STUDIES ON DISTRIBUTION AND FRACTIONATION OF HEAVY METALS IN SEDIMENT OF CAU RIVER, VIETNAM
Keywords:heavy metal, river sediment, fractionation, sequential extraction.
Cau River, one of the major rivers of Thai Binh River Systems, has been under pressure from discharge from the economic and social development activities of the region. Water and sediment samples will be collected along Cau River to determine the spatial variability of metal in Cau River. Sediments collected from Cau River were extracted sequentially to investigate the distribution and fractionation of metal in Cau River. Results showed that the presence of certain metals in water and sediment with the concentrations ranged in a wide variation. In water Cu (58-181 μg/L), Pb (0.6-1.85 μg/L), Zn (18.1-32.5 μg/L), Cd (0-0.02 μg/L), Ni (3.04-4.41 μg/L), Cr (2.72-5.07 μg/L); in sediment Cu (27.6-401 mg/kg), Pb (0-282 mg/kg), Zn (3.9-71.9 mg/kg), Cd (0.01-2.44 mg/kg), Ni (2.24-5.89 mg/kg), Cr (4.08-11.5 mg/kg). Sequential extraction for study the distribution of metal species in sediment showed that metal mainly concentrated immobile form of residues fraction, organic compound bound fraction and Fe-Mn oxide associated fraction. This dominant existence of metal result in the tendency of metal assimilation in sediment and low bioavailability. However, some toxic metals such as Cd, Cr found moderated soluble form must be studied more for their release to water phase and and bioaccumulation.