The Variation, Source, and Environmental Impact of Chloride Across China: Summarized Field Results Based on the Aerosol Mass Spectrometer (AMS)

Despite numerous field studies focusing on the chemical composition of particulate matter, systematic investigations on particulate chloride (Cl⁻) are scarce in China. This study examines the spatiotemporal distribution, origin, and environmental impact of Cl⁻ across China via compiling a comprehensive data set of submicron aerosol (PM₁) detected by the aerosol mass spectrometer (AMS). In addition, we integrated high-time resolution aerosol composition data from AMS at six representative sites in China for more detailed insights. The mass concentration of Cl⁻ across China is notably high (1.9 ± 2.7 μg m⁻³) in comparison to the global average (0.3 ± 1.0 μg m⁻³), with a distinguished N–S pattern (North > South) and a distinct seasonality (winter > other seasons). Three categories of Cl⁻ diurnal variations were classified, suggesting the primary combustion emission and gas/particle partitioning are the main drivers for the dynamic variation of Cl⁻. The good correlation between Cl⁻ and combustion tracers corroborates the assertion that coal and biomass combustion are the main anthropogenic sources of Cl⁻ based on emission inventory. Furthermore, the quantified environmental impacts of Cl⁻ on ammonium balances, aerosol liquid water content, and hygroscopicity were systematically explored. In extreme cases, the Cl⁻ can enhance 100% ALWC during polluted periods, signifying its key role in impacting the physiochemistry of aerosols. The mutual promotion between Cl⁻ and other environment effects was also found. In summary, this study enhances our understanding of the distribution, sources, and environmental effects of Cl⁻ across China, indicating that Cl⁻ should be systematically considered in elucidating environment effect of fine particles.