模拟酸雨对钝化剂修复镉污染土壤效果研究

采用土柱试验和盆栽试验方法,研究模拟酸雨淋溶和水淋溶1a期间,海泡石、生物炭和有机肥对四川(SC)和湖南(HN)镉(Cd)污染农田土壤稳定效果及小白菜富集Cd的影响.结果表明:与水淋溶相比,酸雨淋溶降低SC和HN土壤淋出液pH值,增加淋出液电导率(EC)、可溶性有机碳(DOC)和Cd含量,其中SC和HN土壤淋出液Cd含量增加幅度分别为48.85%~77.16%和50.92%~73.44%;而且酸雨淋溶降低两种土壤有机碳(SOC)含量,增加土壤Cd有效态含量(CaCl₂-Cd)和溶出量(TCLP-Cd),促进土壤Cd由残渣态向酸溶态转化,SC和HN土壤残渣态Cd含量平均降低3.61%和2.81%.无论是水淋溶还是酸雨淋溶,海泡石和生物炭均能显著降低两种土壤CaCl₂-Cd和TCLP-Cd含量(P<0.05),但有机肥仅对HN土壤Cd的固定效果显著.与水淋溶相比,酸雨淋溶后抑制小白菜的生长,促进小白菜对Cd的富集.添加海泡石和生物炭后两种土壤的小白菜产量显著增加(P<0.05),且小白菜可食部位Cd含量平均降低58.85%和43.08%.酸雨淋溶后SC土壤加海泡石和生物炭处理,小白菜可食部位Cd含量均满足国家安全食用标准(GB2762-2017) (Cd≤0.2mg/kg),HN土壤仅海泡石处理的小白菜可食部位Cd含量满足国家安全食用标准.本研究表明酸雨淋溶影响钝化剂对Cd的固定效果,进行污染土壤原位修复时要关注酸雨的影响,根据污染土壤性质选择合适的钝化剂.

Effects of passivating agents on Cd immobilization under simulated acid rain condition

To address the effects of sepiolite, biochar and organic fertilizer on Cd immobilization in soil and Cd accumulation in Chinese cabbage (Brassica chinensis L.), both column and pot experiments were conducted onto two Cd contaminated farmland soils (SC and HN) under both pure water and simulated acid rain leaching for one year. The results indicated that simulated acid rain led to the decrease in pH and increase in electrical conductivity (EC), dissolved organic carbon (DOC) and Cd concentration in leaching solution, compared to water leaching. The Cd contents in acid leaching solution of SC and HN soil increased by 48.85%~77.16% and 50.92%~73.44%, respectively. Moreover, simulated acid rain reduced soil organic carbon (SOC) in both soils, increased the fractions of soil CaCl₂-Cd and TCLP-Cd, and promoted the transformation of Cd from residue to acid-soluble in both soils. The mean concentrations of residue Cd in SC and HN soils decreased by 3.61% and 2.81%, respectively. Regardless of water leaching or acid rain leaching, significant decrease on the fractions of CaCl₂-Cd and TCLP-Cd were observed on both tested soils by applying sepiolite and biochar (P<0.05), while only significant decrease on the available Cd fraction was obtained by applying the organic fertilizer on HN soil. Compared to water leaching, simulated acid rain inhibited the growth of Chinese cabbage and enhanced the accumulation of Cd in it. Compared to the control treatment (P<0.05), the yields of Chinese cabbage in SC and HN soils increased significantly with the treatments of sepiolite and biochar. The mean Cd concentrations in edible parts of Chinese cabbage grew in SC and HN soils decreased by 58.85% and 43.08%, respectively. The contents of Cd in edible parts of Chinese cabbage treated with sepiolite and biochar in SC soil met the Food Quality Standard of China (GB2762-2017) (Cd≤0.2mg/kg), and Cd content met the safety food standard with the application of sepiolite in HN soil. This study demonstrated that acid rain leaching can reduce the immobilization effect of passivating agent on Cd. The influence of acid rain should be considered into in situ remediation of Cd contaminated soil, and suitable passivating agent should be selected according to the properties of contaminated soil.