The Analysis On Contents And Sources Of Light-absorbing Particles In Snow/Ice In Tibetan Plateau

Black carbon?BC?,organic carbon?OC?and mineral dust?MD?are three main types of light-absorbing particles in snow and ice.They can be transported long distance before being removed by wet deposition,such as rain and snow,or by dry deposition.When reach the surface of snow and ice,they could strongly absorb solar visible radiation and reduce the albedo of snow significantly,thereby accelerating the ablation of snow and ice,with important impacts on regional and global climate and the hydrological cycle changes.In addition,organic carbon is classified into two categories:water-soluble organic carbon?WSOC?and insoluble organic carbon?ISOC?.The Tibetan Plateau?TP?,also known as the‘third pole'of the earth,is the largest ice and snow reserves except the Earth's north and south poles.However,the glaciers on the Tibetan Plateau have suffered extensive ablation and gradually intensified in recent decades.The presence of light-absorbing particles is thought to be a potential factor in accelerating the ablation of snow and ice.Based on this,a total of 189 snow/ice samples from 67 sites of 7 glaciers in the Tibetan Plateau during 2013-2015 were collected for optical and chemical analysis.Black carbon,insoluble organic carbon and iron?Fe,the main light-absorbing component in mineral dust?in the samples were measured using ISSW and inductively coupled plasma mass spectrometry?ICP-MS?.Furthermore,combining with the analysis of soluble ions and trace elements,we evaluated the sources of light-absorbing impurities in snow/ice samples based on enrichment factors?EF?,positive matrix factorization?PMF?,factor analysis?FA?,and Hybrid Single Particle Lagrangian Integrated Trajectory Model?HYSPLIT?.The results indicated that mass mixing ratios of BC,ISOC,and Fe show large variations of 10-3100 ng g^-1,10-17000 ng g^-1,10-3500 ng g^-1,with mean values of 218±397 ng g^-1,1357±2417 ng g^-1,241±452 ng g^-1 on TP glaciers during the entire snow field campaign,respectively.Meanwhile the mass mixing ratios of BC,ISOC,and Fe all showed a tendency to decrease from north to south.The analysis of the relative light absorption contribution of the three light-absorbing particles at 450 nm showed that BC was the dominant in the Qiyi,Qiumianleiketage,Meikuang,Tanggula,and Yangbajing glaciers,while the relative light absorption contribution from BC and ISOC in the Yuzhufeng and Hariqin glaciers was comparable.The BC and chemical elements were also analyzed for the attributions of the particulate light absorption based on a positive matrix factorization?PMF?receptor model.The results indicated that the industrial pollution?33.1%?,biomass/biofuel burning?29.4%?,and soil dust?37.5%?were the major sources of the light-absorbing impurities in TP glaciers.The source of pollutants in the Qiumianleiketage,Meikuang,and Yangbajing glaciers was mainly soil dust;industrial pollution was dominant in the Hariqin glacier;the pollutions of the Yuzhufeng glacier originated mainly from the soil dust and industrial pollution;the pollutants of Tanggula glacier mainly came from the soil dust and biomass/biofuel burning;whereas,for the Qiyi glacier,the proportions from the soil dust,industrial pollution and biomass/biofuel burning were roughly comparable,while the biomass/biofuel burning was slightly higher.