Noter til vandressourcer PDF

Preview

Summary

Noter om vandets egenskaber og vandforurening (på engelsk)...

Description

Properties of water: 

Water molecules are polar o Therefore, water dissolves polar or ionic substances - and carries materials to and from cells o Universal solvent o Many natural waters are slightly acidic => can dissolve many kinds of componds



Only inorganic substance that (normally) exists as a liquid at temperatures suitable for life



Water molecules are cohesive, creating high surface tension (H2O has the highest surface tension of any common, natural liquid) o Adheres to surfaces (capillary action)



Expands when it crystallizes (as opposed to most other substances) o It expands by about 8% when it freezes, becoming LESS dense o Why Don't Fish Die When Lakes Freeze Over?



Water has a high heat of caporization o Therefore, evaporationg water is an effective way for oraganisms to shed excess heat



Water has a high specific heat o A great deal of heat is absorbed BEFORE it changes temperature o High capacity to store heat o Solar energy warms the oceans => warm oceanic current (Gulf stream) => warms western Europe



Sunlight penetrates water to variable depths, permitting photosynthetic organisms to live below water surface

Vandforurening: Water quality:  Technology o Septic system o Sewage system o Water purification  Treating water Pollutants:  Wastewater: the major pollutant , human waste (and animal waste) o Bacteria/microorganisms needs oxygen to break down the waste  BOD: biochemical-oxygen-demand, measureing how polluted a lake is, for example, by looking at how much oxygen bacteria/decomposers of waste demand  Standard: how many mg O2 / L at 20 °C for 5 days  Uberørt flod: < 1 mg O2 / L  Forurenet flod: 2-8 mg O2 / L

 





Renset spildevand: 20 mg O2 / L "Råt" spildevand: 600 mg O2 / L (Europa)  Can lead to dead zones o Nutrients  Causes eutrophication (abundency of nutrients in a body of water, causing a dense growth of plant life like algea)  Algea bloom = dies off = decomposers break down dead organic matter = requires oxygen = dead zones o Disease  Cholera is an example Chemical poolutants: o Metals: lead, mercury o Acids, synthetic materials (pesticides) and oil Non-chemical pollutants: o Solid waste, sediments, debris (vragrester, skrald)  Not at a molecule-level o Thermal pollution  Heat can lead to water pollution  Power plant moving heat to the nearby water body

Categories Point pollution: pollution coming from one point (pipe, ship, etc.) Non-point pollution: coming from e.g. 'all' the farmers' fields  Runoff - pulling pesticides and nutriends into the water body Ground water pollution: when the pollution has reached the water table...