Knowledge Resource Center for Ecological Environment in Arid Area
| 青藏高原高寒草地持久性有机污染物的气-地交换研究 | |
| 其他题名 | Air-surface exchange of persistent organic pollutants in the alpine grassland of the Tibetan Plateau |
| 王传飞 | |
| 出版年 | 2015 |
| 学位类型 | 博士 |
| 导师 | 王小萍 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 持久性有机污染物（POPs）具有半挥发、难降解的特性，能够随大气进行远距离传输，并在寒冷的高纬度和高海拔地区富集，从而成为一种全球性的污染物。青藏高原海拔高，气候寒冷，其低温的环境可能加速POPs的沉降。故青藏高原被普遍认为是污染物的“汇”。青藏高原大气POPs的研究已经发现南亚排放的污染物在印度季风作用下被传输到青藏高原。但是，缺乏大气POPs与青藏高原地表交换过程及POPs在青藏高原的积累和富集状况的研究。 本研究拟依托大气被动采样网络，对涵盖整个青藏高原面的POPs的气-土交换特征进行研究，探讨不同地表类型（森林、草地、灌丛和荒漠）对POPs气-土交换的影响。在此基础上，以青藏高原面积最大的地表覆被类型——草地为研究对象，采集近地表大气、牧草叶片样品，进一步探讨POPs的气地交换过程。同时，采集酥油生物样品，揭示POPs在青藏高原草场典型食物链（大气-牧草-牦牛）的富集过程。取得的主要研究成果有： 1. 明确了青藏高原土壤、牧草和酥油POPs的浓度水平。土壤DDTs和HCHs浓度略高于欧洲背景山区，HCB、PCBs、PBDEs及PAHs的浓度远低于其它偏远的地区。纳木错牧草POPs浓度低于珠峰、青藏高原东缘的若尔盖草原以及北极地衣。酥油HCB浓度与全球平均水平相当，HCHs、DDTs和PCBs的浓度远低于存在本地源的国家和地区。 2. 依托青藏高原大气被动采样网络，基于二级逸度模型计算青藏高原面POPs的气-土交换趋势和通量，发现青藏高原土壤是DDTs和大分子PAHs的“汇”，其中p,p’-DDE和p,p’-DDT的沉降通量分别为0.5和0.3 ng/m2/h。而小分子POPs（如HCHs、HCB、小分子PCBs和PAHs）则呈现气/土界面平衡或向大气挥发的特征，其中γ-HCH的挥发通量达到7.7 ng/m2/h，这使得青藏高原土壤成为小分子POPs的“二次源”，进而影响POPs的全球归趋。这一发现部分修正了“青藏高原是全球POPs的汇”的假设。受土壤有机碳含量的直接控制，小分子POPs在森林地区呈现沉降特征，而在荒漠地区则倾向于向外挥发。但在高寒草地区，随着温度的季节性变化，POPs的气/土交换趋势可能呈现“沉降-平衡-挥发”更替的状态。为此，本论文对草地POPs气-地交换开展了进一步的研究。 3.选取典型高寒草甸区纳木错作为研究区域，进一步探讨POPs在地气界面的交换趋势。近地表大气POPs垂直分布的观测结果表明POPs与地表的净交换方向为大气向地表沉降，因此牧草以吸收大气沉降的POPs为主。鉴于此，对三种牧草（紫花针茅、委陵菜和弱小火绒草）吸附大气POPs的能力进行了进一步研究：比较三种牧草中的POPs含量和组成，发现牧草吸附POPs不存在种间差异；生长季的动态观测发现牧草中的HCHs可在较短时间内达到吸附平衡状态，而DDTs的浓度在生长季内持续升高；基于大气和牧草POPs浓度计算大气-牧草分配系数（Kpa），发现纳木错牧草大分子POPs的Kpa（如p,p’-DDT的Kpa值达到98 m3/g dw）比欧洲地区相同分子量的POPs高两倍，这说明青藏高原牧草富集大分子POPs的能力更强。总之，青藏高原高寒草甸的土壤和植被均能富集大气POPs，从而成为POPs的“汇”，这将会影响陆生生物对POPs的富集程度。 4. 使用酥油作为研究牦牛吸收POPs的介质，开展POPs沿陆地食物连传递和转化的研究。纳木错地区稳定性强的大分子POPs的比重沿大气-牧草-酥油逐渐升高，说明POPs沿“大气-牧草-牦牛”食物链进行传递。牦牛对牧草POPs的生物富集系数（BCF）都大于1，说明POPs在牦牛体内发生了生物富集。其中p,p’-DDE的BCF是p,p’-DDT的40倍，可能与DDTs在牦牛体内发生了新陈代谢有关。由于牦牛体内POPs来自于食物链的传递，基于Kpa（大气-牧草）和BCF（牧草-酥油），获得了适用于青藏高原的大气-酥油转化系数（TFA:B）。借助该系数，可以使用酥油POPs浓度反演大气POPs平均状况。 |
| 英文摘要 | Persistent organic pollutants (POPs) with semi-volatile and persistence in the environment can travel long-range atmospheric transport (LRAT) and cycle over the world. Influenced by the relatively lower temperature, POPs will be accumulated in the mountain regions. High elevation and cold climate in the Tibetan Plateau (TP) prompt POPs to be deposited. Therefore, TP was seen as a “sink” of pollutants. Previous studies on the atmospheric POPs of the TP revealed that the pollutants discharged by India were transported to the TP driven by the Indian Monsoon. However, limited studies were carried out on the air-surface exchange, accumulation and enrichment level of POPs in the TP. Based on the passive air sampling network, this study was to investigate the air-soil exchange of POPs across the TP, and explore the role of different land covers (forest, grassland, shrub and desert) played on the air-soil exchange of POPs. Furtherly, we chose grassland, the biggest land cover in the TP, to study the air-surface exchange of POPs. Additionally, butter samples were collected to explore the accumulation of POPs along the terrestrial food chain: air-grass-yark in the TP. The main results are as follows: 1. The concentrations of POPs in soil, grass and butter are established. The soil DDTs and HCHs were higher than the background regions in European mountains. Soil HCB, PCBs, PBDEs and PAHs were far lower than the other remote areas. The grass POPs in Namco are lower than those in Mt. Qomolangma, Ruoergai and lichen in the Artic. In the butter, HCB was comparable to the global level but HCHs, DDTs and PCBs were lower than the regions with local source. 2. Based on the passive air sampling network in the TP, two level fugacity model was applied to calculate the fugacity and flux of air-soil exchange of POPs. The results showed that soil was a “sink” of DDTs and high molecular weight PAHs in the TP. The disposition flux of p,p’-DDE and p,p’-DDT were 0.5 and 0.3 ng/m2/h. However, the low molecular weight POPs (such as HCH, HCB, low molecular weight PCBs and PAHs) appeared air-soil exchange equilibrium or re-volatilization, among which the volatilization flux of γ-HCH was up to 7.7 ng/m2/h. This reveals that the Tibetan soil will become a “second source” of low molecular weight POPs and furtherly affect the global migration of POPs. This finding partially corrected the hypothesis that the TP was generally seen as a “sink” of pollutants. Controlled by the SOC, the low molecular weight POPs deposited in the forest soil but re-volatized out from the desert soil. In the alpine grassland, the air-soil exchange of POPs were experienced the cycle of “deposition-equilibrium–volatilization” along with the variety of temperature induced by the seasonal change. Then, further study on the air-soil exchange of POPs was carried out in the grassland. 3. The pastoral region Namco was chose to explore the air-surface exchange trend of POPs. The vertical distribution of atmospheric POPs near the surface reveled that deposition was the main direction for air-surface exchange. Therefore, the grass mainly absorbed POPs from the atmosphere. In view of the results mentioned above, three species of grass (Stipa purpurea, Potentila and Tiny Edelweiss) were chose to study the absorption ability of POPs subsequently. The concentrations and profiles of POPs for three species of grass were not significantly different, indicating the grass absorbed POPs without species’ difference. The observation of uptake process of grass found that HCHs and HCB attained equilibrium but DDTs increased during the growing season. Based on the air and grass POPs, the air-grass participating factor (Kpa) were calculated. The Kpa values of high molecular weight POPs for grass of Namco (i.e. the Kpa of p,p’-DDT were 98 m3/g dw) were two times higher than that the similar molecular weight POPs in the Europe, which suggests that grass in the TP have higher absorptivity for high molecular weig |
| 中文关键词 | 持久性有机污染物 ; 青藏高原 ; 气-土交换 ; 气-草交换 ; 生物富集 |
| 英文关键词 | Persistent organic pollutants (POPs) Tibetan Plateau Air-soil exchange Air-grass exchange Bio-accumulation |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 自然地理学 |
| 来源机构 | 中国科学院青藏高原研究所 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/287564 |
| 推荐引用方式 GB/T 7714 | 王传飞. 青藏高原高寒草地持久性有机污染物的气-地交换研究[D]. 中国科学院大学,2015. |
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