Rolling Revision of the WHO Guidelines for Drinking-Water Quality ...

Figure 1.8 Development of the consumption of mineral nitrogen fertiliser in some
industrialised western countries (After Ministry of Agriculture et al.,
1988:15, in: Conrad, 1992)
1.5 Atmospheric sources
Anthropogenic or anthropogenically-induced emissions of nitrogen compounds into
the atmosphere contribute to increasing pollution of drinking water resources by
nitrate. This is because all nitrogen compounds that are emitted to the atmosphere in
the form of gas (this applies to N2O to some extent only) reach terrestrial ecosystems
sometimes after complex chemical and photochemical transformation processes in the
atmosphere. The various nitrogen compounds emitted may be assigned quantitatively
to their main pollutant source as follows
- N0x emissions (sum of NO + NO2) are produced during all combustion processes
and are predominantly caused by transport and energy production. Although 90%
of emissions from combustion processes are in the form of NO, potentially all of the
NO can be converted very quickly to NO2 in the atmosphere. Thus NOx emissions
are often quoted as total quantities of NO2. Lammel (1993) estimated the annual
world-wide total NOx emissions to be 53 x 10 6 t of NO2, of which 60 % originated
from anthropogenic sources.
- NH3 comes mostly from agriculture, especially from animal husbandry.
- N2O emissions are released predominantly from industrial processes and the
microbial reduction of nitrate on agricultural land. Nitrate is degraded mainly into
molecular nitrogen during denitrification and also into N2O. The share of N2O in the