Polychlorinated biphenyls (PCBs) are classified as persistent organic pollutants (POPs) due to their potential threat to both ecosystems and human health. The Tibetan Plateau (TP), characterized by its low temperatures, pristine ecological conditions, and remoteness from anthropogenic influences, serves as the investigation region. This study analyzed water samples from the temperature glacial watershed and employed the risk assessment method established by the United States Environmental Protection Agency (US EPA) to assess both carcinogenic and non-carcinogenic risks of PCBs in five age groups. The total concentrations of PCBs (& sum;3PCBs) varied from 738 to 1914 ng/L, with a mean value of 1058 ng/L, which was comparable to or exceeded levels reported in the surface water around the TP. Notably, the riverine sites located near the villages and towns exhibited the highest pollution levels. Our analyses indicated that glacier melting, long-range atmospheric transport (LRAT), reductive dechlorination processes, and various anthropogenic activities might be potential sources of PCB emission in the Meili Snow Mountains. According to the established national and international water quality standards, as well as toxic equivalency concentrations (TEQs) for dioxin-like PCBs (DL PCBs), the PCB concentrations detected in this study could result in serious biological damage and adverse ecological toxicological effects. However, the PCBs in all samples posed a negligible cancer risk to five age groups, and a non-carcinogenic risk to adults. These findings contribute valuable insights into the risks and sources of PCBs and may serve as a foundational reference for subsequent study of these compounds in the Meili Snow Mountains area of the southeastern TP.

Due to the impact of climate change and human activities, part of the Yongding River has stopped flowing, and the hydrological environment is damaged. The hydrological condition can be used to assess the ecological environment of the watershed, and analyzing the driving factors affecting the hydrological condition is essential for the environmental restoration of the watershed, but it is particularly challenging on a daily scale. This paper used the Indicators of Hydrologic Alteration and the Range of Variability Approach (IHA-RVA) method to screen out the sensitive indicators in different periods that are representative of each river; determined the hydrological variation periods of the upper Yongding River and the two subbasins, the Yang River and the Sanggan River; and quantitatively identified the contribution of climate change and different human activities (water withdrawals and reservoir storage) to the basin's runoff by constructing a daily-scale model named the Water and Energy Transfer between Soil, Plants, and Atmosphere (WetSpa) model. The results showed that the upper Yongding River, the Yang River, and the Sanggan River had a high degree of variation (87.2%), a low degree of variation (20%), and a moderate degree of variation (37.5%) in 1975-1988, 1980-1986, and 1978-1993, respectively. Human activities were the main driving factors, but their contributions varied across different basins. The Yang River is mostly affected by water withdrawals, with a contribution rate of 125.90%. The Sanggan River was affected mostly by reservoir storage, with a contribution rate of 153.47%. The upper Yongding River was affected mostly by climate change. A stricter management system can reduce the impact of human activities on runoff changes and provide a guarantee for the restoration of the ecological environment of the upper Yongding River.

Atmospheric Brown Carbon (BrC) with strong wavelength-dependence light-absorption ability can significantly affect radiative forcing. Highly resolved emission inventories with lower uncertainties are important premise and essential in scientifically evaluating impacts of emissions on air quality, human health and climate change. This study developed a bottom-up inventory of primary BrC from combustion sources in China from 1960 to 2016 with a spatial resolution at 0.1 degrees x 0.1 degrees, based on compiled emission factors and detailed activity data. The primary BrC emission in China was about 593 Gg (500-735 Gg as interquartile range) in 2016, contributing to 7% (5%-8%) of a previously estimated global total BrC emission. Residential fuel combustion was the largest source of primary BrC in China, with the contribution of 67% as the national average but ranging from 25% to 99% among different provincial regions. Significant spatial disparities were also observed in the relative shares of different fuel types. Coal combustion contribution varied from 8% to 99% across different regions. Heilongjiang and North China Plain had high emissions of primary BrC. Generally, on the national scale, spatial distribution of BrC emission density per area was aligned with the population distribution. Primary BrC emission from combustion sources in China have been declined since a peak of similar to 1300 Gg in 1980, but the temporal trends were distinct in different sectors. The high-resolution inventory developed here enables radiative forcing simulations in future atmospheric models so as to promote better understanding of carbonaceous aerosol impacts in the Earth's climate system and to develop strategies achieving co-benefits of human health protection and climate change.

Wildfires play a dual role in ecosystems by providing ecological benefits while posing catastrophic events; they also inflict non-catastrophic damage and yield long-term effects on biodiversity, soil quality, and air quality, among other factors, including public health. This study analysed the key determinants of wildland fires in Spain using openly available spatial data from 2008 to 2021, including fire perimeters, bioclimatic variables, topography, and socioeconomic datasets, at a resolution of 1 km(2). Our methodology combined principal component analysis (PCA), linear regression analysis, and one-way analysis of variance (ANOVA). Our findings show that scrub/herbaceous vegetation (average 63 +/- 1.45% SE) and forests (average 19 +/- 0.76% SE) have been highly susceptible to wildfires. The population density exhibited a robust positive correlation with wildfire frequency (R-2 = 0.88, p < 0.0001). Although the study provides insights into some fire-related climatic drivers over Spain, it includes only temperature- and precipitation-based variables and does not explicitly consider fuel dynamics. Therefore, a more advanced methodology should be applied in the future to understand the local specifics of regional wildfire dynamics. Our study identified that scrub/herbaceous areas and forests near densely populated regions should be prioritised for wildfire management in Spain, particularly under changing climate conditions.

Known as the roof of the world , 50%-56% area of the Qinghai-Tibet Plateau (QTP) is covered by seasonal frozen ground (SFG), which has an important impact on local and global climate change, terrestrial ecosystems, and regional energy and hydrological cycles. In this study, long-term observational data of air and soil water (precipitation and soil moisture) and heat [surface air temperature (SAT) and soil temperature (ST)] at 30 meteorological stations were used to study the temporal and spatial changes of SFG and their possible causes for the central-eastern QTP (CEQTP). The results showed that latitude and altitude are the key factors affecting the spatial distributions of seasonal freeze-thaw activities of CEQTP. The stations with deeper freeze depths and more freeze days are mainly located in high-altitude and high-latitude regions, and those with shallower freeze depths and fewer freeze days are mainly located in the low-altitude and low-latitude regions of the southern QTP. This may be the reason that latitude and altitude are the key factors determining the temperature distribution on the CEQTP. SAT, ST, precipitation, and soil moisture are all significant correlations with the freeze depth, freeze days, freeze start date (FSD) and thaw end date (TED), and the abrupt change years of them are also consistent; they are the important factors affecting the freeze-thaw changes (FTCs) of SFG. Among them, ST is the key factor influencing the FTCs of SFG, and the variations of monthly average soil temperature (MAST) at 0-320 cm depths are the inverse of those of the monthly average freeze depth and freeze days during the year. Using the MAST data at 0-320 cm depths and the 0? ST threshold, the soil freeze-thaw processes at different depths on the CEQTP are revealed. Affected by global warming, SAT and ST at different depths on the CEQTP have shown the upward trends since the 1980s. Additionally, precipitation and soil moisture have also increased substantially, especially since the late 1990s. Enhancement of warming and wetting conditions from the land surface to the deep soil have accelerated the thawing of SFG, and led to the delay of FSD and the advance of TED, which further caused the reduction of freeze depth and freeze days of SFG on the QTP, especially since the late 1990s.

Alpine ecosystems play an important role in maintaining carbon sequestration, water balance, ecological security, biodiversity and human well-being. However, climate change and high-intensity human activities lead to the continuous degradation of vulnerable alpine ecosystems. Based on this, we reveal trends in ecosystem change in the Qilian Mountains of China on a 40-year scale and identify the primary driving factors of change in alpine ecosystems from the perspective of ecosystem service value (ESV) change, providing a more comprehensive picture of the interactions between human society and natural ecosystem. The results showed that more than 55 % of ecosystem types changed from 1980 to 2018, with forests, grasslands, glaciers and bare land being the most vulnerable ecosystems to disturbance, and forest and grassland ecosystems having significant ESV potential (43.99 % and 29.57 %, respectively). However, significant land use and land cover (LULC) changes over the last decade have led to a reduction in ESV stability in alpine ecosystems, where human activities have a more significant impact on ESV of sparse woodland, shrubland and grassland ecosystem at 2800-4000 m. The temperature rise had a more noticeable impact on the ESV of glaciers, alpine meadows and bare land ecosystems at 4000-5500 m. In the long terms, climate change and population growth will threaten the restoration and management of alpine ecosystems. Different ecological development strategies need to be adopted along the altitude, and the establishment of cross regional horizontal ecological compensation mechanism should be accelerated to promote the sustainable development of ecology and people's livelihood in mountainous areas. The results of this study will provide relevant theoretical basis and reference for decision makers, and provide a model for scientific management and sustainable development of alpine ecosystem resources worldwide.

The Qaidam Basin of the Qinghai-Tibet Plateau is a cold, hyper-arid desert that presents extreme challenges to microbial communities. As little is known about variations between surface and subsurface microbial communities, high-throughput DNA sequencing was used in this study to profile bacterial communities of the soil samples collected at different depths in three regions in the Qaidam Basin. The alpha-diversity indices (Chao, Shannon, and Simpson) indicated that bacterial abundance and diversity were higher in the east and the high-elevation regions compared to the west region. In general,Firmicuteswas dominant in the west region, whileProteobacteriaandAcidobacteriawere dominant in the east and the high-elevation regions. The structure of the bacterial communities differed greatly across regions, being strongly correlated with total organic carbon (TOC) and total nitrogen (TN) content. The differences in bacterial communities between the surface and the subsurface soil samples were smaller than the differences across the regions. Network analyses of environmental factors and bacterial genera indicated significant positive correlations in all regions. Overall, our study provides evidence that TOC and TN are the best predictors of both surface and subsurface bacterial communities across the Qaidam Basin. This study concludes that the bacterial community structure is influenced by both the spatial distance and the local environment, but environmental factors are the primary drivers of bacterial spatial patterns in the Qaidam Basin.