Air Pollution Flashcards
Air Pollutants
Dust/particulates, Oxides of Nitrogen, Tropospheric ozone, Hydrocarbon vapours, PANs, Oxides of Sulphur, Carbon Monoxide. Greenhouse gases also air pollutants even though they are not studied as part of Pollution and should be considered in longer answer questions
Factors affecting the dispersal of atmospheric pollutants
Wind velocity, wind direction, temperature inversions, presence of light/UV, precipitation
Sources of particulate pollution
Combustion of coal and diesel (oil), combustion of wood, crop waste, forest fires, heather moorland, burning of other waste
Size of particulates
PM stands for particulate matter, PM10 - less than 10 microns, PM5 - less than 5 microns, PM1 - less than 1 micron. Smaller particle sizes remain airborne for longer and are more likely to be inhaled.
Effects of particulate pollution on people
Worsening and new respiratory issues (asthma, bronchitis, lung cancer), damage to cilia therefore increased infection
Effects of particulate pollution on other living things
Particulates block light and reduce photosynthesis. Particulates may also contain other toxins such as heavy metals and acids
Effects of particulate pollution on non living things
Adsorption of particulates to buildings, discoloration. Damage to buildings due to acids often present with particulates in particular to limestone structures.
Effects of particulate pollution on climate
Increased albedo by particulates in the atmosphere reduces absorption of solar energy at Earth’s surface leading to global cooling
Effects of particulate pollution on ozone in the stratosphere
Particulates in the atmosphere contribute to ozone depletion by acting as surfaces for chemical reactions that break down ozone molecules.
Smoke smog
Atmospheric pollution event involving smoke and fog
Controls of particulate pollution
Diesel Particulate Filters, coal pretreatment, Improved combustion efficiency, Turbo chargers, Bag filter, Clean Air Act (1956), Cyclone separator, Electrostatic precipitator, Scrubbers
Diesel Particulate Filters
Fitted to the exhaust pipe of diesel engines, traps up to 80% of smoke particulates caused by diesel combustion
Coal pretreatment (for particulates)
Heating coal before combustion to drain off tar to produce smokeless coal.
Turbo chargers
Enables more air (oxygen) to be delivered to the combustion chamber to increase the efficiency of combustion and reduce organic particulates
Bag filter
A method reducing smoke and particulate matter by trapping particulates in fabric filters
Clean Air Act (1956)
UK legislation to control smoke pollution by the establishment of Smoke Zones by making Control Orders in large urban areas.
Cyclone separator
Remove suspended particles from gaseous effluents. Air rotates in a cylindrical chamber which throws suspended particulates to outside surfaces where they fall and collect before the gas is discharged to the atmosphere.
Electrostatic precipitator
Equipment used to remove suspended particles from gaseous effluents by attracting them to electrically charged wires or plates, where they fall and are collected as fly ash.
Scrubber
use of a fine water spray to wash particulates from the air, also used to remove soluble gas pollutants.
Photochemical smogs
Atmospheric pollution events in which primary pollutants such as hydrocarbons, NOx and (secondary) tropospheric ozone interact to produce more toxic secondary pollutants such as PANs (peroxyacetyl nitrates).
Sources of photochemical smogs
NOx from high temperature vehicle combustion engines, O3 produced from the breakdown of NOx by UV, Hydrocarbons from unburnt fuel and fuel stations
Effects of photochemical smogs
NOx and O3 cause respiratory problems on their own however PANs become toxic at very low concentrations and cause eye irritation, breathing difficulties, asthma, emphysema, bronchitis and heart disease
Controls of photochemical smogs
Catalytic convertors to control NOx, Control of hydrocarbon vapours at fuel stations. Low emission zones, tax incentives and grants for electric cars.
Acid precipitation
Any precipitation that is more acidic than pH 5.6. Remember rainwater is naturally acidic due to the reaction of CO2 with water producing carbonic acid. Acid rain usually involves other stronger acids.
Formation of acid rain
SO2 dissolves in water and forms sulphurous acid. Sometimes SO2 oxidises further to form SO3 which reacts with water to produce sulfuric acid. Oxides of Nitrogen also dissolve in water to produce Nitric acid. Hydrogen Chloride from the combustion of coal and chlorine containing wastes can also form hydrochloric acid
Sources of acidic pollution
Combustion of coal, smelting of sulphide ores producing SO2. High temperature combustion in power stations and vehicle engines producing Nitrogen oxides, Combustion of coal and incineration of waste producing Hydrogen Chloride, secondary reactions producing SO3 and ozone.
Effects of acidic pollution on non living things
Corrosion of railway lines, pipelines, pylons and other metal structures.
Effects of acidic pollution on living things
Low pH denatures enzymes. Tissue damage caused by direct contact with acid in particular stomata, root hairs, fish eggs, fish gills and germinating seeds. Dissolution of calcium carbonate exoskeletons. Respiratory problems eg. asthma
Indirect effects of acidic pollution
Increased solubility of metals in acidic conditions leads to the leaching of essential metals from soils or the concentration of toxic metals. The loss of essential metals such as calcium and magnesium in soils leads to the adsorption of more toxic metals such a aluminum and Lead onto clay particles in soil harming plants and other soil organisms
Reduction of acidic pollutants SO2
Pre-combustion Desulphurisation of coal, oil and gas, Post-combustion desulphurisation of power station emissions (flue gas)
Desulphurisation
The removal of sulfur or compounds containing sulfur such as sulfur dioxide.
Natural gas desulphurisation
Gas is dissolved in an amine solution or reacted with iron particles to remove hydrogen sulphide
Crude oil desulphurisation
Sulphur compound are removed from oil by using molybdenum catalysts during distillation
Coal desulphurisation
Sulphur in coal is in the form of dense iron pyrites. Coal is crushed and and flowing water carry the coal particles and leave behind the sulphur rich iron pyrites - separation via density
Flue gas desulphurisation (FGD)
Processes that remove oxides of sulphur from gaseous effluents (wet or dry).
Dry flue-gas desulphurisation (dry FGD)
A method of removing sulfur oxides from effluent gases using a slurry of crushed lime (mainly calcium carbonate).
Wet flue-gas desulphurisation (wet FGD)
A method of removing sulfur oxides from effluent gases by dissolving them in a solution such as a spray of sodium sulphite solution.
Reduction of acidic pollutants NOx
Catalytic converters, Low temperature combustion, urea sprays
Catalytic converter
A device that reduces emissions of pollutant gases from petrol and diesel engines. Catalysts such as platinum, palladium and rhodium catalyse reactions with oxides of nitrogen reducing NOx back to N2 and O2, also reduces carbon monoxide and unburnt hydrocarbons
Urea spray
A method of reducing NOx emissions e.g. from coal-fired powered power stations. NOx reacts with urea to produce Nitrogen gas, carbon dioxide and water
Low temperature combustion
Increasing the surface area for combustion maintains a high combustion rate at lower temperatures. Use of a fluidised beds suspend particles increasing surface area of fuel enables rapid combustion at lower temperatures
Sources of tropospheric ozone
NO2 (mostly from vehicle emissions) is broken down by UV producing NO and O. The monatomic oxygen reacts with O2 and produces O3
Effects of tropospheric ozone
Toxic to plants, reduces growth rate of trees and crops, breathing difficulties and asthma in humans, secondary pollutants involved in the formation of photochemical smog and acid rain.
Controls tropospheric ozone
as ozone forms from the breakdown of NOx, all controls of NOx also control tropospheric ozone ie catalytic converters, low temp combustion and urea sprays
Sources of carbon monoxide
Combustion of carbon based materials with a shortage of oxygen - incomplete combustion produces CO rather than CO2
Effects of carbon monoxide
CO binds to haemoglobin and prevents the transport of oxygen from the lungs to tissues and cells. Low levels cause flu-like symptoms and increase the effects of heart disease. High levels will cause brain damage and death.
Haemoglobin
The protein in red blood cells that carries oxygen.
Controls of carbon monoxide
Catalytic converters oxidise CO to CO2. Increase oxygen to the combustion site eg turbo charger.
What I must never do when camping
NEVER pull the BBQ coals into the tent or the tent entrance even when the coals appear to be out, they will continue to produce CO, it won’t end well!
Temperature inversion
A situation in the troposphere where the temperature is lower than normal so that relatively warm air lies above cold air. This stops the rising and dispersal of warm pollutant gases trapping them at ground level.
Factors that make temperature inversions more likely to form
- Cold, clear night skies allow IR (heat) to be lost from the ground
- Low wind velocity reduces the mixing of different layers of air
- valleys where cool dense air collects
- mist or fog during the day, water droplets reflects sunlight and slows the heating of the ground that would reverse the inversion
Biotic index
A measure of pollution based on the presence, abundance and state of health of selected living organisms e.g. lichens for acid rain, aquatic invertebrates for water pollution.
Lichen
a symbiotic relationship between algae and fungi which grow of living or non living substrates
How biotic indicators are used to monitor air pollution
Lichens are sensitive to acidic conditions therefore are a good indicator of acidic air pollutants such as SOx and NOx. Flat, crusty lichens are most tolerant of acidic conditions and leafy and crusty lichens with larger surface areas are less tolerant of acidic conditions. Surveying and monitoring the presence of different lichens can indicate levels and changing levels of acidic air pollutants. Eg. leafy lichens are rarely seen in city centres where NOx will be high
