天山典型冰川区雪冰中碳质气溶胶浓度特征研究

Characteristics of Carbonaceous Aerosol Concentration in Snow and Ice of Glaciers in Tianshan Mountains

根据2002年与2004年在天山乌鲁木齐河源1号冰川与奎屯河哈希勒根51号冰川采集的粒雪与冰川冰样品,利用热/光反射法(TOR)分析得到有机碳(OC)与元素碳(EC)的浓度,并探讨了天山典型冰川区雪冰中碳质气溶胶浓度的时空特征与环境意义.结果表明,总碳(TC)浓度从高到低依次为:乌鲁木齐河源1号冰川西支雪坑(1 943 ng.g-1)>乌鲁木齐河源1号冰川东支雪坑(989 ng.g-1)>奎屯河哈希勒根51号冰川雪坑(150 ng.g-1)>乌鲁木齐河源1号冰川东支冰川冰(77 ng.g-1),OC和EC的浓度序列也较为类似;天山冰川区雪层中OC浓度平均值为557 ng.g-1,EC浓度平均值为188 ng.g-1.不同冰川积累区雪层剖面的中下部污化层附近一般都会出现碳质气溶胶浓度峰值,但某些突发性事件会使得表层雪也产生浓度峰值;在季节性碳排放(如居民采暖、农业活动等)与碳传输(如大气环流等)的影响下,雪层中碳质气溶胶浓度在7～11月间总体呈波动下降的趋势;冰川冰与粒雪间碳质气溶胶浓度可能存在着数量级的差异,这主要受到冰川所在环境、雪冰采样时空条件等因素影响;雪层表面是否存在EC对反照率有很大影响,模拟显示在波长为300～700 nm范围内反照率平均降低0.22.

The snow and ice samples,collected at Glacier No.1 at the headwaters of Urumqi River（UG1） and Glacier No.51 at Haxilegen of Kuytun River（HG51） in 2002 and 2004,were analyzed for organic carbon（OC） and element carbon（EC） by thermal/optical reflectance（TOR）.The spatio-temporal characteristics and environmental significance of OC and EC concentration were discussed in details.The concentration order of total carbon（TC） was： snowpack of west branch on UG1（1 943 ng·g-1）snowpack of east branch on UG1（989 ng·g-1）snowpack of HG51（150 ng·g-1）glacier ice of east branch on UG1（77 ng·g-1）,and the concentration order of OC and EC lay similar as TC.The concentration of OC and EC in snowpack of Tianshan Mountains were 557 ng·g-1 and 188 ng·g-1,respectively.Concentration peak of carbonaceous aerosol usually appeared near the dust layer at the bottom section of snowpack,but the some sudden events could increase the concentration in the surface snow.Because of the seasonality of carbon emission（e.g.heating and agricultural activities） and transportation（e.g.atmospheric circulation）,the concentration of carbonaceous aerosol increased from July to November with fluctuations.Difference on the order of magnitude might exist between the concentration in snow（firn） and glacier ice,which was influenced by the glacier surroundings,sampling situation and other factors.EC on the surface snow affected the albedo significantly,and an average albedo reduction of 0.22 in the wavelength of 300-700 nm was simulated by SNICAR（snow,ice,and aerosol radiative） model.