groundwater pollution by nitrate in the vicinity of zayanderud river

to study the spatial and temporal variation of nitrate pollution in groundwater in the vicinity of zayandehrud river in isfahan province monthly water samples were collected from 100 wells in the study area. the average n03-n concentration ranged from 1.2 to 25.7 mg/l (5.4 to 115.6 mg/i as no3) and average n03-n concentration in groundwater was 9.6 mg/i, which is lower than the standard limit (10 mg/i). maximum n03-n concentration (70.8 mg/i) was detected in an agricultural region in west of isfahan province. although nitrate concentration changed in various wells, but there was an increasing trend from baghbaderan to varzaneh. the reason is the extent of agricultural lands and gradual pollution of zayandehrud river due to discharging urban, industrial and agricultural wastewater, and their direct or indirect effects on groundwater quality. the average n03-n concentration in 41 percent of the wells near the zayandehrud river was more than the standard limit for drinking water. the average n03-n concentration in groundwater of agricultural and urban regions was 10 and 7.6 mg/l, respectively.