Hydrochemical characterization, mechanisms of mobilization, and natural background level assessment of arsenic in groundwater of Moradabad district, upper Gangetic plain, India

Abstract

Arsenic-contaminated groundwater is found extensively in most of the Holocene alluvial aquifers in the foreland basin of the Himalayas. Elevated concentrations of arsenic exceeding WHO guidelines (10µg/L) are attributed primarily to the geogenic factors due to favorable biogeochemical conditions found in Holocene aquifers near modern mountain ranges. Different natural factors such as dissolution of carbonate and silicate minerals, aquifer matrix-water interactions, change in climate conditions, availability of organic matters, ion exchange, and prevailing redox conditions are considered to govern the arsenic release mechanisms in groundwater. Human activities, including improper use of fertilizers, mining activities, and use of wood preservatives, could also contribute to arsenic pollution at the local scale. Lower and middle Gangetic plains are well known for their high arsenic concentration in groundwater. Recently, elevated arsenic concentrations have also been reported in the Moradabad district of the upper Gangetic plain, which is considered somewhat safe as compared to the lower parts. In the present study, hydrogeochemical data related to arsenic concentration has been analyzed by plotting arsenic concentrations against various parameters in order to delineate the key processes responsible for elevated arsenic concentrations in groundwater of area. Multivariate statistical methods including, principal component analysis and Pearson’s correlation have also been used to better understand the hydrogeochemical processes that govern the groundwater quality of aquifers in the Moradabad district. The natural background concentration is important factor in evaluation of groundwater pollution. It has also been determined by help of Grubb’s test along with application of cumulative probability plot.