This study presents the first comprehensive global analysis of the variation in mercury (Hg) concentrations in cryoconite, a heterogenous and often organic-rich material found on the surface of glaciers. Samples of cryoconite were collected from 39 glaciers across both hemispheres, comprising 130 samples in total. The highest Hg concentrations were measured in cryoconite from Norway and Alaska (up to 0.965 μg g-1), followed by the European Alps (up to 0.498 μg g-1), reflecting the levels of atmospheric deposition from heavily industrialized and inhabited areas in relatively close proximity to these glaciated regions. To better assess the environmental distribution of Hg in the glacial environment, in addition to cryoconite we also considered other environmental matrices found in glacial and proglacial areas, including algae, soils, and riverine sediments. This included a novel analysis of Hg in red snow algae from Qaanaaq Gletsjer (Greenland). Of all the environmental matrices considered in this study, cryoconite samples contained the highest Hg concentrations. The Pollution Load Index, Geoaccumulation Index, and Target Values for the Netherlands were used as pollution indices to identify hot spots of sediment contamination. According to these pollution indices, samples from the Northern Hemisphere were slightly and moderately polluted by Hg, while those from the Southern Hemisphere were unpolluted. Of the Northern Hemisphere samples, cryoconite from Sweden, Norway and Svalbard had the highest pollution status, while samples from Alaska and the European Alps were generally only slightly polluted. These results highlight the importance of improving our understanding of dynamic and rapidly changing glacial environments in the accumulation, transport, and re-emission of mercury.

Glacier meltwater in the Bogda region is a crucial water source for the Turpan-Hami Basin. In this study, we use three mass balance models with varying complexity to reconstruct the annual mass balance of glaciers in the Bogda region from 2000 to 2021. The performance of these models is validated using geodetic mass change data, MODIS albedo, and specific mass balance observations. All three independent model sets agree that glaciers in the Bogda region experienced a relatively stable negative mass balance between 2000 and 2021. The average annual mass balance was-0.48 m w.e., and the corresponding average meltwater runoff was 1.45 x 108 m3, accounting for 35.12 % of the total streamflow from 2000 to 2018. The primary driver of glacier melt in the region is incoming shortwave radiation (SWnet), with melt being the dominant mass loss process. After 2010, both the mass loss rate and meltwater runoff remained stable, due to the relatively low proportion of snowfall in the melt-season precipitation. Projections under three Shared Socioeconomic Pathways (SSPs) scenarios indicate that glacier mass in the Bogda region will decrease by 35.93 f 8.09 m w.e. (SSP 1-2.6), 41.73 f 8.13 m w.e. (SSP 2-4.5), and 49.79 f 8.26 m w.e. (SSP 5-8.5) by the end of the 21st century. As a result, glacier meltwater runoff will continue to decline.

Tajikistan contains the majority of Central Asia’s glaciers, which cover about 6.00% of the national territory; their rapid shrinkage poses a significant threat to regional water resource security. However, glacier monitoring in Tajikistan was interrupted after 1991, creating a substantial gap in understanding the current state and temporal evolution of these glaciers. Based on glacier inventory data, in situ measurements, and published literature, this study examined the present status and recent variations of glaciers in Tajikistan through data integration and validation, literature collation and comparative analysis, and the application of Geographic Information System (GIS) spatial analysis techniques. As of 2023, Tajikistan possesses a total of 11,528 glaciers, encompassing an area of 7624.48 (±305.58) km2. Small glaciers dominate in number, whereas large glaciers account for the majority of the total area. Over the past two decades, the glacier count has decreased by 2014, and the total area has decreased by 628.98 km2, corresponding to an average annual reduction rate of 0.33%. Regional shrinkage rates range from 4.10% to 22.28%. Glaciers have undergone accelerated mass loss during the past 20 a; only those on the northeastern Pamir Plateau exhibit a weak positive mass balance. Observations of typical monitored glaciers also reveal intensified melting and retreat, consistent with regional trends. In light of the recent acceleration of glacier shrinkage in Tajikistan, focused measures should be implemented to strengthen glacier monitoring, enhance public awareness of glacier preservation, and promote the sustainable development and utilization of glacier tourism. These findings bridge the knowledge gap regarding the spatiotemporal dynamics of Tajikistan’s glaciers over recent decades and provide essential data support for regional water resource management.

Glaciers lost 408 ± 132 Gt of mass during the hydrological year 2025, equivalent to 1.1 ± 0.4 mm sea-level rise. Since 1975, glacier mass loss has totalled 9,583 ± 1,211 Gt, equivalent to 26.4 ± 3.3 mm of sea-level rise, with six of the highest mass-loss years on record occurring in the past seven years.

The streamflow response in three sub-basins of the upstream Urumqi River basin to the summer heatwaves during 2022-2024 was assessed using a combination of long-term observed discharge data and simulations from the previously calibrated, validated, and applied HBV-light model. The analysis revealed significant glacier mass losses at Urumqi Glacier No. 1, with the most pronounced negative mass balance observed in 2024, marking the largest loss since 1959. The observed changes in glaciers were primarily driven by increased solar shortwave radiation and net radiation, as evidenced by energy component analysis. Streamflow responses varied significantly across the sub-basins, reflecting differences in glacier coverage. Sub-basins with glacier coverage exceeding 10% exhibited substantial increases in both ice melt runoff and total runoff. For instance, the UG1 sub-basin recorded total runoff increases of 10% in 2022, 19% in 2023, and 45% in 2024, while the ZK sub-basin showed increases of 18%, 10%, and 42% over the same period. Furthermore, the runoff patterns in these glacierized sub-basins shifted from a single peak to a double peak, with snowmelt runoff occurring approximately 1 month earlier than usual. In contrast, the HX sub-basin, which has only 4% glacier coverage, exhibited a markedly different response. Despite significant increases in ice melt runoff, total runoff in this sub-basin declined by 3% in 2022, 16% in 2023, and 18% in 2024, suggesting that enhanced ice melt was insufficient to offset the increased evapotranspiration. The high-flow period in all sub-basins was notably extended, spanning from June through August, while the timing of ice melt runoff peaks shifted from early August to late July. These findings underscore the differential sensitivities of glacierized and less-glacierized basins to extreme summer heatwaves, highlighting the critical role of glacier cover in shaping high-elevation hydrological responses to climate extremes.

While studies have confirmed that volatile organic compounds (VOCs) emitted directly by tropical island forest vegetation significantly influence ozone (O3) production and climate change through atmospheric oxidation processes, the environmental effects of long-neglected soil and litter emission sources as key potential contributors to VOCs, particularly their driving mechanisms in near-surface O3 pollution formation, remain understudied. This investigation combines field observations with machine learning models to investigate the emission characteristics, sources, and contributions of VOCs from tropical island forests to O3 and secondary organic aerosol (SOA) formation. The results reveal discrepancies between traditional ozone formation potential (OFP) estimates and machine learning-based assessments. OFP calculations identified acetaldehyde and methanol as the dominant contributors to O3 formation, while toluene and monoterpenes were primary drivers of SOA formation. However, the XGBoost model integrated with the SHapley Additive exPlanations (SHAP) framework, which quantifies the dynamic impacts of VOCs under real-world atmospheric conditions, demonstrated that isoprene made the most significant contribution to O3 formation (|SHAP| = 5.9), surpassing other VOCs. For SOA formation, benzene and toluene showed the highest contributions, with |SHAP| values of 1.2 and 0.8, respectively. By calculating initial VOC concentrations and applying the Positive Matrix Factorization (PMF) model, we identified four VOC sources: soil and litter emissions (41 %), oxidative formation (28.5 %), anthropogenic transport (16.6 %), and direct plant emissions (13.9 %). Photochemical reactions caused significant losses of plant-derived VOCs during transport; after accounting for photochemical losses, the contribution of direct plant emissions increased from 4.6 % to 13.9 %. SHAP analysis highlighted that soil and litter emissions contributed most significantly to O3 formation (|SHAP| = 14.7), offering theoretical advantages over traditional OFP estimates that prioritized plant emissions. The SHAP framework, derived from observational data mining, effectively mitigated biases caused by temporal or regional variations and provided a more accurate quantification of rapidly consumed VOCs during active photochemical processes, thereby addressing limitations of conventional OFP methods. These findings indicate that VOCs from soil and litter emissions in tropical forest regions exert a substantial influence on local O3 formation.

Cryoconite granules are microbial aggregations formed by filamentous cyanobacteria with mineral particles on the bare ice surface of glaciers worldwide. Multiple species of filamentous cyanobacteria in cryoconite granules can usually be microscopically and phylogenetically identified. However, the roles of each species in the formation process of granules remain unclear. In this study, the compositions of filamentous cyanobacteria and minerals, as well as the microstructure of cryoconite granules of different sizes collected on a mountain glacier in central Asia, were analyzed. Three distinct morphological taxa of filamentous cyanobacteria (Types A, B, and C) were observed in cryoconite granules, with Types B and C being dominant across all size fractions. Scanning electron microscope observation revealed that Type B often had abundant small mineral particles on its filament surface, while Type C was mostly without or with only a few mineral particles. Abundant clay minerals were found in all size fractions of granules. Our results suggest that cyanobacterial taxa play a different role in binding mineral particles within cryoconite granules and that the presence of multiple taxa of filamentous cyanobacteria contributes to the effective growth of these granules on the glacier surface.

Study region: The Urumqi River, nourished by glaciers in arid regions of northwest China, plays a crucial role in the economic, ecological, and social development of the region. Study focus: Water resource management in arid regions is a perennial concern, compounded by the complex interplay of factors such as global warming and glacial response dynamics. Based on stable isotope and hydrochemistry data of 725 water samples, this study conducts a comprehensive analysis of the hydrochemical characteristics, runoff composition, and mean residence time of the Urumqi River Basin to enhance understanding of the hydrological processes of the river. New hydrological insights for the region: The hydrochemical type of river water is Calcium-Sulphate, with rock weathering as the main influence factor. Using the end-member mixing analysis (EMMA), it was calculated that the contribution ratios of ice and snow meltwater, atmospheric precipitation and groundwater to runoff were as follows: 3.81 %, 60.45 %, 35.75 % in spring; 28.99 %, 15.42 %, and 55.59 % in summer; and 22.72 %, 3.34 %, and 73.94 % in autumn. Based on the convolution integration method, the mean residence time (MRT) of water in the basin was calculated, and the result was 86 weeks (21.5months).

Nitrification plays a crucial role in glacial-degraded forelands as it influences nitrogen cycling and nutrient availability. This study investigated the community composition and microbial interaction patterns of comammox bacteria, as well as canonical ammonia-oxidizing bacteria (AOB) and archaea (AOA), across glacialdegraded forelands. The results revealed that the majority of comammox bacterial sequences fell within Nitrospira clade B (84.44 %) through phylogenetic analysis. Moreover, a significant positive coexistence relationship was observed among the three ammonia-oxidizing microbial groups, with comammox bacteria occupying a central position within the ammonia-oxidizing microbial network of glacial forelands. These findings highlight the central role of comammox bacteria in glacial ammonia-oxidizing microbial networks, and advancing our understanding of microbial succession dynamics related to nitrogen cycling in alpine environments.

Volatile organic compounds (VOCs) are common precursors of ozone (O3) and PM2.5 pollution. This study analyzed the characteristics, sources, and chemical effects of VOCs and PM2.5 from 2017 to 2021 in Lanzhou, China-a complex environment affected by petrochemicals and dust. The study used the photochemical-age-based parametric method, the positive matrix factorization model, and formation potential estimation. The mean concentrations of VOCs and PM2.5 in Lanzhou were 42.5 ppbv and 64.1 μg/m3, respectively. The main constituents of VOCs and PM2.5 were oxygenated VOCs (OVOCs) and mineral dust, respectively. The concentrations of VOCs and PM2.5 were lower during the COVID-19 pandemic. Source apportionment considering photochemical losses showed that the main source of VOCs was solvent use (32.7 %), with the greatest contribution from anthropogenic sources of acetaldehyde. Dust (25.1 %) and industry (24.9 %) were the main sources of PM2.5. Formation potential estimations revealed that acetaldehyde and methanol were the main contributors to O3 generation on O3-polluted days. Toluene, benzene, and α-pinene were the main contributors to secondary organic aerosol generation on PM2.5-polluted days. VOC oxidation explained 37.8 % of secondary organic aerosol formation, with its contribution being 6 % higher on dust-polluted days, when Fe and Ti elements were more likely to contribute to VOC-related secondary organic aerosol generation. Accordingly, control of solvent use, dust, and industrial emissions (OVOCs, aromatic hydrocarbons, and Fe and Ti elements) should be prioritized to mitigate O3 and PM2.5 pollution.

The glacio-hydrological process is essential in the global water cycle but is complex and poorly understood. In this study, we couple the deep Shapley additive explanation (SHAP) with a long short-term memory (LSTM) model to construct a machine-learning (XAI) framework that describes the glacio-hydrological process in Urumqi Glacier No. 1, China. The XAI framework reveals 1) the dominant hydro-meteorological factors have a fivemonth lead time, and each factor has its own active time and degree of contribution; 2) the temperature and precipitation within the lead time dominate the process; 3) identifiable combination of the factors, instead of extreme events themselves, creates the extreme glacio-hydrological phenomena. Generally, the glacial meltwater replenishes the glacial stream runoff, which is influenced by many environmental factors. In particular, the runoff responds to the change in the glacier mass balance with hysteresis within five months. Overall, the temperature and precipitation within the lead time (4-5 months) dominate the runoff processes. This study quantifies the Contribution of each input in the glacio-hydrological process and provides valuable insight into the interaction of various hydro-meteorological factors.

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萨吾尔山是中国西部14座冰川分布的山系之一，横跨中国和哈萨克斯坦两国，尽管冰川规模不大，但因二元政治主体割裂了科学研究的完整性，同时萨吾尔山冰川水资源对于新疆阿勒泰地区吉木乃县可持续发展具有重要意义，为此结合航摄地形图、Landsat及Sentinel卫星遥感影像，并参考已有冰川编目和Google Earth高分辨率历史图像等数据资料，在野外台站现场观测验证基础上对萨吾尔山冰川当前现状和过去30多年间的变化进行了详细研究。结果表明：（1）截止2022年，萨吾尔山共分布冰川31条，总面积11.47 km2，新疆吉木乃县境内的木斯岛冰川为最大规模冰川，面积2.95 km2，其余90%的冰川其面积不足1 km2。（2）过去30多年来，萨吾尔山冰川变化的总体趋势是冰川分裂、面积减小和末端后退持续增加。冰川数量从12条分裂成31条，1989—2022年冰川面积减少8.11 km2，退缩率达41.42%，冰川末端退缩11.30 m。气温升高、冰川反照率降低和冰川破碎程度加大是引起萨吾尔山冰川退缩的主要原因。（3）相较于我国其他13座高大山系，萨吾尔山在过去半个多世纪中冰川面积相对退缩幅度最大。未来在全球气候变暖背景下萨吾尔山冰川极大可能会基本消融殆尽，这对本就干旱贫水的吉木乃县可持续发展将产生重要影响，需提早统筹谋划以应对未来的水资源危机。

Data on particulate matter, gaseous pollutants, and AQI values from three cities (Haikou, Sanya, and Danzhou) between January 2018 and December 2022 were obtained in order to analyze the spatiotemporal distribution characteristics of air pollution, the correlation between pollutants with meteorological conditions, and the potential sources in Hainan Island. The spatiotemporal distribution’s characteristics demonstrated that the annual mean concentrations of SO2, NO2, CO, O3, PM10 and PM2.5 were 4.34 ± 1.11 μg m−3, 9.87 ± 1.87 μg m−3, 0.51 ± 0.06 mg m−3, 73.04 ± 6.36 μg m−3, 27.31 ± 3.63 μg m−3, and 14.01 ± 2.02 μg m−3, respectively. The yearly mean concentrations were trending downward in the past few years and were below the National Ambient Air Quality Standard (NAAQS) Grade II. Summer was the season with the lowest concentrations of all pollutants (3.84 μg m−3, 7.34 μg m−3, 0.42 mg m−3, 52.80 μg m−3, 18.67 μg m−3 and 8.67 μg m−3 for SO2, NO2, CO, O3, PM10 and PM2.5, respectively), and afternoons were the time with the lowest concentrations of pollutants (except for 78.04 μg m−3 for O3). The influence of meteorological conditions on pollutants was examined: there was a prominent positive correlation between temperature and O3 in summer, and relative humidity largely influenced the concentrations of PM. The pollution in Hainan was affected more by regional transport; according to the backward trajectory results, Hainan is susceptible to air masses from Guangdong and Fujian to the northeast, the Indochina Peninsula to the southwest, and the South China Sea to the southeast. The results of PSCF and CWT analyses indicated that Guangdong, Jiangxi, Hunan, and Fujian were the primary potential sources of PM2.5 and O3.

Organophosphate esters (OPEs) are a class of chemicals of emerging concern. However, little is known about the environmental behavior, transformation and ecological risk of OPEs in mid-latitude glacial environments. This study investigated the concentration and composition characteristics of organophosphate triesters (tri-OPEs) and organophosphate diesters (di-OPEs) in the runoff of Urumqi No. 1 Glacier and Koxkar Glacier in the Tianshan Mountains, and estimated the output of them from glacial rivers. The total concentration of tri-OPEs (Σ13tri-OPEs) was 8565 pg/L in glacier surface meltwater and 6568 pg/L in proglacial rivers. Di-OPEs exhibited lower concentrations, with 99 pg/L and 117 pg/L (Σ10di-OPEs) in glacier surface meltwater and proglacial rivers, respectively. Tri-OPEs exhibited clear diurnal variations, which are presumed to be related to environmental temperature, while di-OPEs did not show an obvious trend. Although risk quotients (RQs) indicated that the concentrations of OPEs pose minimal risk to the glacier aquatic environment, the Toxicological Priority Index (ToxPi) score results showed that tris(2-chloroethyl) phosphate (TCEP) has the highest priority and therefore requires more attention. The total output flux of OPEs (Σ13tri-OPEs and Σ10di-OPEs) in glacial rivers throughout the entire Tianshan region was estimated to be ∼ 847 kg/year. Given the continuity of glacial melting and the accumulation of emerging pollutants in glaciers, the process of melting poses an increasing risk to freshwater resources, warranting heightened attention.

Understanding changes in runoff due to climate variations in glacier-dominated headwaters is key to managing water resources and dryland watersheds effectively and rationally. The continuous glacier shrinkage caused by climate warming has significantly impacted the water supply and ecological systems in the vast arid regions of Central Asia, attracting extensive public concern. The study results indicate an increase in total runoff at the Urumqi River source region during both the baseline (1997–2016) and mid-century (2040–2059) periods, encompassing rain, glacier meltwater, and snowmelt components. Compared to the baseline period, the temperature increases by the mid-century under the three climate scenarios (SSP1−26, SSP2−45, and SSP5−85) range from 0.98 to 1.48 °C. In this region, during the period from 1997 to 2016, glacier meltwater was the dominant component of runoff, comprising 42.10–43.79% of the total, followed by snowmelt at 29.64–30.40% and rainfall contributions of 26.56–27.49%. Additionally, glacier storage in this typical catchment responds quickly to temperature fluctuations, significantly impacting runoff. The Urumqi River source region’s runoff exhibits heightened sensitivity to these temperature shifts compared to precipitation effects. We hypothesized three glacier coverage scenarios: unchanged at 100% glaciation, reduced by half to 50%, and fully retreated to 0% glaciation. Analysis of these scenarios demonstrated that glaciers are pivotal in runoff formation. Under the SSP1−26, SSP2−45, and SSP5−85 climate scenarios, glaciers contributed additional runoff increases of 51.61%, 57.64%, and 62.07%, respectively. Generally, glaciers play a critical role in supplying water in dry areas. Thus, accurately forecasting future water resource shifts in high-altitude glacier regions is crucial for downstream water resource management and utilization.