Rice consumption is a potential source of mercury exposure. In the rice paddy ecosystem, mercury is easy to transform into methylmercury (MeHg) and can be accumulated in rice. In this study, we developed a mercury accumulated model in rice to predict biogeochemical cycling of mercury in the rice paddy, and quantify the contribution of soil mercury, atmospheric mercury deposition and irrigation water to mercury concentration in rice. The model took atmospheric mercury deposition, simulated from a global atmospheric chemistry transport model (GEOS-Chem), and soil and irrigation water mercury concentrations obtained from field measurements and literatures respectively. Results showed that soil mercury concentrations and atmospheric deposition explained spatial variability of MeHg concentrations in rice, while atmospheric deposition explained spatial variability of inorganic mercury (IHg) concentrations in rice. We found that the contribution of soil mercury to MeHg concentrations in rice was higher in most areas of southern China, and that of atmospheric mercury deposition to MeHg concentration in rice was higher in most areas of northern China. This study suggests that we should consider the effects of soil mercury and atmospheric deposition on the concentrations of mercury in rice and environmental factors on the accumulation of MeHg in rice.

Mercury; Rice; Methylmercury; Transport and transformation model; Atmospheric mercury deposition