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Zorluk: OrtaClimate Change, Global Warming and Ozone Layer Depletion

Consider the following statements regarding atmospheric ozone and its role in environmental processes:

1. Stratospheric ozone acts as a protective shield against harmful ultraviolet (UV-B) radiation, whereas ground-level tropospheric ozone acts as a toxic air pollutant and greenhouse gas.
2. The catalytic destruction of stratospheric ozone by chlorofluorocarbons (CFCs) is primarily driven by free chlorine radicals generated upon exposure to ultraviolet radiation.
3. Hydrofluorocarbons (HFCs) possess high ozone depletion potential and directly destroy stratospheric ozone molecules.

Which of the statements given above is/are correct?

  1. 1 and 2 onlyCevap
  2. B
    2 and 3 only
  3. C
    1 and 3 only
  4. D
    1, 2 and 3

Cevap

Statements 1 and 2 only are correct.
Stratospheric ozone shields Earth from solar UV-B radiation, whereas tropospheric ozone is a ground-level pollutant and greenhouse gas. Free chlorine radicals from CFCs act as catalysts in stratospheric ozone destruction. Hydrofluorocarbons (HFCs) lack chlorine atoms and have an Ozone Depletion Potential of zero, making the statement identifying them as ozone-depleting substances incorrect.

Adım Adım Çözüm

1
Evaluate Statement 1 regarding atmospheric ozone locations and roles.
Statement 1 is correct. Ozone in the stratosphere shields the Earth from harmful UV-B radiation. In contrast, tropospheric (ground-level) ozone is formed photochemically and acts as a key component of smog, a toxic air pollutant, and a greenhouse gas.
Ozone plays opposite roles depending on the atmospheric layer in which it resides.
2
Evaluate Statement 2 regarding CFC catalytic mechanism.
Statement 2 is correct. Intense solar UV radiation splits chlorine atoms from CFC molecules. A single chlorine radical can break apart thousands of ozone (O3O_3) molecules into oxygen molecules (O2O_2) through a self-regenerating catalytic cycle.
Chlorine radicals initiate and propagate ozone destruction without being consumed in the net reaction.
3
Evaluate Statement 3 regarding Hydrofluorocarbons (HFCs).
Statement 3 is incorrect. HFCs contain hydrogen, fluorine, and carbon, but no chlorine or bromine. Consequently, their Ozone Depletion Potential (ODP) is zero. HFCs are potent greenhouse gases with high Global Warming Potential (GWP), which led to their phase-down under the Kigali Amendment.
HFCs do not destroy stratospheric ozone; their environmental threat is climate forcing.

Anahtar Kavram

Dual Role of Atmospheric Ozone and Chemistry of Ozone Depletion vs Greenhouse Gas Impact
Tahmini Süre:1m 0s
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Konular

Climate Change, Global Warming and Ozone Layer Depletion