摘要
为拦截灌溉水Cd,设计实施了水平潜流与表面流两种工艺组合的植物塘人工湿地系统,在水稻生育期净化处理灌溉水,结合田间水稻种植小区试验,于2017年1月至2018年12月逐月采集水样,同时多次采集水稻和土壤样品,监测分析样品Cd含量,探讨人工湿地系统对灌溉水中Cd的净化效率及对米Cd累积的影响。结果表明:连续两年监测,人工湿地系统进水Cd浓度范围为0.034～0.644μg/L,平均浓度为0.232μg/L,经过植物塘人工湿地系统处理后出水Cd浓度范围为0.001～0.189μg/L,平均浓度为0.059μg/L。一级、二级和三级人工湿地系统对灌溉水中Cd的去除率分别为50.21%、14.06%和7.81%,人工湿地系统总去除率达72.06%;与未净化灌溉水相比,经人工湿地系统净化处理后灌溉的水稻糙米Cd含量下降了10.50%～24.51%。研究表明,植物塘人工湿地系统能有效拦截去除灌溉水中的Cd,减少该途径对稻田土壤Cd输入通量,并降低糙米中Cd累积量。本结果可为典型稻田重金属污染灌溉水的净化及湿地植物的选择、减少稻田重金属输入和粮食安全生产提供理论依据和参考。
An ecological interception system consisted of horizontal subsurface flow and surface flow wetland was attempted to examine the effects of removal of cadmium(Cd) from the effluents of the terminal ditches of the system.The system combined with a paddy trial operated during the period of rice growing. The water samples were collected monthly from January 2017 to December 2018, during which the soil and rice samples were collected simultaneously to monitor and analyze the Cd content of those samples, in order to investigate the Cd purification in water and Cd reduction in brown rice. Results showed that the concentration of Cd in the influent water of the system ranged from0.034 μg/L to 0.644 μg/L, with an average concentration of 0.232 μg/L according to our monitoring data during two consecutive years. After treatment with the system, the concentration of Cd in the effluent ranged from 0.001 μg/L to0.189 μg/L, with an average concentration of 0.059 μg/L. The removal rates of Cd in the effluent water treated by the primary, secondary and tertiary systems were 50.21%, 14.06% and 7.81%, respectively. And the total removal rate of Cd by constructed wetland system reached 72.06%. Compared with unpurified irrigation water, Cd concentration of brown rice irrigated with the effluent water from the wetland system decreased by 10.50% to 24.51%. Therefore the ecological interception system plays an effective role in removing Cd concentration from irrigation water, reducing Cd input flux to paddy soil and Cd accumulation in brown rice. The research can provide theoretical basis and reference for purification of irrigation water in typical paddy fields polluted by heavy metals, selection of wetland plants, to reduce heavy metal input in paddy fields and security of food production.
引文
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