Nitrous Oxide Emissions from Agricultural Fields

Abstract

Nitrous oxide (N2O) is an important atmospheric trace gas because it is a long-lived greenhouse gas and also a major source of stratospheric NO, which plays an important role in ozone layer chemistry (Cuceribem, 1989). The atmospheric concentration of N2O, which is 312 ppbv is increasing at the rate of 0.8 ppbv per year. The lifetime of N2O is about 120 years in the atmosphere. The global warming potential (GWP) of each molecule of N2O is about 210 times (20-years horizon) greater than each molecule of CO2 (Houghton et al., 1996). Nitrous oxide currently accounts for 6% of total GWP (Houghton et al., 1996) and could contribute as much as 10% of GWP in near future (Cicerone, 1989). Figure 1 shows estimates of the global and annual average of anthropogenic radiative forcing (in Wm-2) due to changes in concentrations of greenhouse gases and aerosols from pre-industrial times to the present (1992) and to natural changes in solar output from 1850 to the present (Houghton et al., 1996). Nitrous oxide is also involved in the depletion of the ozone layer in the stratosphere which protects the biosphere from the harmful effects of solar ultraviolet radiation (Crutzen, 1981). It has been estimated that doubling the concentration of N2O in the atmosphere would result in a 10% decrease in the ozone layer which would increase the ultraviolet radiation reaching the earth by 20% (Crutzen and Ehhalt, 1977), eventually leading to an increase in the occurrence of skin cancer and other health problems.