Assessment of pollution sources and health risks of black carbon aerosols in industrial cities of Northwestern China using light absorption observations

Abstract

Black carbon (BC) aerosols have notably negative impacts on climate, environment, and public health. However, current knowledge of the sources and health hazards of BC remains limited. Equivalent black carbon (eBC) measurements were conducted using an AE33 aethalometer in Urumqi, China, from July 2022 to April 2023. The temporal variability, potential pollution areas and health hazards of fossil fuel (eBC_ff) and biomass burning (eBC_bb) sources were analysed. The average concentrations of eBC_ff and eBC_bb were 1.3 μg m⁻³ and 0.5 μg m⁻³, respectively, highlighting the dominant role of fossil fuel combustion. In winter, due to increased coal heating and industrial emissions under adverse weather conditions, the contribution rate of eBC_ff surged to 80.3% (2.44 μg m⁻³). The highest concentrations of eBC_bb were observed in spring (0.71 μg m⁻³), influenced by pre-sowing burning of agricultural residues. The concentrations of eBC_ff were higher during the day than at night, with a morning peak due to vehicular emissions. High concentrations of eBC_ff and eBC_bb mainly originate from pollution sources around the observation site, along with residential and agricultural areas to the southeastern. Regional transport between cities on the northern slopes of the Tianshan Mountains and long-range drift from Central Asian countries also had important effects on eBC_ff and eBC_bb. Health risk assessments revealed that carcinogenic risks (CR) from eBC exceeded acceptable levels by two orders of magnitude, with passive smoking equivalents (PSC) four times higher in winter than in summer. Our findings highlight the significant environmental and public health benefits of reducing fossil fuel consumption.