The results showed that concentration of Hg in sediment of most sampling sites were exceeded the National Technical Regulation on Sediment Quality (QCVN 43:2012/BTNMT), while Pb and As were below the regulated level. Ecological risk assessment presented that investigated metals posed medium to high risk to ecology. The estimated ecological risk index (ERI) ranged from to with the order of Hg>As>Pb. The highest ecological risk was found at the stations closed to the Thuan An inlet and ship construction area. | Vietnam Journal of Science and Technology 56 (2C) (2018) 72-79 INVESTIGATION AND ECOLOGICAL RISK ASSESSMENT OF Pb, As AND Hg IN SEDIMENT OF TAM GIANG-CAU HAI LAGOON, THUA THIEN HUE PROVINCE Duong Van Hieu1, *, Tran Tien Dung1, 2, Tran Ngoc Tuan1, Duong Thanh Chung1 1 2 Faculty of Environmental Science, University of Sciences, Hue University, 77 Nguyen Hue Str., Hue city Department of Science and Technology, Thua Thien Hue province, 24 Le Loi Str., Hue city * Email: dvhieu@ Received: 10 May 2018; Accepted for publication: 21 August 2018 ABSTRACT Tam Giang - Cau Hai lagoon plays an important role in coastal ecosystems of Thua Thien Hue Province. The present study aims to determine three toxic elements (Pb, As, Hg) in the surface sediment and to assess the ecological risk of the selected metal in this area. Sediment samples and water quality were collected at 9 stations in rainy and dry seasons. Toxic metals were determined following the USEPA methods 3050A for measuring by atomic absorption spectrophotometer. Concentrations of Hg, Pb and As in the study area were in the range of mg/kg, mg/kg and mg/kg, respectively. The results showed that concentration of Hg in sediment of most sampling sites were exceeded the National Technical Regulation on Sediment Quality (QCVN 43:2012/BTNMT), while Pb and As were below the regulated level. Ecological risk assessment presented that investigated metals posed medium to high risk to ecology. The estimated ecological risk index (ERI) ranged from to with the order of Hg>As>Pb. The highest ecological risk was found at the stations closed to the Thuan An inlet and ship construction area. Keywords: Tam Giang – Cau Hai lagoon, ecological risk assessment, toxic metals. 1. INTRODUCTION The existence of heavy metals in the lagoon sediments are caused by both natural and anthropogenic sources. In past decades, the increasing of human development activities has been accelerated the .
