Enrichment and distribution of metals in surface sediments of the Thanh Hoa coastal area, Viet Nam

Abstract Thirty-two surface sediment samples were collected in the Thanh Hoa coastal area, from the shore to a depth of 30 m. Grain sizes and the contents of 14 major and trace metals were measured with the goal of assessing the impact from the mainland to the coastal area of Thanh Hoa. The sand fraction ranged from 0.5 to 82.7%, and the mud fraction ranged from 17.3 to 99.5%. The contents of major and trace elements-namely, Fe, Cu, Pb, Zn, As, Cr, Co, Ni, Mn, Cd, Mo, Li, V, and Sn—in the sediments were assessed by comparison with Canadian environmental quality guidelines and indices. The concentrations of Cu, Pb, Zn, As, and Cr were higher than the interim marine sediment quality guidelines (ISQGs) benchmark but lower than the probable effect levels (PELs). The geo-accumulation (Igeo) indexes of As and Pb indicated moderate pollution; the enrichment factor (EF) indexes of Cu, Pb, Zn, Cd, As, Li, and Mn indicated minor to moderate pollution; the contamination factor (CF) indexes of Fe, Cu, Pb, Zn, Cd, As, Co, Li, and Mn indicated moderate to considerable pollution, the CF showed considerable contamination for As and Pb in particular; the ecological risk factor (ER) indexes of Cd and As were moderate; and the degree of contamination (CD) of all 14 elements was high. On the basis of this preliminary environmental risk evaluation, the levels of some trace elements indicated potential issues for the Thanh Hoa coastal area, particularly near river mouths and the northern zone, where concentrations were higher. Thus, appropriate monitoring plans based on sound scientific knowledge are imperative for safe and sustainable development.