Overview:
-emitted by the burning of fuels, industry, and through natural (nitrogen
cycle) processes.
-cause ozone and acid rain
-short lived in the atmosphere
Rain Forest:
Due to the short life of these compounds in the tropospheric atmosphere,
areas of concern for the preservation of the rainforest are industrial and
urban sites near or within the rainforest and the burning of the rainforest.
All other sources of NOx will be filtered out of the atmosphere by natural
processes long before reaching the Amazon River Basin Rainforest ecosystem.
Background:
Nitrogen oxides are reactive, greenhouse gases (WMO), including NO and
NO2. When released into the atmosphere through natural (nitrogen cycle) and
artificial sources (combustion of fuel, industry), these compounds enter a
complex reactionary period of a few days. The main products of this reaction
period are tropospheric ozone (O3) and nitric acid (HNO3) (Graedel 152).
NO2 + hv (wavelength less than 410 nm) ' NO + O
O + O2 + catalyst ' O3 + catalyst
NO + O3 ' NO2 + O2
And
R + O2 + catalyst ' RO2 + catalyst
RO2 + NO ' NO2 + RO
What is happening in these reactions is the creation of ozone gas and
its concurrent consumption. However, in the presence of organic molecules
of solely carbon and hydrogen (R), NO favors the second group of reactions
and the ozone is not re-consumed. This process creates high levels of
tropospheric ozone.
Luckily for the condition of the atmosphere, a self cleaning process is
constantly breaking NOx molecules into nitric acid (HNO3) through reaction
with hydroxyl radicals.
HO + NO2 + catalyst ' HNO3 + catalyst
Nitric acid is unreactive in the gas phase, but quite soluble in
water(Graedel 152). Thus the acid concentrates in water droplets. The
resulting acidic rain is damaging to soil processes and at very low pH can
directly damage flora and fauna (Mayer 8).
WMO http://www.wmo.ch/wmo50/e/wmo/today_pages/glob_atm_watch_e.html
Graedel, T. E., Atmospheric Change: An Earth System Perspective.
W. H. Freeman and Company, 1993.
Mayer, Robert; Liess, Siegfried; et al. Atmospheric Pollution
in a Tropical Rain Forest: Effects of Deposition upon
Biosphere and Hydrosphere. Environmental Engineering
Abstracts, 16 August 1999.