Seasonal variation of driving factors of ambient PM2.5 oxidative potential in Shenzhen, China

Reactive oxygen species (ROS) play a central role in health effects of ambient fine particulate matter (PM2.5). In this work, we screened for efficient and complementary oxidative potential (OP) measurements by comparing the response values of multiple chemical probes (OPDTT, OPOH, OPGSH) to ambient PM2.5 in Shenzhen, China. Combined with meteorological condition and PM2.5 chemical composition analysis, we explored the effects of different chemical components and emission sources on the ambient PM2.5 OP and analyzed their seasonal variations. The results show that OPmDTT(mass-normalized) and OPmGSH-SLF were highly correlated (r = 0.77). OPDTT was mainly influenced by organic carbon, while OPOH was highly dominated by heavy metals. The combination of OPDTT and OPOH provides an efficient and comprehensive measurement of OP. Temporally, the OPs were substantially higher in winter than in summer (1.4 and 4 times higher for OPmDTT and OPmOH, respectively). The long-distance transported biomass burning sources from the north dominated the OPDTT in winter, while the ship emissions mainly influenced the summer OP. The OPmDTT increased sharply with the decrease of PM2.5 mass concentration, especially when the PM2.5 concentration was lower than 30 mu g/m3. The huge differences in wind fields between the winter and summer cause considerable variations in PM2.5 concentrations, components, and OP. Our work emphasizes the necessity of long-term, multi-method, multi-component assessment of the OP of PM2.5.