Arsenic mobility in fluvial environment of the Ganga Plain, northern India

• Published in: Environmental earth sciences 2010-02, Vol.59 (8), p.1703-1715
• Main Authors: Singh, Munendra, Singh, Amit Kumar, Swati, Srivastava, Nupur, Singh, Sandeep, Chowdhary, A. K.
• Format: Article
• Language: English
• Subjects: Alluvial rivers; Anthropogenic factors; Arsenic; Biogeochemistry; Biogeosciences; Climatic conditions; Downstream; Drinking water; Earth and Environmental Science; Earth Sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Environmental Science and Engineering; Exact sciences and technology; Fluvial sediments; Freshwater; Geochemistry; Geology; Groundwater pollution; Human-environment relationship; Hydrogeology; Hydrology; Hydrology. Hydrogeology; Hydrology/Water Resources; Hydroxides; Microbial degradation; Mineralogy; Monsoons; Organic carbon; Organic matter; Original Article; Pollution, environment geology; Rivers; Seasons; Silicates; Summer; Terrestrial Pollution; Tributaries; Water analysis; Water column; Water geochemistry; Water resources; Water sampling
• ISSN: 1866-6280; 1866-6299
• DOI: 10.1007/s12665-009-0152-z

In the northern part of the Indian sub-continent, the Gomati River (a tributary of the Ganga River) was selected to study the dynamics of Arsenic (As) mobilization in fluvial environment of the Ganga Plain. It is a 900-km-long, groundwater-fed, low-gradient, alluvial river characterized by monsoon-controlled peaked discharge. Thirty-six water samples were collected from the river and its tributaries at low discharge during winter and summer seasons and were analysed by ICP-MS. Dissolved As and Fe concentrations were found in the range of 1.29–9.62 and 47.84–431.92 μg/L, respectively. Arsenic concentration in the Gomati River water has been detected higher than in its tributaries water and characteristically increases in downstream, attributed to the downstream increasing of Fe 2 O 3 content, sedimentary organic carbon and silt-clay content in the river sediments. Significant correlation of determination ( r 2  = 0.68) was also observed between As and Fe concentrations in the river water. Arsenic concentrations in the river water are likely to follow the seasonal temperature variation and reach the level of World Health Organization’s permissible limit (10 μg/L) for drinking water in summer season. The Gomati River longitudinally develops reducing conditions after the monsoon season that mobilize As into the river water. First, dissolved As enters into pore-water of the river bed sediments by the reductive dissolution of Fe-oxides/hydroxides due to microbial degradation of sedimentary organic matter. Thereafter, it moves upward as well as down slope into the river water column. Anthropogenically induced biogeochemical processes and tropical climatic condition have been considered the responsible factors that favour the release of As in the fluvial environment of the Ganga Plain. The present study can be considered as an environmental alarm for future as groundwater resources of the Ganga–Brahmaputra Delta are seriously affecting the human–environment relationship at present.