1 WATER as A Resource

Drinking Water 2

Water Contamination  How do we know what is “clean water?” In other words, how do we know if water is “safe” for humans and wildlife?  Use “Water Cards” put in order from unsafe  safe drinking water.  Read “The Dose Makes the Poison,” answer questions #1-6 on your paper. Using Bioassays for Environmental Research3

Water Contamination  How do we know what is “clean water?” In other words, how do we know if water is “safe” for humans and wildlife?   Charity Water Video Charity Water Video  Let’s look at Water Quality Indicators Using Bioassays for Environmental Research 4

Units for Measuring Water Quality

PARTS PER MILLION Most dissolved substances found in water are measured in parts per million (ppm) or even smaller amounts. This means that for every one million parts (units) of water there is a certain number of parts of the substance.

It is also expressed as milligrams per liter. There are 1000 milliliters in a liter and 1000 milligrams in a gram. For example, a dissolved oxygen reading of 8 ppm means there are 8 milligrams of oxygen for every 1000 milliliters of water. 8/1000 gram  1000 milliliters = 8/1000 gram  1000 milliliters = 8/1,000,000 (8 parts per million) 8/1,000,000 (8 parts per million)

Concentrations of certain substances are also measured in parts per billion, parts per trillion and so on. These are very small amounts but certain substances can be harmful even at these very low concentrations.

Water Quality Indicators We will now take a look at some water quality indicators. “Water quality” can refer to quality for a healthy “environment” and/or healthy for human consumption

TEMPERATURE Most aquatic organisms live within a temperature range of 32º F (+0º C) to 90º F (32º C). Temperature is measured in Fahrenheit and Celsius degrees. (Temperature, of course, is not a “dissolved substance”)

Rapid temperature change and temperature extremes can stress aquatic organisms. TEMPERATURE

pH pH is the measure of the hydrogen ion (H+) concentration. The pH scale is zero to 14. Seven is neutral, below seven is acidic, and above seven is basic (or alkaline). Most aquatic organisms exist within a pH range of 5.5 to 9.5.

pH pH is usually not a major problem for aqutic organisms or drinking water except in certain situations (acid mine drainage etc.)

Salinity Salinity refers to the salt concentration in water, mostly sodium chloride. Salinity is historically measured in parts per thousand (ppt) or grams per liter.

Salinity Salinity Salinity of the ocean is about ppt. The maximum considered safe for drinking water is 1 ppt (1,000 ppm)

Salinity Saltwater can cause drinking water problems when it replaces fresh groundwater near the coastal areas.

DISSOLVED OXYGEN Dissolved oxygen is a product of photosynthesis and diffusion. Typical range 0 – 14 ppm “Quality” water >6 ppm Diffusion: The movement of molecules, for example oxygen molecules, from an area of higher concentration (e.g. the leaf) to an area of lower concentration (e.g. the water).

DISSOLVED OXYGEN Most aquatic organisms that respire using oxygen need at least 5 or 6 ppm of oxygen in order to survive.

BACTERIA Most bacteria are important in nutrient and other organic cycles. Excess nutrients cause algal blooms. As algae die and decay, the high bacterial load rapidly consumes dissolved oxygen.

TURBIDITY Turbidity refers to water clarity. Sediments suspended in the water increase turbidity.

Certain types of bacteria indicate animal and human waste pollution. Escherichia coli are coliform bacteria found in the intestines of warm-blooded organisms. Most strains are harmless but one E. coli strain can cause severe diarrhea and kidney damage.

Bacteria The goal for drinking water is “zero” however this is often impossible. Therefore, U.S. laws require that drinking water is treated with a disinfectant. Drinking water is periodically tested for bacteria

NITRATE Nitrate is a primary plant nutrient. Nitrate is water soluble and moves easily from surface to groundwater. Excess nitrate causes algal blooms that reduce water quality.

Under normal conditions, the nitrogen cycle keeps the amount of available nitrogen in balance with the demands. However, excessive use of fertilizers and nutrient rich sewage release have created a surplus of nitrate. The result is eutrophication from excess algae and bacteria with reduced dissolved oxygen.

PESTICIDES / HERBICIDES These chemicals are very complex. Effects on aquatic organisms – Moderately to highly toxic to mammals, mollusks, aquatic insects, amphibians and fish.

TOXIC CHEMICALS Toxic chemicals usually come from industry and energy production. The effects are often not known until years after they have entered the environment.

Some toxic chemicals include petroleum products (oil), heavy metals (lead, mercury etc.), and organic compounds (DDT, PCB).

Stop: Activity  Use “Water Cards” put in order from unsafe  safe drinking water.

Using Bioassays for Environmental Research30 BIOASSAYS  Dose/Response Bioassays are used to: Estimate toxicity to humans. Estimate toxicity to humans. Estimate maximum concentrations of specific chemicals allowed to discharge into bodies of water. Estimate maximum concentrations of specific chemicals allowed to discharge into bodies of water. Investigate hazardous waste sites. Investigate hazardous waste sites.

31 Bioassay Species  3 organisms are often used Daphnia Daphnia Duckweed Duckweed Lettuce Seeds Lettuce Seeds  Expose organisms to chemicals and measure how they respond.

Using Bioassays for Environmental Research32 Bioassay Species  Lettuce Seeds In Petri dishes with test samples In Petri dishes with test samples Sensitive to pesticides, solvents and organic compounds Sensitive to pesticides, solvents and organic compounds After 5 day check for: After 5 day check for: germination germination radicle length radicle length

Using Bioassays for Environmental Research33 CONCENTRATION VS. DOSE  LD 50 the Dose that is Lethal for 50% of the test organisms. Used for Daphnia Used for Daphnia  TC 50 the Concentration that causes a 50% drop in growth or health of the test organisms (Toxic Concentration). Used for seeds (they may not die, just not sprout) Used for seeds (they may not die, just not sprout)

Using Bioassays for Environmental Research34 An Introduction To Experimental Design  The Treatments in an experiment represent the factor that you vary while keeping everything else constant.

Using Bioassays for Environmental Research35 An Introduction To Experimental Design  The control is the untreated group, used for comparison with the treatment groups.

Using Bioassays for Environmental Research36 An Introduction To Experimental Design  Replicates are groups of organisms exposed to identical conditions. The more replicates the better. The more replicates the better.

Using Bioassays for Environmental Research37 INTERPRETING BIOASSAY RESULTS  How do interpret LD 50 ’s and LC 50 ’s?  What conclusions are valid about environmental impacts of the compounds being tested?

Using Bioassays for Environmental Research38 INTERPRETING BIOASSAY RESULTS  Bioassays DO NOT specify what chemicals are present in the samples.  They measure the combined toxicity of whatever is in the sample.

Using Bioassays for Environmental Research39 INTERPRETING BIOASSAY RESULTS  Bioassays give us a standard technique to compare:  Samples taken at different times and places.  Samples of environmental samples to known samples.

Using Bioassays for Environmental Research40 TIPS FOR PLANNING AN EXPERIMENT  GO TO 