资源描述：
《专业英语lesson》由会员上传分享，免费在线阅读，更多相关内容在应用文档-天天文库。
1、Lesson14AirpollutionAirpollutionisthehumanintroductionintotheatmosphereofchemicals,particulatematter,orbiologicalmaterialsthatcauseharmordiscomforttohumansorotherlivingorganisms,ordamagesthenaturalenvironment.Airpollutioncausesdeathsandrespiratorydise
2、ase.Airpollutionisoftenidentifiedwithmajorstationarysources,butthegreatestsourceofemissionsismobilesources,mainlyautomobiles.Gasessuchascarbondioxide,whichcontributetoglobalwarming,haverecentlygainedrecognitionaspollutantsbyclimatescientists,whilethey
3、alsorecognizethatcarbondioxideisessentialforplantlifethroughphotosynthesis.Theatmosphereisacomplex，dynamicnaturalgaseoussystemthatisessentialtosupportlifeonplanetEarth.Stratosphericozonedepletionduetoairpollutionhaslongbeenrecognizedasathreattohumanhe
4、althaswellastotheEarth'secosystems.Anairpollutantisknownasasubstanceintheairthatcancauseharmtohumansandtheenvironment.Pollutantscanbeintheformofsolidparticles,liquiddroplets,orgases.Inaddition,theymaybenaturalorman-made.Pollutantscanbeclassifiedasprim
5、aryorsecondary.Usually,primarypollutantsaredirectlyemittedfromaprocess,suchasashfromavolcaniceruption,thecarbonmonoxidegasfromamotorvehicleexhaustorsulfurdioxidereleasedfromfactories.Secondarypollutantsarenotemitteddirectly.Rather,theyformintheairwhen
6、primarypollutantsreactorinteract.Animportantexampleofasecondarypollutantisgroundlevelozone—oneofthemanysecondarypollutantsthatmakeupphotochemicalsmog.Notethatsomepollutantsmaybebothprimaryandsecondary:thatis,theyarebothemitteddirectlyandformedfromothe
7、rprimarypollutants.Majorprimarypollutantsproducedbyhumanactivityinclude:●Sulfuroxides(SOx)especiallysulfurdioxide,achemicalcompoundwiththeformulaSO2.SO2isproducedbyvolcanoesandinvariousindustrialprocesses.Sincecoalandpetroleumoftencontainsulfurcompoun
8、ds,theircombustiongeneratessulfurdioxide.FurtheroxidationofSO2,usuallyinthepresenceofacatalystsuchasNO2,formsH2SO4,andthusacidrain.Thisisoneofthecausesforconcernovertheenvironmentalimpactoftheuseofthesefuelsaspowersources.●Nitrogenoxides(NOx)e
