摘要：The occurrence of high nitrate levels in groundwater has to be recognized as a threat to humans andanimals. Infant methaemoglobinaemia and nitrate poisoning in livestock occur at unexpected times andplaces. Nitrate pollution in the groundwater is one of the major pollution problems. In the last few decadesnitrate concentration in groundwater has increased dramatically. Groundwater contamination by nitrate (NO 3 - )is a global problem and is most often associated with leachates derived from fertilizers and animal or humanwastes. The study presented here was carried out in Varanasi district. The nitrate content in water wasinvestigated during premonsoon (March-April, 2013) and postmonsoon (November-December, 2013) seasonsand compared with the standard values given by WHO. Eighty four, from different cropping systems (i.e.rice-wheat, rice-vegetable, vegetable-vegetable, pulse-pulse, orchard and sugarcane) groundwater sampleswere collected from the bore wells. The analysis of nitrate in these water samples reveals that some villageshave a high concentration of nitrate, exceeding permissible limits of WHO (45 mg/L), which is due to themore than the required quantity of nitrogen based fertilizers, water, manure and pesticides are used extensivelywhich all contribute to the non point source contamination of nitrates in groundwater of the study area.
