Spatiotemporal distributions of As and Sb in sluice controlled tidal reach of Xiaoqing river estuary and their land-to-ocean fluxes estimation

The basic water quality data and concentration data of As and Sb in the sluice controlled river section of Xiaoqing river in three different water conditions in 2015 were obtained. The spatial and temporal distribution characteristics of As and Sb in the river section were analyzed, and we estimated their land-to-ocean fluxes. The results show that the spatial distribution of pH, salinity and temperature in the sluice controlled river section of the Xiaoqing river is closely related to the water situation. The topography of the Xiaoqing river estuary is also an important factor affecting the exchange of water from the upper reaches to the lower reaches. The concentration of As and Sb in water bodies decreased gradually along the reach from Wangdao sluice to the estuary in dry period and flat period, while the concentration of As and Sb in wet period was significantly lower than that in dry and flat periods. The release of As in sediment increased the concentration of As in the pore water, with a maximum value of 24.9 μg/L. In 2015, the land-to-ocean fluxes of As and Sb were about 2618 and 2677 kg, respectively.