IMHE OpenIR  > 山地表生过程与生态调控重点实验室
贡嘎山微量金属的海拔分布特征及潜在生态风险评价
Alternative TitleAltitudinal Distribution and Potential Eco-risk of Trace Metals in Gongga Mountain
Language中文
李睿
Thesis Advisor吴艳宏
2016-05-27
Degree Grantor中国科学院大学
Place of Conferral北京
Degree Name硕士
Degree Discipline自然地理学
Keyword微量金属 海拔分布 潜在生态风险
Other Abstract

城市化和工业化的快速发展导致大量有毒有害微量金属进入到大气,人类活动排放的微量金属能够吸附于气溶胶,通过大气远距离的传输进入到遥远的高山生态系统。高山生态系统具有独特的地形和气候特征,在高山冷凝作用下,人类活动产生的微量金属能够发生沉降,从而对当地乃至下游地区的生态安全产生威胁。贡嘎山是青藏高原东麓典型的高山生态系统,拥有特殊的高山气候和完整的植被带谱,而且远离人类活动的干扰,为开展人类活动产生的微量金属的地球化学特征研究提供了理想场所。但是,目前在贡嘎山地区微量金属的海拔分布特征、来源及其可能造成的生态风险尚不清楚。回答上述问题是评估区域微量金属污染和协同治理的前提,也是我国西南山区生态安全屏障建设的重要依据。本研究选择贡嘎山三个不同坡向(东坡、西坡和北坡),根据海拔梯度和植被类型差异分别采集土壤(剖面)、苔藓(优势种)、植物组织和大气湿沉降(林内和林外)样品。分析了样品中微量金属(Cd、Cu、Pb和Zn)的浓度,调查了不同坡向微量金属的海拔分布模式;利用地球化学、统计分析和Pb同位素示踪技术,结合当地的地质、气象及植被类型等,判识了微量金属的可能来源,并估算了微量金属的大气沉降通量;根据微量金属的化学形态特征、污染指标和生态风险评价指标,评价了贡嘎山地区微量金属目前的污染水平和潜在的生态风险。主要结果和结论如下:(1)贡嘎山东坡土壤中Pb和Cd的浓度随海拔上升呈现“升高-降低-升高”的趋势,Zn的浓度随海拔的升高先降低后升高;Cu的浓度则无显著的海拔差异。北坡土壤中微量金属的浓度均随海拔升高而降低,西坡土壤中微量金属的浓度均显著低于东坡和北坡,而且其海拔变化趋势不明显。贡嘎山东坡和北坡苔藓中微量金属的浓度显著高于西坡中的浓度水平。东坡苔藓中微量金属的浓度随海拔先下降后增加的趋势,北坡苔藓和松萝中微量金属的浓度呈现出随海拔升高逐渐下降的趋势,而西坡苔藓中微量金属浓度没有呈现出明显的海拔变化。综合贡嘎山三个坡向土壤、苔藓和植物组织中微量金属浓度的海拔分布特征可以推断:贡嘎山东坡和北坡低海拔地区微量金属的明显累积受到了当地人类活动的影响,东坡高海拔地区(林线以上)可能受到高山冷凝沉降的影响,而西坡微量金属的累积没有受到明显的人类活动的影响。(2)贡嘎山东坡林内降水(或降雪)中微量金属的浓度呈显著高于林外降水中的浓度,植被对微量金属的拦截作用是造成这种差异的主要因素。林外降水(或降雪)中Pb、Cd和Zn的浓度和沉降通量在海拔2000 m至3700 m范围内总体呈现随海拔升高而下降的趋势,Cu的浓度和沉降通量则没有显著的海拔差异。林内降水(或降雪)中Pb的浓度和沉降通量随海拔升高先升高后降低,Cd和Zn的浓度和沉降通量则随海拔升高逐渐下降,Cu的浓度和沉降通量则无显著的海拔差异。降水(或降雪)中微量金属的海拔分布特征说明林线以下地区大气降水中微量金属的累积主要是受到当地人类活动的影响。季节上,冬季林内外降水(或降雪)中Pb、Cd和Zn的浓度和沉降通量均高于其它季节,这可能和当地及周边地区冬季取暖而燃烧化石燃料有关。(3)Pb同位素示踪技术、地球化学指标法和富集因子指示了贡嘎山地区微量金属的来源。东坡低海拔地区土壤中的微量金属主要来自化石燃料燃烧,而高海拔地区土壤中微量金属主要来自远距离大气输送,矿物开采和金属冶炼导致了微量金属的累积,苔藓中Pb、Cd和Zn明显受到人类活动的影响,Cu则主要来自自然源;北坡土壤中的微量金属主要来自当地化石燃料的燃烧,苔藓中Pb、Cd和Zn主要来自人类活动,Cu则来自自然源;西坡土壤中的微量金属的来源可能与土壤母质有关,苔藓中除了Cd受到人类活动的影响,其余微量金属均主要来自自然源。(4)贡嘎山东坡和北坡土壤C层中Pb、Cd、Cu和Zn均以残渣态为主,O层和A层中Pb、Cd和Zn均以铁铝锰结合态为主,Cu则以有机结合态为主。西坡土壤中Pb和Cd均以铁铝锰结合态为主,而Cu和Zn分别以有机结合态和残渣态为主。东坡和北坡O层和A层中Cd均呈现中度污染,Pb和Zn则以轻度和中度污染为主,Cu则为轻度污染或无污染。西坡O层和A层中Pb、Cd、Cu和Zn均以无污染和轻度污染为主。根据修正的Hakanson生态风险评价方法,Pb和Cu的潜在生态风险均很低,而Cd的潜在生态风险水平较高。本研究选取了土壤、苔藓、部分植物组织和湿沉降样品探讨微量金属在高山生态系统中的赋存特征,未来需要增加沉积物、冰芯等能够反映微量金属累积历史的环境样品,还原贡嘎山地区微量金属的沉降历史。而且,仍需加强干、湿沉降样品的采集密度,提高微量金属大气沉降的时间分辨率,充分认识区域人类活动对遥远的高山生态系统产生的影响。此外,研究提出的改进后的Hakanson潜在生态风险评价方法是基于贡嘎山土壤样品而提出的,其应用性仍需大量研究考证。 

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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. 

Subject Area地球科学
Document Type学位论文
Identifierhttp://ir.imde.ac.cn/handle/131551/17199
Collection山地表生过程与生态调控重点实验室
Affiliation贡嘎山微量金属的海拔分布特征及潜在生态风险评价
Recommended Citation
GB/T 7714
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.
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