|Abstract Title:||Source Appointment of Speciated Mercury in Chinese Rice Grain using a High Resolution Model|
|Presenter Name:||Yuying Cui|
|Session:||Human Exposure and Risk Assessment of Hg|
Abstract Information :
Rice grain consumption is one primary pathway of human mercury exposure. To trace the source of rice grain mercury in China, we developed a Rice-paddy Mercury Transport and Transformation Model (RMTTM) with the grid resolution of 1 km ? 1 km by using unit cell mass conservation method. We found that the simulated total mercury (THg) and methylmercury (MeHg) concentrations in Chinese rice grain were in the range of 0.07-460.0 and 0.02-453.7 ?g/kg in 2017. Atmospheric mercury deposition contributed to 77.9% of rice grain THg on national average. Whereas, soil heterogeneity, especially the variation of soil mercury, led to the wide span of rice grain THg distribution across grids. In situ methylation of inorganic mercury (IHg) in pore water was the main pathway to rice grain MeHg and the spatial variation of soil organic matter significantly impacted the methylation potential in different regions. Based on the high-resolution rice grain THg concentrations, we identified 0.9% of grids as heavy polluted THg grids (rice grain THg>20 ?g/kg). We found that these grids were mainly involved the human activities of nonferrous metal smelters, cement clinker production, as well as mercury and other metals mining. We thus recommended measures targeted on the control of heavy polluted rice grain THg according to their pollution sources. In addition, we observed wide spatial variation range of MeHg to THg ratios not only in China but also in other regions of the world, highlighting the urgency and importance to determine the safety threshold of rice grain MeHg and to better protect human beings and to evaluate the effectiveness of the Minamata Convention on Mercury.