Quantification of anthropogenic and marine sources to atmospheric mercury over the marginal seas of China and impact on the sea–air exchange of mercury

Abstract. Mercury in the atmosphere is a crucial environmental concern due to its toxicity and its ability to travel long distances. In the marginal seas, the contributions of terrestrial anthropogenic vs. natural sources on atmospheric mercury have rarely been quantified and their roles in mercury sea–air exchange are not well understood. To address this issue, this study integrated observations from island, cruise, and inland campaigns. The mean concentrations of total gaseous mercury (TGM) were 2.32 ± 1.02 ng m−3 (Bohai Sea), 2.55 ± 0.55 ng m−3 (Yellow Sea), and 2.31 ± 0.81 ng m−3 (East China Sea), respectively, with coastal regions exhibiting significantly higher values than open ocean areas due to continental outflows. Positive correlations were observed between TGM concentrations and environmental parameters such as temperature, relative humidity, and wind speed, indicating the significant influence of natural sources on atmospheric mercury in the marine environment. By utilizing a receptor model and linear regression analysis, a robust method was developed to quantitatively estimate the contribution of anthropogenic and natural sources to TGM. Anthropogenic sources accounted for an average of 59 %, 40 %, and 27 % of TGM over the Bohai Sea, Yellow Sea, and East China Sea, respectively. The sea–air exchange fluxes of mercury were estimated as 0.17 ± 0.38, 1.10 ± 1.34, and 3.44 ± 3.24 ng m−2 h−1 over these three seas, respectively. Stronger anthropogenic mercury emissions in northern China partially explained the suppressed sea–air exchange fluxes of mercury in the Bohai Sea. This study elucidated the role of anthropogenic emissions in shaping the marine atmospheric mercury and the sea–air exchange fluxes, thereby informing valuable assessments regarding the influence of future reduced anthropogenic mercury emissions on the marine mercury cycle and ecosystems.