典型微塑料对水库缓流区消落带土壤Cu形态的影响及其与DOM的关联

Effect of typical microplastics on soil copper speciation and its association with DOM in water-level-fluctuation zone of slow-flowing area of the reservoir

铜(Cu)是三峡水库蓄水后消落带土壤中的典型重金属,揭示其迁移转化过程对三峡水库水环境保护具有重要意义.为探究微塑料(Microplastics,MPs)对三峡水库缓流区消落带土壤Cu迁移转化过程的影响,本试验以水动力条件弱为背景进行室内水位变化淹水实验,分析了高密度聚乙烯(HDPE)和聚对苯二甲酸乙二醇酯(PET)两种典型MPs对三峡水库缓流区消落带土壤Cu形态的影响,同时结合紫外-可见吸收光谱分析了MPs影响下土壤溶解性有机质(Dissolved Organic Matter,DOM)与土壤Cu形态的关系.结果表明,两种MPs的添加均能导致土壤中残渣态和铁锰氧化物结合态Cu含量的降低及有机结合态Cu含量的增加,且分别能同时增加和降低土壤中可交换态和碳酸盐结合态Cu含量,最终表现为土壤中Cu总量降低.相关性分析结果显示,MPs存在情况下,土壤DOM特性如DOC含量、CDOM浓度(α(355))、芳香性(SUVA_(254))、疏水性(SUVA_(260))、分子量(E2/E3)及来源组分(E2/E4、E3/E4)与土壤Cu形态及总量均具显著相关关系.结果为阐明在MPs和水库水位变化共同作用下三峡水库消落带Cu的环境行为提供了科学基础.

Copper(Cu)is one of the dominating heavy metals in the soil of the water-level-fluctuation zone following the impoundment of the Three Gorges Reservoir.Deciphering its migration and transformation process is of great significance to the protection of the water environment of the Three Gorges Reservoir.To explore the effect of microplastics(MPs)on the migration and transformation process of Cu in the soil of the water-levelfluctuation zone of the slow-flowing area of the Three Gorges Reservoir,an indoor incubation with water-level change flooding experiment was conducted under the background of weak hydrodynamic conditions.The effects of two types of typical MPs,high density polyethylene(HDPE)and polyethylene terephthalate(PET),on speciation of Cu in the soil of the water-level-fluctuation zone of slow-flowing area of the Three Gorges Reservoir were analyzed,and the relationship between dissolved organic matter(DOM)and forms of Cu in the soil under the influence of MPs was analyzed combined with UV-Vis absorption spectrum.The results showed that each of the two kinds of MPs could lead to the decrease of the content of residual and Fe-Mn oxide-bound Cu,while result in the increase of the organic-bound Cu in soil.HDPE could increase the content of exchangeable and carbonate-bound Cu in soil.The content of the two forms in soil could be reduced under the treatment of PET.The changes of the above five forms of Cu ultimately led to the reduction of the total content of Cu in soil.Correlation analysis results showed that the characteristics of DOM,such as DOC content,CDOM concentration(α(355)),aromaticity(SUVA_(254)),hydrophobicity(SUVA_(260)),molecular weight(E2/E3),source and components(E2/E4,E3/E4)were significantly correlated with forms and total content of Cu in soil with the presence of MPs.The results provide a scientific basis for understanding the environmental behavior of Cu in water-level-fluctuation zone of the Three Gorges reservoir under the combined action of microplastics and water-level change.