Nitrogen Dioxide

In its pure state, nitrogen dioxide is a reddish-orange brown gas with a characteristic pungent odor. It is corrosive and a strong oxidizing agent. Nitrogen dioxide comprises about 10% of the oxides of nitrogen (NOx) that are formed when nitrogen in the air combines with oxygen during high temperature combustion. Most of the rest of the NOx emitted by combustion sources is nitric oxide (NO). However during the day most of the NO is photochemically transformed into NO 2 . Thus, essentially all NOx emitted can be assumed too eventually become NO 2 .

Exposure to NO 2 affects the delicate structure of lung tissue. High levels cause lung irritation and potential lung damage. Lower levels have been associated with increased respiratory disease. Oxides of nitrogen can cause serious injury to vegetation, including bleaching or death of plant tissue, loss of leaves, and reduced growth rate. NOx also deteriorates fabrics and fades fabric dyes. Nitrate salts formed from nitrogen oxides have been associated with the corrosion of metals. Nitrogen oxides can also reduce visibility.

The current standard for NO 2 is an annual arithmetic mean (average) value not to exceed .05 ppm. NO 2 is the only gaseous pollutant for which only a long-term (annual average) standard has been established.

Nitrogen Dioxide is monitored at the seasonal site on Cadillac Mountain in Acadia National Park and has routinely been monitored in Portland . The Portland site was teminated at the end of 2006 and a new site is being established near the Deering Oaks Park area and is expected to be in operation by the end of January, 2008. Data from these two sites when they are in operation can be viewed on the air quality web site .

 

 

 

 

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