Water-soluble inorganic ions (WSIs) in the aerosols from Central Asia via transboundary transport measured in Jimunai in 2020

Air pollution is a global issue that often transcends national borders, leading to disputes over environmental concerns and climate-mitigation responsibilities. Between March and July 2020, we collected aerosol samples in Jimunai, a town in western China neighboring Kazakhstan, to assess transboundary air pollution in the region. Our analysis focused on major water-soluble inorganic ions (WSIs), with Ca 2+ and SO 4 2− accounting for almost 60% of the total ion loading. The ratio of cations to anions was greater than one (1.33 ± 0.27), indicating alkaline aerosols during the sampling period. Our results suggest that the pollutants measured were primarily sourced from Kazakhstan, as demonstrated by local meteorological data, air-mass trajectory analysis, and pollutant emission inventories in Kazakhstan. Correlation and primary component analysis indicated that NH 4 + played an important role in neutralizing NO 3 − and SO 4 2− , while Cl − was significantly depleted by the probable reaction HNO 3 ↑ + NaCl = HCl↑ + NaNO 3 . These findings highlight the need for continued monitoring and regulation of air pollution sources in the region to address transboundary air pollution.