Fractionation profile and mobility pattern of trace metals in sediments of Nomi River, Tokyo, Japan

Shaila Sharmin¹*, H. M. Zakir² and Naotatsu Shikazono¹

¹Laboratory of Geochemistry, School of Science for Open and Environmental Systems, Faculty of Science and Technology, Keio University, Hiyoshi 3-14-1, Yokohama 223-8522, Japan.

²Department of Agricultural Chemistry, Faculty of Agriculture, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh.

*Corresponding author. E-mail: shl_sharmin@yahoo.com. Fax: +81-045-566-1551.

Accepted 4 January, 2010

   Abstract

This study provides a geochemical partitioning and mobility pattern of Iron (Fe), Manganese (Mn), Cadmium (Cd), Copper (Cu), Chromium (Cr) and Nickel (Ni) in sediment samples collected from Nomi River, Tokyo, Japan. For the partitioning of particulating trace metals, a widely used 5-step sequential extraction procedure was employed and the concentrations were measured in the liquid extracts by inductively coupled plasma mass spectrometry (ICP-MS) and atomic absorption spectroscopy (AAS) to understand enrichment and metal availability in five geochemical phases. The association of Cd (39.8 - 89.7%) was found highest with adsorbed, exchangeable and carbonate (AEC) fraction, Fe (25 - 44.1%), Mn (11.8 - 76.7%), Cr (12.6 - 46.9%) and Ni (9.8 - 41.8%) were in residual phase and the maximum association of Cu was recorded with amorphous Fe oxyhydroxide phase (24.7 - 51.3%). The order of potential trace metals mobility in the aquatic environment of Nomi River was- Cd > Cu > Cr > Ni > Fe > Mn. According to the risk assessment code applied in the present study Cu, Ni and Cr were under medium and Cd was under high risk category. The X-ray diffraction (XRD) study detected the presence of several clay minerals; those are likely to be the major host of trace metals in sediments.

Key words: Trace metal, fractionation, mobility, pollution, sediments, Nomi River, Tokyo.