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1、水污染-英文版ThreefourthsofthesurfaceoftheEarthiscoveredwithwater.Nearly98%ofthewateronEarth,though,isseawater‑unfitfordrinkingandnotevensuitableformostindustrialpurposes.Somethinglessthan2%ofthewaterisfrozeninthepolaricecaps,leavinglessthan1%availableasfreshwater.Water:UnusualPropertiesM
2、anychemicalsubstancesaresolubleinwater.Thus,theyareeasilydispersedandeventuallyarescatteredtonearlyinfinitedilutionintheocean.Thosepropertiesofwaterthatmakeituniquelysuitedforthesupportoflifealsomakeiteasytopollute.NaturalWaterIsn’tAllH2ORainwatercarriesdustparticlesfromtheatmospher
3、etotheground.Rainwateralsodissolvesalittleoxygen,nitrogen,andcarbondioxideasitfallsthroughtheatmosphere.Duringelectricalstorms,lightningcausesnitrogen,oxygen,andwatervaportocombinetoformnitricacid.AswatermovesalongorbeneaththesurfaceoftheEarth,itdissolvesmineralsandmatterfromdecayin
4、gplantsandanimals.Theprincipalpositiveions(cations)innaturalwateraresodium(Na+),potassium(K+),calcium(Ca2+),magnesium(Mg2+),andsometimesiron(Fe2+orFe3+).Thenegativeions(anions)areusuallysulfate(SO42-),bicarbonate(HCO3-),andchloride(Cl-).hardwaterWatercontainingthesecalcium,magnesium
5、,andironionsiscalledhardwater.Thepositiveionsreactwiththenegativeionsinsoaptoformascumthatclingstoclothesandleavesthemdingylooking.WaterpollutionWaterpollutionisanychemical,physicalorbiologicalchangeinthequalityofwaterthathasaharmfuleffectonanylivingthingWaterpollutioncausedbyhumana
6、ctivitiesisalargesetofadverseeffectsuponwaterbodiessuchaslakes,rivers,oceans,andgroundwaterPollutantsinwaterincludeawideofchemicals,pathogens病原体,andphysicalchemistryorsensorychanges.WaterpollutionWaterpollutionistheleadingworldwidecauseofdeathsanddiseases,andthatitaccountsforthedeat
7、hsofmorethan14,000peopledaily.Effectsofwaterpollutionincludepoisonousdrinkingwater,poisonousfoodanimals,unbalancedriverandlakeecosystems,deforestationandmanyothereffectsSourcesofwaterpollutionTheusedwaterofacommunityiscalledwastewater,orsewage.Ifitisnottreatedbeforebeingdischargedin
8、towaterways,serious
