Carbon Monoxide (2)

How is carbon monoxide produced?

Now, knowing the deadly effects of carbon monoxide, aren't you interested in the source of this gas?

Industrial processes:
Carbon monoxide is formed during the incomplete combustion of compounds containing carbon.

2C +O₂ →2CO

It is also formed in huge quantities during the reaction between carbon-containing materials at high temperatures, such as, in blast furnaces.

CO2 + C→2CO

Carbon monoxide is also produced during the dissociation of CO2 at high temperature, although, being rather rare.

CO emission from vehicle exhaust:
One of the major sources of CO in the ambient air is vehicle exhaust. Internal combustion engines do not burn completely to CO2 and water; some unburnt fuel will always be exhausted, with CO as a component. It tends to accumulate in areas of concentrated vehicle traffic.
For example, the number of motor vehicles on Beijing's roads more than quadrupled from 1 million in 1997 to 4.76 million at the end of 2010, and researches has shown that more than three quarters of total air pollution comes from vehicle carbon monoxide and hydrocarbon emissions in large cities including Beijing, Shanghai and Guangzhou.

Natural processes:
Volcanic action, natural gas emission, electrical discharge during storms, seed germination, marsh-gas production etc, are the natural processes that contribute to a small measure for the presence of CO in the atmosphere. Forest fires contribute to 7.2% of CO emissions and agricultural burning contribute 8.3% of emissions. The atmospheric back ground concentration of CO is 0.1 ppm.



Major sink process:
Now, are you wondering since there are so many sources of carbon monoxide gas, wouldn't people be dying? What on earth controls the amount of carbon monoxide gas?

In soil, the major CO sink is by soil microorganisms. The major sink process in the atmosphere is however is the conversion to CO2 by reaction with hydroxyl radical. This process is however rather slow and the reduction in CO level away from the source area is almost entirely a function of atmospheric
dilution processes. The residence time of CO in the atmosphere is of the order of 4 months
and it is removed from the atmosphere by reaction with hydroxyl radical, HO•:

CO+HOi→CO2 +H..................................................................(3)

The reaction of atomic hydrogen with atmospheric oxygen produces hydroperoxyl radical.