235-8 Delineating Arsenic safe groundwater in parts of Ganga basin, India

Session: Advancing the Understanding and Management of Groundwater Pollution with Arsenic and Other Geogenic Contaminants Using Geospatial Tools, Machine Learning, and Data Science, Part I

Presenting Author:

Tridip Bhowmik

Authors:

Bhowmik, Tridip¹, Bose, Oindrila², Singh, Chander Kumar³, Bose, Nupur⁴, Ghosh, Ashok⁵, Sengupta, Probal⁶, Mukherjee, Abhijit⁷

(1) School of Environmental Science & Engineering, Indian Institute of Technology Kharagpur, Kharagpur, West Bengal, India, (2) Department of Geology & Geophysics, Indian Institute of Technology Kharagpur, Kharagpur, West Bengal, India, (3) Department Natural and Applied Sciences, TERI School of Advanced Studies, New Delhi, Delhi, India, (4) Department of Geography, A.N. College, Patna, Bihar, India, (5) Mahavir Cancer Sansthan and Research Center, Patna, Bihar, India, (6) Department of Geology and Geophysics, Indian Institute of Technology Kharagpur, Kharagpur, West Bengal, India, (7) Department of Geology and Geophysics, Indian Institute of Technology Kharagpur, Kharagpur, West Bengal, India; School of Environmental Science and Engineering, Indian Institute of Technology Kharagpur, Kharagpur, West Bengal, India,

Abstract:

Widespread arsenic (As) pollution in groundwater is a severe problem especially in Ganga basin, India impacting the drinking water needs of millions of people. Therefore, delineation of safe aquifers is important to safeguard the population from drinking water crisis caused due to As contamination. To address this, the present study attempts to characterize the aquifer sediments at shallow depth based on their color, collected through extensive drilling (50 boreholes) in two study sites – Bhagalpur (Bihar) and North 24 Parganas (West Bengal) in the Gangetic basin, India. The lithologic model developed represent the distribution of aquifers based on sediment color – grey sediment (GS) and brown sediment (BS). The groundwater samples hosted by the distinct aquifer sediments was evaluated to understand the concentration of iron (Fe) and arsenic (As). Chemical analysis of the 108 groundwater samples collected from both the study sites revealed that the groundwater hosted by the GS aquifers were highly reduced with low redox potential (Eh), high iron (Fe) and unsafe As levels (>10 μg/L). In contrast, the groundwater hosted by BS aquifers possessed higher Eh, low Fe and safe As concentration (< 10 μg/L) with ~ 85% and ~ 75% of the samples yielding As safe levels in both N24P and BHG. The BS aquifers in N24P are mostly overlained by GS aquifer with an aquitard layer separating the two aquifers which preserves the BS aquifers from contamination. However, in case of BHG the BS aquifers are placed adjacent to GS aquifers without any clay clapping that makes them more vulnerable to contamination. Hence, lithologic setting controls the vulnerability of these aquifers. Further, this study states that the aquifer sediment color can act as a nature-based solution for As mitigation and it can be beneficial in targeting safe aquifers at shallow depth in the affected region. However, more comprehensive assessment is required along with identification of transition zones to implement this technique efficiently for safe drinking water supply.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-5027

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