污灌区玉米地土壤重金属铜化学形态时空变化及风险评价

Temporal and Spatial Variation and Risk Assessment of Soil Copper with Plantation of Maize in a Sewage Irrigation Area

【目的】研究调查土壤中Cu的不同化学形态时空变化,为重金属污染农田的环境及土壤的修复提供科学依据。【方法】以山西省晋中市某污灌区作为研究对象,利用Tessier连续提取法,2016—2019年春季,对不同耕作层(0~20、20~40、40~60 cm),不同小区土壤中重金属Cu各化学形态以及研究区种植玉米籽粒中的Cu含量进行了分析及其风险评价。【结果】该区域污染土壤中全量Cu含量超过国家土壤环境质量标准(GB 15618-2018)。在0~20 cm土层中,随时间推移Cu元素除铁锰氧化物结合态无明显变化外,其余各形态呈下降趋势;在20~40 cm土层中,碳酸盐结合态随时间呈下降趋势,残渣态无明显变化,可交换态、铁锰氧化物结合态、有机结合态呈上升趋势;在40~60 cm土层中,除有机结合态和残渣态无明显变化,其余形态呈上升趋势。根据次生相与原生相分布比值法(RSP)风险评价,污灌区土壤中重金属Cu对土壤环境构成重度环境污染。【结论】玉米种植对该污灌区污染土壤Cu的污染风险有明显降低作用,污染土壤得到一定程度的修复。

【Objective】The purpose of this paper is to investigate the temporal and spatial changes of different chemical forms of copper in soils,and to provide scientific basis for the environmental and soil remediation of heavy metal contaminated farmland.【Method】Chemical speciation and risk assessment of heavy metal Cu in soils of different tillage layers(0~20 cm,20~40 cm,40~60 cm)and different areas were studied for four consecutive years from autumn of 2016 to spring of 2019 with plantation of Maize in a sewage irrigation district in Jinzhong City of Shanxi Province.Tessier continuous extraction method was used for analysis of Cu chemical speciation.【Result】The content of Cu in soil exceeded the National Environment Quality Standard for Soil(GB 15618—2018).From the autumn of 2016 to the spring of 2019,in the 0~20 cm soil layer,except for non-obvious changes in Fe-Mn oxides-bound fraction of Cu,the other forms showed a decreasing trend.In the soil layer of 20~40 cm,the Carbonate-bound fraction decreased with time,the residual fraction did not change significantly,while the exchangeable fraction,Fe-Mn oxides-bound fraction and the Organic-bound fraction increased.In the soil layer of40~60 cm,except for the organic-bound fraction and residual fraction,the other forms showed an increasing trend.Environmental risk was assessed with secondary and primary facies distribution ratio method(RSP),and the results showed that heavy metal Cu in soil in the sewage irrigation areas constitutes a heavy environmental pollution level to the soil environment.【Conclusion】Continuous maize plantation obviously reduced the environmental risk caused by Cu pollution in this sewage irrigation area,and contributed to remediation of contaminated soil to a certain extent.