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Long-range atmospheric transportation (LRAT) of persistent organic pollutants followed by their deposition in cold, arid regions is of wide concern. This problem occurs at Qinghai Lake in the northeastern Tibetan Plateau, a sparsely populated area with extreme weather conditions and little current or historical anthropogenic pollution. The concentrations and distribution patterns of the mono-to octa-chlorinated dibenzo- p -dioxin and dibenzofuran (PCDD/F) congeners in surface soil samples collected from around Qinghai Lake were quantified. Concentration differences between low-(mono-to tri-) chlorinated PCDD/Fs and high-(tetra-to octa-) chlorinated PCDD/Fs were measured. High PCDD/F levels were detected, with total concentrations of 15,108 ± 6323 pg/g for the 27 PCDD/F congeners and 15,104 ± 6324 pg/g for the low-chlorinated PCDD/Fs. The concentrations of 17 2,3,7,8-substituted PCDD/Fs were only 3.1 ± 4.4 pg/g and the corresponding international toxicity equivalency (I-TEQ) was 0.11 ± 0.22 pg I-TEQ/g. Given their higher vapor pressures and lower boiling points, low-chlorinated PCDD/Fs, were predominantly gaseous, whereas high-chlorinated PCDD/Fs were predominantly solid, indicating that there is a higher potential for long-range transport of low-chlorinated PCDD/Fs. Overall, because of their high LRAT potential, low-chlorinated PCDD/Fs may pose a greater risk to local ecosystems in cold, remote areas than high-chlorinated PCDD/Fs. [ABSTRACT FROM AUTHOR]

Summer dust aerosol in the Taklimakan Desert (TD) affects not only the albedo of the snow and ice sheets on the Tibetan Plateau (TP) but also air quality and precipitation in the downstream areas. In this study, the summer extreme dust activity in the TD was jointly investigated by using satellite observations and MERRA-2 reanalysis datasets and divided into two states: dust active period and dust inactive period. The horizontal and vertical distribution of summer dust during both the dust active and inactive periods, as derived from the MERRA-2 dataset, is consistent with satellite observations. By comparing the upper-level circulation and surface meteorological elements at two periods, we identify the South Asian High (SAH) as the dominant factor driving the extreme dust activity in the TD during summer. When the SAH is centered on the Iranian Plateau (IP), the dust aerosol in the TD exhibits increased activity and is lifted to higher altitudes due to significantly enhanced westerly winds, near-surface wind speed, and an ascending motion. Conversely, when the SAH is centered on the TP, the summer dust activity shows the opposite behavior. These new findings on the regulatory mechanism of the SAH on the summer dust activity in the TD are highly significant for understanding the occurrence and transport of summer Asian dust and its potential impact on heavy precipitation in the downstream areas. [ABSTRACT FROM AUTHOR]

Because of its unique geographical location, the Tibetan Plateau has been widely studied in geological research. Several studies revealed the geological structure and evolutionary process of the lithosphere deep beneath the northeastern Tibetan Plateau; however, the deep structural characteristics of the Zhangye Basin, which is in the middle of the Hexi Corridor at the junction of the northeastern Tibetan Plateau and Alxa Block, have not been widely examined. To better understand the geodynamics of the Zhangye Basin, studies are needed to investigate the tectonic mechanism of the northeastern Tibetan Plateau. To determine its subsurface structure, 46 broadband magnetotelluric survey stations were deployed across the basin in 2020. The crustal electrical structure of the basin was modeled via three-dimensional nonlinear conjugate gradient inversion. The results of this inversion revealed a low-resistivity zone in the middle-lower crust of the basin, which was characterized as an intracrustal decollement, thus suggesting decoupling deformation of the crust interior. This conductive body may have formed during continuous growth of the Tibetan Plateau, which may have expanded northeastward below the Hexi Corridor and Helishan Fault. The latter may have partly underthrust southwestward in the lower part of the Hexi Corridor and Tibetan Plateau. These results regarding geothermal formation of the Zhangye Basin improve the understanding of its underground structure and may guide the future development of geothermal resources in this area. • The Zhangye Basin was modeled using three-dimensional inversion. • A conductive body in the middle and lower crust indicates intracrustal decollement. • The conductive body may have formed during the expansion of the Tibetan Plateau. • The Zhangye Basin has the potential for geothermal development. [ABSTRACT FROM AUTHOR]

Methane (CH4) is regarded as one of the most important greenhouse gases due to its radiative forcing. Therefore, in running climate models, it is important to have accurate estimates of CH4 concentrations at an appropriate scale. Although great efforts have recently been undertaken to quantify atmospheric CH4 concentrations based on extensive ground-based measurements, it is still difficult to obtain the spatial variations of the CH4 volume mixing ratio (VMR) on a regional scale. This study analyses the spatial variations of CH4 VMRs in China, based on the retrieved CH4 data from Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) spectra. The results showed that the spatial distribution of CH4 VMRs presented decreasing gradients from south-east to north-east and the lowest CH4 concentrations were located on the Qinghai-Tibet Plateau. Paddy fields were the main sources of CH4 in China, as shown through spatial analysis. Natural wetlands and population also contributed to CH4 VMRs. Plant, climate and soil properties presented a strong positive influence on CH4 concentrations, which could be used to interpret the spatial variations. Stepwise multiple regression modelling results showed that temperature, normalized difference vegetation index (NDVI) and soil total nitrogen could explain 76.9% of the differences in CH4 throughout China, and the average difference between the retrieved and the modelled methane concentrations was 14 ppb. [ABSTRACT FROM AUTHOR]