Characteristics, potential regional sources and health risk of black carbon based on ground observation and MERRA-2 reanalysis data in a coastal city, China

Abstract Black carbon (BC) produced by the incomplete combustion of carbonaceous materials and biomass has become a major factor affecting global climate change and adversely affects health. Based on the ground-measured data and MERRA-2 (Modern-Era Retrospective Analysis for Research and Applications, Version 2) reanalysis data, BC's pollution characteristics and the health risks caused by BC exposure were investigated in Tianjin, China. The results showed that the highest BC concentration occurred in winter, and the annual average concentration of BC on weekends was higher than that on weekdays in winter. The hourly average monitoring concentration variations of BC in four seasons all had two peaks that appeared 6:00–8:00 and 22:00–2:00. For MERRA-2 reanalysis data, there was one peak appeared during 5:00–7:00 in four seasons. The lowest values appeared during 14:00–16:00 for both ground-measured data and MERRA-2. The relationships between BC concentration and meteorological factors showed that wind speed and temperature inversion played important roles in the atmospheric BC diffusion. The wind directions of southwest, southeast, and north were closely associated with BC in 2019. The Potential Source Contribution Function (PSCF) results showed that the southwestern area of Tianjin, especially the southern Hebei, northern Henan and Beijing, would be the potential source areas of Tianjin BC in 2019. The cancer risks of adults and children caused by BC exposure in Tianjin were higher than the risk levels (1 × 10−6 to 1 × 10−4) recommended by the US Environmental Protection Agency (US EPA) in 2019, resulting in more than 3.78 cases of cancer per 10,000 adults (3.78 × 10−4), and more than 1.55 cases of cancer per 10,000 children (1.55 × 10−4), respectively. The relative risk (RR) of BC exposure on mortality showed the highest in winter and the lowest in summer. Compared with all-cause and cardiovascular mortality, respiratory mortality caused by the BC showed the highest risk.