环境中汞的被动采样和形态测定方法及其应用研究
文献类型：学位论文
| 作者 | 马旭 |
| 学位类别 | 博士 |
| 答辩日期 | 2014 |
| 授予单位 | 中国科学院研究生院 |
| 授予地点 | 北京 |
| 导师 | 刘景富 |
| 关键词 | 汞 Mercury 甲基汞 Methylmercury 被动采样 Passive sampling 形态分析 Speciation analysis 自由溶解态 Freely dissolved concentration 天然有机质 Natural organic matter 光化学甲基化 Photochemical methylation |
| 其他题名 | Method development and application of passive sampling and speciation analysis for mercury in environmental sample |
| 中文摘要 | 作为一种全球污染物，环境中的汞给人类健康造成了严重的危害。汞主要以无机汞、甲基汞、乙基汞和苯基汞等多种形态存在，每种形态可能以自由溶解态和结合态等赋存状态存在于环境中。由于不同形态和状态的汞的环境行为和毒性效应各异，发展高效、灵敏、准确的汞形态和状态的采样和测定方法，并研究其环境行为具有重要意义。本文旨在发展水环境中汞和甲基汞的被动采样与形态测定方法，并将其应用于环境中汞的形态转化及区域污染水平研究。论文主要包括以下几个部分： 首先，发展了一种基于微耗损中空纤维支载液膜萃取的生物模拟被动采样技术，用于水体中痕量自由溶解态无机汞和甲基汞的采样富集和生物有效性评价。以聚丙烯中空纤维膜（内径280 μm，壁厚50μm）作为液膜支载体，溶解了1%(m/v)三辛基氧化膦 (TOPO)载体的正十一烷溶液作为液膜，1 mmol/L的硫代硫酸钠溶液作为受体相，构建了被动采样装置，并建立了无机汞和甲基汞的平衡采样方法。进行被动采样时，样品中的无机汞和甲基汞在TOPO载体的作用下被萃取进入液膜，然后与硫代硫酸根形成络合物被反萃取到受体相。平衡透析实验表明，本中空纤维支载液膜采样装置仅采集自由溶解态的无机汞和甲基汞，其对含0.1 mg/L腐殖酸的水中的甲基汞的富集倍数为1164，适合用于模拟生物对水中低浓度无机汞和甲基汞的吸收。基于此采样装置，研究了环境相关因素如pH、氯离子和腐殖酸等对无机汞和甲基汞的生物吸收的影响。本生物模拟被动采样方法的建立，为无机汞和甲基汞的自由溶解态浓度的测定和生物有效性/毒性评价提供了一种新的技术手段。 其次，发展了同位素稀释和气相色谱-电感耦合等离子体质谱联用（ID-GC-ICP-MS）高灵敏、准确测定环境和生物样品中甲基汞（MeHg+）的方法。我们采用实验室合成的富集同位素Me198Hg+作为同位素内标，将已知量的富集同位素内标加入到待测样品中使同位素比例发生改变。当加入的富集同位素与样品中待测元素的自然丰度同位素化学平衡后，通过测定富集同位素加入前后同位素比例的变化从而计算样品中待测元素的含量。在最佳的实验条件下，对0.5 ng/L甲基汞基于峰面积测量值的同位素比例精度为1.4%(相对标准偏差RSD= 1.4%, n=8), GC-ICP-MS联用测定的绝对检出限分别为4.3 pg (198Hg)和8.1 pg (202Hg)，相对标准偏差为3.6% (n=8)。实验对比了本方法与常规内标法 (Tl为内标，连续进样)的准确性，并进一步通过分析标准参考物质(底泥，ERM-cc580; 生物组织, Tort-2)进行验证，结果表明ID-GC-ICP-MS获得的结果与标准参考值一致。 基于上述建立的同位素稀释测定甲基汞的方法，初步研究了水中汞在天然有机质和光照条件下的甲基化过程。结果表明，溶解态有机碳(DOC)浓度影响甲基化过程，太低或太高的DOC均不利于汞的甲基化；湖水与湿地水样均存在甲基化与去甲基化现象。 论文还研究了大连湾区域汞污染水平和分布。实验测定了2012年12月采集于大连湾周边的20个底泥和6个柱芯样品中的总汞和甲基汞含量，并对其分布进行了分析。结果表明，底泥样品中总汞浓度(12-161 μg/kg)为土壤背景浓度的5倍左右，相应的甲基汞浓度为0.015-0.8 μg/kg。同时，该区域底泥中总汞浓度与甲基汞浓度存在很强的相关性(r2 = 0.88)，表明总汞浓度高的污染区域相应的甲基汞浓度也高。表层底泥中并没有发现总有机碳与总汞或与甲基汞存在相关关系，这也表明有机质在汞的地化循环过程中的作用较为复杂。底泥柱子中，总汞在表层底泥(1-10 cm)内的浓度明显高于深层底泥。而甲基汞浓度在底泥中浓度很低，所占权重仅为总汞的0.3 %左右。 |
| 英文摘要 | As a global pollutant, mercury causes a great damage to human health. Mercury exists in the environment mainly in species of inorganic mercury, methylmercury and ethylmercury and dimethylmercury, while each of these species can be present in the form of freely dissolved or matrix bound state. Since the environmental behavior and toxicological effects of mercury are strongly dependent on the species and states, it is of great important to develop efficient, sensitive and accurate sampling and determination methods for mercury speciation, and to further study their environmental behavior. This study aimes at developing methodologies for passive sampling and speciation analysis of inorganic mercury (Hg(II)) and methylmercury (MeHg) in aquatic environment, and applying these methods to further study the species transformation and contamination level of mercury in the environment. This dissertation mainly includes following sections: Firstly, we develop a biomimetic passive sampling methods based on negligible-depletion hollow fiber supported liquid membrane extraction techniques for determining freely dissolved concentrations of Hg(II) and MeHg. The passive sampling device was developed by using a single polypropylene hollow fiber (inner diameter 280-μm and wall thickness 50-μm) as liquid membrane supporter, 1% (m/v) tri-n-octyl phosphine oxide (TOPO) dissolved in n-undecane as liquid membrane, and 1 mmol/L sodium thiosulfate solution as acceptor phase. In the process of passive sampling, Hg(II) and MeHg transport through the liquid membrane with the help of TOPO and was then trapped in the acceptor by sodium thiosulfate. By using equilibrium dialysis technique, it was validated that hollow fiber supported liquid membrane sampling device only collect freely dissolved concentration of Hg(II) and MeHg, with a enrichment factor of 1164 for MeHg in the presence of 0.1 mg DOC/L humic acids. Thus, it is suitable for simulating the uptake of low concentration of Hg(II) and MeHg to the aquatic organisms. Based on these developed sampling device, we studied the influence of environmentally relevant parameters, such as pH, chloride and humic acid on biological uptake of Hg(II) and MeHg. These biomimetic passive sampling method provides an alternative for evaluation of the freely dissolved concentrations and the toxicological effects of mercury. Secondly, by combining isotope dilution with gas chromatography and with inductively coupled plasma mass spectrometry we developed a highly sensitive and accurate ID-GC-ICP-MS method for the determination of methylmercury (MeHg+) in environmental and biological samples. In this developed method, isotope enriched Me198Hg+synthesized in our laboratory was spiked into the samples. Equilibration of the spiked isotope with the natural species in the sample alters the isotope ratio that is measured and used for calculation the concentration of the analyte. Under optimum conditions, the determined isotope precision based on the peak area measurements was 1.4% in relative standard deviation(RSD) at 0.5 ng/L (as Hg) of MeHg+. The absolute detection limits obtained with the ID-GC-ICP-MS were 4.3 pg for 198Hg and 8.1 pg for 202Hg, respectively. The method precision presented as RSD was typically less than 3.6% over eight repeated measurements. The accuracy of the method has been evaluated by compared with the method with Thallium as internal standard, and further validated with certified reference materials (ERM-cc580 for sediments and Tort-2 for the biological tissues).The results obtained by isotope dilution-GC-ICP-MS were in good agreement with the certified reference values. With the above developed highly sensitive and accurate ID-GC-ICP-MS method for MeHg determination, we investigated the sunlight-mediated MeHg production and demethylation processes in the presence of natural organic matter. The results indicated that the dissolved organic carbon (DOC) concentrations can affect the MeHg production. |
| 源URL | [http://ir.rcees.ac.cn/handle/311016/35199]  |
| 专题 | 生态环境研究中心_环境化学与生态毒理学国家重点实验室 |
| 推荐引用方式 GB/T 7714 | 马旭. 环境中汞的被动采样和形态测定方法及其应用研究[D]. 北京. 中国科学院研究生院. 2014. |
入库方式： OAI收割
来源：生态环境研究中心
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