改性污泥对矿区铜、镉污染土壤的修复

城市污泥的重金属含量超标是限制其资源化利用的主要瓶颈,论文采用石灰＋硫粉＋生物淋滤的方法去除重金属,制备改性污泥,探讨其对矿区Cu、Cd污染农田土壤的修复效果,以期实现以废治污的目标。供试水稻土采自江西某矿区附近农田,土壤Cu和Cd的TCLP（Toxicity characteristic leaching procedure）浸出量分别为40.34 mg·kg-1和660.1μg·kg-1,其中Cu的质量分数超过国际标准值15 mg·kg-1。通过室内土培的方法,将改性污泥分别按土重的0%、1%、3%、5%和10%施入供试土壤培养30 d后,分析土壤Cu和Cd的活性、形态变化以及土壤蛋白酶和脲酶活性等指标评价改性污泥对污染土壤的修复效果及作用机理。结果表明,改性污泥对土壤Cu产生显著的钝化作用,且各施用量对Cu的有效态含量表现出显著差异。当改性污泥的用量为土重的5%时,Cu的有效态含量降至12.03 mg·kg-1,低于国际标准。改性污泥对土壤Cd的钝化效果相对较弱。当改性污泥的用量为1%时,土壤Cd的活性反而有所增加。当改性污泥的用量为5%时,Cd的活性显著降低,土壤Cd的浸出量降至539.6μg·kg-1。土壤重金属形态分析的结果表明,土壤Cu主要以碳酸盐结合态、有机结合态和残渣态存在。改性污泥用量增加,可交换态Cu含量下降,当改良剂用量为土重的5%时,可交换态Cu由8.10%降至4.10%。相反,有机结合态Cu含量由26.45%增加至32.34%。土壤的可交换态Cd含量由36.80%降至30.69%。说明施用改性污泥,土壤可交换态Cu、Cd向有机结合态发生转化。土壤蛋白酶和脲酶的活性变化能较好地指示修复效果,且土壤脲酶的指示效果优于蛋白酶。

Remediation of copper and cadmium contamination in farmland surrounding mining area with modified sludge

modified sludge, produced by bioleaching method mixed with elemental sulfur and lime was evaluated for remediation of copper and cadmium contaminated soils affected by a copper mine. The test paddy soils were sampled from the farmland surrounding mining area in Jiangxi province. TCLP （Toxicity characteristic leaching procedure） leaching contents of Cu and Cd in soil were 40.34 mg·kg-1 and 660.1μg·kg-1 respectively, of which the Cu concentration was higher than the international standard value of 15 mg·kg-1. The sludge was applied to soil at four rates （1%, 3%, 5% and 10% of soil weight） and compared with no sludge treatment. After 30 days of soil incubation in lab, bioavailability and fraction change of Cu and Cd as well as protease and urease activities of the test soil were analyzed to evaluate the remediation effect and its mechanism. The results showed that modified sludge could deactivate soil Cu significantly, and the more the sludge was applied, the greater deactivation effect could be observed. When the sludge was applied at the rate of 5%of the soil weight, TCLP leaching content of soil Cu decreased to 12.03 mg·kg-1, which was lower than the standard limitation. Modified sludge could also deactivate soil Cd, but the deactivation effect was less marked than soil Cu. When the sludge was applied at the rate of 1%, leaching content of soil Cd increased conversely compared with control. However, when the rate was 5%, leaching content of soil Cd decreased to 539.6μg·kg-1. Results of sequential extraction procedure showed that the main fractions of Cu were carbonate-bound, organic-bound and residual Cu. When the sludge application rate was 5%, the percentage of exchangeable Cu decreased from 8.10% to 4.10 %, while the percentage of organic-bound Cu increased from 26.45% to 32.34%. Meanwhile, the percentage of exchangeable Cd reduced from 36.80% to 30.69%. So the transformation of Cu and Cd fractions caused by the modified sludge was mainly between exchangeable concentration and organic-bound conc