电感耦合等离子体质谱法研究云南某矿区周边不同样品中砷污染水平和风险评价

砷(As)污染不仅会影响土壤肥力和作物生长，而且还会通过空气、土壤、水和食物等途径暴露于人类，对人体健康产生重大威胁。矿产开采是As环境问题产生的重要来源之一。本文选择云南省某开采历史悠久的铅锌矿区周边9个村落(S₁—S₉)为研究区域，以20 km外的县城(S₁₀)为对照区域，采集了76份土壤、306份农作物和86份人发，利用微波消解对样品进行前处理，通过控制酸用量、温度和持续时间三个变量得到不同样品的最佳消解方案，并采用电感耦合等离子体质谱法(ICP-MS)测定各样品中As含量，以探究多介质中As污染水平并对人体暴露和健康风险进行评估，对当地矿产资源开采引起的As污染提出防治或改善建议。结果表明：(1) 经微波消解前处理后获得的土壤、农作物和人发样的As检出限为0.01~0.12 μg·L-1，回收率分别为92.43%~112.23%，97.88%~114.72%和91.44%~109.65%，相对偏差小于5%，结果令人满意。(2) 土壤中As的平均含量为70.66 mg·kg-1，是云南土壤背景值3.84倍。参照GB 15618—1995《土壤环境质量标准》二级标准和单因子污染指数结果，农田土壤受As污染为中度污染；在S₁采样点As含量最高，这可能与矿区多年开采、冶炼和运输密切相关。农作物样品中，块茎类蔬菜的As平均含量为1.75 mg·kg-1，其次叶菜类为0.77 mg·kg-1，玉米和根茎类蔬菜分别为0.52和0.51 mg·kg-1。参照我国《食品中污染物限量》标准，研究区域的农作物样品中As含量超标率为80.64%。(3) 采用风险评价指数(HI)、总致癌风险(TCR)、目标危害商数(THQ)和致癌风险(CR)对研究区域As通过多暴露途径对暴露人群产生的致癌风险和非致癌风险进行评价和分析。结果表明，土壤和农作物中As对成人和儿童的非致癌风险总和分别为1.13~1.20，为不可接受风险，而致癌风险均在10-3水平，大于美国环保局(USEPA)推荐的最高接受水平10-4 ，研究区居民有较大的致癌风险。饮食摄入是As主要暴露途径，研究区人群食用蔬菜的致癌风险均超过10-4，且儿童的总致癌风险高于成人。鉴于矿区周边蔬菜受As污染的高风险，我们建议当地居民可以通过外地食物的输入来规避当地As污染带来的健康风险，也可以考虑在污染的耕地上种植食用部位不易积累As的农作物来替代原有作物以减小As污染带来的危害。(4) 矿区人发中As含量均显著高于县城(S_{20 km}, p<0.05)。其中矿区居民头发As平均含量 (0.97 μg·g-1) 是县城发As含量 (0.22 μg·g-1)的4.41倍，超出卫生部推荐发As标准值(0.6 μg·g-1)。矿区男性发样As含量高于女性，随着年龄增长，矿区人发样中As含量水平呈现第二年龄组(Group Ⅱ, 19～40岁)高于第三年龄组(Group Ⅲ, ≥41岁)的趋势。这是因为处于19～40岁的男性是采矿冶炼等活动的主要参与者，是As的易感人群，具有较高的As暴露风险。(5) 本文为矿区多介质的As污染研究和居民人体健康风险暴露和评估提供有力的依据。

Level and Risk Assessment of Arsenic in Muti-Media near Mining Area in Yunnan by Using Inductively Coupled Plasma Mass Spectrometry

Arsenic (As) pollution not only affects soil fertility and crops growth, but also exposes to humans through air, soil, water and food, posing a major threat to human health. Mineral exploitation is one of the most important sources of As environmental problems. In this study, the nine villages (S₁—S₉) in the vicinity of a Pb-Zn mining area in Yunnan province were chosen as study area, and the county town 20 km away from mining was selected as reference area (S₁₀). The samples including 76 cultivated soils, 306 crop/vegetables and 86 human hairs were collected. Microwave digestion was used to pretreat these samples by controlling the three variables of acid dosage, temperature and duration to get the optimal solution of muti-media. The Inductively Coupled Plasma Mass Spectrometry (ICP-MS) were used to determine the contents of As in order to investigate the As pollution level and human health risk in muti-media. The results will provide a reference for policy decision on the prevention and treatment of As pollution caused by mining. Results showed that: (1) after these samples were pretreated by microwave digestion, As detection limits for soil, crops and human hair ranged from 0.01 to 0.12 μg·L-1, and accepted recoveries ranges were 92.43%～112.23% (soil), 97.88%～114.72% (crop/vegetable) and 91.44%～109.65% (hair), respectively, and relative standard deviation was less than 5% with satisfactory results. (2) The mean content of As in soil was 70.66 mg·kg-1, which was 3.84 times higher than that of the background value in Yunnan province. According to GB 15618—1995 of “soil environmental quality standard” (Grade Ⅱ) and the single-factor pollution index (P_i), cultivated soil was severely polluted by As. Furthermore, the highest As content was detected in S₁, which might be closely related to the mining, smelting and transportation for many years. In crop/vegetables samples, the mean As content of tuber-vegetables was 1.75 mg·kg-1, followed by leafy-vegetables (0.77 mg·kg-1), which was higher than the maize (0.52 mg·kg-1) and root-vegetables (0.51 mg·kg-1). Based on the maximum permissible standard set by China, the excessive rate of As content in crops was 80.64%. (3) The potential health risk assessments of As exposed to multiple pathways among local residents were evaluated by the hazard index (HI), the total carcinogenic risk (TCR), the target hazard quotient (THQ) and carcinogenic risk (CR), respectively. The total non-carcinogenic risk of As for adult and child were 1.13～1.20, which was unacceptable risk. The carcinogenic risk was as high as 10-3, exceeding the general risk acceptable level (10-4) recommended by the United States Environmental Protection Agency (USEPA). Besides, diet was the dominant exposure pathway. The THQs (>1) and CRs (>10-4) of As in vegetables showed that a potential risk did exist, and the TCR of As for child was higher than that for adult. In view of high As risk of vegetables grown in local area, so we suggested that the nonlocal foods were input to avoid health risks of As pollution and those crops whose edible parts are not easy to accumulate As should be largely planted. (4) The contents of As in hair samples in mining area were 0.97 μg·g-1, which was 4.41 times higher than that in S_{20 km} (0.22 μg·g-1) (p<0.05) and beyond the recommended standard of the Ministry of Health (0.6 μg·g-1). The contents of As from male were higher than that from female, and the Group Ⅱ (19～40 years) were higher than Group Ⅲ (≥41 years). It meant that the males in 19～40 years who acted as the major participant in mining and smelting activities were more vulnerable to exposure to As than others. (5) This study provided a powerful basis for the As pollution level in muti-media of the mining area, but also for the assessment of As exposure risk to local human health.