ABSTRACT
Under natural conditions, the levels of nitrogen compounds in groundwater (i.e. background concentrations) are very low: 3.41 mg 1 NOs" and 0.56 mg I""1 NH4+ according to Shvartsev (1978) for groundwater of upper aquifers. The usual sources of nitrogen inputs to ground water are mainly gas and dust emissions from industrial and domestic activities including fossil fuel combustion, industrial effluents, mineral and organic fertilisers, livestock effluents, municipal wastes and silo effluents. The concentrations of nitrogen compounds in these sources may exceed hundreds and even thousands of milligrams per litre (Krainov and Zakutin, 1993). Inputs from these sources can affect groundwater quality not only at a local level but also at a regional level. In addition, the formation of higher concentrations of NH4+ in groundwater (up to several mg I"1) occurs under certain biochemical conditions as a result of ammonification processes (Zakutin and Chugunova, 1992). 7.2 Intensity of pollution with nitrogen compounds Water pollution and its intensity can be characterised by the ratio of average concentration to MAC, referred to here as the pollution index (Goldberg and Gazda, 1984). The MACs are 45 mg T1 NO3~ and 0.5 mg 1 NH4+. In wet areas, and for groundwaters with natural background levels of NC>3~, the pollution index is < 0.02 for NC>3~ whereas the pollution index for arid areas is 0.02-0.2. Polluted waters with higher concentrations of NOs" resulting from anthropogenic activities are characterised by three ratios depending on the level of pollution. A pollution index from 0.2-0.5 reflects low pollution, an index from 0.5-1 is characteristic of moderately polluted water and an index > 1 characterises highly polluted water (Figure 7.3). A similar approach has been used to
assess nitrogen contamination of groundwaters in the USA (Madison and Brunett, 1984).
