Resource and Environmental Engineering, Wuhan University of Science and Technology, Wuhan, 430081, China; Hubei Key Laboratory for Efficient Utilization and Agglomeration of Metallurgic Mineral Resources, Wuhan University of Science and Technology, Wuhan, 430081, China.
College of Resource and Environmental Engineering, Wuhan University of Science and Technology, Wuhan, 430081, China.
Ecotoxicol Environ Saf. 2020 Dec 15;206:110949. doi: 10.1016/j.ecoenv.2020.110949. Epub 2020 Aug 31.
A better comprehensive understanding of the influence of soil/solution properties on cadmium (Cd) phytotoxicity is essential for soil Cd ecological risk assessment. The toxicity of soil spiked Cd to Ligustrum japonicum 'Howardii' seedling growth was conducted by the greenhouse pot experiments using 13 typical forest soils selected from mainland of China. The results showed that the ranges of Cd toxicity thresholds of 10% seedling growth inhibition (EC) and 50% inhibition (EC) followed the order: soil pore water Cd (EC on average 0.88 mg L with the variation of 54.9 folds and EC on average 2.28 mg L with variation of 41.8 folds), DTPA extractable Cd (EC on average 5.4 mg kg with 20.9 folds variation and EC on average 17.86 mg kg with 6.6 folds variation), total added Cd (EC on average 6.55 mg kg with 16.7 folds variation and EC on average 22.11 mg kg with 5.1 folds variation), which suggested that whatever the available Cd expressed, its toxicity is largely affected by soil properties. The empirical multiple equations were well developed between different fractions of Cd toxicity thresholds ECx (x = 10 or 50) and soil/solution. The results also showed that the pH inversely correlated with EC (r = 0.54, P < 0.01) and EC (r = 0.63, P < 0.001) based on soil pore water, indicating the ECx decreased with more toxicity as pH increased. No single significant soil solution properties were found for ECx in DTPA extractable Cd. For the ECx of DTPA extractable and total Cd, the content of aluminum oxides in soil and soil pH were the two significant factors inversely related with ECx, which explained 68%-79% of the inter-soil variation, respectively. Overall, soil or solution pH was the most important factor controlling Cd toxicity thresholds. Meanwhile, significant negative correlations existed between the soil solution pH and the slopes of parameter (b) of the dose-response curves for different fractions of Cd, implying that the growth of toxic effect enhanced as unit Cd dosage increased in low pH soils. These results will be helpful to evaluate the metal ecological risk in forest soils.
更好地综合理解土壤/溶液性质对镉（Cd）植物毒性的影响，对于土壤 Cd 生态风险评估至关重要。通过温室盆栽实验，用从中国大陆选择的 13 种典型森林土壤对 Ligustrum japonicum 'Howardii' 幼苗生长进行了土壤添加 Cd 的毒性研究。结果表明，10%幼苗生长抑制（EC）和 50%抑制（EC）的 Cd 毒性阈值范围依次为：土壤孔隙水 Cd（EC 平均 0.88mg/L，变化范围为 54.9 倍，EC 平均 2.28mg/L，变化范围为 41.8 倍）、DTPA 可提取 Cd（EC 平均 5.4mg/kg，变化范围为 20.9 倍，EC 平均 17.86mg/kg，变化范围为 6.6 倍）、总添加 Cd（EC 平均 6.55mg/kg，变化范围为 16.7 倍，EC 平均 22.11mg/kg，变化范围为 5.1 倍），这表明无论以何种方式表示可利用的 Cd，其毒性在很大程度上都受到土壤性质的影响。不同 Cd 毒性阈值 ECx（x=10 或 50）与土壤/溶液之间建立了良好的经验多方程。结果还表明，基于土壤孔隙水，pH 值与 EC（r=0.54，P<0.01）和 EC（r=0.63，P<0.001）呈负相关，表明随着 pH 值的升高，ECx 降低，毒性增加。在 DTPA 可提取 Cd 中，没有发现单一显著的土壤溶液性质与 ECx 相关。对于 DTPA 可提取 Cd 和总 Cd 的 ECx，土壤中氧化铝含量和土壤 pH 是两个与 ECx 呈负相关的重要因素，分别解释了土壤间变异的 68%-79%。总体而言，土壤或溶液 pH 是控制 Cd 毒性阈值的最重要因素。同时，土壤溶液 pH 值与不同 Cd 分数剂量反应曲线参数（b）斜率之间存在显著负相关，这表明在低 pH 值土壤中，随着单位 Cd 剂量的增加，毒性效应的增强。这些结果将有助于评估森林土壤中的金属生态风险。
