Nitrate Pollution of Drinking Water in Pakistan.

Excessive N fertilization and high nitrate content sewer water for crop irrigation are common problems in Pakistan. Nitrate by itself is non-toxic.  However, nitrate metabolites in potable water can be related to public health concerns. This study evaluated the extent of nitrate pollution of drinking water systems in 35 districts of Punjab province, Pakistan. In each district, 20 samples from 5 different sources (deep, medium, shallow, tube-wells, and bottled) were randomly collected in summer and winter. Water samples were analyzed for nitrate and other characteristics. Results showed that where intensive agricultural fertilization was used (17 mg NO3 L-1), or where sewer water was used for irrigation (14 mg NO3 L-1), nitrate pollution significantly increased. Except for deep well (6 mg NO3 L-1) and bottled (3 mg NO3 L-1) water, nitrate pollution was always more abundant in medium (15 mg NO3 L-1), shallow (18 mg NO3 L-1) and tube-well (16 mg NO3 L-1) water in densely populated areas. Averaged across water sources, water collected from areas under sandy loam (19 mg NO3 L-1) was more polluted than other soils (10 to 12 mg NO3 L-1).