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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]

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]