Geo-chemical Analysis of Arsenic in Medium Aquifers and Its Relation with Physical Parameters: A Study of Ballia District, India

Abstract

The main objective of this paper is to assess the spatial variation of arsenic (As) in medium aquifer and to relate it with surface elevation and slope generated using Shuttle Radar Topography Mission (SRTM) satellite data and water table. Water samples were collected in both pre- and post-monsoon season in 2011. The analysis of water samples for As were carried out by using atomic absorption spectrophotometer (AAS). Total 33 water samples from medium aquifer (80–120 feet) were taken both in pre- and post-monsoon season in 2011 from the 17 blocks of the Ballia district the eastern most district of Uttar Pradesh. Inverse Distance Weighted (IDW) model was used for interpolation of As concentrations. Descriptive statistical analysis was applied to examine the nature of relationships and statistical association amongst the variables. The results show that high As is generally found in areas of low surface elevation, low slopes and low water table in the district. The relationships among groundwater As, slopes and water table are non-linear and these variables have inverse relationships. On the basis of scatter plot and statistical analysis between groundwater As and elevation, As and slope, and As and water table shows the linear relationships among all these variables. The correlation of coefficient (r²) value between As and surface elevation were 0.78 and 0.68, respectively in pre- and post-monsoon. The scatter plots show that the correlation coefficients (r²) between As and slope are 0.69 and 0.65 in pre- and post-monsoon respectively. Correlation of coefficients (r²) between As and water table are 0.74 and 0.71 in pre- and post-monsoon respectively. The results show that more than 90% areas contain As above the permissible limit of 10 ppb in both pre- and post-monsoon seasons.