水体富营养化英文

.,Eutrophicationofwater,.,Definition,Eutrophicationisoneofthewaterpollution.Itismainlycausedbyhumanactivities.Whenalargeamountofnutrients,suchasnitrogenandphosphorus,aredischargedintolargelakes,estuaries,baysandotherwaterbodieswhichflowslowly,itwillcauseaphenomenonthatalgaeandotherplanktoninwatermultiplyrapidly,dissolvedoxygendecreases,waterqualitydeterioratesandalargenumberoffishandotherorganismsdie.,.,Mechanism,Excessnutrients(N、P),Autotrophicorganisms(especiallyblue-greenalgaeandredalgae)growquickly,OtheralgaespeciesgraduallyreducePlanktonandothersmallorganismsdie,Bedecomposedbyaerobicmicroorganismconsumedissolvedoxygeninwater,Fishandotheraquaticlifedie,OrbedecomposedbyanaerobicmicroorganismProducehydrogensulfideandothergases,.,Identificationindex,Nitrogencontent0.20.3ppmBiochemicaloxygendemand(BOD)10ppmPhosphoruscontent0.010.02ppmThenumberofbacteriaismorethan100000inpermlofwater(pH=910)Thecontentofchlorophyllaincharacterizedalgae10mg/L,.,Source,Excessnitrogenandphosphorusinthewaterbodymainlycomefromindustrialwastewateranddomesticsewage,organicwaste,livestockandpoultrymanureandagriculturalchemicalfertilizer.,.,Controlmethod,Engineeringmethods,DiggingupthelakesedimentsItisthemainwaysofreducingtheself-concentrationofnitrogenandphosphorusineutrophiclake.DeepaerationTakingartificiallakedeepaerationandsupplementingoxygenfromtimetotimeisconducivetoinhibitthereleaseofphosphorusfromsediment.InjectwaterInjectingwatercontaininglowconcentrationsofnitrogenandphosphorusintolakescandilutenutrientconcentration.,.,Controlmethod,Chemicalmethods,CoagulationandsedimentationManykindsofcationscancausethephosphorustoprecipitatefromtheaqueoussolutioneffectively,suchasiron,aluminumandcalciumForexample,thelonglakeinwesternWashingtonstateisaeutrophicwaterbody.InOctober1980,peopleaddaluminumsaltintothelaketoprecipitatethelakesphosphate.Inthesummeroffourthyearsaftertheadditionofaluminumsalt,phosphorusconcentrationinthelakewaterbecamefromtheoriginal65g/Lto30g/L,thewaterqualityofthelakehasbeensignificantlyimproved.,.,Controlmethod,Inthechemicalmethod,anotherwayistokillalgaewithalgaecide.Thismethodissuitableforthewaterbodyofthelakewaterbloom.Afteralgaecidekillsthealgae,thedecompositionofalgaewillstillreleasephosphorus.Therefore,algaekilledbyalgaecideshouldbepromptlyremoved,orsomeappropriatechemicalsshouldbeaddedintothewaterbodytomakephosphateprecipitate.,.,Controlmethod,Biologicalmethods,Useaquaticlifetoabsorbnitrogenandphosphorusinordertoremovenitrogenandphosphorusinwater.Forexample,