城市与区域生态国家重点实验室知识库

       矿产资源的过度开发 和利用 不可避免地 会 引发 很多环境污染问题，重金属污染 目前 已 成为矿区环境污染的主要问题之一。 采矿 过程中会产生 大量 含有重金属的废水、废气 和 矿渣 这些废弃物会迅速 扩散到 矿区周边的 土壤、水体和大气中，通过 食物链、呼吸 和皮肤接触等 途径 被 人体摄入， 对 人体健康产生极大的危害 。因此矿区 重金属污染 治理 和风险管控 工作 势在必行 。
       本研究 以 韶关市翁源县铁龙林场 （镇 为 研究对象 首先 对 研究区 土壤重金属污染特征和污染源进行分析， 然后 对当地环境暴露 特征 和生物暴露水平分别进行探究，并对 研究区 进行健康风险评价，最终通过确定主要污染介质、污染元素和暴露途径，对该地区实施 重金属 风险管控措施。 主要研究结果如下：
       （1 ）通过对比 研究区 农地、林地和绿地三种类型土壤的重金属含量， 发现研究区农田 土壤 污染情况最为严重 ，其中 Cd 污染属于超重度污染， Pb 和 Zn 同样存在一定程度的污染。通过体外模拟 实验 ，发现 Cd 21.24% 和 Pb 37.92%较高的生物可利用性 可能会对人体造成潜在的健康危害。 综合农田土壤空间分布特征和 聚类分析 的分析结果 ，推断 农田 土壤 Pb 污染主要是由水泥厂所引起 ，而采矿活动带来了大部分的 Cd 和 Zn 污染 。通过 PMF 模型分析发现 采矿活动对当地农田重金属 的 富集 影响最大，贡献 值 为 59.3% 。
        （2) 对研究区 6 种不 同类型的作物重金属含量进行检测，发现所有作物重金属含量均未超过 国家 食品安全阈值 可 被人 体安全食用 。研究区灌溉水受到一定程度的污染，而地表水中的悬浮颗粒不断沉积导致底泥重金属含量较高，其中底泥 Cd 平均含量已经超出农用地污染风险管控值。研究区不同采样点和月份之间对重金属的沉降速率并没有显著影响，表明大气重金属沉积主要受当地人为活动影响，其中 大气沉降 中的 Pb 和 Zn 含量较高需要引起重视。
       （3) 人发和尿液可以分别作为研究人体长期和短期重金属暴露的指标。 本研究 随机采集了 铁龙林场 76 名居民的 人发样本和 53 名 居民的尿液样本 对其重金属含量进行检测。 通过 与其他 国家或 地区居民重金属 平均 暴露水平相比， 发现当地居民人发 中的 Pb 含量 和尿液中 的 Cd 含量较高，其中儿童头发 Pb 含量已经超出国家安全阈值，由此判断当地居民（尤其是儿童）的重金属暴露水平较高 。
       （4) 根据人体日均重金属暴露量 计算公式，确定土壤对研究区 居民 Pb 的积累影响最大，而食物 为居民 Cd 积累的主要构成。 另外 本文 引用 人体健康风险评价模型 ，发现研究区儿童 Pb 的潜在非致癌性健康风险最高，非致癌风险指数大于 1 ；另外研究区居民 暴露于 Cd 的 致癌风险指数大于最大安全值 10 4 。食物的摄入对居民 （尤其是 儿童 非致癌和致癌风险影响最大 因此 应当着重 采取风险控制措施降低儿童 对 重金属 的摄入 量 。
       （5) 基于 前期的调查与分析，确定研究区主要污染介质为农田土壤，主要污染元素为 Cd 。通过 对 农田土壤重金属输入通量 的 计算 发现 污水灌溉 为 农田Cd 的主要贡献因素 。因此 在进行风险 管控措施时 首先要 关闭污染源（矿区、水泥厂）和清洁水渠 来 切断重金属 污染 来源 。研究区农田 重金属浓度 空间差异较大，为确保农田土壤的可持续利用与农产品的生态安全， 应当分区 分级 制定不同的农田安全利用技术。本研究在重度污染区开展种桑养蚕替代种植技术，中轻度污染区主要采用钝化修复 低吸收品种作物种植技术 。 目前 研究区重金属 风险管控工作已经取得了较好的环境效益和经济效益 。

       The excessive exploitation and utilization of mineral resources inevitably bring many problems of environmental pollution, and heavy metal contamination has become one of the main problems of environmental pollution in mining areas. A large amount of waste water, gas and slag containing heavy metals are produced during the mining,
these wastes will quickly spread to the soil, water and atmosphere around the mining area, and will be ingested by the human body through food chain, respiration and skin contact , which will pose great harm to human health. Therefore, this is a n urgent need for the risk management and control on heavy metal contamination in mining areas.
       In this study, the Tielong town of Wengyuan county, Shaoguan city was collected as the research object. This paper analyze d the characteristics and the source of heavy metal contamination, and explore d the exposure level of the local environment and creature, assess ed the health risk on the Tielong town. Finally, the risk management
measures were implemented by identifying the main contaminated environmental med ia, contaminated elements and the exposure pathway. The main results of the research were as follows:
         (1) The pollution level of agricultural soils was the most severely by comparing the heavy metal concentrations among the agricultural soils, woodland soi ls and grass land soils in the study area. T he results showed that t he level of Cd pollution belong s to the super severe pollution, Pb and Zn also exis t certain degree pollution in the agricultural soils. The agricultural soils in the study area exist ed relative high Cd and Pb bioaccessible concentrations according to the in vitro method, which lead to the high potential health risk. Combined with the results of the characteristic of the spatial distribution and cluster analysis, we can infer that the Pb contamination is highly related with the cement plant, the Cd and Zn are mainly derived from mining activities. Mining activities has the greatest influence on the enrichment of the total heavy metals in agricultural soils with the proportion of 59.3% by PMF model.
       (2) Six different species of crops were collected in the field. The heavy metal contents of crops were all under the national fo od safety limits, which suggest that all the crops can be consumed safely. The continuous deposits of suspended part i culates from surface water lead to the relative ly high contents of heavy metals in the sediment,
the average Cd concentration in the sediments has exceeded the risk control value of agricultural soils. The interaction of sampling locations and months had no significant effect deposition rates, suggesting that heavy metal deposition was mainly governed by local anthropogenic activities.
        (3) Human hair and urine are suitable indicators for the long term and short term exposure of heavy metal,respectively. 7 6 hair samples and 53 urine samples were selected from the local residents at random and tested for the heavy metal concentrations By combining with the average exp osure level of heavy metal in residents of other un exposure countries or regions, t he leve ls of hair Pb and urinary Cd contents in local inhabitants were relatively high. The mean concentration of Pb in local children w as higher than the national safety threshold value, indicating that local residents (especially for children) exposure level is relatively high.
        (4)According to the calculation of the average daily dose of heavy metals via various exposure pathways, the soil had the greatest influence on the accumulation of Pb in the human body, and food constituted the main component of Cd accumulation. In addition, t he model of human health risk asse ss ment model was cited in the study,the results showed P b presents the highest potential non carcinogenic health risk to local children, with a HI value greater than 1; and the cancer risk of C d in local inhabitants was higher than the maximum safe value 10 4 . Risk control sho uld be taken to red uce the food ingestion exposure level of local residents (especially for children )),which was the dom inated contribution to the non cancer and cancer eff ect.
        (5)Based on the results of former investigation and analyses the mainly contaminated environmental media was agricultural soils, and Cd was identified as the most contamin at ed element. By calculating the input and output fluxes of heavy metals in agricultural soils in the study area, the sewage irrigation was the main contribution factor of soil Cd. Therefore, the source of pollution should be controlled by shutting down the mine area or cement plant, and clean ing the water channel before the resto ration work , to prevent the agricultural soil being re contaminated. Th e significant spatial variation means that different safe utilization techniques are needed in the study area, to ensure the sustainable utilization of agricultural soils and the ecolog ical safety of agricultural products. The heavy metal in soil can be effectively uptaken by planting mulberry and prevented from entering the human body by breeding silkworms in the severely polluted area , and heavy metal contents in crops are effectively reduced in moderate/mild polluted area by the selection of different remediation technology and low absorbing crop varieties. Now , the restoration of agricultural soil has achieved good environmental and econo mic benefits.