Peculiarities of migration of mercury in water and bottom sediments of the estuary area of the Red River (Vietnam)

The paper assessed the content of mercury in water and bottom sediments in the mouth area of the Red River of Vietnam. Given the spatial distribution of mercury in the dissolved, suspended forms and in sediments. The studies were conducted at 30 stations 2 times a year (during the flood and low-water periods) in 2014-2016. Samples of bottom sediments were collected in the surface layer. The spatial distribution of mercury was carried out using the kriging method in ArcGIS 10.2.2. During the study period it was found that the concentration of mercury in the water of the Red River varies from 0,05 to 0,08 μg/l during low-water periods and 0,07 to 0,11 μg/l during the flood period. Towards the sea, the concentration of dissolved mercury decreased. Mercury concentrations in suspended form and bottom sediments increase towards the sea and reach a maximum in the marginal filter. In river waters, the main forms of mercury existence are dissolved and suspended, and in the marginal filter - in bottom sediments. The bottom sediments of the estuary area of the Red River are distinguished by a higher content of Hg compared to uncontaminated soils in reservoirs of temperate and northern latitudes, as well as with bottom sediments of water bodies in another region of Vietnam.