Chapter 17 Water Sample Analysis
Water sample analysis Key Knowledge • existence of water in all three states at Earth’s surface including the distribution and proportion of available drinking water • sampling protocols including equipment and sterile techniques for the analysis of water quality at various depths and locations • the definition of a chemical contaminant and an example relevant to a selected water supply.
Water sources on Earth Location of water State of matter Volume (km3) Oceans Liquid 1 300 000 000 Ice caps and glaciers Solid 24 000 000 Groundwater 23 000 000 Ground ice and permafrost 300 000 Lakes 180 000 Soil moisture 17 000 Water vapour in the atmosphere Gas 13 000 Rivers 2 100
The water cycle
Main processes in the water cycle Heat from the sun causes the water to evaporate Water vapour is transported around the globe and condenses to form clouds Water precipitates as rain, hail and snow and falls to the ground
Australia’s water supplies 40% of the worlds population lives where there is limited fresh water. Australia has close to 5% of the worlds land mass but only 1% of the water carried by rivers. Australia is the worlds driest inhabited continent and has variable rainwater. Look up the ‘Great Artesian Basin’ – what is it and why is it important?
Potable water (clean drinking water) Sources Reservoirs filled by run-off from rivers and streams Water obtained directly from rivers and lakes Groundwater (bore water) Recycled water Desalinated water
Drinking water in Victoria Most Victorians drinking water is supplied by mains supply (reticulated water) Other sources include – rainwater tanks, bores, dams, rivers and creeks Lowest risk Mains water Rainwater Deep groundwater Shallow groundwater Highest risk Surface water
Water Quality We are lucky in Australia that our drinking water is of such high quality. This is not the case worldwide. Chemical contamination can occur from time to time and this section looks at the types and how samples are obtained for analysis
Chemical contaminants Many different types of substances are soluble in water. Water pollution may be caused by human activity. Contamination can occur from Run-off from farms and cities Run-off from industrial and mining wastes Lead used in solder in copper water pipes Chemical contaminants can be naturally occurring or synthetic. The main types of chemical contamination involve Heavy metals Pollutants from fertilizers Organic pollutants
Heavy metal containation Heavy metals such as Lead and Mercury can contaminate water and cause serious health effects such as Cancer Organ and nervous system damage Even death Guidelines in Australia about safe drinking water values are monitored by local water authorities. Heavy metal Guideline value (mgL-1 or ppm) Arsenic 0.01 Cadmium 0.002 Copper 2 Chromium 0.05 (as Cr(VI)) Lead Mercury 0.001
Water sampling To make sure water is safe to drink testing takes place. Decision have to be taken about where to take samples from and the protocols that will be used. PROTOCOLS Containers being used Sampling methods Sampling depth Sampling location
Checklist Read Chapter 17 and make your notes 17.1 Q 1-4 p434 Chapter review p441-442 Worksheets 40 and 41 from the student workbook