Monitoring Water Quality 2.1 Monitoring Water Quality

A. Water Quality water that looks clean may not be clean there are many toxic dissolved substances monitoring water quality is an accurate way of keeping track of what is in water systems there are two indicators used to monitor water quality: biological and chemical slide 1 of 14

B. Biological Indicators biological indicators alert scientists to potential environmental problems the types of organisms that live in the water are an indication of conditions like the amount of dissolved oxygen and pH slide 2 of 14

two main types of biological indicators are: 1. microorganisms eg) bacteria 2. aquatic invertebrates (animals without backbones) eg) shrimp, leeches, worms high amounts of harmful bacteria like E. coli would result in water treatment being necessary slide 3 of 14

C. Chemical Indicators six types of chemical indicators can directly be measured: 1. dissolved oxygen (needed for animal cells) 2. acidity (if pH is less than 5.0, fish could die) 3. heavy metals (eg. copper, mercury) 4. plant nutrients (eg. potassium, nitrogen) 5. (eg. DDT) pesticides 6. salts (eg. NaCl, MgSO4) slide 4 of 14

D. Measuring Concentration the concentration of chemicals in the environment is usually measured in parts per million (ppm) or milligrams per litre (mg/L) it is calculated as follows: 1,000,000 (one million!) solute volume (mL) solution volume (mL) ppm = slide 5 of 14

Example Calculate the concentration if 1 mL chlorine is dissolved to make 10,000 mL of solution. 1,000,000 solute volume (mL) solution volume (mL) ppm = 1 mL 10,000mL ppm = 1,000,000 = 100 ppm slide 6 of 14

E. Dissolved Oxygen oxygen dissolves in water by diffusion from air dissolved oxygen is removed by: 1. decomposition (rotting) of organic material 2. cellular respiration (fish gills) slide 7 of 14

level of dissolved O2(g) depends on 4 factors: 1. temperature 2. wind/water turbulence 3. amount of photosynthesis 4. number of organisms slide 8 of 14

F. Nitrogen and Phosphorus plant growth is stimulated by nutrients such as nitrates and phosphates increasing the concentration of these nutrients in water increases plant production slide 9 of 14

plants eventually die and decomposers (bacteria) break down the dead plants and use up a lot of dissolved O2(g) the invertebrate and fish populations start to die off and you are left with leeches, worms and mosquitoes slide 10 of 14

G. Acidity normal rain has a pH of 5.6 while acid rain can be much lower (3.0) as pH goes down (more acidic) so does the amount of biodiversity most fish die if pH goes below 4.5 slide 11 of 14

this can weaken the eggs of organisms and kill their young acid can build up in snow and ice in the winter and then be released all at once in the spring…called spring acid shock this can weaken the eggs of organisms and kill their young slide 12 of 14

H. Heavy Metals heavy metals are metals with a minimum density of 5 g/cm3 eg) lead, copper, mercury occur naturally in small amounts human activities like industries and farming tend to concentrate them in ecosystems they harm the normal development of humans and other organisms slide 13 of 14

I. Measuring Toxicity scientists use a measurement called LD50 to measure toxicity LD50 is the amount of a substance given all at once that causes 50% of a test group of animals to die the more toxic the substance, the lower the LD 50 number slide 14 of 14

Assignment worksheet 5 and 6