Transcript Slide 1
Effects of Air Pollutants • • • • • Effects on human health Effects on vegetation and animals Effects on materials and structure Long term effects on the planet Risk Assessment Sources and Sinks Effects on human health • Pollutants enter body via inhalation, ingestion and dermal contact TOTAL BODY BURDEN: the way a trace material accumulates in the human system • Chemicals can be stored in the body compartments; blood, urine, soft tissue, hair,teeth and bone. • Body can eliminate the trace material over a period of few hours to days or longer • Accumulation results when the material is much more rapidly stored than eliminated. • Pollutants can be stored in the blood, urine, soft tissue, hair and bone. • Effect on human health mostly depends on the quantity of pollutants and the rate of removal. Human respiratory system • Primary function: to deliver O2 to the bloodstream and remove CO2 from body. • Respiratory system may be divided into 3 as Nasal (nose and mouth) Tracheobronchial (trachea and bronchial tubes) Pulmanory (bronchia and alveolar sacs) Regional particle deposition Particle Size conventions • Inhalable fraction (<100 μm AED) Can be breathed into nose or mouth • Thoracic fraction (<25 μm AED) Can penetrate head airways and enter lung airways • Respirable fraction (<10 μm AED) Can penetrate beyond terminal bronchioles to gas exchange region Particle and gas behavior in the lung • Gases: Solubility dependent • Particle behavior depends on aerodynamic characteristics Very large particles, nasal openings allow Smaller particles deposits in the trachebronchial and pulmanory regions. Very small particles penetrates into alveolar membrane CO and the human body • Ambient CO • Indoor CO In the body O2 is moved for biochemical oxidation and CO2 (waste) removed. Hemoglobin-O2 This complex is stong enough to transport gases in the circulatory system. But not strong enough to Hemoglobin-CO2 prevent delivery to lungs and cells. CO forms a much more stable complex with hemoglobin(Hemoglobin-CO, COHb), so it reduces the number of free hemoglobins for transport of CO2 and O2. Molecular View of Carbon Monoxide Poisoning EOS Impact of air pollution on humans Health effects data can be obtained by • Clinical • Epidemiological • Toxicological studies AIR POLLUTION EFFECTS Dose Response Relationship Dose-response curve response No threshold type doseresponse curve Threshold type doseresponse curve dose Threshold value: under which no adverse effect was observed Harmful Dosage (int ake rate by inhalation (removal rate ) d (time ) Effects on vegetation and animals Injury vs damage Injury: An observable alteration in the plant when exposed to air pollution Damage: An economic or aesthetic loss due to interference with the use of a plant Injury. - Generally, pollution injury first appears as leaf injury. Spots between the veins, leaf margin discoloration, and tip burns are common. Crossection of a leaf Two ways of pollutant entrance to plant • Direct way: Through stomates which open and close to allow air through the interior parts • Indirect way: Through the root system. Pollutants deposit in soil and water and these pollutants were taken by the roots of the plant. Leafs are important because of its functions • Photosynthesis accomplished by chloroplasts 6CO2+6H2O C2H12O6+6O2 • Transpiration: Movement of water from the root system up to the leaves. Nutrient movement and cooling • Respiration:Oxidation of carbonhydrates, energy producing process. • C2H12O6+6O2 6CO2+6H2O Ozone Injury Ozone, the major component of oxidants is formed by the action of sunlight on products of fuel combustion and can be moved to nearby growing areas by wind. Symptoms vary depending on the concentration of ozone in the air and the length of exposure, Ozone injury occurs on the most recently emerged leaves. Typical ozone injury may not be evident on leaves exposed to a mixture of pollutants. Symptoms differ in different areas of the province. foliage with flecking "pepper spotting" injury typical of ozone injury. Huntsville, Ontario. PAN injury typical of Peroxyacetyl Nitrate (PAN) creates a glazy bronzing on the underside of newly expanded potato leaves. SO2 Damage: SO2 causes an interveinal necrosis. Note the green veins in these samples. Ozone damage Note stippling symptoms on leaves Fluorine Damage: Note the marginal necrosis (this is similar to salt damage). Effects on materials Effects on metals • Rusting • Corrosion due to moisture, temperature and pollutants • Alteration of electrical properties Effects on stone • Discoloration • Blackening • gypsum formation • Cracking Gypsum formation CaCO3+H2SO4+2H2O CaCO3+H2CO3 CaSO4.2H2O+H2CO3 Ca(HCO3)2 These damaged areas seem to receive rain or rain runoff and seem to be formed by sulfur dioxide uptake, in the presence of moisture, on the stone surface. Subsequent conversion of the sulfur dioxide to sulfuric acid results in the formation of a layer of gypsum on the marble surface. Effects on the atmosphere, visibility degradation • Visibility is reduced due to light scattering or absorption by the gases and particulates. Scattering is wavelength dependent. Longer wavelenths scatter less. • Light absorption by NO2 Absorbs shorter blue causing red lights to be seen Atmospheric haze • Reduced visibility caused by the presence of fine particles or NO2 in the atmosphere • Particles are in the range of 0.1-1.0 um. The major component of atmospheric haze is sulfate, nitrate, graphitic material, fly ash and aerosols. • Primary and secondary particulate matters cause haze. Kualo Lumbur,2005, Malasia Emergency was announced on august 2005. API was greater than 500 • Primary particulate matter: Combustion processes emit PM less than 1um size. Large quantities of NO2 and SO2 are also emitted. Secondary particulate matter: gas to particle conversion. Gaseous molecules transformed to liquid and solid particles Gas to particle conversion occurs via • Absorption: gas goes into solution of liquid phase (solubility dependent) • Nucleation: thermodynamically stable clusters formed. • Condensation:collisons between a gaseous molecule and an esisting aerosol. Long term effetcs on the planet • Global warming • Ozone hole The Ozone Layer The ozone layer is a band of the stratosphere about 20 km thick, centered at an altitude of about 25 to 30 km Ozone absorbs ultraviolet (UV) radiation, and the ozone layer thus protects life on Earth The Ozone Layer Ozone is produced in the upper atmosphere in a sequence of two reactions involving free radical oxygen atoms O2 + hv O + O O2 + O + (M) O3 + (M) Of all the human activities that affect the ozone layer, release of chlorofluorocarbons (CFCs) is thought to be the most significant EOS CFCs and ozone • CFCs have long residence time in the atmosphere FCCl3+hv CCl2F+ Cl Cl +O3 ClO +O2 ClO +O O3+O Cl +O2 2O2 CO2 and the Greenhouse Effect The greenhouse effect occurs when radiant energy is retained in the atmosphere and warms it Some atmospheric scientists think that global warming is already under way There are many natural sources that contribute significantly to “greenhouse” gas production that cannot be controlled by humans The main strategy for countering human contributions to possible global warming is to curtail the use of fossil fuels EOS The Greenhouse Effect EOS Acid rain • Formation HNO3 and H2SO4 in water droplets due to SO2 and NOx www.epa.org Deposition of pollutants Water droplets aerosols with bound HOCs sorption dissolution desorption volatilization HOC vapors Washout of particles Washout of vapors Deposition of particles Wet deposition Dry deposition ACID RAIN How do we measure acidity of the rain • Rain water has a natural pH of 5.5 (less than 7) • Collect rain water • Measure pH Rain sampling