The following units of measurement are used throughout: -
- ppb – parts per billion
- ppm – parts per million
- ,ugm - microrganisms per cubic meter
- ,um – micro meter (one millionth of a meter)
Before I discuss the main pollutants and their health effects, below is a diagram of how NO2 and SO2 are formed.
- Burning fossil fuels is the main cause of atmospheric pollution.
- Factories and cars use fossil fuels.
- They release Carbon dioxide, which contributes to the green house effect, and Sulphur dioxide and Nitrogen oxides, which cause acid rain.
- Smoke from burning contains particles of soot (carbon) which can blacken buildings and collect on plants, preventing them from photosynthesising.
- Acid rain kills fish and trees and damages buildings, particularly those made of limestone.
- Acid rain falls into lakes and poisons fish and birds.
Oxides of Nitrogen are formed due to the usage of fossil fuels – usually car combustion engines. The engines also produce other pollutants such as carbon monoxide, unburned hydrocarbons, and if leaded petrol is used, then compounds of lead. The oxides of nitrogen are formed when the air petrol mixture is sparked. The temperature is very high, up to 2500C and this provides enough activation energy for nitrogen to react with oxygen forming nitrogen monoxide.
N2 +O2 –> 2NO
Nitrogen monoxide (is also a greenhouse gas) easily reacts with more oxygen to form nitrogen dioxide, with water and more oxygen nitric acid is formed which can lead to acid rain.
2NO + O2 –> NO2
4NO2 + 2H2O + O2 –> 4HNO3
Nitrogen dioxide also reacts with the oxygen or hydrocarbons in the presence of sunlight to form an irritating photochemical.
This is the same with sulphur dioxide. There are small amounts of sulphur in fossil fuels so when the fuel is burnt it reacts with the oxygen to form sulphur dioxide. Again when in the air and reacts with more oxygen and water a weak solution of sulphuric acid is formed. This can be transported by wind over many hundreds of miles, and deposited as acid rain.
Oxides of Nitrogen (Nox)
- Nox is a collective term used to refer to two species of oxides of nitrogen: nitric oxide (NO) and Nitrogen Dioxide (NO2).
- Globally, quantities of nitrogen oxides produced naturally (e.g. volcanic actions) far outweigh anthropogenic (man-made) emissions. Anthropogenic emissions are mainly due to fossil fuel combustion from both stationary sources, i.e. power generation (21%) and mobile sources, i.e. transport (44%). Other atmospheric contributions come from non-combustion processes, for example nitric acid manufacture, welding processes and the use of explosives
Sulphur dioxide (SO2)
- SO2 is a colorless gas, it reacts on the surface of a variety of airborne solid particles. It is soluble in water and can be oxidised within airborne water droplets.
- Natural background levels (hourly) are about 2 ppb.
- The most important sources of SO2 are fossil fuel combustion, smelting, manufacture of sulphuric acid, conversion of wood pulp to paper, incineration of refuse and production of elemental sulphur. Coal burning is the single largest man-made source of SO2 accounting for about 50% of annual global emissions, with air burning account for a further 25 – 30%
Carbon Monoxide (CO)
- CO is a colorless, odorless, tasteless gas that is slightly lighter than air.
- CO is an intermediate product through which all carbon species must pass when combusted in oxygen (O2). In the presence of a sufficient supply of O2 most CO produced during combustion is oxidised to carbon dioxide (CO2). However, this is not the case in spark ignition engines, especially under idling and deceleration conditions. Thus, the major source of atmospheric CO is the spark ignition combustion engine. Smaller contributions come from processes including the combustion of organic matter, for example in power station and waste incineration.
Ozone O3
- O3 is the tri-atomic form of molecular oxygen, it is a strong oxidising agent, and hence highly reactive.
- Most O3 is formed indirectly by the action of sunlight and Nitrogen dioxide.
Particulate Matter
- Particulate matter is emitted from a wide range of sources, the most significant primary sources being road transport (20%), homes (20%), construction, mining, and quarrying (13%), industrial combustion plants and processes (10%) and public power generation (10%). Natural sources are less important; these include volcanoes and dust storms. Particulate matter can also be formed by the transformation of gaseous emissions such as oxides of Sulphur and Nitrogen and VOCs.
Volatile Organic Compounds (VOCs)
- Hydrocarbons are emitted from petrol evaporation and incomplete combustion, and from leakage of natural gas from distribution systems. Oxygenates arise in vehicle exhausts and via atmospheric chemical reactions. Evaporation of solvents, used in paints or industrial processes, cause a release of hydrocarbons, oxygenates and hydrocarbons in the atmosphere.
Benzene (C6H6)
- C6H6 is a colorless clear liquid. It is fairly stable but highly volatile (i.e. readily evaporates).
- About 80% of man-made emissions come from petrol-fuelled vehi9cles. This results from both the benzene content of the fuel and partial combustion of the petrol. A further5% comes from the handling, distribution and storage of petrol and approximately 1%come from oil refining. Emissions also come from benzene – producing and handling industries, the burning of wood and other organic material, and the use of benzene as a laboratory reagent (a chemical substance that reacts with another, used to detect the presence of another).
Health Effects
SO2
- Fall in lung function for asthmatics
- Tightness in the chest
- Coughing
Particles PM10
- Cause inflammation to people of heart and lung diseases.
- May carry surface-absorbed carcinogenic compounds into the lungs
Carbon Monoxide (CO)
- Prevents transport of O2 by blood.
- Results in reduction in the supply of O2 to the heart.
Nitrogen Dioxide (NO2)
- Irritates the lungs
- May cause respiratory illness in children
Ozone (O3)
- Irritates airways of the lungs
- Increases symptoms of asthmatics
Volatile Organic Compounds (VOCs)
- Causes cancer
- Liver and kidney damage
- Reproductive disorders
- Birth defects
- Central Nervous System disorders.
Everyone can help reduce Air Pollution. This is especially important when pollution levels are high.
On the road: - Road vehicles are a major source of many pollutants in urban areas. They are responsible for a further 50% oif the emissions of Nitrogen oxides and over 75% of Carbon Monoxide emissions in the U.K.
Before using your car think to yourself: -
- Do I really need to make this journey?
- Could I walk or cycle instead of taking the car?
- Could I take a bus or a train?
If you must drive:
- Drive smoothly, you’ll save fuel, and your engine will also emit less pollution.
- Maintain your car, keep the engine properly turned and the tyres at the right pressure.
At home: -
- Buy water-based or low solvent paints, varnishes, glues, and wood preservatives.
- Avoid burning solid fuels if possible
- Never burn plastic and rubber.
SO2 and NO2 Sources of the UK
In London, at DEFRA monitoring stations the following pollutants are measured: -
Carbon Monoxide
Nitrogen Dioxide
Sulphur Dioxide
Ozone
Particles PM10
1,3 – Butadiene.
Conclusion
I have found that the levels of SO2 in urban areas are normally higher than the levels of SO2 in rural areas. This is because there is more traffic, industries as well as other sources of SO2 in urban areas. Whilst doing research I also found that there is small amounts of sulphur present in fossil fuels, which when burnt is released. This sulphur reacts with the oxygen in the air and becomes sulphur dioxide, again this reacts with more oxygen to form a weak solution of sulphuric acid. This acid is transported by wind and is deposited as acid rain, which causes harm to buildings as well as fish.
As a result, my prediction was correct of the levels of pollution being higher in urban areas rather than in rural areas. My prediction also coincides with theory.
Evaluation
I think that my results were quite reliable as they were from the government. However, the average amount of SO2 produced at 18:00:00 in the rural area exceeds the average amount of SO2 in the urban area. I therefore find that there could be an error here. An explanation for this error could be that this rural area might be quite near an urban area, there might be a festival or a natural source of SO2 might have caused this error.
If I were to do this investigation again then I would calculate the levels of the pollutants from quite a few parts of the area and then work out an average for this. This result would be more accurate. I would also record the levels of different pollutants, or even record the levels of all the different pollutants and then calculate an average. I would also like to compare the pollution levels of different seasons, as some factories may have less working hours during the winter. I should have also used another source for my results as governmental sources may hide some information from the public which non-governmental sources would not do. I would also like to know whether there is some other equipment available to record the levels of pollution, and then use this new equipment to record my levels of pollution. I would also carry out the same investigation again but recording the levels of pollution for a week at a certain time. I would also record the pollution levels of different places of the world and not just England. I would also change my planning by taking readings every 15 minutes to make my results more precise. I would also choose two sets of places i.e. The North and South to compare the results, or even chose places with higher levels of pollution.