RiverPollution

　　Itseemsthatalmosteverydaythereisanotherstoryaboutpollutionofoneformoranother,inthefoodweeat,thewaterwedrinkandtheairwebreathe.Veryoftenourownactionsleadtothatpollutionandinmanycaseswecandosomethingaboutit.Thesenotesexplainhowyoucaninvestigatepollutionandadviseonpositiveactiontoimproveourrivers.

　　Over97%ofallthewateronEarthissaltyandmostoftheremaining3%isfrozeninthepolarice-caps.Theatmosphere,rivers,lakesandundergroundstoresholdlessthan1%ofallthefreshwaterandthistinyamounthastoprovidethefreshwaterneededtosupporttheEarth'spopulation.Itisestimatedthat,withtheexpectedincreaseinpopulation,therewillbea200%increaseinworldwaterneedsbytheyear2000.Freshwaterisapreciousresourceandtheincreasingpollutionofourriversandlakesisacauseforalarm.

　　Mostfreshwaterpollutioniscausedbytheadditionoforganicmaterialwhichismainlysewagebutcanbefoodwasteorfarmeffluent.Bacteriaandothermicro-organismsfeedonorganicmatterandlargepopulationsquicklydevelopusingupmuchoftheoxygendissolvedinthewater.Normallyoxygenispresentinhighquantitiesbutevenasmalldropinthelevelcanhaveaharmfuleffectontheriveranimals.Animalscanbelistedaccordingtotheirabilitytotoleratelowlevelsofoxygen.Inthefollowinglistanimalswhichindicateahighlevelofdissolvedoxygenareatthebeginningwhileanimalsindicatingalowlevelofoxygenareattheend:stone-flynymphs,mayflynymphs,freshwatershrimps,freshwaterhoglice,bloodworms,tubifexwormsandrat-tailedmaggots.

　　Ifyouseedeadfishfloatingontheriverornoticethatthewaterisdiscolouredandsmellyanyoneofthefollowingformsofpollutionmaybethecause:

　　fertilisers

　　industrialwaste

　　oil

　　warmwater

　　AllincidentsofriverpollutionshouldbereportedtothePollutionControlofficerattheWaterAuthoritygivingasmuchdetailasyoucan:date,time,exactplaceandpreciselywhatyousaw.

　　a)Fertilisers

　　Iflargeamountsoffertiliserorfarmwastedrainintoarivertheconcentrationofnitrateandphosphateinthewaterincreasesconsiderably.Algaeusethesesubstancestogrowandmultiplyrapidlyturningthewatergreen.Thismassivegrowthofalgae,calledeutrophication,leadstopollution.Whenthealgaedietheyarebrokendownbytheactionofthebacteriawhichquicklymultiply,usingupalltheoxygeninthewaterwhichleadstothedeathofmanyanimals.

　　b)IndustrialWaste

　　Chemicalwasteproductsfromindustrialprocessesaresometimesaccidentallydischargedintorivers.Examplesofsuchpollutantsincludecyanide,zinc,lead,copper,cadminandmercury.Thesesubstancesmayenterthewaterinsuchhighconcentrationsthatfishandotheranimalsarekilledimmediately.Sometimesthepollutantsenterafoodchainandaccumulateuntiltheyreachtoxiclevels,eventuallykillingbirds,fishandmammals.

　　Occasionallypoisonoussubstancesaredeliberatelydumpedintoriversandifyouseethisso-called'fly-tipping'goingontaketheregistrationnumberofthevehicleandifpossiblethenameofthefirm.Reportthemattertothepolicewhowillthentakeitfurther.

　　c)OilPollution

　　Ifoilentersaslow-movingriveritformsarainbow-colouredfilmovertheentiresurfa