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#photochemical smog

3 public questions tagged with this topic.

Applied Ecology

What are the pollutants formed by VOCs and NOx under sunlight?

Sunlight acting on nitrogen oxides and volatile organic compounds generates photochemical oxidants. Nitrogen dioxide photolysis creates ozone, while VOC-derived radicals support ozone accumulation and form aldehydes and peroxyacyl nitrates. These secondary pollutants irritate eyes and lungs and injure vegetation. They differ from greenhouse gases as a functional class, from acids formed by sulfur and nitrogen oxidation, and from elemental heavy metals. At organismal level, respiratory surfaces are especially exposed because large volumes of air contact thin, moist epithelia designed for rapid gas exchange. Sound classification links the source, atmospheric fate, exposure route, and mechanism of toxicity rather than relying only on the pollutant's name. Effective management combines cleaner fuels, emission standards, monitoring, urban planning, and protection of populations with high exposure or physiological vulnerability. The distinction is ecologically important because emission control must target either the directly released precursor or the product formed after atmospheric transport and reaction. Exposure depends on concentration, duration, ventilation, weather, and individual susceptibility, so a pollutant's presence alone does not fully predict biological harm.

Ref: Campbell Biology, Urry et al., 12th Ed., Unit 8 Ecology

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Applied Ecology

Which gas is a major component of Los Angeles-type smog?

Los Angeles-type smog is oxidising photochemical smog, and ground-level ozone is one of its major components. Strong sunlight drives reactions among nitrogen oxides and volatile organic compounds emitted chiefly by traffic and industry. Sulfur dioxide is more characteristic of traditional coal-smoke or London smog, whereas carbon monoxide may be present but does not define this smog type. The distinction is ecologically important because emission control must target either the directly released precursor or the product formed after atmospheric transport and reaction. Exposure depends on concentration, duration, ventilation, weather, and individual susceptibility, so a pollutant's presence alone does not fully predict biological harm. Atmospheric inversions can trap contaminants near the surface, while wind, turbulence, precipitation, and chemical transformation determine their eventual distribution and removal. At organismal level, respiratory surfaces are especially exposed because large volumes of air contact thin, moist epithelia designed for rapid gas exchange. Sound classification links the source, atmospheric fate, exposure route, and mechanism of toxicity rather than relying only on the pollutant's name.

Ref: Campbell Biology, Urry et al., 12th Ed., Unit 8 Ecology

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Applied Ecology

Photochemical smog is mainly caused by the reaction of VOCs with which compound?

Photochemical smog develops when volatile organic compounds react through radical chemistry with nitrogen oxides in sunlight. Nitrogen dioxide photolysis releases oxygen atoms that form ozone, while reactions involving VOC-derived peroxy radicals regenerate nitrogen dioxide without consuming ozone. The resulting mixture includes ozone, aldehydes, and peroxyacyl nitrates rather than being a simple accumulation of primary emissions. Effective management combines cleaner fuels, emission standards, monitoring, urban planning, and protection of populations with high exposure or physiological vulnerability. The distinction is ecologically important because emission control must target either the directly released precursor or the product formed after atmospheric transport and reaction. Exposure depends on concentration, duration, ventilation, weather, and individual susceptibility, so a pollutant's presence alone does not fully predict biological harm. Atmospheric inversions can trap contaminants near the surface, while wind, turbulence, precipitation, and chemical transformation determine their eventual distribution and removal. At organismal level, respiratory surfaces are especially exposed because large volumes of air contact thin, moist epithelia designed for rapid gas exchange.

Ref: Campbell Biology, Urry et al., 12th Ed., Unit 8 Ecology

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