Sulphur dioxide&Nitrogen oxides 急急急

The main natural sources of sulphur dioxide are volcanoes, forest fires and oceans. The main human sources of sulphur dioxide are burning fossil fuels, smelting, paper manufacture and the production of sulphuric acid via the Contact Process.

At ambient temperatures, the oxygen and nitrogen gases in air will not react with each other. In an internal combustion engine, combustion of a mixture of air and fuel produces combustion temperatures high enough to drive endothermic reactions between atmospheric nitrogen and oxygen in the flame, yielding various oxides of nitrogen. In areas of high motor vehicle traffic, such as in large cities, the amount of nitrogen oxides emitted into the atmosphere can be quite significant.

I hope this can help your understanding. =)