Environmental chemistry Environmental chemistry air pollution Option E in Paper 3 study of the effect of human activity on the chemical processes in the environment concerns political and natural borders global issue applied chemistry

Main topics: core air pollution acid deposition greenhouse effect ozone depletion dissolved oxygen in water water treatment soil waste

Main topics: AHL ozone depletion smog acid deposition water and soil

Where is the air? Where is the air?

How does the temperature change in the atmosphere?

Primary air pollutants waste products from human activity added directly to the air pollutant = chemical in the wrong concentration in the wrong place primary air pollutants: CO NO x particulates SO x volatile organic compounds (VOCs)

Air pollutants For each air pollutant you need to know: sources: natural and man-made (effects on health) methods of reducing its emissions any relevant balanced symbol equations

Carbon monoxide Carbon monoxide: sources Natural: atmospheric oxidation of methane CH 4 + 1/2O 2  CO + 2H 2 natural forest fires Man-made: incomplete combustion of carbon-containing fuels ; mainly in cities: localized problem as well as fluctuations during the day forest fires

Carbon monoxide Carbon monoxide: health effect CO combines with Fe in haemoglobin in blood – bonds 320 times stronger than oxygen – oxygen cannot bond onto heamoglobin Less oxygen supplied to body cells Effects: headaches, shortness of breath, in case of high concentration (e.g. rush hour): unconsciousness, death

Carbon monoxide: reduction (1) Lean burn engines: Decrease fuel /air ratio, for instance from 1:14.7 (stoichiometric ratio) to 1:18. (or increase air /fuel ratio)

Carbon monoxide Carbon monoxide: reduction (2) Catalytic converter in car exhaust system: oxidation of CO and unburnt hydrocarbons reduction of nitrogen oxide equations: 2CO (g) + O 2 (g)  2CO 2 (g) 2NO (g) + 2CO (g)  2CO 2 (g) + N 2 (g) 2C 8 H 18 (g) + 25O 2 (g)  16CO 2 (g) + 18H 2 O (g)

Catalytic converter

Sulphur oxides Sulphur oxides: sources Natural: volcanoes sea spray biological decay of organic matter which contains sulphur reduction of sulphates Man-made: coal-burning power stations ( equation starting from S in coal) roasting of metal sulphides e.g. ZnS and Cu 2 S ( equation)

Sulphur oxides Sulphur oxides: health effects acidic oxides lung irritants, affect in particular those suffering from respiratory problems e.g. asthma formation of sulphuric acid aerosols (droplets of sulphuric acid) ( equation) (often catalysed by metal particulates); effects of aerosols: irritant to the eyes irritate vessels in lungs causing impaired breathing

Sulphur oxides Sulphur oxides: methods of reduction use of “low-sulphur content” fuels removal of SO 2 from fumes before they are released : limestone based fluidised bed ( equations showing decomposition of calcium CaCO 3 reaction of CaO with SO 2 ) alkaline scrubbing (wet scrubber) (also called flue gas desulphurization): ( equations showing reaction of CaO and Mg(OH) 2 )

Sulphur oxides Sulphur oxides: reduction (1) Wet scrubber

Sulphur oxides Sulphur oxides: reduction Limestone based fluidized bed

Nitrogen oxides Nitrogen oxides: sources Natural: Electrical storms release enough energy to cause oxidation of atmospheric nitrogen: ( equations showing oxidation of nitrogen and further oxidation of NO) Decomposition of organic matter containing nitrogen Man-made: Combustion of fossil fuels produces enough heat to cause oxidation : ( equation showing oxidation of nitrogen)

Nitrogen oxides Nitrogen oxides: health effects choking irritating gas, affects eyes and people with respiratory problems forms nitric acid aerosols/acid rain ( equation showing dissolution of nitric acid in water) nitric acid also increases the rate of oxidation of SO 2 (see later) plays an important role in the formation of secondary pollutants e.g. ozone and smog

Nitrogen oxides Nitrogen oxides: reduction catalytic converter lean burn engines: high air/fuel ratio or low fuel/air Recirculation/reburn of exhaust gases: nitrogen oxide emissions are reduced by reintroducing exhaust gases into the fuel mixture, lowering peak combustion temperatures as it is the high temperature in the combustion engine which causes nitrogen oxide production.

Particulates Particulates: sources particulates = airborne/suspended liquid and solid particles Natural: volcanic eruptions large forest fires Man-made: burning fossil fuels e.g. diesel forest fires industrial emissions; chemical processes incinerators

Particulates Particulates: health effects particulates penetrate lungs and may block air passages some are poisonous e.g. Pb and asbestos adsorb chemicals and can act as catalysts in reactions producing secondary pollutants by adsorbing also increase concentration and rate of reaction reduce visibility

Particulates Particulates: reduction Electrostatic precipitator: particulates are charged negatively and then attracted onto positively collection plates.

Particulates Particulates: reduction

Volatile organic compounds: sources Natural sources: methane: bacterial anaerobic decomposition of organic matter (e.g. in rice paddies) from plants e.g. terpenes leakage from natural fossil reserves Man-made: evaporation of fuels partial combustion of fuels leakage from storage reservoirs

VOCs VOCs: health effects photochemical smog can lead to carcinogenic compounds fatigue, weakness respiratory problems VOCs VOCs: reduction catalytic converter