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1、WaterpollutionItcovers71%oftheearth'ssurfaceandmakesup65%ofourbodies.Withouttheseeminglyinvaluablecompoundcomprisedofhydrogenandoxygen,lifeonEarthwouldbenon-existentWaterisEssentialforLifeThreefourthsofthesurfaceoftheEarthiscoveredwithwater.Nearly98%ofthewateronEarth,though,
2、isseawater‑unfitfordrinkingandnotevensuitableformostindustrialpurposes.Somethinglessthan2%ofthewaterisfrozeninthepolaricecaps,leavinglessthan1%availableasfreshwater.Water:UnusualPropertiesManychemicalsubstancesaresolubleinwater.Thus,theyareeasilydispersedandeventuallyarescat
3、teredtonearlyinfinitedilutionintheocean.Thosepropertiesofwaterthatmakeituniquelysuitedforthesupportoflifealsomakeiteasytopollute.NaturalWaterIsn’tAllH2ORainwatercarriesdustparticlesfromtheatmospheretotheground.Rainwateralsodissolvesalittleoxygen,nitrogen,andcarbondioxideasit
4、fallsthroughtheatmosphere.Duringelectricalstorms,lightningcausesnitrogen,oxygen,andwatervaportocombinetoformnitricacid.AswatermovesalongorbeneaththesurfaceoftheEarth,itdissolvesmineralsandmatterfromdecayingplantsandanimals.Theprincipalpositiveions(cations)innaturalwaterareso
5、dium(Na+),potassium(K+),calcium(Ca2+),magnesium(Mg2+),andsometimesiron(Fe2+orFe3+).Thenegativeions(anions)areusuallysulfate(SO42-),bicarbonate(HCO3-),andchloride(Cl-).hardwaterWatercontainingthesecalcium,magnesium,andironionsiscalledhardwater.Thepositiveionsreactwiththenegat
6、iveionsinsoaptoformascumthatclingstoclothesandleavesthemdingylooking.WaterpollutionWaterpollutionisanychemical,physicalorbiologicalchangeinthequalityofwaterthathasaharmfuleffectonanylivingthingWaterpollutioncausedbyhumanactivitiesisalargesetofadverseeffectsuponwaterbodiessuc
7、haslakes,rivers,oceans,andgroundwaterPollutantsinwaterincludeawideofchemicals,pathogens病原体,andphysicalchemistryorsensorychanges.WaterpollutionWaterpollutionistheleadingworldwidecauseofdeathsanddiseases,andthatitaccountsforthedeathsofmorethan14,000peopledaily.Effectsofwaterpo
8、llutionincludepoisonousdrinkingwater,poisonousfoodanimals,unbalancedriveran
