Role of suspended particulate matter in metal distribution within an estuarine environment: A case of Mandovi Estuary, Western India

Abstract

Suspended matter in the estuary is an important factor influencing the bioaccumulation of inorganic contaminants. Considering that mining, dredging and transportation by barges as well as mechanized boats can influence the levels of suspended particulate matter in the estuarine environment, an attempt has been made to study the component composition and elemental concentration of suspended matter in the estuarine environment of the river Mandovi, western India. Surface and bottom water samples, collected along the estuarine channel during monsoon, post-monsoon and pre-monsoon seasons were analyzed for suspended particulate matter and particulate metals. Systematic seasonal variation of Total Suspended Matter (TSM) along the estuarine region was observed. During the monsoon, TSM concentration was high towards the lower portion of the estuary while higher concentrations were observed in upper portions of the estuary especially in the bottom waters during non-monsoon. On an average, TSM was higher in pre-monsoon followed by monsoon and post-monsoon in both surface and bottom waters. To understand inter-seasonal variation, the salinity and TSM data along with particulate metals (Fe, Mn, Ni, Zn and Co) were plotted on Isocon diagrams. When monsoon and post-monsoon data were compared, salinity is most prominent in postmonsoon whereas, TSM and particulate Fe are prominent in monsoon season in both surface and bottom waters. Comparison of post-monsoon and pre-monsoon data indicated that salinity and TSM concentrations were higher during premonsoon both in surface and bottom waters. Pronounced levels of particulate Fe, Mn and Co in surface waters and Fe, Mn and Zn in bottom waters are observed during post-monsoon. Plots of premonsoon and monsoon showed salinity and TSM dominant in pre-monsoon season and particulate Fe was significant in monsoon season in both surface and bottom waters.