A large number of white hard clam farms are in the estuary shoreline of Saigon-Dongnai Rivers, which flow through Ho Chi Minh City, a megacity, and numerous industrial zones in the basin catchment area. In this study, eleven trace elements (Mn, Fe, Co, Ni, Cu, Zn, As, Se, Cd, Hg, and Pb) in the hard clam Meretrix lyrata and its habitats including surface water, suspended particulate matter, and sediment were evaluated to understand the bioaccumulation of trace metals from the environment into the whole tissues of the hard clam as well as its different organs. The samples were collected monthly in dry, transition, and wet seasons of the southern part of Vietnam from March to September 2016. The results showed that seasonal and spatial variations of the studied metal concentrations in the hard clam M. lyrata might be influenced by the sea current as well as the surface runoff in the rainy season. The relationship between condition index and the element concentrations in M. lyrata might be affected by the living environment conditions and farming methods. In addition, the hazard index values of all trace elements in the hard clam M. lyrata harvested in the sampling time show that the hard clams farmed in the study area were safe for local consumers.

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The coastal area surrounding Mekong Delta-Vietnam (MDV) is one of the largest clam farming sites in Vietnam. Furthermore, previous studies showed that the rapid growth of urbanization, industrialization, and agriculture lead to the contamination of heavy metals in MDV. Therefore, this study is aimed to evaluate the presence of cadmium (Cd), cooper (Cu), lead (Pb) and zinc (Zn) in sea water, sediment, as well as hard clam (Meretrix lyrata) around coastal area of Tien River Estuary named Tan Thanh. The results showed that all studied metals’ concentrations in sediment were lower than the limits of marine sediment quality guidelines, except Zn. The levels of studied metals in clam samples were less than the maximum values of metals in food which regulated by Commission Regulation 1881/2006 and some countries. Concentrations of Cd, Cu, Pb and Zn in the clam flesh were ranging between 0.01 and 1.34 mg kg-1, 1.1 and 15.8 mg kg-1, not detected and 0.6 mg kg-1, as well as 9.9 and 192.5 mg kg-1, respectively. Among the studied metals, Cd is considered as the most influential parameter for the health risk assessment of local clam consumers. According to this study, the daily intake of 100 g clam flesh (wet weight) is recommended as the largest amount of clam for local consumers.

This study aimed at understanding the concentrations of selected heavy metals including arsenic, iron, manganese, cadmium and mercury in groundwater used for domestic purposes in Dak Nong Province of Vietnam. A total number of 572 groundwater samples including 61 duplicates were collected during October, 2018 – April, 2019. The collected samples were measured onsite for pH and preserved with 2% HNO3 before being analyzed in the laboratory for heavy metals by inductively coupled plasma mass spectrometry. The relative percent differences of all duplicate samples were less than 30%, indicating that the analytical results were within acceptable ranges. The average concentrations of As, Fe, Mn, Cd, Hg and Pb in groundwater were 9.53±46.36, 307.1±1,178, 166±478, 4.66±6.2, 1.0±1.8 and not detected, respectively. Amongst all the analytical results, however, some values on the concentrations of studied metals exceed the Vietnamese regulation values for groundwater quality and for domestic use requirements. The research results therefore suggest that groundwater containing rather high concentrations of heavy metals at the studied area should not readily be used for domestic purposes without proper treatments.

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