Distribution of Mercury in Water and Bottom Sediments of the Estuary Area of the Red River (Vietnam)

Abstract

The paper determined the content of mercury in water-bottom sediments and the feature of its spatial distribution in the estuary area of the Red River (Vietnam). The studies were conducted at 30 stations during the main hydrological seasons of 2014-2016 (during the flood and low water). Samples of bottom sediments were collected on the surface layer with a depth 0…10 cm. The spatial distribution of mercury was carried out using the Kriging interpolation method in ArcGIS 10.2.2. The concentration of mercury in the water of the Red River varied from 0.05 to 0.08 µg/l in low water and 0.07…0.11 µg/l during the flood. Towards the sea, the concentration of dissolved mercury decreased. The spatial distribution of the suspended form and phases of bottom sediments of mercury in the estuary area of the Red River was characterized by an increase in the concentration in the Delta watercourses towards the sea, the presence of a maximum in the marginal filter and a general decreasing gradient at the coast. The Hg content in the suspended form varied from 0.008 to 0.7 µg/l, and in bottom sediments within 0.1…1.25 mg/(kg dry weight). In river waters, the main forms of mercury were dissolved and suspended, and in the marginal filter – in bottom sediments. Bottom sediments of the estuary area of the Red River were characterized by a higher content of Hg compared to unpolluted soils in temperate and northern latitudes, as well as bottom sediments of water bodies of another region of Vietnam.