2.1 Monitoring Water Quality

Overview How water quality is determined Biological indicators Based off of the 5 main uses Biological indicators Microbes and aquatic invertebrates Chemical factors that affect organisms Dissolved oxygen, acidity, pesticides, heavy metals, nutrients, salts Measuring chemicals and toxicity ppm calculations LD50

Question Is clear water an indicator of higher water quality? Answer: not necessarily! Lakes affected by acid rain are usually clear, but they are also inhabitable When lake transparency decreases, the property values of the surrounding real estate (houses, cottages, etc.) also decreases

How is Water Quality Determined? It depends on what the water is being used for The 5 main uses of water are: Human drinking water Recreation Livestock drinking water Irrigation Protection of aquatic wildlife

Biological Indicators Microbes Bacteria, viruses, and plankton If present in large amounts, they may be harmful and additional water treatment may be required Use up dissolved oxygen Aquatic Invertebrates Insects, crustaceans, worms, and mollusks Do not cause illness, but can show the effects of pollution e.g. some mayflies are sensitive to acidity and low dissolved oxygen

Chemical Factors that Affect Organisms (and Water Quality) Dissolved oxygen Acidity Pesticides Heavy metals Nutrients Salts

Dissolved Oxygen Essential for aquatic life such as fish, insects, and microorganisms Dissolved oxygen levels depend on: Temperature Turbulence due to wind, or the speed the water moves at Amount of photosynthesis by plants and algae The number of organisms using up the oxygen The acceptable level for most living things is 5 ppm (parts per million) or 5 mg/L

Acidity Remember: rain and snow normally have a pH of about 5.6 Anything less is acidic When this enters water systems, it lowers their pH Most fish begin to disappear when the pH drops below 5.0 Acidic deposits become a problem when the soil and water do not contain natural bases to neutralize the acid e.g. the Canadian shields Spring Acid Shock: occurs after acids have built up in the ice and snow over the winter; once they melt during the spring, the water flows into our aquatic systems

Pesticides May remain in the environment long after they are needed New pesticides are designed to only remain the environment for a single season Can potentially lead to insect-resistance, leading to the development of new pesticides This introduces other chemicals to the environment Pesticides can enter our water systems Seeing as we use multiple types of pesticides, although they enter the water systems in small amounts, their combinations can increase their overall toxicity (i.e. how poisonous they are)

Heavy Metals Defined as metals that have a density of 5 g/cm3 (5 g per cubic centimeter) or more 5 or more times heavier than equal volumes of water! e.g. copper, lead, zinc, mercury, cadmium, and nickel May occur naturally in rocks, soil, and sometimes water In their natural forms, they are generally not available to plants and animals However... They may also occur in the environment due to human activity Acid rain can dissolve the lead in metal pipes Cadmium is present in some fertilizers Plants can take up these sources of heavy metals, and animals that eat these plants may experience some health effects as a result

Nutrients Nitrogen and phosphorus Comes from sewage outfalls, and runoff from fertilized fields Dissolved oxygen is affected by increases of nutrients in water An increase in nutrients increases algae and plant life Decomposing bacteria eat the plants and algae once they die The population of bacteria increases due to the increase in food available, and as a result they use up more dissolved oxygen (decreasing it) A decrease in dissolved oxygen kills many fish and insects

Measuring Chemicals: ppm Chemicals in the environment are usually measured in ppm (parts per million) or mg/L (milligram per litre) - where 1 ppm = 1 mg/L This means that one unit of an element or chemical can be found in one million units of solution e.g. a single drop of food colouring in a half-full bathtub is about 1 ppm In the example above, the food colouring would be the solute, and the water in the bathtub plus the drop of food colouring would be the solution Let’s try an example

Suppose you add 10 mL of vinegar to 390 mL of water Suppose you add 10 mL of vinegar to 390 mL of water. What is the concentration of vinegar in ppm?

Measuring Toxicity: LD50 Toxicity: how poisonous a substance is LD50: the amount of a substance that causes 50% of a group of test animals to die if they are given that substance all at once e.g. if the LD50 of a substance is 0.3 mg and a group of 400 test animals was given that dosage, how many animals would die? 200