Potential factors impacting PM2.5-Hg during haze evolution revealed by mercury isotope: Emission sources and photochemical processes

Abstract

In this study, Hg isotopes, backward trajectory, and emission inventory were utilized to explore the effects of possible emission sources and photochemical pathways on fine-particle bound mercury during two single haze events in February 2017 and January 2018 at Gucheng (38.31°N, 115.25°E). Results showed that (a) the large variations of odd-mass mass-independent fractionation values in fine-particle bound mercury showed the joint contributions of different source regions during haze evolution; (b) biomass burning significantly contributed to fine-particle bound mercury during winter haze in northern China; (c) fine-particle bound mercury during haze evolution at Gucheng (an inland site in China) was impacted by marine aerosols; (d) photoreduction had a significant impact on fine-particle bound mercury during haze evolution and a relatively more intense solar radiation may be conducive to photoreduction during haze. These findings provide a theoretical basis for developing methods and strategies to control fine-particle bound mercury pollution.