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    不同耕作类型下土壤-农作物系统中汞、砷含量与生态健康风险评价

    Hg and As contents of soil-crop system in different tillage types and ecological health risk assessment

    • 摘要: 针对废弃矿山遗留生态环境问题,选择贵州丹寨废弃金汞矿为研究区,基于野外系统样品采集,通过原子荧光法和电感耦合等离子体质谱法分析了区内土壤和农作物中的汞(Hg)、砷(As)浓度,采用单指标污染标准指数法、单因子污染指数法、潜在生态危害指数法和目标危险系数法评价了区内Hg、As污染程度及生态健康风险。结果显示:旱地土壤Hg、As平均浓度均超农用地土壤重金属风险筛选值,超标率分别为75.47%和67.92%;土壤Hg污染严重,总体呈极重污染级别,土壤As则以中—极重污染级别为主;玉米地上部分(以下简称玉米)Hg、As超标率分别为36.36%和4.55%,玉米Hg处于轻污染水平,玉米As总体未受污染。相比于旱地-玉米系统,水田土壤Hg的超标率和污染程度均更高,超标率高达89.19%,呈极重污染级别,而水田土壤As超标率仅为22.22%,As污染水平低于旱地土壤;水稻地上部分(以下简称水稻)Hg、As平均浓度均略超食品安全标准,超标率分别为54.55%和18.18%,水稻Hg、As污染均高于玉米,污染等级处于轻-中污染水平。生态健康风险评价表明,土壤Hg以极强生态风险为主、As以轻微生态风险为主;虽然土壤富集Hg,但其向农作物籽实的迁移量小,因此食用玉米和大米对人体健康尚不构成Hg非致癌风险。然而,水稻As富集导致食用大米对人群产生明显的As非致癌和致癌健康风险。该研究对保障矿区居民生活健康具有重要意义,研究结果可为矿区生态环境影响评估及生态恢复提供科学依据。

       

      Abstract: Aiming at the problems of ecological environment left behind by abandoned mines, the abandoned gold-mercury mine in Danzhai, Guizhou Province was selected as the research area. Based on the field systematic sampling, the concentrations of mercury (Hg) and arsenic (As) in the soils and crops were analyzed by atomic fluorescence spectrometry and inductively coupled plasma mass spectrometry. The heavy metal pollution level and ecological health risk of soils and crops were evaluated by single factor standard index, single factor index method, potential ecological hazard index and target hazard quotient. The results show that the average concentrations of Hg and As in dryland soil exceed the screening value of heavy metals in agricultural soils, with the exceeding rates of 75.47% and 67.92% respectively. Dryland soil Hg is seriously polluted, showing extremely heavy pollution level, while soil As is mainly medium to extremely heavy pollution. The exceeding rates of Hg and As in aboveground parts of corn (hereinafter referred to as corn) are 36.36% and 4.55% respectively. Corn Hg is slightly polluted, and corn As is not polluted in general. Compared with the dryland-corn system, the Hg over-standard rate and pollution degree of paddy soil are higher, with the exceeding rate of 89.19%, showing an extreme pollution level. However, the over-standard rate of As in paddy soil is only 22.22%, and the As pollution level is lower than that of dryland soil. The average Hg and As concentrations of aboveground rice (hereinafter referred to as rice) are slightly higher than the food safety standards, and the exceeding rates are 54.55% and 18.18% respectively. The Hg and As pollution levels of rice keep higher than those of corn, and the pollution levels is in the light to medium range. The potential ecological hazard index shows that Hg ecological risk in soils is mainly extremely strong, and As ecological risk is mainly slight. It is difficult for Hg to migrate to crop seeds, so there is no obvious non-carcinogenic risks by eating corn and rice. However, the accumulation of As in rice can result in significant non-carcinogenic and carcinogenic health risks. This study is of great significance to ensure the health of mining residents, and the results can provide scientific basis for the ecological environment impact assessment and ecological restoration in mining areas.

       

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