含砷地下水浇灌对菜田土壤和蔬菜砷的含量、赋存形态及其健康风险的影响

Impact of Geogenic Arsenic-Contaminated Groundwater Irrigation on Arsenic Accumulation and Speciation in Agricultural Soil-Vegetable Systems and Associated Health Risk in South China

  • 摘要:
    目的 含砷(As)地下水浇灌的农田土壤在全球广泛存在,本研究旨在探讨含砷地下水灌溉对农田土壤中砷含量、形态、生物可给性的影响,并评估蔬菜中砷的累积效应,相关结果可为保障农产品安全和降低人群健康风险提供数据支撑。
    方法 自含砷地下水灌溉农田分两批次采集土壤和蔬菜样品,分析土壤中砷铁含量与逐步提取的砷形态组分,运用二乙烯三胺五乙酸(DTPA)提取法评估土壤中砷的植物有效态含量,采用体外胃肠道法(IVG)测定生物可给性组分,借助美国环境保护署(EPA)健康风险模型,评估直接摄入、吸入和皮肤接触三种途径对当地人群可能造成的非致癌风险和致癌风险。
    结果 研究区域内,农田土壤中砷含量空间分布较为均匀,平均浓度为26.0 ± 2.2 mg kg−1,显著高于当地背景值,但仍低于农用地土壤砷污染风险筛选值。韭菜和油菜中砷含量均低于国家食品安全标准。相较于土壤中总砷含量,DTPA提取态砷含量占比低于0.46%,IVG生物可给性组分占比低于8%。土壤中生物有效态或生物可给态砷含量较低,主要归因于砷以铁氧化物吸附态和残渣态存在,水溶态砷和专性吸附态砷总和低于10%。基于生物可给性校正的健康风险评估结果表明,土壤颗粒直接摄入是造成健康风险的主要途径。通过摄入、接触和吸入三种途径产生的非致癌风险指数HI < 1,致癌因子CR < 0.0001,当地人群面临的非致癌风险和致癌风险水平均可忽略不计。
    结论 该含砷地下水浇灌区域土壤和蔬菜等农产品中砷含量低于农用地土壤的砷污染风险筛选值和食品安全国家标准,土壤中砷的生物可给性较低,不会对当地人群健康造成潜在风险,整体处于安全可控范围。本研究结果可为受污染地下水浇灌农田的农业可持续生产以及农产品安全评价提供科学依据。

     

    Abstract:
    Objective Groundwater containing arsenic (As) is widely used for irrigation worldwide, yet there is limited research on how arsenic in groundwater affects the total concentration, speciation, and bioavailability of arsenic in irrigated soils, as well as its accumulation in vegetables. Such studies are crucial for ensuring agricultural safety and assessing human health risks.
    Method Two batches of soil and vegetable samples were collected from farmland irrigated using geogenic arsenic-contaminated groundwater. Arsenic and iron concentrations were analyzed and plant-available arsenic was assessed with DTPA method. Bioavailable arsenic was determined via the IVG method. Health risks were evaluated using the EPA model for three routes: direct ingestion, inhalation, and dermal contact;
    Result The average arsenic concentration in soil was 26.0 ± 2.2 mg kg−1, higher than the local background value but below the agricultural soil risk threshold. The arsenic concentrations in leeks and rapeseed were within the national food safety limits. DTPA-extractable arsenic accounted for less than 0.46% and IVG-based bioavailability was below 8%. The lower bioavailability is attributed to the stronger adsorption by minerals such as iron oxides in the soils identified by sequential extraction. The bioavailability-based health risk assessment indicated that direct soil ingestion is the primary exposure route, with a non-carcinogenic risk index (HI) <1 and carcinogenic risk (CR) < 0.0001, suggesting negligible health risk from arsenic exposure;
    Conclusion The arsenic levels in vegetables from the study area are safe for consumption. The arsenic bioavailability in the irrigated soil poses a negligible health risk to local populations. The findings support the safe use of groundwater for agricultural irrigation and provide a basis for the sustainable management of arsenic contaminated soil.

     

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