Reference no: EM133333813

1. The hydroxyl (HO) radical is a highly reactive species in the troposphere known as the 'atmosphere's detergent'. Describe the steps that lead to the formation of HO in the troposphere, the removal of carbon monoxide (CO) by HO, and the subsequent regeneration of HO (in the absence of NO). Include the relevant chemical reactions.

2. Explain how the regeneration of HO described in (a) above occurs via a different reaction in the presence of nitric oxide (NO). What are the implications for ozone (O₃) in the troposphere in the presence of NO?

3. Carbonyl sulphide (COS) is the most abundant sulphur-containing compound in the atmosphere. It is hydrolysed (reactions involving water) by enzymes in plants and soil organisms to CO₂ and H₂S; that is COS + H₂O → CO2 + H₂S. (Note: this process is not covered in the module but that does not matter for this question).

1. Place COS, CO₂ and H2S in order from least to most oxidised. Explain your answer.

2. The half-life of COS in the troposphere is 264 days. Calculate the life-time of COS in the troposphere.

3. Chlorofluorocarbons (CFCs) are industrial gases that release potentially ozone-depleting Cl atoms to the atmosphere. In the first instance these Cl atoms are locked up in chlorine reservoir molecules. Explain how conditions in the Antarctic stratosphere over winter and spring lead to stratospheric ozone depletion.