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Carbonaceous aerosols (CAs) scatter and absorb incident solar radiation in the atmosphere, thereby influencing the regional climate and hydrological cycle, particularly in the Third Pole (TP). Here, we present the characteristics of CAs at 19 observation stations from the Atmospheric Pollution and Cryospheric Change network to obtain a deep understanding of pollutant status in the TP. The organic carbon (OC) and elemental carbon (EC) concentrations decreased noticeably inwards from outside to inland of the TP, consistent with their emission load and also affected by transport process and meteorological condition. Urban areas, such as Kathmandu, Karachi, and Mardan, exhibited extremely high OC and EC concentrations, with low and high values occurring in the monsoon and non-monsoon seasons, respectively. However, remote regions inland the TP (e.g., Nam Co and Ngari) demonstrated much lower OC and EC concentrations. Different seasonal variations were observed between the southern and northern parts of the TP, suggesting differences in the patterns of pollutant sources and in distance from the sources between the two regions. In addition to the influence of long-range transported pollutants from the Indo-Gangetic Plain (IGP), the TP was affected by local emissions (e.g., biomass burning). The OC/EC ratio also suggested that biomass burning was prevalent in the center TP, whereas the marginal sites (e.g., Jomsom, Dhunche, and Laohugou) were affected by fossil fuel combustion from the up-wind regions. The mass absorption cross-section of EC (MAC EC) at 632 nm ranged from 6.56 to 14.7 m2 g−1, with an increasing trend from outside to inland of the TP. Urban areas had low MAC EC values because such regions were mainly affected by local fresh emissions. In addition, large amount of brown carbon can decrease the MAC EC values in cities of South Asia. Remote sites had high MAC EC values because of the coating enhancement of aerosols. Influenced by emission, transport process, and weather condition, the CA concentrations and MAC EC presented decreasing and increasing trends, respectively, from outside to inland of the TP. Image 1 • CA concentrations decrease remarkably inwards from outside to inland of the TP. • CA seasonal variation suggest a different source pattern between south and north parts of TP. • The TP is affected by local biomass burning in addition to long-range transport pollutants. • MAC EC increase from outside to inland of the TP because of aging and coating processes. [ABSTRACT FROM AUTHOR]

Water-soluble organic carbon (WSOC) widely stored in glaciers from local and distant sources, and then released it to downstream environments under a warming climate. Climatic driven changes to glacial run-off are larger and represent an important flux of organic carbon. However, very few WSOC data are currently available to fully characterize WSOC variation in the temperate glacierized regions of the Tibetan Plateau (TP). This study first systematically evaluated the concentration characteristics and light absorbing property of WSOC, and insoluble particulate carbon (IPC) in snow and ice of a typical temperate glacier on Mt. Yulong. Average concentrations of WSOC were 0.61 ± 0.21 mg L−1 in Baishui glacier on Mt. Yulong. WSOC concentrations in surface aged snow were dramatically decreased with the time extension during the entire monsoon season due to extensive glacial melting and scavenging effects by meltwater. The MAC values of WSOC calculated at 365 nm was 6.31 ± 0.34 m2 g−1 on Mt. Yulong, and there exists distinct spectral dependence of MACwsoc within the wavelength range (260 - 700 nm). The low AAE330-400 values suggest the light absorption of WSOC is more spectrally neutral. The flux of WSOC in Baishui glacier was 0.99 gC m−2 yr−1, while the IPC flux was 4.77 gC m−2 yr−1. Total WSOC storage in the Baishui glacier was estimated to be 1.5 tone C and total IPC storage was 7.25 tone C (1 tone = 106 g). Moreover, glacial melting was reinforced by the soluble and insoluble light absorbing impurities (ILAIs) in glaciers, Baishui glacier can be considered as a fraction of carbon source under the scenario of a warming climate, more importantly, WSOC in snow and ice needs to be taken into account in calculating the radiative forcing of ILAIs and accelerating glacial melting. [ABSTRACT FROM AUTHOR]

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 Earth's 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 < 5000 m asl) 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 894 ng g − 1 in snow of a typical temperate glacier on Mt. Yulong, the associated instantaneous RF will be 76.38–146.96 W m − 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. [ABSTRACT FROM AUTHOR]

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 (4300–4850 m asl) 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 (0.39 mg L − 1 ), while fresh snow had the highest (2.03 mg L − 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 snow's quick-melt effects. The surface snow had low DOC and TN depletion ratios in the melt season; specifically, the ratios were − 0.79 and − 0.19 mg L − 1 d − 1 , respectively. In the winter season, the ratios of DOC and TN were remarkably higher, with values of − 0.20 mg L − 1 d − 1 and − 0.08 mg L − 1 d − 1 , respectively. A reduction of the DOC and TN content in glaciers was due to snow's quick melt and sublimation. Deposition of these light-absorbing impurities (LAPs) in glaciers might accelerate snowmelt and even glacial retreat. [ABSTRACT FROM AUTHOR]

• WSOC in water bodies from cryosphere region has significant elevation dependency. • Atmospheric deposition of OM over TP was transported to plateau lakes via rivers. • The deposition rate of OC in the periphery of the TP was extremely high. • Alpine runoff made primary contribution (45%) to the altitude dependency of OM. Our understanding of water-soluble organic constituents and their transformation in the unique aqueous continuum over cryosphere region is scarce. Here, dissolved organic carbon (DOC), dissolved organic nitrogen (DON), and dissolved total nitrogen (DTN) and water-soluble inorganic ions in multiple water bodies from the eastern Tibetan Plateau (TP) cryosphere are systematically determined from a suite of field campaigns, laboratory experiments, linear regression analysis, and multiple comparisons, etc. We found that the water bodies located at high elevation have much lower DOC contents compared to the samples at lower elevation, there has significant altitude dependence of DOC abundance in water bodies over the study area (elevation range: 1971–4700 m asl). Comparison of optical properties, source apportionment, chemical analysis and model simulation of the water bodies provide evidence that the atmospheric deposition of organic species in high mountains is transported to plateau lakes in the northeast of TP via alpine runoff (45%) and snow/ice meltwater (20%). Further, dominance of anthropogenic activities in lower elevations can contribute (35%) to the observed altitudinal dependency. Thus, this preliminary study represents the first systematic investigation of the transport and cycling of organic carbonaceous matter and nitrogenous matter in eastern TP and warrants more robust in-situ observations and measurements in future in High Mountains of Asia. [ABSTRACT FROM AUTHOR]

Investigating the migration and transformation of carbonaceous and nitrogenous matter in the cryosphere areas is crucial for understanding global biogeochemical cycle and earth's climate system. However, water-soluble organic constituents and their transformation in multiple water bodies are barely investigated. Water-soluble organic carbon (WSOC) and organic nitrogen (WSON), and particulate black carbon (PBC) in multiple types of water bodies in eastern Tibetan Plateau (TP) cryosphere for the first time have been systematically investigated. Statistical results exhibited that from south to north and from east to west of this region, WSOC concentrations in alpine river runoff were gradually elevated. WSOC and nitrogenous matter in the alpine river runoff and precipitation in the glacier region presented distinct seasonal variations. WSON was the dominant component (63.4%) of water-soluble total nitrogen in precipitation over high-altitude southeastern TP cryosphere. Water-soluble carbonaceous matter dominated the carbon cycle in the TP cryosphere, but particulate carbonaceous matter in the alpine river runoff had a small fraction of the cryospheric carbon cycle. Analysis of optical properties illustrated that PBC had a much stronger light absorption ability (MAC- PBC : 2.28 ± 0.37 m2 g−1) than WSOC in the alpine river runoff (0.41 ± 0.26 m2 g−1). Ionic composition was dominated by SO 4 2−, NO 3 −, and NH 4 + (average: 45.13 ± 3.75%) in the snow of glaciers, implying important contribution of (fossil fuel) combustion sources over this region. The results of this study have essential implications for understanding the carbon and nitrogen cycles in high altitude cryosphere regions of the world. Future work should be performed based on more robust in-situ observations and measurements from multiple environmental medium over the cryosphere areas, to ensure ecological protection and high-quality development of the high mountain Asia. [Display omitted] • WSOC and WSON contents in multiple types of water bodies have been investigated. • WSON was the dominant component (63.4%) of rainwater WSTN over the southeastern TP. • Post-depositional process has obvious effect on redistribution of WSOC in snowpit. • PBC and POC in mountainous river runoff make up a small fraction of carbon cycle. • Water-soluble carbonaceous matter dominates the carbon cycle in TP cryosphere. [ABSTRACT FROM AUTHOR]

• This is the first study on WSOC in multiple samples in a glacierized region. • Light-absorbing properties of WSOC have been thoroughly investigated. • There exists spatio-temporal heterogeneity of WSOC over the Mt. Yulong. • Inorganic ions were the most abundant species in snow and river water samples. • The transfer process of WSOC in the summer precipitation-atmosphere-snow-river water continuum has been examined. Atmospheric aerosols are a branch of active research in recent decades. The deposition of light-absorbing substances on high-altitude glaciers causes substantial adverse impacts on the cryospheric environment, cryosphere-hydrology, and climate system. Although, the concentrations of water-soluble organic carbon (WSOC) in snow/ice on glaciers of Tibetan Plateau (TP) have been reported, their transfer processes and optical properties in the context of summer precipitation-atmosphere-snow-river water continuum are seldom studied. In this study, we have systematically examined some scientific issues associated with WSOC concentrations and light absorption properties of WSOC in various forms of samples from the Mt. Yulong region. Statistical results demonstrate that the spatial distribution of WSOC in the snow of Baishui glacier was heterogeneous. The average WSOC concentrations of each snowpit were significantly decreased, and its light-absorbing properties were significantly elevated with the time extension. Aerosol WSOC concentrations and light absorption have distinct spatial disparity and seasonal variation. Pre-monsoon and monsoon have the highest and lowest WSOC content, respectively. Whereas the light-absorbing properties present contrasting seasonal trends. Rivers of which runoff was supplied by glacier meltwater have significantly lower WSOC concentrations (e.g., 0.42 ± 0.03 mg L−1) compared with other forms of water bodies. Mass absorption cross-section of WSOC (MAC- WSOC) in multiple snow and meltwater samples was significantly different and type-dependent. Atmospheric aerosol has the lowest MAC- WSOC value among the four types of samples, which was likely associated with exhaust emissions from private vehicles and tour buses. Statistical results indicated that the average AAE 330-400 values of various snow/ice samples are subequal. Snow of glaciers supplies a desirable platform for the deposition of gaseous materials which experienced long-range transport in high altitude zones. Biomass-burning emissions made an immense contribution to the WSOC deposition over the study area, as demonstrated by the distribution of active fire points. However, this preliminary study represents the first systematic investigation of WSOC deposition in southeastern TP. Further robust in-situ field investigations and laboratory measurements are urgently necessary to improve our understanding of the transfer process and optical property of WSOC. [ABSTRACT FROM AUTHOR]

Black carbon (BC), dust, and organic carbon (OC) aerosols, when deposited onto the surface of glaciers, can absorb light and decrease the snow albedo. These impurities in snow are referred to as ILAIs (i.e., insoluble light absorbing impurities). Atmospheric chemical models have been extensively used to simulate the transport and deposition of atmospheric aerosols in glacierized areas. However, systematic investigations of ILAIs in snowpack of glaciers on the Tibetan Plateau (TP) are rare. In this study, observations of ILAIs in snow and simulations of ILAIs of atmospheric aerosol at surface over four glaciers on the TP have been analyzed. Strong correlation between BC and dust was found in surface aged-snow, and their correlation significantly varied with snowpit depth. BC and OC concentrations in snowpit tended to decrease with depth. Significant differences of ILAI concentrations among depth intervals reflect their diverse hydrophilicities, physiochemical properties and post-depositional processes in snowpit, offering important observational constraints on the related processes. Monthly variation of atmospheric ILAIs at surface over glaciers is characterized by distinct spatial heterogeneity. The statistical results show higher ILAI concentrations in the summer of 2015 than 2014, which is in qualitative agreement with CALIPSO observations, likely reflecting the effects of inter-annual variation of summer monsoon on snow ILAI loadings. Optical attenuation (ATN) of BC is gradually decreased with depth of snowpit, whereas the trend of mass absorption cross-section (MAC) of BC throughout the profile of snowpit is opposite to that of ATN. The scanning electron microscopy (SEM) imaging demonstrates that calcium and silicon rich particles dominate over biological, quartz and flying ash particles in the cryoconite, providing additional constraints on the sources of dust-in-snow and can facilitate better understanding of the physicochemical properties and climatic effects of particles in the glacial cryoconite. Unlabelled Image • The monthly trend of ILAIs is characterized by distinct spatial heterogeneity. • Snowpack BC and OC concentrations tended to decrease with snowpit depth. • Mass absorption cross-section (MAC) of BC throughout the profile of snowpit is increased. • Calcium and silicon-rich particles dominate over other particles in glacier cryoconite. [ABSTRACT FROM AUTHOR]

In this study, we collected 60 snowpit samples in nine glaciers from the northern to the southern Tibetan Plateau (TP), to study the levels and spatial distributions of levoglucosan and dissolved organic carbon (DOC). The lowest concentration of levoglucosan was found in the Yuzhufeng (YZF) glacier with a mean value of 0.24 ± 0.08 ng mL − 1 , while the highest concentration of levoglucosan was detected in the Gurenhekou (GRHK) glacier with a mean value of 11.72 ± 15.61 ng mL − 1 . However, the average DOC concentration in TP glaciers were comparable, without significant regional differences. The levoglucosan/DOC ratio ranged from 0.02 to 6.03% in the Tibetan Plateau glaciers. This ratios and the correlations between levoglucosan and DOC suggested that biomass burning products contributed only marginally to DOC levels in the TP glaciers. Moreover, the analysis of air mass backward trajectories suggested that levoglucosan and DOC in TP glaciers should be transported from the northwestern TP, internal TP, Central Asia, South and East Asia regions. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

• Surface snow experiences post-depositional processes. • Snowpack in the accumulation period is a record of winter precipitation. • Wind is an crucial factor for isotopes in the accumulation period. • Isotopic exchange is the controlling factor for isotopes in the ablation period. Stable isotopes are useful for obtaining hydroclimatic and past environmental information. The record of stable isotopes in snow not only reflects the deposition condition but also provides information on post-depositional processes, which benefits ice core studies. In this study, δ 18O and δ D in new snow, surface snow and snowpack were measured to analyze deposited and post-depositional processes on a temperate glacier at the southeast margin of the Tibetan plateau. The results indicated that new snow and surface snow were relatively depleted in heavy isotopes during the post-monsoon period and enriched in heavy isotopes during the westerly and pre-monsoon period. Surface snow was enriched in 18O and D relative to new snow sampled during the same period. Isotopic homogenization was observed in May and June snowpack, illustrating the effect of melting on isotopes. The relatively low slope (<8) for the δ D– δ 18O line during the post-monsoon period and high slope (>8) during the westerly and pre-monsoon periods corresponded to temperature change. Although the vertical isotopic composition of snowpack sampled in April recorded the deposited information of winter precipitation, the post-depositional processes could have altered the isotopic composition of snow. During the accumulation period, wind drift was an crucial factor leading to abrupt isotopic modification in snow, which was verified using the energy-balance model and wind regime. During the ablation period, the decreasing trend of the slope and the gradual enrichment of 18O and D in the leaving snow mainly resulted from the isotopic exchange between liquid and solid water. The study enhanced our understanding of the controlling post-depositional processes on temperate glaciers. [ABSTRACT FROM AUTHOR]