Classifying ozone as an air pollutant in the lower atmosphere In tropospheric air quality, ozone is best described as which type of pollutant?
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Aa primary pollutant.
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Ba secondary pollutant.
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Cimpervious to ultra-violet rays.
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Dboth (b) and (c)
Answer
Correct Answer: a secondary pollutant.
Explanation
Introduction / Context:Ozone plays two contrasting roles: beneficial in the stratosphere where it absorbs harmful ultraviolet radiation, and harmful in the troposphere where it is a key component of photochemical smog. Understanding how tropospheric ozone forms is vital for controlling urban air pollution.
Given Data / Assumptions:
- Context is ground-level (tropospheric) ozone, not stratospheric ozone.
- Precursor emissions include nitrogen oxides (NOx) and volatile organic compounds (VOCs).
Concept / Approach:Tropospheric ozone is not emitted directly; it forms through sunlight-driven reactions involving NOx and VOCs. Therefore, it is a classic secondary pollutant. The statement that ozone is “impervious to UV” is incorrect; stratospheric ozone absorbs UV-B and part of UV-C, which is why the ozone layer protects life on Earth.
Step-by-Step Solution:
Identify pollutant type: emitted vs formed in air.Recall photochemical pathways creating O3 from NOx + VOCs + sunlight.Conclude: tropospheric ozone is a secondary pollutant.Verification / Alternative check:Air quality management focuses on precursor reductions, not direct ozone emissions, reinforcing the classification.
Why Other Options Are Wrong:
Primary pollutant: False for ozone at ground level.Impervious to UV: Incorrect description of ozone’s interaction with UV.Both (b) and (c): Invalid because (c) is false.Common Pitfalls:Conflating stratospheric and tropospheric ozone; the former is protective, the latter is a pollutant.
Final Answer:a secondary pollutant.