Total mercury flux and offshore transport via submarine groundwater discharge and coal-fired power plant in the Jiulong River estuary, China

A mass balance of total mercury (Hg-T, dissolved + particulate) is constructed for China's Jiulong River estuary based on measured Hg-T concentrations in the surface water, sediment, porewater, and groundwater for May, August, and November 2009, combined with data from the literature. The Hg-T mass budget results show that the dominant source (39-55%) is desulfurized seawater discharged from the Songyu coal-fired power plant. Submarine groundwater discharge (SGD)-derived Hg-T flux into the estuary is equivalent to 8-58% of the Hg-T input from the Jiulong River, which is remarkable when compared with SGD-derived Hg-T fluxes reported in coastal systems worldwide. Hence, SGD is a significant pathway for the transport of Hg-T into the Jiulong River estuary. The primary Hg-T sinks is export to the Taiwan Strait (53-88%), which has important environmental implications on the Hg cycling and marine ecosystems in marginal seas.