【作者】 仇广乐；

【导师】 冯新斌；

【作者基本信息】 中国科学院研究生院（地球化学研究所） ， 地球化学， 2005， 博士

【摘要】 汞是有毒、人体非必需元素。近年来,随着全球环境的不断恶化以及人们对汞的毒性的深入认识,世界上不同国家和地区的大型汞矿山陆续停产、闭坑。汞矿山闭坑后,一方面,矿区内的大量炉渣、矿山废水以及废气,会依然持续不断地向周围环境中排放大量的汞元素;另一方面,不同价态的无机汞在进入环境后,自然条件下通过微生物活动或光化学作用,会转化为毒性更强的甲基汞,并通过各种途径进入食物链,构成对人类的危害。因此,废弃汞矿山环境中的汞污染问题以及汞的甲基化问题,已经越来越受到人们的关注和重视。 贵州省位于全球环太平洋汞矿化带中,境内分布着大量的汞矿床,是我国最重要的汞工业基地。贵州省汞资源丰富,汞金属储量88000t,占全国总储量近80%。境内汞矿开采、冶炼历史悠久,大规模的汞矿山活动长达630年。目前,贵州省境内的汞矿山,例如:万山、务川、丹寨、铜仁、滥木厂和开阳等,大规模的生产活动均已经停止。为了深入了解这些汞矿山闭坑后的矿区环境汞污染以及汞的甲基化特征,论文以贵州典型汞矿山,万山汞矿和滥木厂汞矿为例,系统阐述了矿区内炉渣、土壤、水体、大气和不同生物体中汞的分布、迁移规律以及汞的甲基化特征,并初步探讨了矿区居民汞暴露以及由此而导致的健康风险。 1.贵州典型汞矿区汞的环境地球化学特征 冶炼炉渣是矿区内堆积的重要废弃物之一,它是含辰砂矿石高温焙烧的产物。由于受冶炼工艺及回收率等的影响,炉渣中的汞含量可达5.7～4450mg·kg（-1）,并以高温次生矿物,如:黑辰砂、含汞多形硫化物、含汞氯化物、氧化汞、含汞硫酸盐以及单质汞等形态存在。这些矿物较辰砂更易溶于水中进行迁移,从而造成环境的严重汞污染。炉渣中存在的大量易溶富汞次生矿物,还会导致炉渣及周围环境介质成为汞甲基化的最有利的场所。因此,汞矿区内露天堆积的大量的冶炼炉渣,是造成矿区环境严重汞污染的主要汞源,同时还是矿区环境中甲基汞污染的潜在来源。 汞矿矿区和对照区土壤分析结果表明,无论是总汞含量还是甲基汞含量,矿区土壤均高出了对照区,同时也远远超出了国家农业土壤质量限制标准规定的总汞含量1.5mg·kg^-1。测定结果显示,汞矿区污染土壤总汞含量5.1～790mg·kg^-1,甲基汞含量0.13～15μg·kg^-1;对照区土壤总汞含量0.1～1.2mg·kg^-1,甲基汞含量更多还原

【Abstract】 Mercury is known as a toxic and unessential element. There are many large Hg mines worldwide abandoned recently because of more attentions to the toxicity of Hg and increasing environmental concerns. On the one hand, those abandoned Hg mines continue to impact local environments through mine-wastes, drainage, and elemental mercury vapor. On the other hand, different forms of inorganic Hg that released into the surroundings may, under certain conditions, be converted into MeHg, which is an organic Hg form and is more toxic than inorganic Hg. This organic Hg is readily accumulated by biota owning to its lipophilic and protein-binding properties and eventually enters the human body through food chains. Therefore, heavy Hg-contaminations from abandoned Hg mines pose increasing environmental concerns worldwide.Guizhou province located in a big natural circum-Pacific mercuriferous belt owns many large mercury mineral deposits, and as result, it is an important Hg production centre in China. The cinnabar deposits in Guizhou amount to about 88000 tons of metal Hg and consist of 80% of the total in whole China. The industrial scale of Hg production in Guizhou had been performed during last 630 years. Recently, large mercury mines in Guizhou, such as Wanshan, Wuchuan, Danzhai, Tongren and Lanmuchang, had been abandoned. In order to assess the environmental impacts and environmental geochemistry of those abandoned Hg mines, total Hg and MeHg in soils, plants, as well as different Hg species in stream-waters in Wanshan and Lanmuchang Hg mines were determined. Simultaneously, the risk assessment on exposure and human health of Hg was discussed.1. Mercury environmental geochemistry in typical Hg-mined areas in GuizhouOne of the most important mine wastes termed calcines, were formed during the retorting of the cinnabar ore at high temperatures. Because of the inefficient and incomplete process of retorting, calcines found at most Hg-mined sites enrich in mercury ranging from 5.7 to 4450 mg·kg^-1, containing large quantities of secondary mercury phases, such as metacinnabar, polymorph of sulfide, corderoite, chloride, mercury sulfates, oxides, and elemental mercury. These secondary mercury phases aremore soluble than cinnabar and cause Hg deposits to contaminate the surroundings. Large quantities of water-soluble secondary mercury phases in calcines may also result in favorable conditions for methylation in calcines and surroundings. Therefore, huge quantities of mine-wastes calcines are the dominate Hg-sources related to the environmental Hg-contaminations and potential sources of MeHg-contamination in Hg-mined areas.Data show that total Hg and MeHg concentrations in surface soils from Hg-mined areas are elevated higher than those that obtained in soils from control sites, which greatly exceed the maximum Hg concentration of 1.5 mg-kg"1 recommended by the Chinese National Standard Agency for arable soils. Total Hg and MeHg concentrations measured in polluted soils range from 5.1 to 790 mg-kg"1 and from 0.13 to 15 jug-kg’1, respectively. Total Hg concentrations in soils from control sites range from 0.1 to 1.2 mg-kg"1, MeHg from 0.10 to 0.28 //g-kg"1. In Hg-mined areas, MeHg concentrations in different types of arable soils vary differently. MeHg concentrations in rice paddies as well as vegetable soils are generally higher than those that found in cornfields, suggesting conditions favorable for methylation in paddies. Analytical results show that variety of MeHg levels among different arable soils in Hg-mined areas may own to Hg sources, physical and chemical characters, and TOC in soils. The reclaim and rebuild wasteland to paddies in Hg-mined areas may accelerate the conversion of Hg methylations and the bioaccumulations of MeHg.Surface waters from Hg-mined areas are heavily impacted by mine-waste calcines. Total Hg concentrations in surface waters affected by calcines are elevated high, reaching up to jMg-L"1. Total Hg in water samples that obtained in the downstream especially in the tributaries isolated from Hg-mined areas are relatively low, less than 50 ng-L"1, which may be considered as a baseline value. High abilities of Hg methylation were also obtained in the Hg-contaminated aquatic systems owning to calcines. The peak values of different mercury species measured in surface water samples are: total Hg 9260 ng-L"1, particulate Hg 9210 ng-L"1, dissolved Hg 430 ng-L1, reactive Hg 400 ng-L’1, total MeHg 25 ng-L"1, particulate MeHg 7.3 ng-L"1, and dissolved MeHg 22 ng-L"1. Data of Hg species show that （1） a strong positive correlation between total Hg and particulate Hg form are displayed in the water samples collected from Hg-mined areas with the proportion higher than 80%;（2） highlevels of participate Hg always match high concentrations of TSS;（3） Concentrations of total Hg and paniculate Hg in water samples collected during the flood-flow season are higher than those that obtained in the base-flow season, whereas, concentrations of dissolved and reactive Hg are lower with the peak values observed in water samples collected in the base-flow season. Observations suggest that the dominate Hg species in waters is particulate form and suspended particles in surface waters would present as a primarily transport pathway in contaminated aquatic system. Reasons for the characters of Hg species in different seasons are （1） summer in Guizhou is, in general, always a rainy season, therefore, the rivers that have a strong hydrodynamic force can scour and carry large quantities of particles enriched in mercury, and as result, leading to the increasing of concentrations of particulate Hg and total Hg;（2） water-soluble Hg forms would be diluted by the increasing of flow-rate of rivers in summer season, resulting in the decreases.Atmospheric Hg concentrations in studied areas are strongly correlated with the mining activities. Total gaseous Hg concentrations near the abandoned smelting facilities or small retorts vary from 1220 to 15590 ng-m"3. Results for Hg fluxes between mine-waste calcines and air exhibit that calcines are an important Hg source for atmospheric Hg. The rate of Hg emission from calcines is strongly consistent with the solar radiation. A positive correlation between Hg flux and the solar radiation were obtained. Annual estimating Hg emissions from calcines in Wanshan range from 0.96 to 3.0 kg-yr"1. In addition, there is a positive relationship between Hg concentrations in mosses and the total gaseous Hg concentrations in the ambient air, indicating that the sources of Hg in naturally growing mosses in Hg-mined areas are primarily from the atmospheric Hg deposition, suggesting that the naturally growing moss is an effective bio-monitor of local air Hg pollution.Agricultural corps and vegetables collected from Hg-mined areas present highly elevated total Hg concentrations. Total Hg concentrations in vegetables range from 120 to 18000 jig-kg"1 and exceed the National Standard of 10 <Mg-kg"x for edible vegetables 12 to 1800 times. Total Hg concentrations in rice range from 40 to 1280 /Mg-kg"1 and exceed the National Standard of 20 ^g’kg"1 for edible crop 2 to 64 times. More attentively, the rice exhibits a high accumulation ability of MeHg with a highly elevated value of 19 /jg-kg*1. And the proportion of MeHg in rice samples is high, reaching up to 90%. In addition, MeHg concentrations obtained in rice samples alsoexceed the values found in other agricultural corps and vegetables from Hg-mined areas. The rice in Hg-mined areas presents a high ability of MeHg accumulation. Since the traditional food of residents in Guizhou is the rice not the fish, high MeHg in rice may suggest that the primary route of exposure to MeHg for residents in Hg-mined areas is consumption of the contaminated rice not the fish. This observation, therefore, breaks the inter-common understanding of that the primary route of exposure to MeHg for human is consumption of the fish.2. Risk assessment on exposure and human health of mercuryTotal Hg and MeHg concentrations in hair samples collected from the residents living in Hg-mined areas range from 1.5 to 16 mg-kg"1 and from 0.70 to 4.4 mg-kg"1, respectively. High average concentration of 5.5 mg-kg1 in total and 1.9 mg-kg"1 in MeHg were found in hairs from the residents whose daily routine nearby the Hg-mined areas, while, low average concentration of 3.3 mg-kg"1 in total and 1.2 mg-kg"1 in MeHg were found in hairs from the residents who lived far from the Hg-mined areas. However, total Hg and MeHg concentrations in hair samples from control sites are lower, ranging from 0.32 to 1.7 mg-kg"1 and from 0.16 to 1.2 mg-kg"1, with the average values of 0.81 mg-kg"1 and 0.52 mg-kg"1, respectively. Results indicate that local people are heavily impacted by environmental Hg pollutions, and Hg concentrations in hairs from residents depend on their living regions.Routes of the daily Hg uptakes in the local people include contaminated air inhaling, water drinking, and contaminated food consumption. The risk assessment shows that the dominate pathway of exposure to Hg for residents is rice, with a high daily uptake of 2.4 jug-kg’1, which greatly exceeds 0.71 iag-kg"1-day"1 recommended by WHO. The daily uptake of Hg through vegetables consumption is 0.60 /ig-kg’1,and 0.21 ^gkg"1 for the inhalation route, respectively. A greatly risk associated with HI of 4.5 is presented in rice, and 0.85 for vegetable, 0.30 for atmosphere, indicating that the greatest risk to local people is the consumption of rice.更多还原