Explanation:

Excessive use of nitrate including manure may be responsible for the presence of toxic substance in groundwater. Phosphate can also enter the groundwater via excessive use of fertilizers. High application rates of nitrogen containing fertilizers combined with the high-water solubility of nitrate, leads to increased runoff into surface water as well as leaching into groundwater, thereby causing groundwater pollution. Only a fraction of the nitrogen-based fertilizers, is converted to produce and other plant matter. Nitrate pollution in groundwater comes from pit latrines, it can cause blue baby syndrome.