The Atmosphere

bonkysleuth SG

During peak hours, the levels of CO in the atmosphere is high due to incomplete combustion of petrol in vehicle engines. This is caused by the traffic congestions when cars idle and little O2 is available for combustion for idling vehicles.

The amount of another air pollutant, NO2, throughout the day shows a similar trend as CO.(high levels of NO2 during peak hours) Why?

Not really sure about this. Please help.

SBS2601D SG

Because when the oxygen is abundent, more NO2 will be produced. In an engine, nitrogen oxides that are not necessarily NO2 will be produced. The most abundant in oxygen-starved environment will usually be NO.

NO reacts with more oxygen to form NO2. Of course, provided the oxygen is available. Just like CO and CO2.

anpanman SG

NO reacts with more oxygen to form NO2. Of course, provided the oxygen is available. Just like CO and CO2.

They didn't say O2 is in abundant. In fact, the cars are idling so how can there be a lot of O2?

Forbiddensinner SG

The amount of another air pollutant, NO2, throughout the day shows a similar trend as CO.(high levels of NO2 during peak hours) Why?

Not really sure about this. Please help.

http://en.wikipedia.org/wiki/Nitrogen_dioxide

Hope this helps.

Scroll down to the Safety and pollution consideration section.

SBS2601D SG

They didn't say O2 is in abundant. In fact, the cars are idling so how can there be a lot of O2?

NO has a higher tendency to react with O2 in oxygen-rich environment.

The high concentration of NO from the exhaust pipe is therefore converted to NO2 in the atmosphere.

Given NO is the majority NOx group formed in idling engines, that should be the case. Combustion at varying levels of oxygen concentration yields various compositions of the NOx constituents.

Excess air will form more of the other types of nitrous oxides, and therefore less NO2 will form.

nightzip SG

“In any particular setting the answer will depend on the relative contributions of outdoor and indoor sources and on personal activity patterns. A direct relationship between personal exposure and outdoor concentrations is found in the absence of exposure to indoor sources such as unvented cooking or heating appliances using gas, and tobacco smoking. However, since outdoor NO2 is subject to wide variations caused by differences in proximity to road traffic and local weather conditions, the relationship of personal exposure to measurements made at outdoor monitoring stations is variable.

Meaning when there is traffic congestion, people start to smoke cigarettes when they waited, resulting in higher NO2! Razz

nightzip SG

Another possibility, due to traffic congestion, there are more cars on the road, then would be a smoother traffic condition, where the cars would have reached their destination (at a more efficient combustion of engine).

Thus, more cars running during congestion implies more NO2. Smile