Bài giảng Environmental Sciences - Chapter 20 Atmosphere Climate Ozone

Chapter 20AtmosphereClimateOzoneLayers of the AtmosphereTroposphere (lowest layer) ---------TropopauseStratosphere --------- StratopauseMesosphere --------- MesopauseThermosphere (highest layer @100 km)Composition of the troposphere78% N220% O2Less than 2% H2O vapor (.01%-4%)Argon gas (1%)CO2 (0.04%)Trace gasesStructure & Temp of AtmosphereLook at Fig. 20-2 and Table 20-1Troposphere = lowest layer; tropics  10 miles (16km); higher altitudes  5 miles (8km)Water vapor & cloudsGreenhouse gasesColder w/ altitude (generally)Pollutants reach top w/in a few days Structure & Temp of Atmosphere cont.Tropopause ---- separate Troposphere from stratosphereStratosphere - temp increases w/ altitude  40 miles - contains the ozone shield - Ozone absorbs UV radiation from the sun & filters the rays - No precipitationGlobal warming Global warming occurs when humans contribute too much of these greenhouse gases leading to a small (1-3 degree C) but significant rise in the global average temperature.Analogy – Car on a sunny dayThe greenhouse effect is natural and important to keep the earth warm enough for life to existBuild up of Greenhouse gases:CO2Fossil Fuel useDeforestationMethane (CH4)Microbial fermentation (Landfill)Coal and oil depositsNatural gas pipelinesCows (manure)Methane is the second most important green house gas (next to CO2)Nitrous OxidesBiomass burningChemical fertilizersFossil Fuel BurningCFC-ChlorofluorocarbonsRefrigerantsSolventsPesticidesAerosols (Old)Ozone (O3)Stratospheric ozone is GOOD It shields us from the harmful UVB rays of the sun.Ozone depletion is the thinning of the stratospheric ozone shield (mostly over the South Pole)Analogy – Stratospheric O3 is like sunscreen for the earth.Tropospheric ozone is BADIf we breath it, it causes lung damageIt is also a greenhouse gasThe Making of OzoneO2 + UVB (280 – 320 nm more energetic) O + OThe free O bonds to existing O2 (O + O2)Ozone is made (O3)O2 + UVB  O + O ; O + O2  O3The Destruction of OzoneO3CFC – chlorofluorocarbonsCl – FC (UV rays breaks bond)The free Cl “attacks ozone”O3 + Cl  O2 + (Cl – O)Cl – O is unstable so the bond will break and the Cl will “attack” another ozone molecule Greenhouse Effect TroposphereTraps heat near the Earth’s surfaceWater vapor, carbon dioxide, methaneGlobing warmingOzone shield Stratosphere filters UV radiation Oxygen gas, Ozone gasOzone depletion  more UV  cancerWhere?What Happens?Which gases?Problem?The End