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Air Quality 101 Rice Air Curriculum Teacher Training Leading Atmospheric Constituents • • • • • Nitrogen (N2) Oxygen (O2) Argon (Ar) Water Vapor (H2O) Carbon dioxide (CO2) 78% 21% 1% 0-3% 0.039% Most air pollutants are in very small quantities (parts per million or billion) but affect our health and climate. 2 Categories of Atmospheric Compounds • Air pollutants: Substances that directly harm health of humans, wildlife, or vegetation – – – – Air toxics: Carcinogens, mutagens, neurotoxins Respiratory irritants Substances that cause cardio-vascular impacts Substances that damage crops, forests, ecosystems • Particulate matter: Solid or liquid microscopic particles suspended in air • Ozone depleters: Substances that destroy stratospheric ozone • Climate-influencing compounds: Greenhouse gases and particles that impact radiative budget 3 Particulate Matter 4 Particulate Matter • Aerosol: Liquid or solid particles suspended in air • Wide range of chemical composition • Sizes range from <1nm to >10 μm – Large particles settle out quickly – Fine particles (<2.5 μm (PM2.5)) most damaging to visibility & health (respiratory, cardio-vascular, mortality) 5 Impacts of PM • Health effects – Fine particles go deep in lungs, to bloodstream – Respiratory and cardiovascular disease – Mortality • Visibility/Haze • Climate • Regulatory concern – Houston barely attains current standard – EPA tightened 24-hr but not annual standard 6 Ozone (O3) 7 Stratospheric & Tropospheric Ozone: “Good up high, Bad nearby” • In stratosphere, ozone forms naturally when Sun’s intense UV rays split oxygen: – – – – O2 + hv O + O O + O 2 O3 This “good ozone” blocks UV rays Stratospheric ozone can be destroyed by CFCs • In troposphere, intense UV rays already blocked. Ozone instead forms as a pollutant: – Nitrogen oxides + Hydrocarbons + Sunlight O3 – “Bad ozone”: air pollutant and greenhouse gas Stratospheric Ozone Hole 9 Montreal Protocol drastically curtailed ozone depleting emissions 10 WMO/UNEP Scientific Assessment of Ozone Depletion, 2010 Impacts of Montreal Protocol: Halocarbon Concentrations 45 yr lifetime 5 yr lifetime 100 yr lifetime 35 yr lifetime 11 NOAA Ozone projected to recover as halocarbon levels decline 12 Ground-level Ozone “Smog” Sunlight & Heat RO2 HO2 NO VOC OH NO2 VOC NOx Hydrocarbons Nitrogen Oxides O3 O3 13 Tropospheric NOx Cycle HO2 and CH3O2, other RO2 O3 CO, CH4, VOCs N2O O(1D) O NO hν hν Direct emissions * NO2 ClO, BrO ClONO2 BrONO2 * hν HNO3 NO3 O3 N2O5 Red: Ox destruction Green: Ox production Black: No change in Ox Blue: Reservoir Species *: Dominant pathway during daytime Sources of Ozone-forming Emissions • Nitrogen Oxides – Vehicles – Power plants – Other industry and equipment • Hydrocarbons – Natural vegetation – Vehicles – Refineries / Chemical plants – Other sources 15 Ozone Impacts • Health effects – Asthma and other respiratory illnesses – Recently linked to mortality • Regulatory concern – Houston, Dallas, many other cities fail to attain limits • Atmospheric oxidant – Oxidizes certain VOCs – Contributes to formation of OH oxidant • Greenhouse gas 16 Emissions Trends 17 Strong declines in ozone, but many cities still exceed 75 ppb Houston http://www.tceq.state.tx.us/assets/public/implementation/air/ sip/hgb/hgb_sip_2009/09017SIP_Ch5_ado.pdf US Cities 18 Ozone Non-attainment: 75 ppb standard 19 Map from US EPA Climate Change Overview • Is Earth warming? • Natural or anthropogenic causes? – Overview Earth’s radiative balance & greenhouse effect • Impacts 20 Evidence of recent climate change 21 IPCC, 2007 Global US 22 National Geographic Additional evidence of warming 23 IPCC, Physical Basis Technical Summary, 2007 Past decade was warmest recorded 24 Hansen et al 2010 This summer’s weather Anomaly (°C) relative to 1951-1980 mean http://www.columbia.edu/~mhs119/Temperature/ 25 In the news: Arctic sea ice reaches all time minimum extent, August 26, 2012 Yellow line shows average minimum, 1979-2010 26 NASA: http://climate.nasa.gov/news/index.cfm?FuseAction=ShowNews&NewsID=767 Climate Fundamentals: Earth’s Radiative Balance and Greenhouse Effect Yellow: Solar UV and Visible Radiation Beige: Infrared Radiation Radiation proportional to TK4 (Trenberth et al., BAMS, March 2009) 27 28 Greenhouse gases absorb and re-radiate infrared at atmosphere’s cooler temperature 29 30 Earth’s Carbon Cycle 31 (IPCC 2007, Physical Basis Chapter 7) Rising Greenhouse Gas Levels CO2 CH4 N2O Total Radiative Forcing 32 IPCC, 2007 Causes of Radiative Forcing, 1750-2005 Greenhouse gas radiative forcing (W/m2) well understood 33 IPCC, 2007 Key Scientific Uncertainty: How much warming per radiative forcing (°C/W-m2) 34 Both anthropogenic and natural forcings are needed to model temperature record IPCC, 2007 36 IPCC, 2007 Projected Impacts of Further Warming 37 IPCC, Impacts SPM, 2007