2PollutionPollution is the release of waste matter or energy into the environment by man so that it causes damage or deterioration to living systems and/or environment.Photo from National GeographicSociety - Exploring your world
3PollutantsNO2C6H6COC particlesA pollutant is any substance brought about by human activities or source of energy which, at an unacceptable level, causes damage to the environment or is harmful to living systems.
4Some air pollutants Carbon monoxide Sulphur dioxide Nitrogen oxides HydrocarbonsOzoneParticulates
5Carbon monoxide A poisonous gas, can cause death. Combines with haemoglobin in red blood cells to form stable complex, carboxyhaemoglobin.The haemoglobin is NOT available for carrying oxygen. May cause death.
6Sulphur DioxideCauses damage to respiratory systems and increase in asthma attacks(哮喘).Acid rain – damage buildings, thought to be responsible for the deaths of large numbers of trees in Europe and America.
7Nitrogen oxidesA poisonous gas that damage lung tissues and blood vessels.Acid rainGive rise to photochemical smog.
8Hydrocarbons Cause photochemical smog. Some hydrocarbons, e.g. benzene, are known carcinogens.
9OzoneIrritates the eyes.Makes more serious asthma.Damages plants.
10ParticulatesImpair lung function by constricting respiratory passage and damaging lung tissue, cause respiratory disease.Certain particles are suspected to cause cancer.
11Harmful effect Concentration (ppm) Duration of exposure CO 4000 ppm or higher cause death in 1 hour ( or 1000 ppm for 4 hours)
12Concentrationsppm = number of molecules of pollutants per million (106) molecules of air% by volumeMicrogram per cubic metre ( g m-3)
13Concentrations Convert 0.05 ppm of CO into other concentration units % volumeg m-3
14Answers a. 0.000005% In 1 m3 , there is 0.05/106 m3 of CO Using Ideal gas equation,m = pVMr / RTMass of CO = 101x103 x 0.05 x 10-6 x 28 / 8.31 x 298= 5.71 x g = gThus, the concentration = g/m3
15Acid rain Normal rainwater pH = 6.5 pH 2.5 has been recorded in some parts of the worldSO2 + H2O H2SO3SO2 + O2 SO3 H2SO44NO2 + 2H2O + O2 4HNO3
16Effect of acid rainpH < 4.5, calcium metabolism in fresh water fish will be affected, poor health and growth.Soil of pH < 4.5, absorption of cations by plants will be affected, death of plants.Corrodes metals and accelerates the deterioration of building, rock and statue.
17Photochemical smog NO2 NO + O (under U.V. light) O + O2 + M O3 + M O + hydrocarbons aldehydesO3 + hydrocarbons aldehydesHydrocarbons + O2 + NO2 CH3- C-O-O-NO2 (PAN molecule)O
18Photochemical smog Smoke + Fog (Brownish haze) Reaction initiated by sunlight + NOx + hydrocarbonsEffects:1. Cause headaches, eye, nose andthroat irritations.2. Impair lung function, coughing.3. Cause rubber and fabrics to deteriorate.4. Damage plants, loss of crops.
19Sources and properties of Ozone In lower part of atmosphereNO2 NO + O (under UV light)O + O2 O3From air by electric sparks in engines, photocopiers, motors.LightningToo reactive to remain for a long timeAdverse effect on health
22Chlorofluorocarbons (CFCs) Unreactive , low flammability and toxicity.Use as : Aerosol propellants, solvents, refrigerants, blowing agents in foam plastic.Causes for accumulation:Unreactive, lifetime about 75 yearsInsoluble in water
23Depletion of ozone layer CFCs give Cl free radicals which destroy ozone.CCl3F+uv light CCl2F. + Cl.Cl. + O3 ClO. + O2 (1)ClO. + O Cl. + O2 (2)Repeat (1) (2)Step (1) is considerably faster than O + O3 2O2Disturb the balance in the production and destruction of ozone.
24Adverse effect of ozone depletion Reduced crop yieldHigher incidence of skin cancer and eye cataract
25Control of the ozone depletion problem Control the production and consumption of CFCs (Montreal Protocol)Recycling of CFCsUsing substitutes
26Possible alternatives for CFCs Hydrochlorofluorocarbons (HCFCs) such as CF3CHCl2 , they break down more quickly in atmosphere, though lower % of Cl, could damage if overused.Hydrofluorocarbons (HFCs) such as CF3CH2F, no chlorine and ‘ozone safe’, toxicity problem still unsolved.
27Possible alternatives for CFCs Hydrocarbons such as butane and propane, no chlorine, flammable and poisonous.Water and steam, effective for some cleaning applications.
28Pollution control in H.K. Environmental protection department (EPD), established 1986Formulating policyMonitoringEnforcing legislationPlanningHandling complaints and enquiries
29Measures to improve air quality Use of unleaded petrolInstallation of catalytic converters in carLimitation of sulphur content in fuelDesulphurization of Flue GasInstallation of Electrostatic Precipitators in power plantsLow nitrogen oxide burners