deeper groundwater flow and chemistry in the arsenic affected western bengal basin, west bengal

272 Pages·2017·11.83 MB·English

by  Abhijit Mukherjee

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University of Kentucky Doctoral Dissertations Graduate School
2006
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Abhijit Mukherjee
University of Kentucky, [email protected]
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Mukherjee, Abhijit, "DEEPER GROUNDWATER FLOW AND CHEMISTRY IN THE ARSENIC AFFECTED
WESTERN BENGAL BASIN, WEST BENGAL, INDIA" (2006). University of Kentucky Doctoral Dissertations.
368.
https://uknowledge.uky.edu/gradschool_diss/368
This Dissertation is brought to you for free and open access by the Graduate School at UKnowledge. It has been
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ABSTRACT OF DISSERTATION

Abhijit Mukherjee

The Graduate School
University of Kentucky
2006

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DEEPER GROUNDWATER FLOW AND CHEMISTRY IN THE ARSENIC AFFECTED
WESTERN BENGAL BASIN, WEST BENGAL, INDIA

______________________________________________________

ABSTRACT OF DISSERTATION
______________________________________________________

A dissertation submitted in partial fulfillment
of the requirements for the degree of Doctor of Philosophy in the
College of Arts and Sciences
at the University of Kentucky

By
Abhijit Mukherjee
Lexington, Kentucky

Director: Dr. Alan E. Fryar, Associate Professor of Earth and Environmental Sciences
Lexington, Kentucky
2006
Copyright © Abhijit Mukherjee 2006

ii
ABSTRACT OF DISSERTATION

DEEPER GROUNDWATER FLOW AND CHEMISTRY IN THE ARSENIC AFFECTED
WESTERN BENGAL BASIN, WEST BENGAL, INDIA

A regional-scale hydrogeologic study was conducted in a ~21,000-km2 area of West
Bengal (Murshidabad, Nadia, North and South 24 Parganas districts), India, with severe, natural
arsenic contamination of shallow groundwater jeopardizing ~13.5 million inhabitants. The study
evaluated the suitability of deeper water as an alternate drinking water source.
A hydrostratigraphic model (resolution: 1000 m × 1000 m × 2 m, ≤ 300 m below MSL)
indicates a continuous, semi-confined sand aquifer (main aquifer) underlain by a thick clay
aquitard. The aquifer deepens toward the east and south. In the south, there are several deeper,
laterally connected, confined aquifers. Based on observed hydrostratigraphy, eight seasonal
groundwater models (resolution: 1000 m × 1000 m × 15 m) were developed with presence of
pumping (2001), absence of pumping (pre-1970s) and projected irrigational pumping (2011 and
2021). Simulations indicate topographically controlled, seasonally variable regional groundwater
flow, which has been severely distorted by pumping.
Samples of deep groundwater, river water and rainwater were collected for major and
minor solutes, dissolved gases and stable isotopes. A δ18O-δ2H bivariate plot of groundwater
falls subparallel to the constructed local meteoric water line (δ2H = 7.24 δ18O + 7.73), suggesting
a predominance of meteoric recharge (from monsoonal rainfall of present-day composition) with
some evaporation. A trend of δ18O depletion of groundwater was observed northward and
westward from the Bay of Bengal, indicating a continental effect. Major solutes indicate the
presence of hydrochemically distinct water bodies in the main and deeper isolated aquifers.
Spatial trends of major and redox-sensitive solutes and geochemical modeling indicate that
carbonate dissolution, silicate weathering, and cation exchange along with seawater and connate-
water mixing control the major-ion chemistry. The suboxic main aquifer water exhibits partial
redox equilibrium, with the possibility of oxidation in micro-scale environments. The redox
processes are depth-dependent and hydrostratigraphically variable.

Deeper water was found unsafe with elevated (≥10 μg/L) As in ~60% of samples. The
presence of As is related to coupled Fe-S redox cycles. Deeper water is probably polluted by
groundwater flow though interconnected aquifers with reduced sediments. Deep irrigational
pumping has potentially attracted shallower, polluted water to greater depths.
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KEYWORDS: Arsenic Contamination, Hydrostratigraphy, Groundwater Flow Modeling,
Hydrogeochemistry, West Bengal, India

Abhijit Mukherjee
3 July 2006

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DEEPER GROUNDWATER FLOW AND CHEMISTRY IN THE ARSENIC AFFECTED
WESTERN BENGAL BASIN, WEST BENGAL, INDIA

By

Abhijit Mukherjee

Alan E. Fryar
Director of Dissertation

Susan M. Rimmer
Director of Graduate Studies

3 July 2006

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RULES FOR THE USE OF DISSERTATION

Unpublished dissertations submitted for the Doctor’s degree and deposited in the University of
Kentucky Library are as a rule open for inspection, but are to be used only with due regard to the
rights of the authors. Bibliographical references may be noted, but quotations or summaries of
parts may be published only with the permission of the author, and with the usual scholarly
acknowledgements.

Extensive copying or publication of the thesis in whole or in part also requires the consent of the
Dean of the Graduate School of the University of Kentucky.

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DISSERTATION

Abhijit Mukherjee

The Graduate School

University of Kentucky

2006

iii
DEEPER GROUNDWATER FLOW AND CHEMISTRY IN THE ARSENIC AFFECTED
WESTERN BENGAL BASIN, WEST BENGAL, INDIA

_______________________________________________________

DISSERTATION

_______________________________________________________

A dissertation submitted in partial fulfillment
of the requirements for the degree of Doctor of Philosophy in the
College of Arts and Sciences
at the University of Kentucky

By
Abhijit Mukherjee
Lexington, Kentucky

Director: Dr. Alan E. Fryar, Associate Professor of Earth and Environmental Sciences
Lexington, Kentucky
2006

Copyright © Abhijit Mukherjee 2006

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This dissertation is dedicated to my parents Kajali and Barindra Lal Mukherjee, my loving wife
Abira, and my friend, philosopher, and guide Dr. Alan E. Fryar, without whose inspiration this
work would not have been possible.

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