5.2 Detection and Monitoring of Pollution

Direct measurement is performed by monitoring the level of the pollutant itself, e.g. nitrates in a lake or temperature levels in a lake or stream. Indirect method would monitor the effects of the pollutants on other factors, e.g. dissolved oxygen, B.O.D.5, Indicator Species presence or absence of indicator species

Direct Measurement Some direct measurements might include: 1.Measuring temperature in several locations along the length of a river, or at different times during the year with thermometers as an indication of thermal pollution. 2.Take baseline measurements and then 3.Monitor in a systematic manner to determine changes. measuring nitrate levels/ammonia levels/chloride levels as an indication of nutrient overload. Use the same process as above measuring TSS (Total Suspended Solids) or TDS (Total Dissolved Solids) as an indication of material entering the lake or stream. (see next slide)

Indirect Measurement BOD is the measure of the amount of dissolved oxygen that is used by aerobic bacteria to break down the organic matter in a specific volume of water. Therefore the greater the amount of organic matter/nutrient (sewage, agricultural run-off, fertilizer etc.) in the body of water, the higher the BOD will be. The less organic matter, the lower the BOD. It is not uncommon for the BOD of incoming water to a sewage treatment plant to be around 120.

This is done by measuring the DO (dissolved oxygen) on day Keep samples at 20 degrees Celsius for 5 days in the dark during that time. Measure the DO again on the 5th day. This measures the respiration going on and not photosynthesis.

Natural factors that influence dissolved oxygen: Aquatic life-animals: Stonefly living in water use up dissolved oxygen. Bacteria take up oxygen as they decompose materials. Elevation: the amount of oxygen in the atmosphere decreases as elevation increases. Since streams get much of their oxygen from the atmosphere streams at higher elevations will generally have less oxygen. Salinity: Salty water holds less oxygen than fresh water. Temperature: Cold water holds more dissolved oxygen than warmer water. Turbulence: More turbulence creates more opportunities for oxygen to enter streams. Vegetation: riparian vegetation directly affects dissolved oxygen by releasing oxygen into the water during photosynthesis. It indirectly affects dissolved oxygen concentrations because vegetation shading a stream may decrease water temperatures.

Human factors that influence dissolved oxygen: Factories and powerplants Factors and powerplants will emit hot water from effluent ponds. These emissions will impact the DO of the body of water as they enter. Clearing land (e.g., construction, logging)-may send excess organic matter into streams. Organic matter is decomposed by microorganisms, which use up oxygen in this process. Therefore, if there is a lot of organic waste in the stream the microorganisms use more oxygen than can be replaced in the stream. Destruction of riparian areas (e.g., development or overgrazing) decreases the amount of shade and increases the water temperature. Warmer water holds less DO than colder water.

BOD5 Level BOD Level (in ppm) Water Quality 1 - 2 Very Good There will not be much organic waste present in the water supply. 3 - 5 Fair: Moderately Clean 6 - 9 Poor: Somewhat Polluted Usually indicates organic matter is present and bacteria are decomposing this waste. 100 or greater Very Poor: Very Polluted Contains organic waste.

Indirect measurement Indirect measurement involves the monitoring and measurement of organisms in the ecosystem and more specifically indicator species or index species. These are species that by virtue of their abundance or absence will indicate the level of pollution in that ecosystem.

Macroinvertebrate indicator species Easy to see and identify e.g. mayflies, caddisflies, true flies, snails (see keys) Have a life cycle of at least a year Relatively sedentary, confined to the area being sampled They have a range of responses to different pressures. Individual species have specific tolerance ranges and habitat requirements

Aquatic Invertebrate Data Recording Sheet

Using the biotic index These scores are then combined to produce a single value which can be used to interpret the current state of the environment. Examples of biotic indices Trent Biotic Index, the Chandler Score and the Biological Monitoring Working Party (BMWP) score

The damselfly larva Calopteryx splendens

The damselfly larva Calopteryx splendens The presence of this larva indicates clean water Slow flowing water and a silted river bed. It is also intolerant of acidification and increased salinity Species like C. Splendens are used to formulate biotic indices based on acidification, flow velocity and siltation

Pollution Tolerant Species: Presence of these species indicate water of low quality, however they may be present in all types of water. blackfly larvae Flatworms Leeches Roundworms Blood worms/midge larvae

Moderately Tolerant Species: Presence of these species in great numbers may be a sign of fair water quality. caddisfly larvae dragonfly nymphs damselfly nymphs

Pollution Intolerant species Presence of these species in great numbers may indicate good water quality. mayfly nymphs stonefly nymphs

Comparison of diatoms to blue-green algae provides similar information Measuring the coliform levels can also indicate the presence of sewage dumping in the ecosystem.

The Macroinvertebrate biotic index To arrive at an indication of your sites biotic index level, multiply the number of organisms collected by the tolerance rating. Add all the numbers in the organism column and all the numbers in the tolerance value column. Divide the tolerance value with the organisms total. This results the biotic index based on the biological specimens collected.

Example of Biotic Index Calculation Using Macroinvertebrate Information You may find in an aquatic ecosystem: 25 Mayfly larvae 15 Caddisfly larvae 20 Stonefly larvae 20 leeches 20 Midge larvae

Multiply each by the Biotic Value: No of organisms X biotic value Biotic value 25 Mayflies 5.5 15 Caddisflies 20 Stoneflies 1.5 20 leeches 8.0 20 Midge larva 4.0 Total number of organisms = TOTAL biotic value =

Very poor > 9.0 poor 7.6-8.9 Fair 6.1-7.5 good < 6.0 Divide total biotic value by the total number of organisms to get the biotic index value Water Quality Biotic Index The biotic index value is ……………. Use chart to determine water quality based on Biotic Index Value Based on the Biotic Index Value, the water quality is ……………………… Very poor > 9.0 poor 7.6-8.9 Fair 6.1-7.5 good < 6.0

Worked example: BIOTIC VALUE 25 Mayflies 5.5 25 x 5.5 137.5 15 Caddisflies 15 x 5.5 82.5 20 Stoneflies 1.5 20 x 1.5 30 20 leeches 8.0 20 x 8 160 20 Midge larva 4.0 20 x 4 80 Total number of organisms = 100 TOTAL biotic value = 490

Very poor > 9.0 poor 7.6-8.9 Fair 6.1-7.5 good < 6.0 Divide total biotic value by the total number of organisms to get the biotic index value Water Quality Biotic Index 490/100 = 4.9 Use chart to determine water quality based on Biotic Index Value Based on the Biotic Index Value, the water quality is good. Very poor > 9.0 poor 7.6-8.9 Fair 6.1-7.5 good < 6.0

Diatoms

Fecal Coliform

Blue-green algae

Overall the diversity of the whole system is often the best indicator while a general rule to follow is that presence is better evidence than absence.