Influencing mechanisms of multiple factors on seasonal variation of atmospheric polybrominated diphenyl ethers and their internal exposure risk in cold region

Atmospheric pollutants exhibit seasonal variations in their concentrations and associated exposure risk due to seasonal alternations. The influencing mechanisms of multiple factors on the seasonal variation of concentration of polybrominated diphenyl ethers (PBDEs) in atmosphere were studied in cold region of China by a multimedia fugacity model (S-L4MF Model). The significant seasonal variations were found: gaseous PBDEs exhibited higher concentration in summer and lower concentration in winter, while particulate PBDEs presented opposite trend. The influencing mechanisms of eight key driving factors on PBDEs concentrations were identified that zonal wind, air emission and snow as predominant factors governing gaseous concentration fluctuations, whereas air temperature, TSP and precipitation emerged as primary factors on particulate concentration variations. Subsequently, the seasonal differences in internal exposure risk of PBDEs were investigated by constructing a fugacity-based human model. Similarly, the internal exposure risk of PBDEs also presented seasonal variations. Notably, the internal exposure risk of particulate PBDEs demonstrated distinct size-distribution characteristics: the unimodal pattern in summer versus the bimodal pattern in winter. The study provided new insights into the understanding of seasonal variations and influencing mechanisms of atmospheric pollutants, which provided significant implications for developing seasonal-specific risk assessment frameworks.