Assessment of the Accumulation of Polycyclic Aromatic Organic Compounds (16 PAHs) and their Pollution Sources in River Sediments of Some Northern Border Provinces of Vietnam

This study assessed the occurrence and distribution of 16 common polycyclic aromatic hydrocarbons (PAHs) in sediments from four regional rivers in northern Vietnam: the Lo River (Ha Giang), the Da River (Lai Chau), the Red River (Lao Cai), and the Ka Long River (Quang Ninh). Twenty sediment samples were collected during the 2024 rainy season and analyzed by GC-MS using Environmental Protection Agency (EPA) standard methods (3540C and 3630C). The results detected the presence of 10 PAHs (Naphthalene, Acenaphthylene, Acenaphthene, Fluorene, Anthracene, Phenanthrene, Fluoranthene, Pyrene, Benz[a]anthracene and Chrysene), of which Naphthalene, Anthracene, and Phenanthrene were with quite high contents. Total PAH concentrations ranged from 20.25 to 48.83 µg/kg, with the highest in sediments from the Ka Long River, where Naphthalene although is significantly lower than the threshold specified in river sediments according to QCVN43:2017 BTNMT, it has levels exceeded the Canadian ISQG threshold by 1.62 times. The concentration of PAHs in the upstream sediments of the four rivers was still much lower than the regulations on PAHs in freshwater sediments according to QCVN 43: 2017 BTNMT. In addition, the Phenanthrene/Anthracene ratio was less than 4 (in the range of 0.89 - 2.85), indicating that low-temperature combustion was the main source of PAHs. The findings showed initial signs of organic pollution in river sediments and raised the need for more effective and adequate monitoring and pollution control in transboundary river systems.