| The cryosphere plays a vital role in the global climatic system, it has high reflectance to the solar radiation, low thermal conductivity, and huge calorific capacity, as well as plays important roles in droving deep-sea circulations. At present, global and regional climate change is a hot topic and attracting many scientists concerning it. Atmospheric pollution and haze are significantly affecting human health and social sustainable development. As one of the vital factors affecting climate change, the effects of atmospheric dust aerosols on climate and environment need deep research. Study on dust particles deposited in the snow and ice can provide a new cognition on the interrelations of geographical spheres, and is helpful for the deep understanding of dust migration and transformation mechanisms. Snow or ice is the storage tank for atmospheric materials, dust aerosols can be well recorded and preserved in the snow or ice. Dust particles deposited in the high mountain snow and ice can well reflect and indicate atmospheric environment conditions, research on insoluble dust particles deposited in the ice cores has important roles in recovering and rebuilding climate and environment change. Dust particles are the important components of atmosphere, and can affect radiation balance of earth surface, neutralizing acidic materials in precipitation, as one of radiative forcing factors of earth system, dust particles, combined with greenhouse gases and solar radiation, as well as variations of earth surface features, they are driving factors of climate change, which playing important roles in changing earth system’s energy balance. Yulong Snow Mountain （Mt. Yulong） is located in the southeastern Tibetan Plateau and southernmost Hengduan Mountains. The climate of the Mt. Yulong area is special and simultaneously suffered from the influence of many circulation systems, i.e. southwest and southeast winds, and the westerlies. Glaciers and atmospheric precipitation distributed in the Mt. Yulong area are very sensitive to climate change, and the glaciers developed at the summit of the Mt. Yulong are important water resources （or solid water tower）, thus the study on dust deposition has great scientific values and practical significance. Atmospheric dust first transferred from source areas, then in the transportation processes dust aerosol experienced transmission, deposition, and exhibited different characteristics when passed through distant and adjacent areas. Therefore, conduct the research on microparticles deposited in snow and atmospheric precipitation in the Mt. Yulong region, and make comparison with relevant researches carried out in the Northern Hemisphere and other areas, is profound to complete and expand the atmospheric circulation and deposition mechanisms.This study mainly analyzed the micoparticle concentrations and deposition characteristics in the typical snow and atmospheric precipitation in the Mt. Yulong region, and also analyzed snow chemistry and rainfall chemistry. Results of microparticles analysis showed that the number concentrations, mass concentrations of microparticles and the modes of volume size distributions performed great differences at the spatial and temporal scales. The difference of microparticles in the water bodies exhibited the influences of regional environment on the dust deposition. Correlations among dust concentrations and the typical dust ions at lateral direction of the snowpits revealed that there exist distinct dust layers in the snowpit. Volume size distributions of dust particles in water bodies showed mono-modal structure having a volume median diameter of3-21μm, comparable with the modal size of micro-particles in other sites. Dust concentration peaks and high number concentrations of microparticles in non-monsoon season revealed that there exists big inter-annual variation, and also signifies that dust deposition in the Mt. Yulong snow was sensitive to atmospheric environment change. Overall, the number concentrations of microparticles in the snow of Mt. Yulong was relatively low, and few coarse particles made big contributions to the higher mass concentrations. Dust concentrations of microparticles deposited in the Mt. Yulong snow were comparable to that detected in Dasuopu, Laohugou glacier, Tienshan area, while the mass concentrations were significantly higher than that measured in Penny ice cap, Devon Ice cap.Ion concentrations of surface snow and fresh snow showed that non-monsoon ion concentrations were substantially higher than that monsoon one, which exhibited distinct seasonal variation. SO42-and Ca2+with the highest concentrations in the pre-monsoon and post monsoon snow, respectively. At the end of monsoon season, dust concentrations in the atmospheric precipitation were gradually increased with the decrease of precipitation amount and the frequency of rainfall events. As for the spatial distribution of dust concentrations in water bodies in the Mt. Yulong area, the southern and pre-monsoon water bodies with the highest microparticle concentrations. While in monsoon season the western water bodies with the highest concentrations of microparticles, which simultaneously exhibited spatial and temporal variations of microparticles in the water bodies in Mt. Yulong area.Precipitation chemistry can reveal air conditions of the Mt. Yulong area, results showed that concentrations of microparticles, volume-size distribution, and chemical composition of precipitation performed distinct seasonal variations. Different with the scenarios found in snow cover and surface water bodies, the concentrations of microparticles in atmospheric precipitation were relatively low, which can reflect preferable air quality of the Lijiang city. Micro-particles with d＜1μm and total number concentration of particles in each rainfall sample display amazing consistent variation over the entire rainy season, though it seems that particles with d＜1μm are more sensitive to reflect the variations of atmospheric particles suspended in the rainfall.The frequency of pH values resulted in a nearly log-normal distribution, with73%of the rain events with a pH value between5.6and7.0, and23%with a pH value ranged from4.5to5.6, indicating that the majority of rainwater had a neutral or alkaline character in the study area. Ca2+and SO42-were the most abundant cations and anions among the detected nine ion species in the rainwater, accounting for40%and25%of the total ion mass, respectively. The association of SO42-,NO3-with NH4+and Ca2+revealed the neutralization of rainwater by CaSO4,（NH4）2SO4and NH4NO3, and the contribution of other ion species in the acidification and neutralization processes in rainwater was negligible.The application of factor and cluster analysis facilitates the interpretation of rainwater characteristics, highlighting the contribution of anthropogenic activities and crustal sources. In addition, monsoon-carried sea salts made up a minor contribution to the origins of Cl-and part of Na+in the rainwater of the Mt. Yulong region. Our studies on rainwater chemistry revealed that elevation differences and the different extents of local anthropogenic activities might account for the differences in the chemical composition of rainwater.The atmospheric backward trajectories calculated with HYSPLIT4transport model show that the origins of dust aerosols were different in monsoon and non-monsoon seasons, i.e. originated from western and southwest directions of the Mt. Yulong. Re-analysis data calculation indicated that the moisture origins and air moistures of the two seasons with big difference, which has huge influence on the mircroparticles transmission and deposition in the atmosphere. Moreover, high concentrations of major ions during the non-monsoon seasons may due to the frequent dust events occurred in those seasons. It is also noteworthy that the bare rock of snow-free terrain on the Mt. Yulong and mineral dust particles from rock weathering are important sources for the dust in the water bodies there. |
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