From HSC Online.. Equations are always important if you want to gain maximum marks.
There is extensive evidence for an increase of over 25% in atmospheric carbon dioxide levels over the last two hundred years. The evidence comes from quantitative analysis of trapped air bubbles in Antarctic ice and measurement of carbon isotopes in old trees, grass seeds in museum collections and calcium carbonate in coral.
Finding evidence for increases in atmospheric sulfur oxides and nitrogen oxides is more difficult for the following reasons:
Whereas atmospheric CO2 concentrations are about 360 parts per million (ppm), the levels for SO2 and NOx are only about 0.001 ppm in populated parts of the Earth.
The chemical instruments able to measure very low concentrations, like those for SO2, have only been commercially available since the 1970s.
CO2 changes to carbonate ions when it dissolves in water and most carbonates are insoluble. Seashells and coral are made up of carbonates that came from atmospheric CO2. Isotope ratio measurements using mass spectrometers on shells and corals of different ages give clues as to past atmospheric CO2 concentrations.
On the other hand, SO2 eventually forms sulfate ions and NO2 forms nitrate ions. Most sulfates and all nitrates are water-soluble. Soluble sulfates and nitrates circulate in the hydrosphere and biosphere and are chemically changed while insoluble carbonates tend to stay in inert forms such as shells or coral.
