英语演讲稿水污染英文省公共课一等奖全国赛课获奖课件.pptx

waterenvironmentenvironment第1页Water is the source of all thingsIts the only water,but its the liquid wonder that makes our world possible.Water is able to dissolve more substances than any other liquid.Its takes a lot of water to keep life going.第2页123Some data water use&pollution what can we do第3页 71%of earths surface is covered with waterAre the water sources abundant?第4页 less than 3%Of total waterLow layer0.3%of fresh water第5页China water resource rank fourth in the world.China isnt rich in water resources.Obviously,the prospect of Chinese water resources isnt optimistic.Water Issues in China with water resources per capita being2200m3 or so,only 1/4 of that of the world.water resources per capita 第6页South:population 53%waterresource:78%North:population:47%water resource:22%Uneven distribution of water resources 第7页nWater is considered polluted if a substance or condition is present that renders the water useless for a particular purposenThe sources of water pollutionnDirect sources neffluent outfalls from factories,refineries(精炼厂）,waste treatment plants.nIndirect sourcesncontaminants that enter the water supply from soils/groundwater systems and from the atmosphere via rain water.第8页Agricultural Water UseFour common irrigation methods:Surface/FloodRequires extensive canal systemsSprayUse pumpsTrickleStrategically places openingsSub-irrigationPipes can be used for drainage as well第9页nExcessive fertilizer use may lead to eutrophication（水体富营养化）in many aquatic habitats.nAgricultural runoff from large,open expanses is major source of water pollution.Agricultural Water Pollution第10页Industrial Water UseAccounts for nearly 50%of all water withdrawal in U.S.,and 23%worldwide.90%of water used by industry is for cooling,and is returned to the source.Very little actually consumed.Most processes involve heat exchange.Water used to dissipate and transport waste.Toxic and overload wastes lead Stream and lake degradation.第11页Industrial Water PollutionAll kinds of industry generate trade waste (工业废水）Iron and steel industryFood industryComplex organic chemicals industryNuclear industryPollutants:organics,oil,metal,acidMay require special wastewater treatment.第12页Domestic Water Use70%used as solvent to carry wastes.30%used for lawn and garden.Very small fraction used for drinking.Natural purification processes cannot cope with highly concentrated urban wastes.Must be treated before release.第13页Domestic water pollutionWaste water from Bathing,dishes,toiletsNo toxic substance,abundant in nutrients with nitrogen(N，氮）and phosphorus(P，磷）Eutrophication（水体富营养化）Trash or garbage(e.g.paper,plastic,or food waste)discarded by people on the ground,along with accidental or intentional dumping of rubbish,that are washed by rainfall into storm drains and eventually discharged into surface waters.第14页For governments1.To establish urban sewage treatment system(城市污水处理系统)2.To restructure Industrial3.To encourage the development of new water sources4.To strengthen legislation,severe punishment第15页For plants1.To reduce water consumption2.To buy equipment of sewage treatment 3.Dont discharge sewage into water4.To use water recycling system第16页For individuals1.Dont use cleaner conclude P2.Dont throw the garbage into the rivers 3.To promote awareness of preserving water resources4.To tell the persons around you to protect the water resources第17页World Water Day (World Day for Water)On March 22 the United Nations General Assembly（联合国（联合国大会）大会）in 1993 aim:to arouse publics awareness of economizing water sources,and to protect itone theme per year:water for cities第18页Thank you!第19页