Concentrations are elevated by hot, sunny days: 2. increases exposure of organisms to ultraviolet light: 3. caused by halocarbons, such as chlorofluorocarbons (cfcs): 4. forms from emissions of sulfur dioxide: 5. montreal protocol aimed to reduce emissions that cause this: 6. a reaction between pollutants and atmospheric compounds that creates over 100 different chemicals: 7. leaches plant nutrients from soils: 8. most pronounced in cities prone to inversion events:

1. Concentrations are elevated by hot sunny days: photochemical smog.
A photochemical smog is a type of smog that occurs when sunlight in the atmosphere reacts with chemicals produced by the combustion of fossil fuels. This smog consists a pollutant and it is very common in large and densely populated cities. In hot sunny days, the ultraviolet light from the sun is at high levels, therefore, the photochemical smog is elevated.

2. The correct answer is stratospheric ozone depletion.
The Earth's stratosphere (which is one of the atmosphere's layers) has a layer with high ozone concentration, called ozone layer. The ozone layer absorbs most of the ultraviolet radiation that the Earth receives from the Sun. The ozone depletion is a term referring to the phenomenon of the gradual thinning of the ozone layer.

3. The correct answer is again ozone depletion.
The thinning of the ozone layer (as described above) is mainly caused by chemicals produced by the industry and other human activities. These chemicals belong to the category of ozone-depleting substances (ODS) and include halocarbon refrigerants, solvents and propellants. They are released from the surface of the Earth and transferred through the wind up to the stratosphere. When in the stratosphere, they undergo photolysis and release their halogen atoms. This, in turn, causes the breakdown of ozone into oxygen.

4. Acid deposition forms from emissions of sulfur dioxide.
Acid deposition is a term referring to the phenomena of acid rain, acid fog and acid mist. It is an environmental problem caused by the pollutants and gases from fossil fuel combustion and other human activities. In particular, power stations, house fires, car exhausts and melting processes emit sulfur dioxide which reacts with water molecules in the atmosphere and converses into sulfuric acid. This reaction lowers the pH of the rain, fog and mist and causes problems to the organisms and the infrastructure on Earth's surface.

5. Montreal protocol aimed to reduce emissions that cause the ozone depletion.
Montreal protocol is a protocol of the Vienna convention for the protection of the ozone layer and constitutes an international treaty. It controls the production, emission and consumption of the substances responsible for the ozone depletion (ODSs) on a global level. The implementation of this protocol resulted in a slow recovery of the ozone layer.

6. The correct answer is photochemical smog.
As described in question 1, the photochemical smog constitutes a mixture of several air pollutants. It is a product of the chemical reaction between the sunlight, nitrogen oxides and volatile organic compounds. The photochemical smog is a mixture of over 100 different chemicals, including nitrogen oxides, peroxyacetyl nitrate, tropospheric ozone and aldehydes.

7. Acid deposition leaches plant nutrients from the soil.
Acid deposition can cause soil acidification, a term referring to the pH of the soil becoming acidic. It has been observed that plants in areas where acid deposition is more common, grow more slowly or are unable to grow and die. This happens because the acid deposition releases toxic substances in the soil, such as aluminium. In addition, it happens because acid deposition removes minerals and nutrients from the soil and kills some of the microorganisms necessary for the plants to grow.

8. The correct answer is photochemical smog.
A temperature inversion is the reversal of the normal behaviour of the temperature above the surface of the Earth, meaning that temperature does not decrease with height as it is supposed to. These inversion effects reduce the atmospheric mixing and, in turn, reduce the dispersal of pollutants in the atmosphere. Therefore, this causes an increase in the concentration of pollutants and an increase in the production of photochemical smog.

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