Assessment of the potential hazards of nitrate contamination in surface and groundwater in a heavily fertilized and intensively cultivated district of India

Abstract

We made an inventory of nitrate (NO₃-N) enrichment in surface and groundwater systems in the Hooghly district of India owing to intensive farming with high fertilizer doses as a function of quantity of fertilizers use, soil characteristics, types of crop grown, depth of groundwater sampling and also N-load in soil profiles. Water samples were collected from different sources at 412 odd sites spread over in 17 blocks of the district along with representative soil profiles. On average, the study area had high clay and NO₃-N in soil profiles with an increasing and decreasing trends along depth, respectively. The NO₃-N content both in surface and groundwater varied from 0.01 μg mL⁻¹ to 4.56 μg mL⁻¹, being well below the threshold limit of 10 μg mL⁻¹ fixed by WHO for drinking purpose. The content decreased with increasing depth of wells (r = −0.39**) and clay content of soil profiles (r = −0.31**). It, however, increased with increasing rate of fertilizer application (r = 0.72**), NO₃-N load in soil profiles (r = 0.85**) and was higher in areas where shallow- rather than deep-rooted crops are grown. Results indicated even under fairly high quantity of fertilizer use, groundwater of the study area is safe for drinking purpose.