Assess the evidence which indicates increases in atmospheric concentration of oxides of sulfur and nitrogen:
– The gases NO and NO2 are collectively referred to as NOx.
– It is difficult to quantitatively state that oxides of sulfur and nitrogen have been increasing in the atmosphere because these oxides occur in relatively low concentrations, such as 0.01 ppm (parts per million).
– Chemical instruments able to measure very low concentrations, like those for SO2, have only been commercially available since the 1970s, so there is no reliable data for these gases before this time.
– HOWEVER, analysis of gas found in ice-core samples excavated from Antarctica shows that levels of N2O in the atmosphere has increased by about 10%.
– It can also be stated that the increased burning of fossil fuels after the Industrial Revolution did indeed lead to a rise in oxides of sulfur; evidence for this is that the air quality of major industrial cities, such as London, deteriorated greatly.
– NO2 leads to the formation of photochemical smog, a direct indicator of excessive levels of nitrogen oxides in the atmosphere.
– In 1952, the so called “Great Smog of December” killed some 4000 people, mainly the frail and elderly, due to the effects of sulfur and nitrogen compounds in the air.
– The increase of the incidence of acid rain also points to the increase in atmospheric concentrations of SO2 and NOx compounds.
– Acid rain forms when atmospheric water reacts with these compounds; hence an increase in acid rain points to an increase in these compounds.
– Using chemical instruments in recent times, it has been measured that global atmospheric concentrations of these oxides is not increasing greatly over long periods of time, but simply peaks every now and then.
Analyse information from secondary sources to summarise the industrial origins of sulfur dioxide and oxides of nitrogen and evaluate reasons for concern about their release into the environment:
– See ABOVE for industrial sources of sulfur dioxide and oxides of nitrogen.
– Reasons for CONCERN about these Oxides:
– Acid Rain: Sulfur dioxide and nitrogen dioxide are acidic oxides that react with water in the atmosphere to form acids:
– SO2 (g) + H2O (l) H2SO3 (aq) (sulfurous acid)
– 2NO2 (g) + H2O (l) HNO3 (aq) + HNO2 (aq) (nitric and nitrous acid)
These acids then combine with rain droplets, forming acid rain. Acid rain is very destructive; it can decimate entire forests, corrode limestone structures and disrupt natural ecosystems by altering natural pH levels.
– Health Problems: Sulfur dioxide is a severe respiratory irritant and can cause breathing difficulties at concentrations as low as 1 ppm. It triggers asthma attacks and aggravates emphysema. Nitrogen dioxide is also a respiratory irritant. At concentrations above 3 ppm, it can begin to destroy tissue, as it forms the strong acid, nitric acid.
– Photochemical Smog: NO2 causes the formation of smog. This is a form of air pollution in which sunlight reacts nitrogen dioxide, hydrocarbons and oxygen to form ozone, PAN (peroxyacylnitrates) and haze. It greatly affects visibility, while ozone has harmful effects at concentrations as low as 0.1 ppm.
)) I hope it rains cookies at your place tonight
