Arctic regions are highly impacted by the global temperature rising and its consequences and influences on the thermo-hydro processes and their feedbacks. Theses processes are especially not very well understood in the context of river-permafrost interactions and permafrost degradation. This paper focuses on the thermal characterization of a river-valley system in a continuous permafrost area (Syrdakh, Yakutia, Eastern Siberia) that is subject to intense thawing, with major consequences on water resources and quality. We investigated this Yakutian area through two transects crossing the river using classical tools such as in-situ temperature measurements, direct active layer thickness estimations, unscrewed aerial vehicle (UAV) imagery, heat transfer numerical experiments, Ground-Penetrating Radar (GPR), and Electrical Resistivity Tomography (ERT). Of these two transects, one was closely investigated with a long-term temperature time series from 2012 to 2018, while both of them were surveyed by geophysical and UAV data acquisition in 2017 and 2018. Thermodynamical numerical simulations were run based on the long-term temperature series and are in agreement with river thermal influence on permafrost and active layer extensions retrieved from GPR and ERT profiles. An electrical resistivity-temperature relationship highlights the predominant role of water in such a complicated system and paves the way to coupled thermo-hydro-geophysical modeling for understanding permafrost-river system evolution.

Situated in the south edge of the Tibetan Plateau, the Himalayas is expected to receive direct anthropogenic Hg perturbations from South Asia, yet the measurements of atmospheric Hg deposition in the Himalayan region remain scarce. Here we report wet Hg deposition measured in the Yarlung Tsangpo Grand Canyon of the Eastern Himalayas, which is the deepest and longest canyon on earth. The precipitation Hg concentration (56.3 ng L-1) and wet Hg deposition flux (84.7 mu g m(-2) yr(-1)) from the Motuo station were observed among the highest ever reported for the Tibetan Plateau. Together with analysis of principal component suggesting Hg was mainly clustered with anthropogenic ions and backward trajectories indicating 88.8% of air masses came from South Asia, our results show that transboudary pollution influences from South Asia could be largely responsible for the unexpectedly high levels of wet Hg deposition. Moreover, the wet Hg flux measurements (84.7 mu g m(-2) yr(-1)) are found an order of magnitude (similar to 13 times) higher than the GEOS-Chem estimates (6.8 mu g m(-2) yr(-1)), most likely due to the underestimation of transboundary Hg pollution influence by this model. Our study has important implications for better understanding Hg dynamics and verifying atmospheric Hg models in the Tibetan Plateau and Himalayas region.

Glaciochemical records serve as one of the best archives and as good proxies to indicate regional and global anthropogenic influences. The Himalayas, with fragile ecosystems and pristine environments, hold the third largest reservoir of glacier ice and represent an ideal region to investigate trace metal pollution using glacier records. Limited studies on glacially recorded trace metals in the Himalayas usually collect samples from individual glaciers and report a few trace metals in different seasons. We provide a comprehensive and in-depth understanding of the glacially recorded trace metals in the central Himalayas regarding their spatial distribution, seasonal variability, and anthropogenic signals. We analyzed six representative metals (Cu, Zn, Cd, Cr, Pb, Co) and found that the trace metal concentration range largely varied between the studied metals and sampling sites. The Zn metal concentration is higher, attributed to the contribution of natural sources (e.g., forest fires, dust storms) and anthropogenic sources, including industrial and traffic-related emissions. The Pb concentration showed striking seasonality due to the relatively natural input of local material during the monsoon season and the regional and long-range transport of anthropogenic sources during the non-monsoon season. There was a clear spatial variation in certain trace metals, such as Cu, Zn, and Pb, showing decreasing trends with increasing elevation. The enrichment factor (EF) results showed that Zn metal was highly enriched, followed by Cu and Cd, indicating that Zn metal was relatively highly susceptible to intensified human activities. The seasonal paradox between the enrichment factor and metal concentration revealed that the EF of the monsoon season was usually higher than that of the non-monsoon season, and vice versa regarding metal concentrations primarily associated with metal deposition in regional climate regimes, particularly atmospheric circulation. We suggest that the analytical method can influence the trace metal concentration and EF calculation, resulting in a previously unrecognized bias in the seasonality of trace metals. Future research should prioritize stable isotopes of trace elements (e.g., Pb, Cu) in glaciers that would provide valuable information in identifying the potential source of anthropogenic inputs and the degree of extent affecting the glaciochemistry of the Himalayas.

Linking snow cover frequency (SCF) and atmospheric circulation is vital for comprehension of hemispheric-scale change mechanisms and for accurate forecasting. This study combined MODIS imagery with meteorological observations to investigate the variation of annual SCFs in the Qilian Mountains. Results indicated that more than 80% of annual SCF is distributed at high elevations and mostly on northern slopes, and that SCF is greater in the west than in the east. Abrupt change in the increase in annual SCF was not detected; however, significant (0.05 confidence level) variation with quasi-3-year and quasi-5-year periods indicated potential connection with monsoons. Topographically, SCF increased at high elevations and decreased in valleys. Moreover, SCF increased significantly with a rise in slope below 23 degrees and then decreased between 23 degrees and 45 degrees, and it decreased with a change in aspect from 70 degrees to 200 degrees and then increased from 200 degrees to 310 degrees. Annual SCF variation in the Qilian Mountains is dominated by precipitation rather than by temperature. In the years with high SCFs, southeasterly winds associated with an anticyclone over southeastern China and southwesterly winds associated with the cyclone over the Iranian Plateau brought warm moisture across northwestern China, favoring snowfall in the Qilian Mountains. Meanwhile, cold moisture outbreaks from the Arctic into the mid-latitudes are conducive to maintaining snow cover. However, in the years with low SCFs, the cold air might be difficultly transporting out of the Arctic region due to the strengthening polar vortex. Moreover, the water vapor was less than that of the mean state and divergence over the Qilian Mountains, which difficultly conduced snowfall over the Qilian Mountains.

Microplastics are widely detected in terrestrial environments. However, microplastic features in the soil of remote areas are still sparse. In this study, microplastic pollution in soil across the Tibetan Plateau was systematically investigated. The results revealed that microplastic was ubiquitous in the soil of the Tibetan Plateau with an average abundance of 47.12 items/kg-dry weight (range: 5-340 items/kg). Compared with the published data of soil microplastic pollution in other regions, the microplastic pollution in the Tibetan Plateau was relatively low. Fibers represented 43.54% of microplastic particles detected, followed by fragments (32.20%) and films (23.78%). They mainly consisted of polyvinyl chloride, polyethylene, polypropylene, and polystyrene. Transparent and white microplastics were prevalent, and small microplastics (50-500 mu m) occupied approximately 66% of all microplastics. High values of microplastics were found near Lhasa, Naqu, and Linzhi. Furthermore, microplastic pollution was found to be negatively related to the distance to the nearest city (p < 0.01), wind velocity (p = 0.014), altitude (p = 0.181), yet positively related to precipitation (p = 0.024). This work presents new insights into the magnitude of microplastics contamination in the soil across the Tibetan Plateau and supplies valuable data for future research on ecotoxicology, ecosystem impacts, and earth system feedback of microplastics on terrestrial ecosystems.

This article presents a review of information related to the influence of potential permafrost degradation on the environmental fate of chemical species which are released and stored, classified as potential influence in future Antarctic environment. Considering all data regarding climate change prediction, this topic may prove important issue for the future state of the Antarctic environment. A detailed survey on soil and permafrost data permitted the assumption that this medium may constitute a sink for organic and inorganic pollution (especially for persistent organic pollution, POPs, and heavy metals). The analysis of the environmental fate and potential consequences of the presence of pollutants for the existence of the Antarctic fauna leads to a conclusion that they may cause numerous negative effects (e.g. Endocrine disruptions, DNA damage, cancerogenicity). In the case of temperature increase and enhanced remobilisation processes, this effect may be even stronger, and may disturb natural balance in the environment. Therefore, regular research on the environmental fate of pollution is required, especially in terms of processes of remobilisation from the permafrost reserves. (C) 2018 Elsevier B.V. All rights reserved.

Aerosol optical properties are analyzed for the first time over Desalpar (23.74 degrees N, 70.69 degrees E, 30 m above mean sea level) a remote site in western India during October 2014 to August 2015. Spectral aerosol optical depth (AOD) measurements were performed using the CIMEL CE-318 automatic Sun/sky radiometer. The annual-averaged AOD(500) and angstrom ngstrom exponent (alpha(440-870)) values are found to be 0.43 +/- 0.26 and 0.69 +/- 0.39, respectively. On the seasonal basis, high AOD(500) of 0.45 +/- 0.30 and 0.61 +/- 0.34 along with low alpha(440-870) of 0.41 +/- 0.27 and 0.41 +/- 0.35 during spring (March-May) and summer (June-August), respectively, suggest the dominance of coarse-mode aerosols, while significant contribution from anthropogenic sources is observed in autumn (AOD(500)= 0.47 +/- 0.26, alpha(440-870)= 1.02 +/- 0.27). The volume size distribution and the spectral single-scattering albedo also confirm the presence of coarse-mode aerosols during March-August. An overall dominance of a mixed type of aerosols (similar to 56%) mostly from October to February is found via the AOD(500) vs alpha(440-870) relationship, while marine aerosols contribute to similar to 18%. Spectral dependence of a and its second derivative (alpha') are also used for studying the aerosol modification processes. The average direct aerosol radiative forcing (DARF) computed via the SBDART model is estimated to range from -27.08 W m(-2) to -10.74 W m(-2) at the top of the atmosphere, from -52.21Wm(-2) to -21.71Wm(-2) at the surface and from 10.97W m(-2) to 26.54 Wm(-2) within the atmosphere. This atmospheric forcing translates into heating rates of 0.31 - 0.75 K day(-1). The aerosol properties and DARF are also examined for different trajectory clusters in order to identify the sources and to assess the influence of long-range transported aerosols over Desalpar. (C) 2016 Elsevier B.V. All rights reserved.

Two main types of grasslands on the Qinghai-Tibet Plateau, alpine swamp and alpine meadow, were selected for this study. Monitoring plots were constructed on each type of grassland with varying degrees of vegetation degradation. The impacts of alpine grassland cover changes on the hillslope water cycle were analyzed in terms of runoff generation, precipitation interception, dew water formation, and soil water dynamics of the active layer, etc. The results showed that different types of grasslands led to different runoff generation regimes; namely, runoff varied linearly with precipitation in alpine swamp, whereas in alpine meadow, runoff exhibited an exponential precipitation-dependence. The decrease in vegetation cover in alpine swamp leads to a decrease in soil moisture content in the top 20 cm of the soil, a delay in the thawing start time in the spring, and a decrease in both surface runoff and subsurface interflow. In alpine meadow, however, the decrease in vegetation cover led to a significant increase in the depth of topsoil moisture content during the thawing period, earlier occurrence of thawing, and an increase in the runoff generation ratio. The alpine meadow vegetation canopy had a higher maximum interception ratio and saturation precipitation than alpine swamp vegetation. With the decrease in vegetation cover, the rainfall interception ratios decreased by almost an identical range in both the alpine meadow and alpine swamp grasslands. Dew water commonly occurs on alpine grassland, accounting for about 12.5-16.5% of precipitation in the same period, and thus, is an important component of the water cycle. With the degradation of vegetation, surface dew water decreased; however, the ratio of dew water formed in the air to the total amount of dew water rose significantly. At the hillslope scale, the changes of alpine vegetation cover had a great influence on the water cycle, which were partly attributed to that the changes of alpine vegetation cover directly altered the surface energy balance, surface water cycle processes, and the thermal and hydraulic properties of active soil. (C) 2012 Elsevier B.V. All rights reserved.