Isotope and Trace Element Geochemistry of the Ganga (Hooghly) River Estuary, India: Sources, Cycling and Fluxes

Samanta, Saumik (2017) Isotope and Trace Element Geochemistry of the Ganga (Hooghly) River Estuary, India: Sources, Cycling and Fluxes. PhD thesis, Indian Institute of Science Education and Research Kolkata.

PDF (PhD thesis of Saumik Samanta (11RS035)) Thesis_Saumik_Samanta.pdf - Submitted Version Restricted to Repository staff only Download (9MB)

Abstract

The Ganga (Hooghly) River, the largest river system in India in terms of water and sediment discharge, is a part of the Ganga-Brahmaputra (G‒B) River system and is located in the eastern margin of the G‒B delta. This work is an effort aimed at investigating estuarine processes that bring about changes in the geochemistry of the dissolved and particulate phases, and understanding of the sources, cycling and fluxes of inorganic carbon, selected trace elements and heavy metals in the Ganga (Hooghly) River estuary. These objectives have been achieved through comprehensive measurement of (i) salinity, dissolved oxygen (DO), major ions (Ca²⁺, Mg²⁺, Na+ and K⁺), dissolved inorganic carbon (DIC), ƍ¹³CDIC, trace elements (Ba, Sr and Mn) and heavy metals (Co, Cu and Ni) in estuary water, groundwater, industrial effluent water and urban wastewater, (ii) major elements (Ca, Mg, Na, K, Mn, Al and Fe), trace elements (Mn, Ba and Sr), heavy metals (Co, Ni and Cu) and ƍ¹³CPOC in the estuarine suspended particulate matter and (iii) major elements (Ca, Mg, Na, and K), trace elements (Mn, Ba and Sr) and heavy metals (Co, Ni and Cu) in the exchangeable phases of the particulate matter. To date, this is the most comprehensive study on the Hooghly River estuary and is based on investigation of water and suspended sediment samples collected during six periods of contrasting water discharges over two years 2012 and 2013. The results and findings of this study have brought out the importance of estuarine processes in generating DIC, Ba and heavy metals in the Hooghly River estuary. While degradation of organic carbon and dissolution of particulate carbonate phases are responsible for estuarine production of DIC, solute-particle interaction is the underlying mechanism for generation of Ba, Co, Ni and Cu. The significance these processes is evident from the observation that contributions of DIC, Ba, and heavy metals from the Hooghly estuary, when normalized with its water contributions to the global river water flux, are the highest in the world among the major tropical estuaries. The results and observations of this study thus provide impetus to carry out studies that are focused on internal cycling of nutrients, trace elements and heavy metals in estuaries influenced by tropical monsoon climate.

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