Hewen Niu

In-situ measurements of light-absorbing impurities in snow of glacier on Mt. Yulong and implications for radiative forcing estimates

The Tibetan Plateau (TP) or the third polar cryosphere borders geographical hotspots for discharges of black carbon (BC). BC and dust play important roles in climate system and Earths energy budget, particularly after they are deposited on snow and glacial surfaces. BC and dust are two kinds of main light-absorbing impurities (LAIs) in snow and glaciers. Estimating concentrations and distribution of LAIs in snow and glacier ice in the TP is of great interest because this region is a global hotspot in geophysical research. Various snow samples, including surface aged-snow, superimposed ice and snow meltwater samples were collected from a typical temperate glacier on Mt. Yulong in the snow melt season in 2015. The samples were determined for BC, Organic Carbon (OC) concentrations using an improved thermal/optical reflectance (DRI Model 2001) method and gravimetric method for dust concentrations. Results indicated that the LAIs concentrations were highly elevation-dependent in the study area. Higher contents and probably greater deposition at relative lower elevations (generally <5000masl) of the glacier was observed. Temporal difference of LAIs contents demonstrated that LAIs in snow of glacier gradually increased as snow melting progressed. Evaluations of the relative absorption of BC and dust displayed that the impact of dust on snow albedo and radiative forcing (RF) is substantially larger than BC, particularly when dust contents are higher. This was verified by the absorption factor, which was <1.0. In addition, we found the BC-induced albedo reduction to be in the range of 2% to nearly 10% during the snow melting season, and the mean snow albedo reduction was 4.63%, hence for BC contents ranging from 281 to 894ngg-1 in snow of a typical temperate glacier on Mt. Yulong, the associated instantaneous RF will be 76.38-146.96Wm-2. Further research is needed to partition LAIs induced glacial melt, modeling researches in combination with long-term in-situ observations of LAIs in glaciers is also urgent needed in the future work.

Water-soluble elements in snow and ice on Mt. Yulong

Melting of high-elevation glaciers can be accelerated by the deposition of light-absorbing aerosols (e.g., organic carbon, mineral dust), resulting in significant reductions of the surface albedo on glaciers. Organic carbon deposited in glaciers is of great significance to global carbon cycles, snow photochemistry, and air-snow exchange processes. In this work, various snow and ice samples were collected at high elevation sites (4300-4850masl) from Mt. Yulong on the southeastern Tibetan Plateau in 2015. These samples were analyzed for water-soluble organic carbon (DOC), total nitrogen (TN), and water-soluble inorganic ions (WSIs) to elucidate the chemical species and compositions of the glaciers in the Mt. Yulong region. Generally, glacial meltwater had the lowest DOC content (0.39mgL-1), while fresh snow had the highest (2.03mgL-1) among various types of snow and ice samples. There were obvious spatial and temporal trends of DOC and WSIs in glaciers. The DOC and TN concentrations decreased in the order of fresh snow, snow meltwater, snowpit, and surface snow, resulting from the photolysis of DOC and snows quick-melt effects. The surface snow had low DOC and TN depletion ratios in the melt season; specifically, the ratios were -0.79 and -0.19mgL-1d-1, respectively. In the winter season, the ratios of DOC and TN were remarkably higher, with values of -0.20mgL-1d-1 and -0.08mgL-1d-1, respectively. A reduction of the DOC and TN content in glaciers was due to snows quick melt and sublimation. Deposition of these light-absorbing impurities (LAPs) in glaciers might accelerate snowmelt and even glacial retreat.

Trace elements and rare earth elements in wet deposition of Lijiang, Mt. Yulong region, southeastern edge of the Tibetan Plateau

In order to investigate the compositions and wet deposition fluxes of trace elements and rare earth elements (REEs) in the precipitation of the southeastern edge of the Tibetan Plateau, 38 precipitation samples were collected from March to August in 2012 in an urban site of Lijiang city in the Mt. Yulong region. The concentrations of most trace elements and REEs were higher during the non-monsoon season than during the monsoon season, indicating that the lower concentrations of trace elements and REEs observed during monsoon had been influenced by the dilution effect of increased precipitation. The concentrations of trace elements in the precipitation of Lijiang city were slightly higher than those observed in remote sites of the Tibetan Plateau but much lower than those observed in the metropolises of China, indicating that the atmospheric environment of Lijiang city was less influenced by anthropogenic emissions, and, as a consequence, the air quality was still relatively good. However, the results of enrichment factor and principal component analysis revealed that some anthropogenic activities (e.g., the increasing traffic emissions from the rapid development of tourism) were most likely important contributors to trace elements, while the regional/local crustal sources rather than anthropogenic activities were the predominant contributors to the REEs in the wet deposition of Lijiang city. Our study was relevant not only for assessing the current status of the atmospheric environment in the Mt. Yulong region, but also for specific management actions to be implemented for the control of atmospheric inputs and the health of the environment for the future.

Chemical compositions of snow from Mt. Yulong, southeastern Tibetan Plateau

The snow and ice in Mt. Yulong offer a unique opportunity to investigate changes in climate and large scale atmospheric circulations over Asia. During February and April 2012, surface snow samples were collected from the Baishui Glacier No. 1 at different altitudes along the eastern slope of Mt. Yulong. Two snowpits were also excavated from Mt. Yulong at altitudes of 4780 and 4730 m a.s.l. in February 2012. The concentrations of inorganic ions were higher at an elevation of 4506 m a.s.l. in the glacier with significant contribution of anthropogenic (mainly NH4+

Levels and spatial distributions of levoglucosan and dissolved organic carbon in snowpits over the Tibetan Plateau glaciers

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Water isotopes and hydrograph separation in different glacial catchments in the southeast margin of the Tibetan Plateau

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Analysis of Herbaceous Plant Succession and Dispersal Mechanisms in Deglaciated Terrain on Mt. Yulong, China

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Distributions and light absorption property of water soluble organic carbon in a typical temperate glacier, southeastern Tibetan Plateau

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Chemical composition of rainwater in the Yulong Snow Mountain region, Southwestern China

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Rural household energy consumption and its implications for eco-environments in NW China: A case study

and crustal (mainly Ca 2+) constituents. Concentration of HCOO − in surface snow exhibited large variability, ranging from 0.04 to 6.8 μeq L −1, attributed to dominant contribution from biomass burning emissions. Ion balance (ΔC) and Na +/Cl − calculations indicated an excess of cations (particularly higher Ca 2+ concentrations) and Cl − in snow, considering the sea-salt ratio, respectively. Monsoon season (June–September) ion concentrations in snowpit samples were generally two-fold lower than in other seasons. Principal component analysis was used to identify different sources of ions. Three main factors, accounting for more than 80% of the total variance, were related to different sources, including agricultural activities, biomass burning, and crustal aerosols.