|Alternative Title||Altitudinal Distribution and Potential Eco-risk of Trace Metals in Gongga Mountain|
|Place of Conferral||北京|
|Keyword||微量金属 海拔分布 潜在生态风险|
The rapid development of urbanization and industrialization has resulted in toxic trace metals emitting into the atmosphere. These metals adsorbed on the surface of fine particles will be transported at a long distance and deposit in remote high mountain ecosystems under the cold trapping effects. Mountain ecosystem has a unique terrain and climate characteristics. Mountains have been found to preferentially accumulate these compounds carried by long-range atmospheric transport due to cold trapping effect, thereby threatening alpine ecosystems themselves and fresh water downstream. As a typical mountain ecosystem eastern Tibetan Plateau, Gongga Mountain has special mountain climate and complete vegetation type, without the interference of human activities, providing the ideal place for the research about geochemical characteristics of trace metals. However, the altitudinal distribution characteristics of trace metals in site area, source and its possible ecological risk is unclear. Answering the questions above is not only the premise of assessing regional trace metal contamination and collaborative governance, but also important basis for the construction of mountainous ecological security barrier Southwestern China. Three slope directions were choosen to collect the samples of soil profiles, dominant mosses, vegetation and atmospheric wet deposition according to the variations of altitude and differences between vegetation types. The concentrations of trace metals were determined to investigate the elevation pattern . Sources and deposition fluxes were identified and estimated using Pb isotope, geochemical index method and statistics combining geology, climate and vegetation type, respectively. The contamination level and potential eco-risk were assessed based on the characteristics of trace metals speciation and potential eco-risk. Main results and conclusions are as follows:(1) The concentrations of Pb and Cd in the soils of eastern slope were shown “higher-lower-higher” and Zn decreased firstly and then increased, while the concentrations of Cu had no marked variations along the altitude gradients. The concentrations of trace metals in the northern slope decreased along the altitude. However, the concentrations of trace metals in the soils had no significant alitutinal variations and were remarkablely lower than other slope directions. The concentrations of trace metals in the mosses of eastern and northern slope were higher than western slope. The concentrations of trace metals in the mosses of eastern slope decreased firstly and then increased along the altitude. The concentrations of trace metals in the mosses of northern slope decreased with the increased altitude. However, trace metals had no obvious altitudinal variations in the western slope. The results can be inferred: accumulation of trace metals in the lower altitude of eastern and northern slopes were affected by human activities, while the higher altitude in the eastern slope were influenced by cold trapping effect. The cumulation of trace metals in the western slope were seldom affected by human activities.(2) The concentrations of trace metals in the wet deposition under the forest were higher than in the outside forest. Canopy interception was main factors causing the difference. The concentrations and deposition fluxes of Pb, Cd and Zn under the forest decreased along the altitude, while Cu had no obvious altitudinal variations. The concentration and deposition flux of Pb increased firstly and then decreased along the elevation gradients; the concentrations and deposition fluxes of Cd and Zn decreased with the increased altitude; Cu had no marked elevation differences. The altitudinal characteristics of trace metals in the wet deposition indicated that the accumulation of trace metals in the wet deposition was mainly affected by human activities. Trace metals in the wet deposition inside and outside the forest were higher in the winter than other seasons, which was attributed to combustion of fossil fuels.(3) Sources of trace metals were identified using Pb isotope, geochemical index method and enrichment factor. At the elevation lower than 2770 m (a.s.l), trace metals were mainly sourced from fossil fuels combustion, while above the timberline they were mainly from ore smelting via long-range transportion. In the eastern and northern slope, Pb, Cd and Zn in the mosses were probably affected by human activities, while Cu was sourced from natural source. In the western slope, all the trace metals except Cd were mainly from natural source.(4) In the soils of eastern and northern slopes, the primary speciation of trace metals in the C horizon was residue fraction. The main speciation of Pb, Cd and Zn were reducible fraction in the O and A horizons, while the speciation of Cu was oxidizable fraction. The main speciation of Pb and Cd were reducible fraction. However, the primary speciation of Cu and Zn were oxidizable and residue fraction. In the O and A horizons, the pollution level of Cd and Cu was moderate and low, respectively, while the contamination level of Pb and Zn were both low in the eastern slope. All the trace metals were given priority to low contamination level in the western slope. According to the revised Hakanson ecological risk assessment method, potential ecological risk of Pb and Cu were very low, but ecological risk level of the Cd was higher. The soil, moss, plant tissue and wet deposition samples were selected to explore the occurrence characteristics of trace metals in the alpine ecosystem. The sediments and ice cores can be used to reflect the pollution history of trace metal in the future. Moreover, the collection density settlement of dry and wet samples were strengthened to improve the trace metal atmospheric precipitation time resolution, realizing impacts of regional human activity on distant mountain ecosystem. In addition, the improved Hakanson potential ecological risk assessment method was put forward based on the soil samples in Mt. Gonggga, and its application still needs a lot of researches.
|李睿. 贡嘎山微量金属的海拔分布特征及潜在生态风险评价[D]. 北京. 中国科学院大学,2016.|
|Files in This Item:|
|正式答辩.pdf（5699KB）||学位论文||开放获取||CC BY-NC-SA||View Application Full Text|
|Recommend this item|
|Export to Endnote|
|Similar articles in Google Scholar|
|Similar articles in Baidu academic|
|Similar articles in Bing Scholar|
Items in the repository are protected by copyright, with all rights reserved, unless otherwise indicated.