MAJOR SOURCES AND EFFECTS OF NOX EMISSIONS

NOx emissions are basically made up of nitric oxide, nitrous oxide and nitrogen dioxide. They are usually formed when nitrogen combines with oxygen during combustion of fossil fuels. Nitrogen dioxide and nitric oxide gases can last in the air for seven days while nitrous oxide can last up to 170 days. Nitric oxide is colorless, odorless and tasteless. It is quite unstable and easily combines with oxygen to form nitrogen dioxide. NO2 has a reddish color and a choking odor. It absorbs light and could easily lead to poor vision in cities. It forms one of the major components of smog. Nitrous gas is a sweet smelling nonpoisonous colorless greenhouse gas used as an anesthetic. It occurs naturally in the atmosphere.

About 10% of the NOx emissions from fossil fuels is composed of harmful nitrogen dioxide. For this reason, the emissions have to be treated in order to avoid environmental pollution. Treatment is done on some of the major sources of the emissions. These include diesel engines, heavy machinery running on diesel in industries, and off-road trucks as well. However, these are not the only sources of NOx. The gases occur in nature as a result of lightning, bacterial processes, biological decay and growth, and forest fires.

Nitric oxide is usually the most produced gas in NOx emissions. Some of it exists as nitrous oxide while the rest is converted to nitrogen dioxide. The amount of NO2 produced varies depending on the heat of combustion. High temperature combustion leads to production of more NO2. As seen earlier, a large percentage of these emissions is produced through burning of fossil fuels. For instance, in Alberta 41% of the nitrogen oxide emissions comes from oil & gas industry. 25% comes from various means of transportation, 17% from electrical utilities, and the rest from other commercial, industrial and residential users.

The effects of NOx can either be mild when low concentrations are emitted or adverse when critical concentrations are reached. Even though nitric oxide is harmless, it is readily converted to harmful NO2 gas. Research shows that nitrogen dioxide can be toxic to plants when in high concentrations. It leads to lower yields and productivity in agriculture. NO2 can also combine with ozone or SO2 and cause adverse effects even in low concentration. Nitrous oxide is one of the major greenhouse gases. It leads to the depletion of ozone in the stratosphere. All these harmful effects make it necessary for the fossil fuel users to incorporate various treatment methods for NOx emissions.