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Daily precipitation samples were collected from June 2012 to May 2013 at four observation sites in Xiamen, a coastal city of Southeast China. Concentrations of Total mercury (THg) and methyl mercury (MeHg) in precipitation were rigorously treated and determined. The annual volume-weighted mean concentrations of THg and MeHg at four sites were 12.3 and 0.053 ng L −1 , and wet deposition fluxes of THg and MeHg were 14.04 μg m −2 yr −1 and 58.2 ng m −2 yr −1 , respectively. MeHg could account for 0.43% of THg, and dissolved Hg contributed 55.4% to THg. There was no significant difference in THg concentration between monsoon and non-monsoon seasons, which was consistent with neither the general seasonal pattern of inland cities of China nor the report from the Gulf coast. Higher wet deposition flux of THg in monsoon season was a function of intense rainfall, whereas higher MeHg flux in non-monsoon season could attribute to increased MeHg concentration. Atmospheric Hg was more efficiently scavenged during the earlier period of the rain event. Positive correlations between precipitation depth and wet deposition fluxes suggested that rainfall played an important role in scavenging atmospheric Hg rather than diluting concentrations. Pearson correlation analysis combined with ions ratios implied that sea salt aerosols had an important impact on rainwater, but coal combustion and traffic emission could be the dominant factors influencing THg in precipitation. [ABSTRACT FROM AUTHOR]

Aerosols have a significant impact on both direct and indirect radiative effects and are considered to be one of the largest contributors to the uncertainty in global climate change assessment. In this study, continuous one-year-round in-situ observations of aerosol optical properties were conducted in the southeastern coastal city of Xiamen, China, and the effects of chemical composition on aerosol optical properties were analyzed to assess the environmental and climate effects of aerosols. The scattering coefficient (σ sp), absorption coefficient (σ ap), single scattering albedo (SSA) showed significant seasonal variations. The σ sp and σ ap showed obvious bimodal diurnal patterns, with peaks occurring in the morning peak and evening, while the diurnal patterns of SSA were reversed. The results of the chemical component-based estimation reconstruction of σ sp illuminated that OM, NH 4 NO 3 , (NH 4) 2 SO 4 were the main contributors to the σ sp. The concentration weighted trajectory (CWT) method was used to characterize the contributing sources of each chemical component affecting σ sp. The main contributing source areas were elucidated and varied slightly with species and season. The wind dependence analysis reflected that σ ap was mainly influenced by local emissions, while σ sp was affected by both local emissions and regional transport. The contribution sources of σ sp and σ ap were investigated using potential source contribution function (PSCF) method. The contributing source of σ sp and σ ap in Xiamen were clarified, and varied slightly with seasonal differences. This study revealed the aerosol optical properties in the southeastern coastal urban areas of China and provided a scientific basis for the estimation of the factors affecting climate change. • This is the first report of one-year-round in-situ observation of the aerosol optical properties in Xiamen. • Apparent diurnal variations of the aerosol optical properties were identified. • Regional transport and local emissions were responsible for the σ sp and σ ap , respectively. • NH 4 NO 3 dominated the contribution to the σ sp in winter, while OM dominated in the other seasons. [ABSTRACT FROM AUTHOR]