Natural and anthropogenic influence on the fluoride and nitrate concentration of groundwater in parts of Nalgonda district, Andhra Pradesh, India Brindha K., Rajesh R., Murugan R., Elango L.* Department of Geology, Anna University, Chennai-600025, India *elango34@hotmail.com, elango@annauniv.edu
Abstract Groundwater forms the major source of drinking water in the rural areas of most of the developing nations of the world. Presence of high concentration of fluoride and nitrate in groundwater is a major problem in many countries as it causes health related problems. The present study was earned out with the objective of determining the causes for higher fluoride and nitrate concentration in groundwater in parts of Nalgonda district, Andhra Pradesh, India. Fluoride and nitrate concentration in groundwater of this area was analysed by collecting groundwater samples from forty six representative wells. Samples were collected once in two months from March 2008 to January 2009. The fluoride and nitrate concentration was analysed in the laboratory using Metrohm 861 advanced compact ion chromatograph. Fluoride concentrations in groundwater samples varied from 0.1 mg/l to 8.8 mg/l. Nearly 29.5% of the groundwater samples have fluoride content greater than that of the maximum permissible limit of 1.5 mg/l prescribed for drinking purpose while 15.8% of the samples possessed fluoride less than the minimum required limit of 0.6 mg/l. Possible source of fluoride in groundwater are weathering and leaching of fluoride bearing minerals from me basement granitic rocks of this region under alkaline environment. By nature, the granitic rocks of this area possess fluoride greater than the world average of fluoride content in granitic rocks. The highest concentration of nitrate recorded during the sampling period was 879.65 mg/l and the lowest concentration was below detection limit. Taking into consideration 45mg/l of nitrate as the maximum permissible limit for drinking water set by BIS, it was found that 13.78% of the groundwater samples collected from this study area possessed nitrate concentration beyond the linm. Overall, wells present in agricultural fields had nitrate levels within permissible limits when compared to those groundwater samples from wells present m settlements which were used for domestic purpose. This indicates that the high nitrate concentration in groundwater of this area is due to leaching from indiscriminate dumping of animal waste. Anthropogenic activities like application of fertilizers for agriculture contribute only little to the groundwater nitrate as well as fluoride. The wells in the investigated region have been demarcated into safe and unsafe wells for consumption of water with respect to fluoride and nitrate. Top Keywords Groundwater, Fluoride, Nitrate, Anthropogenic, Nalgonda, India. Top |