Sources of Nitrate in Ground Water Aquifers of the Semiarid Region of Tanzania

Table 1

The measure of central tendency and Wilcox signed-rank test results for NO₃⁻, NO₂⁻, and NH₄⁺ in boreholes and shallow wells between the dry and wet seasons.

	Dry season				Wet season				Wilcox signed-rank test
Parameter	Min.	Median	Max.	SD	Min.	Median	Max.	SD	value	value
NO3^−	1.8	72.8	929.6	118.5	2.4	65.6	1620.0	312.3	0.8	0.5
NO2^−	0.0	40.0	6470.0	540.0	0.0	40.0	2300.0	450.0	1670.0	100.0
NH4^+	20.0	120.0	1800.0	120.0	10.0	120.0	8500.0	1710.0	1224.0	220.0

Min.: minimum; Max.: maximum; SD : standard deviation; : statistics; : value; NO₃: nitrate (value in ppm); NO₂⁻ and NH₄⁺ (values in ppb).