Nitrate and nitrite content of well water in Enugu, Southeast Nigeria

Water samples from 20 artesian wells, chosen by the multistage sampling procedure from 5 zones in the city of Enugu, Southeast Nigeria, were analyzed by the disulfonic acid method in duplicate for the presence of nitrate (NO3) and nitrite (NO2). The zonal mean values for NO3 were 0.45 mmol/l, 0.46 mmol/l, 0.55 mmol/l, 0.59 mmol/l, and 0.65 mmol/l (mean = 0.54 mmol/l), and for NO2 the values were 0.34 mmol/l, 0.32 mmol/l, 0.21 mmol/l, 0.14 mmol/l, and 0.20 mmol/l (mean = 0.24 mmol/l), respectively. The mean values were reciprocally related (r = -.7356, p = 0.0002), indicating fecal contamination of well water. There were no significant differences between the mean values and the sum of the NO3 and NO2 values of the samples (p > 0.05), indicating uniform nitrogen content in the region. The mean value for NO3 (0.54 mmol/l) was below the guideline values set by the World Health Organization, but the mean NO2 concentration of 0.24 mmol/l was much higher (290%) than what is considered safe for humans.