Organochlorine Compounds in Commercial Bivalves from the Mekong and Saigon-Dong Nai River Deltas (South Vietnam)

Persistent organic pollutants (POPs) are distributed in the environment worldwide. These pollutants are found ubiquitously in the environment, including commercially valuable aquatic organisms. Vietnam is one of the world's largest exporters of seafood, including bivalves. At the same time, comprehensive monitoring studies of aquatic ecosystems in Vietnam are insufficient and not coordinated and are mainly aimed at detecting heavy metals. We studied concentrations of organochlorine pesticides (OCPs (DDT, HCH)) and polychlorinated biphenyls (PCBs) in bivalves of four genera (Corbicula, Geloina, Ensidens, Scabies) collected from the Mekong Delta and Saigon-Dong Nai River Delta as well as purchased freshly caught at local markets in the spring of 2017 and 2018 before the rainy season. The studied watercourses and waterbodies can be arranged in the following order of increasing pollution: Lake Binh Thien - Hau River - Tien River - Ba Lai River - Saigon-Dong Nai River. The surveyed areas of mangrove ecosystems in the provinces of Kien Giang and Bac Lieu cannot be included in this order, since they are inhabited by mangrove clams Geloina sp. of the family Cyrenidae, which are bivalves with narrow specialization. Currently, the major factors responsible for the OCP pollution in South Vietnam may be agricultural activities and industrial sectors which disregard the recommendations and bans on the use of these hazardous compounds, along with the persisting unfavorable background in the form of DDE being a consequence of the wide application of DDT until 1995.