WATERSHED TESTING
pH
* Potential of hydrogen: it is a measure of the amount H+ ions (or H3O+ ions) in a solution * In a neutral pH (7), the number of H+ ions equals the number of OH- ions.
* The concentration of H+ ions in pure water is 1 x 10-7 Moles per Liter (Molarity)
pH is found by taking the negative log of the H+ ion concentration
* Water is a very good solvent, so the pH of natural water tends to vary between 6.0 and 8.5
* Organisms have specific pH ranges:
Excellent : 6.5 to 7.5
Good : 6.0 to 6.4 or 7.6 to 8.0
Fair: 5.5 to 5.9 or 8.1 to 8.5
Poor: below 5.5 or above 8.5 (may not support fish)
* Many plant and animal species cannot live below a pH of 5 or above 9.5
* An extreme pH may indicate industrial discharge, in parts of the country it is a result of mining
* Draw pH scale (0-14) and label strong acid, weak acid, neutral, weak base, strong base
Nitrates and Phosphates
* Some primary sources of nitrates are fertilizers, sewage, and industrial wastes
* Some primary sources of phosphates are fertilizers, detergents, sewage
* Short-term effects include plant growth, algal blooms, and reduced light penetration
* Long-term effects include the above plus eutrophication, reduced DO, increased BOD and
turbidity, sedimentation that covers organisms and eggs on the bottom
Nitrate-nitrogen readings:
Excellent: below 1.0 ppm
Good: between 1.1 and 3.0 ppm
Fair: between 3.1 and 5.0 ppm
Poor: greater than 5.0 ppm
Phosphate readings:
Excellent: below 1.0 ppm
Good: between 1.1 and 4.0 ppm
Fair: between 4.1 and 9.9 ppm
Poor: greater than 10.0 ppm
Dissolved Oxygen
* Primary sources of DO are photosynthesis and stream turbulence trapping air
* Higher DO generally means cleaner water
* Temperature ↑, DO ↓ (inverse relationship)
* BOD, Nitrates, and Phosphates ↑, DO ↓
* Organisms have minimum DO levels:
Trout – 6.5 mg/L, Mosquito larva – 1.0 mg/L,
Smallmouth Bass – 6.5 mg/L, Catfish – 2.5 mg/L
* Warmer water holds less dissolved oxygen (inverse relationship → temp.↑, DO↓) low DO #s
are an indicator of organic pollution
* Sometimes DO is given as percent saturation. This compares the amount of O2 that is
dissolved with how much could be dissolved at a specific temperature.
* At 20°C, 9-10 ppm DO represents the maximum level (saturated)
* At 20°C, a DO below 4.0 ppm many fish populations start to decline
Biochemical Oxygen Demand
* BOD is indirect measure of the amount of oxygen required, by microorganisms,
to decompose the organic matter in a sample of water.
* Some of the main sources of organic matter are dead plants, leaves, sewage,
food waste, and manure.
* Increasing nitrates and phosphates increases BOD: These plant nutrients increase
plant and algae growth, which then die and are decomposed by aerobic bacteria
that consume oxygen.
* BOD↑, DO↓
* Test procedure was described in on the worksheet.
BOD readings:
Very Good: between 1.0 and 2.0 ppm
Moderate: between 3.0 and 5.0 ppm
Partially Polluted : between 6.0 and 9.0 ppm
Polluted: greater than 10.0 ppm
Temperature
* Organisms have specific temperature ranges: Trout – 5 - 20°C, Mosquito larva – 10 - 25°C,
Smallmouth Bass – 5 - 28°C, Catfish – 20 - 25°C
* There is an inverse relationship between temperature and DO.
* There is a direct relationship between temperature and BOD. (temp. ↑, metabolic rate ↑)
* Healthy rivers should have less than 3°C temperature change along a particular stretch.
Turbidity
* Turbidity refers to how clear or cloudy the water is.
* The lower the turbidity, the clearer the water.
* High turbidity tends to be the result of suspended particles in the water such as
soil (erosion and runoff), sediments (stirred up from human activity),
sewage (leaking or facility discharge), and algae and plankton (nutrients).
* Suspended particles:
block out sunlight and lower the rate of photosynthesis (DO ¯)
absorb heat from the sunlight and warm the water (DO ¯)
cover bottom dwelling organisms and their eggs
clog the gills of fish and lowers their ability to see
* Turbidity can be measured using a meter (NTUs – Nephelometric Turbidity Units),
a kit (JTUs), or Secchi disk (usu. for lakes)
Good: between 0.0 and 2.0 NTUs, 1.6m or more for Secchi disk
Normal: between 2.0 and 10.0 NTUs, 1.0m to 1.6m for Secchi disk
High: above 10.0 NTUs, less than 1.0m for Secchi disk
Fecal Bacteria
* An indication of contamination from fecal matter (usually from sewage or septic tanks)
* Recommended fecal coliform bacteria counts are: * Drinking Water: 0 colonies per 100 mL sample of water * Swimming Water: < 200 colonies per 100 mL sample of water * Boating/Fishing: < 1000 colonies per 100 mL sample of water
Macroinvertebrates and Applications
* Macroinvertebrates refers to a group of aquatic insects, crustaceans, and molluscs that are
large enough to see with the naked eye and whose presence (or lack of) serves as an
indicator of water quality in streams.
* Different macroinvertebrates have various sensitivities to polluted water. Healthy aquatic
ecosystems support a diversity of all these organisms. Unhealthy ecosystems lack the
pollution-sensitive species and are inhabited by more the pollution-tolerant species.
* Macroinvertebrates are divided into three categories when used to evaluate water quality.
* Class I indicates good water quality, Class II indicates fair water quality, and Class III
indicates poor water quality. Some examples are listed below.
Class I Class II Class III
Mayfly larvae Crayfish Leeches
Caddisfly larvae Damselfly Blackfly larvae
Stonefly larvae Dragonfly Midge fly larvae
Riffle Beetle adult Riffle Beetle larva Aquatic worms
Planaria Cranefly larvae Lung Snails
Hellgrammite Clam or Mussel
Water Penny Scuds
Conductivity
* Total Dissolved Solids (TDS) are solids in water that can pass through a filter.
* It is primarily an indicator of total salts dissolved in the water.
* This material can include carbonate, bicarbonate, chloride, sulfate, phosphate,
nitrate, calcium, magnesium, sodium, organic ions, and other ions.
TDS can be measured by evaporating a water sample, that has been filtered, until
the weight of the dish no longer changes and then weighing the solids left behind (mg/L). * TDS can be roughly estimated by measuring the conductivity of the …water sample because increasing the amount of salts dissolved in water …increases its ability to conduct electrical currents.
Pollutants such as salts from streets, wastewater from houses, and fertilizers …from lawns can be washed into streams and rivers.
A certain level of dissolved minerals is essential for aquatic life,
but levels that are too high or low can limit growth and even lead to death.
This is due to changes in the concentration gradient that affect the flow
of water into and out of an organism’s cells.
Water with high TDS often has a bad taste and/or high water hardness
Biological Magnification – The increasing concentration of a harmful, and
usually toxic, substance as it moves up the food chain. The toxins tend to
be stored in the fatty tissues of the animal. Ex. DDT was 400x more
concentrated in top carnivores (eagles, ospreys) than in the producers.
Other pollutants that tend to biomagnify include mercury, lead, and PCBs.
Eutrophication – The process where bodies of water are overloaded with
nutrients. It is often the result of human activities. Examples include
fertilizer runoff, detergents, and leaking sewage. It can lead to the rapid growth of algae (algal bloom) in aquatic ecosystems that ultimately depletes the oxygen levels in the water and reduces water quality. Dissolved oxygen levels drop as excess algae die and decomposers consume the D.O.