沼渣腐殖质对Cd污染土壤的淋洗效果及性质影响

Effects of biogas residue humus on the leaching efficiency and properties of Cd contaminated soil

针对湖南水稻田土壤Cd污染问题,用沼渣中提取的腐殖质作为土壤淋洗剂,研究沼渣腐殖质溶液对农田土壤中重金属Cd的淋洗效果。通过室内模拟试验,采用振荡淋洗方式研究沼渣腐殖质溶液对不同含量Cd污染土壤中Cd去除效果和土壤性质的影响,并对淋洗过程中的土壤重金属含量进行动力学分析,最后初步探讨沼渣腐殖质溶液淋洗去除土壤中Cd的机理。结果表明:当液土比为4∶1(质量比),淋洗时间为120 min时,沼渣腐殖质溶液淋洗低含量和高含量Cd污染土壤对土壤中Cd去除率分别为57.73%和54.66%。沼渣腐殖质淋洗土壤的过程为非均相扩散过程。淋洗后土壤中可提取态Cd去除效果明显,同时有机质、氮、磷、钾等营养元素含量有所提高,酶活性先下降后上升。与淋洗前土壤上种植的水稻相比,淋洗后2种土壤上水稻种子发芽率以及幼苗株高、鲜质量和干质量都有所提高。沼渣腐殖质溶液淋洗Cd污染土壤可破坏土壤中的O-Cd键。说明沼渣腐殖质在Cd污染农田修复和Cd污染工业场地修复领域具有一定的应用潜力。

Aiming at the problem of Cd pollution in the paddy soil in Hunan province,the effect of biogas residue humus on heavy metal Cd in farmland soil was studied by using humus extracted from biogas residue as soil leaching agent.Through indoor simulation experiments,the effects of biogas residue humus solution on Cd removal effect and soil properties in contaminated soil with different contents of Cd were studied by oscillating washing method,and the kinetics analysis of heavy metals content in soil was performed.Finally,the mechanism of removing Cd in soil by leaching with biogas residue humus solution was preliminarily discussed.The results showed that when the liquid-to-soil ratio was 4∶1 and the washing time was 120 min,the Cd removal rates of low Cd contaminated soil and high Cd contaminated soil by washing with biogas residue humus solution were 57.73% and 54.66%,respectively.The leaching of biogas residue humus solution was a heterogeneous diffusion process.After washing,the extractable Cd in the soil was obviously removed,the contents of nutrients such as organic matter,nitrogen,phosphorus and potassium were improved,and the enzyme activity decreased first and then increased.Compared with rice planted on the soil before leaching,the seed germination rate,plant height,fresh weight and dry weight of rice planted on both soils after leaching were also increased.In addition,leaching Cd contaminated soil with biogas residue humus solution could destroy the O-Cd bonds in the soil.The results of this study proved that biogas residue humus had certain application potential in the field of Cd contaminated farmland and industrial site remediation.