Characteristics and sources of mercury in precipitation collected at the urban, suburban and rural sites in a city of Southeast China

Weekly precipitation samples were collected simultaneously at the urban, suburban, and rural sites in Xiamen, China during 2016-2017 to investigate the characteristics and sources of total mercury (THg) and methyl mercury (MeHg) in precipitation. The annual volume-weight mean (VWM) concentrations of the three areas were in the ranges of 7.9-8.9 ng L-1 for THg and 0.070-0.089 ng L-1 for MeHg, and the wet deposition fluxes were 8.8-11.4 mu g m(-2) and 0.074-0.12 mu g m(-2) for the study period of 11 months, respectively. ANONA test revealed that no significant difference of THg concentration among sites, however, the seasonal characteristics of THg strongly depended on the types of locations. THg concentration was the highest in summer at the urban and suburban sites and elevated in winter at the rural site. Urban/suburban THg deposition was closely correlated to both of concentration and precipitation amount, but rural THg deposition was only correlated to precipitation amount. Principal component analysis (PCA) extracted a source factor with high loading for both of THg and MeHg along with secondary inorganic ions. The result suggested that the scavenging of GOM oxidized from GEM in the atmosphere was probably the important source of Hg in precipitation. The oxidation processes also had a positive effect on the formation of MeHg during the study period.