Practice question

Sulfur dioxide from refineries, combustion, and other sources around Agra contributes to marble deterioration and discoloration. Atmospheric oxidation produces sulfuric acid and sulfate; these react with calcium carbonate in marble to form gypsum, which is more soluble and traps soot and dust, creating a yellowed or darkened surface. Nitrogen oxides and particulates may contribute, so attributing all damage exclusively to one pollutant is a simplification. 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. 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.