Pollutants in the atmosphere:
- move very rapidly due to winds and therefore have dispersal over a large area.
- interact easily with electromagnetic radiation coming from the sun, undergoing photochemical reactions
- interact with infra-red energy radiated from the earth.
All rain is slightly acidic (pH 5.6) because naturally occuring CO2 dissolves to produce a dilute solution os carbonic acid. Acid rain is rain that is more acidic than this. Major gases that cause acid rain:
- Sulphur dioxide - burning coal and fuel
- Sulphur trioxide - burning coal and fuel
- oxides of nitrogen - car exhausts
- ozone - photochemical reactions involving oxides of nitrogen and oxygen.
Effects of acid rain on non-living things:
Can corrode metals = damage to railway lines, water pipes, power lines.
Buildings made of limestone damaged
Effects of acid rain on living organisms:
Acids are toxic to living organisms. They denature proteins in cell membranes and can inhibit enzyme action.
Tissues and organs that are particularly effected:
- cells inside stomata
- plant root hairs
- germinating seeds
- invertebrates with exoskeletons may die as the acids dissolve the calcium compounds that form the skeleton
- lichens - biotic index
Increase in acidity = change in solubility of many ions, including metals that become more soluble.
The acidic solutions leach metal ions from the soil. Essential plant nutrients such as calcium and magnesium are lost first. Toxic ions are mobilised which inhibit enzyme action and can affect the health of plant roots and soil organisms as well as aquation organisms in rivers and lakes. Aluminium ions associated with Alzheimers disease.
Effects of tropospheric ozone:
Ozone is toxic to plants and reduces growth rates in trees and crops. In humans ozone causes breathing difficulties and may be linked to increased rates of asthma. Normal atmospheric concentrations are within the range of 20-60ppbv, a concentration of 120ppbv causes breathing difficulty. A concentration of 1000 ppbv is fatal.
Tropospheric ozone is a secondary pollutant produced by chemical reactions involving primary pollutants - pollutants released directly by human activities.
2 common reactions:
1. Nitrogen is broken down by UV-A sunlight to produce monotomic oxygen
2. The monotomic oxygen reacts with a normal oxygen to produce ozone. O+O2=O3
As it's a secondary pollutant, it can be controlled by reducing levels of primary pollutants that produce it
e.g.nitrogen dioxide, which is mainly produced by vehicle engines and power stations
Cities that suffered from serious smoke pollution didnt receive enough sunlight for photochemical pollutants to be produced. However, these have become more of a problem as smoke levels have declined.
Smoke pollution, smoke smogs and photochemical smogs
Smoke consists of small, suspended solid particles in the atmosphere produced by incomplete combustion.
PM10 - suspended particles smaller than 10um in diameter which, being very small, are likely to remain suspended in the atmosphere for longer.
Main sources of smoke:
- burning vegetation
- burning fossil fuels
Effects of smoke on the climate:
Smoke particles are small and can remain suspended…