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新疆干旱区某金矿厂周边重金属污染特征与风险评价
Alternative TitlePollution Characteristics and Risk Assessment of Heavy Metals Around a Gold Mine in Arid Area of Xinjiang, China
杨伟光
Subtype硕士
Thesis Advisor陈卫平
2019-06
Degree Grantor中国科学院生态环境研究中心
Place of Conferral北京
Degree Name工程硕士
Degree Discipline生物工程
Keyword金矿厂,土壤,植物,重金属污染,风险评价 gold Mine, Soils, Plant, Heavy Metal Pollution, Risk Assessment
Abstract

        我国西部干旱地区生态系统结构单一,稳定性低,是典型的生态脆弱区。频繁的矿业活动对生态脆弱区的生态系统功能和结构带来较大的环境负荷,造成土壤、植物和水体的重金属污染,受到社会各界的广泛关注。矿山开采是带动西部经济的重要一环,针对矿区开展土壤、植物和水体重金属污染调查及生态风险评估是实现环境保护和资源可持续开发的关键,并为当地政府部门开展综合治理规划提供科学依据。
        本研究以新疆某金矿厂周边的土壤、水体和植物为研究对象,应用ArcGIS分析土壤重金属全量和有效态含量的空间分布特征,并研究其纵向迁移规律;应用UNMIX 模型、因子分析并结合实地调查分析土壤重金属污染来源;基于土壤重金属生物有效性,结合重金属全量进行污染风险评价,以土壤-水体-植物系统为基础,构建矿区生态系统评价体系以及人体健康风险评价体系,为我国矿区综合风险评价、风险管控和污染治理提供科学支持。主要研究结果如下:
        (1)研究区土壤Mn、Ni、Co、Cu 和As 全量和有效态含量空间分布格局类似,而土壤Zn、Cd、Pb 全量和有效态含量空间分布格局不同。土壤重金属有效态含量在受矿区影响较弱的北部,有效态含量和全量在纵向迁移类似,而在金矿厂以东,及以南地区出现分布不一致的趋势,这主要是重金属在不同方位活性差异所致。此外根据UNMIX 模型源解析结合因子分析以及实地调查结果,发现As、Cu、Ni 和Co 主要来源尾砂库和收砷房,其贡献率分别为44.1%、47.6%、43.3%和46.6%;Mn 元素主要来源于成土母质,其贡献率为46.6%;而Pb、Zn和Cd 来源于矿山开采和其他活动,贡献率分别为47.1%、40.7%和34.6%。
        (2)土壤为主要污染介质,研究区域土壤Co、Cr、Ni、Cd、Zn 和Pb 在个别样点存在超标现象,但是总体上累积水平较低。土壤Cu 和As 累积特征显著,为主要污染物。土壤Cu 的最大值和平均值分别达到1809 和108 mg/kg,分别为背景值14 倍和4 倍;土壤As 的最大值和平均值分别为1730 mg/kg 和206 mg/kg,为背景值的43 倍和16 倍。然而潜在生态风险和风险编码法(RAC)评价结果显示研究区绝大部分样点As 和Cu 污染风险较低,多介质迁移风险较小,高风险区域主要集中在厂区的西南和东南部分区域。健康风险评价结果显示研究区土壤Cu 的非致癌风险非常低,As 致癌风险仅部分区域较高,两者均在国家规定的范围内,健康风险整体处于可控水平。此外,土壤pH、Eh 和重金属有效态是影响矿区重金属潜在生态风险的3 个重要因素。因此,在进行土壤重金属污染评价时不仅要关注全量,还应关注重金属的有效态含量。
        (3)研究区内地表水和地下水重金属含量均在国家安全标准以内。牧草As含量略高于新疆其他地区牧草As 含量,Cu 含量与新疆其他地区牧草Cu 含量较为一致,重金属富集系数(PUF)均小于1。研究区土壤-水体-植物生态系统健康状态整体良好,矿区生态系统健康指数H 为0.375,属于健康状态,受重金属As 和Cu 的胁迫影响较小。
        (4)根据土壤重金属全量和有效态含量空间分布和纵向迁移特征、以及污染风险评价结果和矿区生态系统健康评估结果,建议对新疆某金矿厂周边土壤重金属污染采取的风险管控措施为管控源头和切断重金属迁移扩散途径,修复严重污染点位土壤和建立污染点位风险预警机制。

Other Abstract

        The arid regions in western China have single ecological structures with low stability, and are typical ecologically fragile areas. Frequent mining activities have brought about large environmental loads on the ecosystem functions and structures of the local ecologically fragile areas, which result in heavy metal pollution of soils,plants and water bodies, receiving extensive attention from all walks of life. Mining is the indispensable part of economy in western China. The investigation of soil, plant and water pollution and ecological risk assessment are the key to realize environmental protections and sustainable developments of resources, and can also provide a scientific basis for local government to carry out comprehensive management and planning.
        The objective of this research was the soil, water body and plants around a gold mine in Xinjiang. The spatial distribution characteristics of total and available part of heavy metals in soils were analyzed by ArcGIS. At the same time, the vertical migration characteristics of total and available part of heavy metals in soils were
studied. The UNMIX model sources identification, factor analysis method and field investigation were used to analyze the sources of heavy metal pollution in soils. The bioavailability combined with the total risk assessment of heavy metals, constructed a regional ecosystem evaluation system and a human health risk assessment system based on the soil-water-plant system, which could provide scientific support for comprehensive risk assessment, risk management and pollution control in mining areas in China. The main findings were as follows:
        (1) The spatial distribution patterns of total and available concentrations of Mn, Ni, Co, Cu and As were similar, while were different for Zn, Cd and Pb in the soil of study area. The available concentrations of soil heavy metals were low in the northern part of the gold mine. The total and available concentrations were similarly in the
longitudinal migration, but there was a tendency of inconsistent distribution in the east and south of the gold mine mainly because of the distinctive activity of heavy metals in different orientations. In addition, according to the UNMIX model sources identification, factor analysis and investigation results, it was found that the sources of
As, Cu, Ni and Co were the tailing dump and arsenic collection chamber, which contribute for 44.1%, 47.6%, 43.3% and 46.6% of total contamination for each metals.Mn element was mainly derived from the parent material and contribution rate was 46.6%, while Pb, Zn and Cd were derived from from mining and other sources, and the contribution rate were 47.1%, 40.7% and 34.6% for each metals.
        (2) Soil is the main pollutant medium. The soils of Co, Cr, Ni, Cd, Zn and Pb in the study area were over-standard in a few samples, but the overall accumulation level was low. The soil Cu and As concentrations were high and the accumulation characteristics were significant. The maximum and average concentrations of Cu reached 1809 mg/kg and 108 mg/kg, which were 14 and 4 times of the background concentrations. The maximum and average concentrations of As were 1730 mg/kg and 206 mg/kg, which were 43 and 16 times the background in soils. However, the results of potential ecological risk assessment and risk assessment coding showed that most of the samples in the study area had low As and Cu pollution risks, and the risk of multi-media migration was small. The high-risk areas were mainly concentrated in the southwest and southeast parts of the field. The results of health risk assessment showed that the non-carcinogenic risk of soil Cu was very low, but the carcinogenic risk of soil As had a relatively high carcinogenic risk in some part of area. The non-carcinogenic and carcinogenic risks of Cu and As were also within the range prescribed by the state, and the overall health risk was at a controllable level. In addition, soil pH, Eh and heavy metal availability are three important factors affecting the potential ecological risk of heavy metals in mining areas. Therefore, in the evaluation of soil heavy metal pollution, not only the full amount should be paid attention, but also the available concentration of heavy metals should be paid attention.
        (3) The concentrations of heavy metals in surface water and groundwater were all satisfied national safety standards in the study area. The concentration of As in pasture was slightly higher than that in other parts of Xinjiang. The concentration of Cu in pasture was consistent with that in other areas of Xinjiang, and the plant uptake factor (PUF) was less than 1. The soil-water-plant ecosystem in the study area was in good condition overall. The regional ecosystem health index H was 0.375, which belongs to a healthy state and was little affected by the stress of heavy metals As and Cu.
        (4) According to the spatial distribution and vertical migration characteristics of heavy metal’s total and available concentration, and pollution risk assessment, regional ecosystem quality assessment, the risk management and control measures for soil heavy metal pollution around a gold mine in Xinjiang were taken as the source
control and cut off heavy metals. The migration and diffusion path would be used to repair the serious points of pollution and establish an early warning mechanism for pollution points.

Pages111
Language中文
Document Type学位论文
Identifierhttp://ir.rcees.ac.cn/handle/311016/42362
Collection土壤环境科学实验室
Recommended Citation
GB/T 7714
杨伟光. 新疆干旱区某金矿厂周边重金属污染特征与风险评价[D]. 北京. 中国科学院生态环境研究中心,2019.
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