“…In 1992, U.S. emissions of anthropogenic nitrogen oxides were estimated to be 23 million tons. Of this, 45% was from mobile sources and the remainder came from stationary sources (Ozkan et al, 1995). The seven oxides of nitrogen that may be present in ambient air are NO, N0 2 , N 2 0, N0 3 , N 2 0 3 , N 2 0 4 and N 2 0 5 .…”