【作者】 叶浩；

【导师】 付强；

【作者基本信息】 兰州大学 ， 大气物理学与大气环境， 2013， 硕士

【摘要】 黑碳气溶胶作为大气中首要的吸收性气溶胶成分,沉降到冰雪表面后,能够显著吸收太阳辐射,减小积雪反照率,加速冰雪融化,减小地表反照率,在大气和地表能量的收支乃至全球气候变化中所起的重要作用,使其成为造成全球变暖的一个潜在因子。本论文介绍了2010年和2012年冬季的两次野外观测实验的采样点和积雪分布状况,分析了积雪中等效黑碳含量及其分布;利用HYSPLIT-4后向轨迹模式分析了采样点在11月～2月的逐日后向轨迹,并对轨迹进行聚类分析,得到了各个采样点主要的污染物传输路径。2010年冬季的野外观测试验共获得46个采样点的积雪样品,其中祁连山地区和内蒙古草原地区季节性积雪中主要的吸收性杂质为沙尘,东北地区主要的吸收性杂质为黑碳。在内蒙古草原地区,表层积雪中等效黑碳含量大多在200～700ngg-1之间,表层以下积雪中平均等效黑碳含量在150～900ng g-’之间;在东北北部的森林地区,积雪中等效黑碳含量低于200ngg-1,最北端采样点积雪中的平均等效黑碳含量仅为30ngg-1,与西伯利亚北极沿岸积雪中的黑碳含量相当；在东北南部的工业区,表层积雪中等效黑碳含量在400-1000ngg-1,受到局地工业和人类活动排放污染物的影响；祁连山地区积雪稀少,积雪中存在大量沙尘,表层积雪中等效黑碳含量在100-750ngg-1之间。东北区域的采样点20-40的表层积雪中等效黑碳含量随纬度的增加而显著降低,这一趋势表明,我国东北地区排放的黑碳气溶胶大部分在我国境内被湿沉降清除,只有很小部分可能被向北输送到北极,对于北极地区积雪中黑碳的贡献有限。2010年野外观测试验采样点中,内蒙古草原地区的污染物传输路径可分为北路、西北路和西路三条路径,随着经度增加,西路路径所占比例逐渐减少,西北路径所占比例增加；东北北部地区主要的传输路径来自西侧的西西伯利亚平原,来自北侧的局地污染物输送会对积雪中黑碳含量有较大影响：东北南部地区主要的传输路径来自于中西伯利亚高原北部和西部,来自南侧的输送路径虽然所占比例不大,但所经过地区排放的大量污染物会对积雪中黑碳含量有很大贡献。2012年野外观测试验在新疆北部的32个采样点进行了采样,积雪中主要的吸收性杂质为黑碳；天山地区受到周边城市冬季人类活动和工业排放的影响,积雪中等效黑碳含量主要在30～200ngg-1之间,天山一号冰川附近采样点积雪中等效黑碳含量(20～30ngg-1)能够代表天山区域积雪中黑碳的背景值；阿尔泰地区积雪中等效黑碳含量主要在20-200ngg-1之间,其中最北部采样点积雪中的等效黑碳含量仅为20ngg-1,同加拿大极区、阿拉斯加极区以及Svalbard等地积雪中黑碳含量相当；丘陵地区积雪中等效黑碳含量大多低于100ngg-1。新疆北部积雪中的黑碳含量与海拔高度呈负相关的关系,海拔高度越高,积雪中黑碳含量越低；海拔高度可能是影响积雪中黑碳含量的一个因素。新疆北部的采样点中,天山地区和丘陵地区主要的污染物传输路径为西南路径；阿尔泰地区的后向轨迹比较分散,西南路径和西方路径所占比例相当；在丘陵地区和阿尔泰地区,局地轨迹所占比例很大(50%以上),表明局地排放的污染物会对积雪中等效黑碳含量存在很大的贡献。更多还原

【Abstract】 Black carbon (BC) particles are the most absorptive aerosol in the atmosphere. When BC particles deposit into snow and ice, they can significantly absorb solar radiation and reduce the albedo of snow and ice, and consequently accelerate the melt of snow and ice and reduce the surface albedo. BC particles have important impacts on the energy budget in the global climate system, making BC as a potential factor contributing to the global warming.Two field campaigns have been carried out across northern China covering46sites during the winter of2010and40sites during the winter of2012. The equivalent BC content in the seasonal snow and its spatial distribution are investigated. The daily back trajectories of each site are simulated with the HYSPLIT-4model from November to February. The main transport paths of pollution are analyzed at each site with cluster analysis of the back trajectories.Snow samples were collected at46sites in2010. The main absorbing impurity in the seasonal snow was dust at Qilian Mountains and Inner Mongolia and was black carbon at Northeast China. Across Inner Mongolia, the equivalent BC contents (mass fractions) were mostly between200and700ng g-1in the surface snow and were between150to900ng g-1under the surface layer. The equivalent BC contents in snow across the northern forest part of the Northeast China are less than200ng g-1, with a value of30ng g-1at the most northern site which was comparable to those of the Siberian Arctic. Across the south Northeast China, the equivalent BC contents in snow were influenced by the local pollution from industry and human activities, with the values from400to1000ng g-1in the surface snow. The snow at Qilian Mountains was patchy and thin with equivalent BC contents between100-750ng g-1, dominated by large amount of dust. The equivalent BC content in the surface snow at sites20～40decreased as the latitudes increasing, which showed that most BC aerosols emitted from Northeast China were deposited by precipitation within China and little can be transported to Arctic.In the2010field campaign, the pollution could be transported to the sites across the Inner Mongolia though three paths, i.e. north, northwest and west. The influences of west paths decreased but northwest paths increased as the longitudes of sites increase. The main path of sites across northern Northeast China was from West Siberian Plain, and the local pollution from north had large influence on the BC content in snow. Across southern Northeast China, the pollution was mainly from Central Siberian Plateau and the pollution from the south could have significant impacts on BC content even with a less percentage.Snow samples were collected at32sites in northern Xinjiang during the winter of2012. The main absorbing impurity in seasonal snow was BC. The equivalent BC contents across Tianshan Mountains ranged from30to200ng g-1, with influence from the local human activities and industry emission. The equivalent BC content in snow of20ng g-1at site near Tianshan No.1Glacier can be regarded as the background value across Tianshan Mountains. Across the Altai Mountains in the north, equivalent BC contents in snow ranged from20to200ng g-1, with the lowest value of20ng g-1at the most site which was comparable to those of Canadian Arctic, Alaskan Arctic and Svalbard. The equivalent BC contents were mostly less than100ng g-1across the hilly areas between the two mountain ranges. The BC content of seasonal snow in northern Xinjiang showed a negative correlation with the altitudes of the sites and decreased as the altitudes increase, indicating that the altitudes of sites may be one factor influencing the BC mass fractions.The main transport path of pollution across Tianshan Mountains and hilly areas was from the southwest. Across Altai Mountains, the transport paths from the southwest and west were roughly equivalent. The local back trajectories had large percentage; mostly more than50%across hilly areas and Altai Mountains, indicating that the pollution from local emission could have significant impacts on the BC content of seasonal snow in those regions.更多还原