Water Chemistry Parameters

• I. Temperature
• II. Dissolved Oxygen
• III. pH (parts hydrogen)
• IV. Nitrates and Ammonia
• V. Phosphorus
• VI. Conductivity
• VII. Turbidity
• Interpreting the Data
• Water Quality Standards (Numeric Criteria)
• Water Quality Standards (General Criteria)

Water Quality Monitoring Procedures

• Visual Survey
• Turbidity Tube Instructions
• pH Pocket Meter
• Operating Procedure
• Calibration
• Troubleshooting
• Conductivity Pocket Meter
• Operating Procedure
• Calibration
• Troubleshooting
• Nitrate Test Kit Instructions
• Dissolved Oxygen Test Kit Instructions

Care of Standard Solutions

Disposal of Standard Solutions and Chemical Reagents

Water Chemistry Parameters

Chemical parameters play an important role in the health, abundance, and diversity of aquatic life. Excessive amounts of some constituents, such as nutrients, or the lack of others, such as dissolved oxygen, can result in imbalances in water chemistry. Imbalances can degrade aquatic conditions and harm aquatic life. An imbalance in chemical constituents can also make water unsuitable for human consumption, or greatly increase the cost of water treatment before it can be used.

I. Water Temperature (page 177 of the Streamkeepers Field Guide-SFG)

A. Water temperature is important because most of the physical, chemical, and biological characteristics of a river are directly affected by temperature. In general, water temperature affects:

• The amount of oxygen that can be dissolved in the water.
• Cool water can hold more oxygen than warm water.
• Warm water promotes chemical reactions.
• The rate of photosynthesis by algae and other aquatic plants.
• The metabolic rates of aquatic organisms.
• The sensitivity of organisms to toxic wastes, parasites, and diseases

B. Human-Caused Changes in Temperature

• Thermal pollution is water entering the stream that is warmer than the water already present in the river. One source is industries, like nuclear power plants, which discharge cooling water. Another source is storm water runoff from heated surfaces such as parking lots.
• Riparian cover removal. Impacts water temperature by eliminating shade.
• Soil erosion. This increases the amount of suspended solids carried by the river. The cloudy water absorbs the sun's rays, which warms the water.

C. Changes in Aquatic Life

• The rate of photosynthesis and plant growth increases with warmer temperatures. When plants die, they are decomposed by bacteria that need oxygen. Oxygen levels in the water are lowered by this process.
• The metabolic rate of organisms increases. This results in a higher oxygen demand for fish, aquatic insects and aerobic bacteria.
• Extreme water temperatures can exceed the tolerance limit for some organisms. (See chart, page 177, SFG)
• Organisms become more vulnerable to toxic wastes, parasites and disease.

Go to beginning of Module 11

II. Dissolved Oxygen (page 170 SFG)
Dissolved oxygen (DO) is oxygen gas that is literally dissolved in water. The presence of oxygen in streams and other bodies of water is a good thing, since most aquatic life needs oxygen to live. For example, fish need to breathe in dissolved oxygen through their gills. But if their watery home contains too little DO to meet their physiological needs, the fish will drown. In streams, DO levels that are too low to support aquatic life are a sure sign of severe pollution.

Most dissolved oxygen gets into the water from air. Waves on lakes and slow-moving rivers, water tumbling over riffles or waterfalls on fast-moving rivers mixes oxygen into the water. Plants and algae also add oxygen to the water as they do photosynthesis. Because plants need light to do photosynthesis, dissolved oxygen levels tend to be highest in the late afternoon and lowest at dawn.

Temperature has a very big affect on oxygen levels. It may seem strange but cold water holds more dissolved oxygen (and other dissolved gases) than warm water. Think about it this way, if you opened two cans of pop and placed one in the refrigerator and left one at room temperature. Which do you think would lose its fizz first? In the winter, dissolved oxygen levels are usually higher than in summer. That is why fish kills (due to low DO) usually occur in late summer just before dawn.

Climate can affect oxygen levels in other ways. During dry seasons water levels decrease and the flow rate (or discharge) of a river is lower. As the water moves slower, it mixes less with the air; and the dissolved oxygen level goes down. During rainy seasons oxygen levels tend to be higher.

The main man-made factor causing dissolved oxygen levels to change in a negative way involves the build-up of organic wastes. Organic wastes are the remains of any living or once-living thing. Leaves, grass clippings, dead plants or animals, and sewage are examples of organic wastes. Organic wastes are decomposed by bacteria which take oxygen out of the water. When people dump organic wastes into lakes and streams it causes dissolved oxygen levels to decrease which can harm the aquatic life.

When dissolved oxygen levels get lower, they can cause major changes in the types and amounts of aquatic organisms found living in the water. Certain aquatic species need high levels of dissolved oxygen (such as mayfly nymphs, stonefly nymphs, caddisfly larvae, pike, trout, and bass), and these will try to migrate from an area or die if DO levels fall below what they can tolerate. They will then be replaced by organisms such as sludge worms, blackfly larvae, and leeches which can tolerate lower levels of DO.

A. Sources of Dissolved Oxygen

• Atmosphere. The air we breathe contains approximately 21% oxygen which equates to 210,000 ppm oxygen. Most surface waters contain between 5 and 15 ppm dissolved oxygen. Waves and tumbling water act to mix atmospheric oxygen with water.
• Algae and rooted aquatic plants. Plants deliver oxygen to the water when they are photosynthesizing.
  

B. Natural Influences on Dissolved Oxygen (page 170 SFG)

• Temperature. Gases, like oxygen, are more easily dissolved in cooler water than in warmer water. River temperatures respond to changes in air temperature, though due to water's special thermal properties, river temperatures generally rise and fall more slowly than air temperatures do.
• Flow. Discharge can also be related to an area's climate. Dry periods often result in severely reduced flow and increased water temperatures. This combination acts to reduce dissolved oxygen levels. Wet weather or melting snows increase flow and the possibility for mixing of atmospheric oxygen.
• Dissolved or suspended solids. Oxygen dissolves more readily in water that does not contain a high concentration of salts, minerals, or other solids.
• Aquatic plants. During the day, when the sun is shining, dissolved oxygen levels rise due to photosynthesis. As the sun sets, photosynthesis stops, but plant and animal respiration continues to consume oxygen. Just before dawn, dissolved oxygen levels fall to their lowest level. Large fluctuations in oxygen from late afternoon to early morning are characteristic of waterways with extensive plant growth.

Diel fluctuation in dissolved oxygen (note that the term "diel" refers to period of 24 hours)

C. Human-Caused Changes in Dissolved Oxygen

• Organic wastes. These wastes include the bodies of once-living plants and animals, the feces of living animals, and the effluent from industies that process organic materials. Organic wastes take the from of sewage, discharges from paper-making and food processing factories, and runoff from cropland, animal operations (feedlots, zoos, etc.), golf courses, lawns, and gardens. Organic wastes act as fertilizer to stimulate aquatic plant growth. As these plants die, they too become organic waste. Aerobic bacteria (bacteria that need oxygen) consume dissolved oxygen in the process of decomposing organic matter that is in water.
• Urban runoff. Rain carries salt, sediment and other pollutants off of impervious surfaces (streets, roofs, and parking lots) into streams. This raises the total solids in the water and reduces the amount of dissolved oxygen it can hold.
• Dams. Some dams are constructed so that water is released from the bottom of a lake or reservoir. This water, which is far removed from the atmosphere, can be almost devoid of oxygen. The opposite problem can occur when water is released from the top of a dam or spillway. This can cause excessive uptake of oxygen from the atmosphere and results in water that is super saturated.
• Removal of vegetation in reparian corridor. Lack of shade, which causes increased water temperature, and lack of protection from erosion, which causes increased solids, can work together to reduce oxygen levels.

D. Changes in Aquatic Life

• Depletion of dissolved oxygen can cause major shifts in the kinds of aquatic organisms present in the stream from pollution sensitive species to pollution tolerant species. Nuisance algae and anaerobic organisms (those that live without oxygen) may also become abundant in waters of low dissolved oxygen.

E. Calculating Percent Saturation

The amount of dissolved oxygen present at a given temperature can be used to determine how saturated the water is with oxygen. Percent saturation is a more meaningful water quality indicator than a dissolved oxygen reading alone. For instance, an oxygen reading of 8.0 mg/L could be an excellent result during the summer, when water temperatures are high and the water's ability to hold oxygen is low. That same reading, however, could indicate problems if that result were obtained during the winter months when water temperatures are low and oxygen holding capacity is high. Rivers with a 90 percent saturation may have large amounts of oxygen demanding materials, such as organic wastes.

• Mathematical calculation of saturation (page 175 SFG)
• The "Quick and Easy" method (page 176 SFG)

Go to beginning of Module 11

III. pH (parts hydrogen)

A. Water (H₂O) contains both H+ (hydrogen) ions and OH- (hydroxyl) ions. pH measures the H+ ion concentration of substances and gives results o a scale from 0 to 14. Water that contains equal numbers of H+ and OH- ions is considered neutral (pH7). If a solution has more H+ than OH- ions, it is considered acidic and has a pH less than 7. If the sample contains more OH- ions than H+ ions, it is considered basic with a pH greater than 7. It is important to remember that every one unit change on the pH scale is a tenfold change in how acidic or basic the sample is.

B. Human-Caused Changes in pH

In the U.S., the pH of rivers is usually between 6.5 and 8.5. Rain water is more acidic and normally has a pH between 5.0 and 5.6. Increased amount of nitrogen oxides (NO_x) and sulfur dioxide (SO₂), primarily from automobile and coal-fired power plant emissions, are converted to nitric acid and sulfuric acid in the atmosphere resulting in acid rain or snow. In many areas of the United States, the geology of the area determines the acidity of the local water. If limestone is present, the alkaline (basic) limestone neutralizes the effect acid rain might have on lakes and streams.

C. Changes in Aquatic Life

Most organisms have adapted to life in water of a specific pH and may die if the pH changes even slightly. At extremely high or low pH values (11.0 or 4.5) the water becomes lethal to most organisms (page 167 SFG). pH is also important because of how it affects other pollutants in the water. Very acidic waters can cause heavy metals to be released into the water column. The metals can then be taken up and accumulated in the food chain. Metals in the water, such as copper and aluminum, can accumulate on the gills of fish or cause deformities in young fish, reducing their chance of survival. Ammonia compounds convert to a toxic form in water that is basic. The more basic the water, the more toxic the ammonia that is present.

Go to beginning of Module 11

IV. Nitrates and Ammonia (page 179 SFG)

A. Nitrogen is an essential plant nutrient required by all living plants and animals for building protein. In aquatic ecosystems, nitrogen is present in different forms. The usable forms of nitrogen for aquatic plant growth are ammonia (NH₃) and nitrate (NO₃). Excess amounts of nitrogen compounds can result in unusually large populations of aquatic plants and/or organisms that feed on plants. For instance, some algal blooms are a result of excess nitrogen. As aquatic plants and animals die, bacteria breakdown the organic matter into the final product, ammonia. Ammonia (NH₃ or NH₄) is oxidized (combined with oxygen) by bacteria to form nitrites (NO₂) and nitrates (NO₃)

The cycle for breaking down organic matter (both the biological process and the chemical process) uses up the oxygen present in the water.

B. Sources of Excess Nitrates and Ammonia in Streams

• Poorly functioning septic systems.
• Inadequately treated wastewater from sewage treatment plants.
• Storm drains.
• Runoff from feed lots and barnyards.
• Runoff from crop fields and lawns.

Septic systems are a common wastewater treatment method in many areas. Instead of a centralized wastewater treatment plant, which exist in most urban settings, people with septic systems have individual wastewater treatment. A septic system is comprised of a main pipe from the house to the septic tank, and a number of pipes with holes in them leading from the septic tank. These pipes are arranged in a grid that usually lies over stone and gravel and is called a "drain Field." Wastes from toilet, kitchen sink, bathtub and washing machine flow through an underground pipe to a septic tank. In the septic tank solid matter settles out and floating grease is skimmed off. The remaining liquid enters the drain field through the holes in the pipes and trickles through the stone, gravel, and soil. In properly functioning systems, soil particles remove nutrients, like nitrates and phosphates, before they reach groundwater or surface water. People who neglect septic tank maintenance may allow their tanks to overfill with solids. This results in wastes going directly to the drain field instead of settling in the tank. The drain field becomes plugged and the liquid wastes are no longer filtered through the soil. In this condition, household sewage may pool on the ground and enter surface water through runoff.

Go to beginning of Module 11

V. Phosphorus (page 180, SFG)

A. Phosphorus usually take s the form of phosphate (PO₄) in water. Phosphorus is also a plant nutrient. It is often the limiting nutrient for plant growth, as it is less prevalent in the surface water than nitrogen. Small increases in phosphorus, however, can result in a large impact on the growth of aquatic plants. Phosphorus binds readily with soil particles. Soil must be highly saturated with phosphorus before excess amount s are detectable in shallow ground water that can enter streams and cause a negative impact.

B. Sources of Phosphorus in Streams

• Septic systems and wastewater from sewage treatment plants.
• Runoff from feed lots, poultry farms, and from the application of animal wastes on fields.
• Runoff of commercial fertilizer from crop fields, lawns, golf courses, etc.

NITRATES + NITRATES as NITROGEN in mg/L

TOTAL AMMONIA as NITROGEN in mg/L

TOTAL PHOSPHORUS in mg/L

Go to beginning of Module 11

VI. Conductivity (page 181, SFG)

A. Conductivity is a measurement of the amount of electrical current that can pass through water. This is determined by the amount of solids that are dissolved in the water. Rainfall, interacting with the atmosphere, the biosphere, and the rocks and soil, is a major source of dissolved solids in streams. Groundwater entering streams is another source. Water is uncommonly good at dissolving a wide variety of materials. It is the medium that allows the necessary biochemical reactions in organisms to proceed, carries needed minerals and nutrients to living organisms and transports wastes away.

B. Seven common substances make up about 99% of the dissolved solids in streams. These include in their approximate order of abundance in Missouri waters:

• Bicarbonate
• Calcium
• Magnesium
• Sulfate
• Chloride
• Sodium
• Potassium

It is not surprising that the three most abundant dissolved substances come from the dissolution of limestone and dolomite, Missouri's most abundant rocks. The remaining one percent of dissolved substances can vary considerably, but can include nitrates, metals, ammonia, phosphorus, and manmade compounds such as pesticides and fuels. Conductivity is a general indicator of water quality. Unexplained changes in conductivity can indicate problems in the watershed.

C. Conductivity varies primarily due to the influence of rainfall or snow melt. Because precipitation is low in dissolved solids, an un-impacted stream which has recently received rainfall will have a lowered conductivity value. The conductivity values below are typical reading for various waters and geographic regions.

Go to beginning of Module 11

VII. Turbidity (page 182, SFG)

Turbidity measures the clarity of water. Cloudy water is most often caused by suspended matter (such as soil particles) and plankton (such as algae.) By measuring turbidity, therefore, you can evaluate whether excess soil erosion or algal growth is occurring. Previously discussed methods for measuring nutrient loads can determine if a stream is at risk for excess algal growth. Some measurement of suspended solid matter is necessary, however, to look at the issue of erosion. Situations indicating a need for turbidity monitoring include:

• Developing areas where a great deal of construction and land disturbance is occurring.
• Downstream from quarries and gravel mining operations. These activities can result in fines entering a stream and smothering habitat.
• Agricultural areas that have not adopted best management practices to prevent soil erosion.

The water chemistry and biological data can show variation between streams in a general area, and even for the same location. There are seasonal variations and even time of day variations. In reviewing the data, there are several questions that can be asked, and those answers will provide some clues in assessing the overall ecological health of the stream.

Does the stream meet the minimum standards for water quality? The following excerpts from the state's water quality standards. The water quality standards are state rules established by the Missouri Clean Water Commission and set the minimum requirements for water quality for all waters of the state. A comparison of data against these minimum criteria will show whether there are any serious violations of the state standards.

Are there apparent impacts on water quality that need to be addressed? Are these impacts within the normal variation of the stream or the area, or do they appear to be significant and beyond what might be expected?

Are there readily apparent sources for the impacts that are seen? Are these sources similar to the types of activities that are regulated through permits, or are they sources that might be improved by voluntary actions?

Dissolved Oxygen:

Cold Water Fisheries: 6 mg/L minimum

All other Waters: 5 mg/L minimum

pH:

1. to 9 units

Temperature:

Cool Water Fisheries: <5 increase, 84 maximum

Cold Water Fisheries: <2 increase, 68 maximum

All other Waters: < 5 increase, 90 maximum

Nitrate:

10 mg/L (applies to drinking water supplies)

Ammonia:

Variable depending on water pH and temperature which affect ammonia toxicity.

Conductivity:

There is no numeric standard for conductivity. There are, however, numeric standards for sulfate and chloride. Conductivity values in excess of 1200 µmhos/cm could mean an exceedance of the sulfate or chloride standard for public drinking water supply sources. If the conductivity value exceeds 2800 µmhos/cm then the sulfate plus chloride standard for protection of aquatic life could be exceeded. Both of these scenarios would warrant further investigation

* Streams with permanent flow or permanent pools in dry weather capable of supporting diverse aquatic fauna.

Water Quality Standards General Criteria

The following water quality criteria shall be applicable to all waters of the state at all times, including mixing zones. No water contaminant, by itself or in combination with other substances, shall prevent the waters of the state from meeting the following conditions:

Waters shall be free from substances in sufficient amounts to cause the formation of putrescent, unsightly, or harmful bottom deposits or prevent full maintenance of beneficial uses;

Waters shall be free from oil, sum, and floating debris in sufficient amounts to be unsightly or prevent full maintenance of beneficial uses;

Waters shall be free from substances in sufficient amounts to cause unsightly color or turbidity, offensive odor or prevent full maintenance of beneficial uses;

Waters shall be free from substances or conditions in sufficient amounts to result in toxicity to human, animal or aquatic life;

There shall be no acute toxicity to livestock or wildlife watering;

There shall be no significant human health hazard from incidental contact with the water;

Waters shall be free from physical, chemical, or hydrologic changes that would impair the natural biological community; and

Waters shall be free from used tiers, car bodies, appliances, demolition debris, used vehicles or equipment and solid waste as defined in Chapter 260.200, RSMo, except as the use of such material is specifically permitted pursuant to section 260.200-260.247.

Reproduced from the "Volunteer Water Quality Monitoring Program", Chapter 4, pages 1-18.

VISUAL SURVEY

• fill the turbidity tube completely full with stream water and look down the tube to see if you can see the two black lines at the bottom of the tube.
• If you can see the lines, record a value of 0 JTU next to your entry for water color on line #13 on the Visual Survey.
• If you cannot see the black lines, pour water out of the tube little by little until you can see them. Determine the level of water in the tube and read the number off the outside of tte tube that most closely matches the level of the water.
• If the water level is between two numbers, you can record half values.
  

pH PROCEDURE

Operating Procedure:

• Remove the protective cap and turn the meter on by pressing or pushing the small black on/off switch at the top end of the unit.
• Immerse the end with the pH electrodes into the stream. Do not immerse to a depth greater than 1.5 inches; this depth is indicated by the raised line that encircles the electrode-end of the unit.
• Gently stir the water with the immersed end of the meter until the digital display stabilizes.
• Record the pH value on your data sheet and turn the meter off.
• After you are finished, rinse the electrodes with clean water to minimize contamination.
• Replace the protective cap and put the meter back in your groupÕs equipment bag.
• For long term storage, put a few drops of pH 7 buffer solution in the meter's protective cap.

Calibration Procedure:

• Pour a small amount of pH 7 buffer (enough to cover the glass bulb and white wick on the bottom of the pen) into a clean, dry cup.
• Submerge the pen in the pH 7 buffer, stir gently and wait for he reading to stabilize.
• Insert a small screwdriver into the hole in the back of the pen. A precision or eyeglass screwdriver less than 2 mm will work.
• Turn the screw until the reading indicates a pH of 7.0. This completes calibration.
• Discard the used pH 7 buffer. Do not reuse it.

Troubleshooting the pH pen:

• If you turn the pen on and get a blank digital readout, replace the batteries. The batteries are located in the top of the pen and can be accessed by GENTLY removing the black, rectangular top. The battery holder is attached by wires to the mechanism and the wires may separate if force is applied.
• If the digital readout continually drifts in one direction or if the readout bounces around between numbers, try these procedures in the following order:
• Allow the pen to soak in buffer or tap water for approximately 10 minutes. The white wick on the bottom of the pen must be saturated for the passage of hydrogen ions upon which pH readings are based.
• If readings continue to be erratic, wash the bottom of the pen with dish soap and warm water. Deposits on the wick or glass bulb can cause errors in measurement.
• The final step is to soak the bottom of the pen in a weak acid (such as vinegar) and/or a weak solvent (such as alcohol). Rinse pen after a few minutes of soaking.
• Some problems with the electronic pens are caused by temperature extremes. If your equipment malfunctions in the field, try it again after it has been at room temperature for a few hours. If it works at room temperature, be more cautious about how the equipment is transported to the field, paying particular attention to avoiding extreme temperatures.
• If the pH pen continues to malfunction after trying these procedures, contact the Volunteer Water Quality Monitoring Coordinators for replacement.

CONDUCTIVITY PROCEDURE

Operating Procedure:

• Remove the protective cap and turn the unit on by sliding the on/off switch on the top of the unit to the outside (or "on") position. Be very careful not to touch the metal sensors.
• Immerse the sensor-end of the unit into the water to be tested. Be sure that the sensors are completely submerged, but do not immerse the unit deeper than 1.5 inches; this depth is indicated by small raised marks on the front and back side of the unit.
• Wait for the displayed value to stabilize.
• Multiply the stabilized value by 10, and record this number on your data sheet.
• Turn the unit off and replace the protective cap.

Calibration Procedure:

• Pour a small amount of the sodium chloride standard into a clean, dry cup. A volume that will cover the two metal rods on the bottom of the pen is sufficient.
• Insert a screwdriver into the back of the pen and turn until a reading of 100 appears in the display. The label on the solution lists several different values. 1,000 (plus or minus 5 mg/L) µmhos/cm is the value used for calibrating the conductivity pen. All conductivity readings are multiplied by 10 to arrive at the final measurement. Hence, 100 x 10 = 1,000, the true value of the standard solution. This multiplication factor is indicated by a small 10 in the upper left hand corner of the digital readout.

Troubleshooting the Conductivity Pocket Meter:

• Troubleshooting the conductivity pocket meter is similar to the pH pen with one exception. The two rods on the bottom of the meter function as an anode and a cathode. Because of the principle on which this measurement is based, the pen drying out does not cause measurement error. It is unnecessary, therefore, to soak the pen in tap water.
• If the conductivity meter continues to malfunction after trying the troubleshooting procedures, contact the Volunteer Water Quality Monitoring Coordinators for a replacement.

NITRATE TESTING PROCEDURE

• Take the Water Sample Bottle from the nitrate3 testing kit and fill it with stream water.
• Fill one of the two test tubes to the 2.5 mL line with water from the sample bottle. Hold on to the remaining water in the Water Sample Bottle for use in the next test (the dissolved oxygen test)
• Add Mixed Acid Reagent to the same test tube, filling it to the 5 mL line. Replace the lid on the reagent bottle.
• Place a blue cap on the test tube, shake it, and wait 2 minutes.
• Using the 0.1 gram spoon, add one level measure (avoid any excess) of Nitrate Reducing Reagent to the test tube. Place the blue cap back on the tube and gently invert the tube back and forth for one minute. Wait 10 minutes.
• Insert the test tube into the Nitrate-N Comparator. Match the color of the sample with one of the standard colors in the comparator. Record this value on your data sheet.
• Properly dispose of sample and return everything to its appropriate place in the test kit box.

DISSOLVED OXYGEN TESTING PROCEDURE

• Take the Dissolved Oxygen bottle (the round bottle with the glass stopper) from the dissolved oxygen testing kit and fill it with sample water. Do this by immersing the bottle into the stream and allowing water to flow over it for 2 to 3 minutes.
• After the bottle is filled, incline the bottle slightly and insert the stopper. Take care not to trap any bubbles in the bottle. If you do, you should start over.
• Using the scissors provided, open one Dissolved Oxygen 1 Reagent Powder Pillow and one Dissolved Oxygen 2 Reagent Powder Pillow. Add the contents of each of the pillows to the bottle.
• Add a little of the leftover water from Water Sampling Bottle from the nitrate test. Then replace the stopper with a quick thrust, being careful to avoid trapping any air bubbles in the bottle. If you do, youÕll need to start over.
• Gripping the bottle and stopper firmly, shake it vigorously to mix the sample water and the reagents. A flocculant precipitate (or, simply, a floc) should form. If oxygen is present, the precipitate will be brownish orange in color. A small amount of powdered reagent may remain stuck to the bottom of the bottle; this will not affect the results.
• Allow the sample to stand until the floc has settled halfway in the bottle, leaving the upper half of the sample clear. Shake the bottle again, and again let it stand until the upper half of the sample is clear.
• NOTE: The floc will not settle in samples with high concentrations of chloride. No interference with the test results will occur as long as the sample is allowed to stand for 4 to 5 minutes.
• Using the scissors, open one Dissolved Oxygen 3 Reagent Powder Pillow. Remove the stopper from the bottle and add the contents of the pillow. Carefully place the stopper back on the bottle and shake to mix. The floc will dissolve and a yellow color will develop if oxygen is present.
• Fill the plastic measuring tube level full of the prepared sample. Pour the sample into the square mixing bottle.
• Add Sodium Thiosulfate Standard Solution drop by drop to the mixing bottle, swirling to mix after each drop. Hold the dropper vertically above the bottle and count each drop as it is added. Continue adding drops until the sample changes from yellow to colorless.
• Each drop used to bring about the color change is equal to 1 mg/l of dissolved oxygen (D.O). Record this value on your groupÕs Water Chemistry Summary Sheet. HOWEVER, if the result of your test is very low number (3 mg/L or less), your group will need to do the Low Range Test.
  

• Use the prepared sample that's left in the sample bottle from the High Range Test. Pour off the contents of the sample bottle until the level just reaches the 30 mL mark on the bottle.
• Add Sodium Thiosulfate Standard Solution drop by drop directly to the sample bottle. Count each drop as it is added and swirl the bottle constantly to mix while adding the titrant. Continue adding drops until the sample changes from yellow to colorless.
• Each drop of Sodium Thiosulfate Standard Solution used to bring about the color change is equal to 0.2 mg/L of dissolved oxygen. Multiply number of drops by 0.2 the concentration of dissolved oxygen in m/L. Record this value on your groupÕs Water Chemistry Summary Sheet
• When your group is finished with its dissolved oxygen test, return everything to the test kit box and put the box back in your groupÕs equipment bag. Make sure that you wrap a small piece of paper around the stopper before putting it in the sample bottle for long-term storage.

CARE OF STANDARD SOLUTIONS

• Cap all solutions tightly. Evaporation can change the value of the standards and effect all subsequent readings.
• The pH and conductivity standards are sodium chloride and potassium chloride solutions, both common salt solutions. To prevent contamination, instruments should be rinsed with tap or deionized water before calibration procedures. This minimizes the problem of contamination by what may be on the pen from previous usage. Excess wat4er from the rinsing process, however, can also contaminate a standard by diluting it. Gently pat the instruments dry before inserting into the standards.

DISPOSAL OF STANDARD SOLUTIONS AND CHEMICAL REAGENTS:

• All reagents should be placed in a container and disposed of after the monitoring event. Do not dispose of reagents by dumping them into the monitored stream. Most standards and reagents can be safely disposed of by pouring down a drain and letting the tap run for several minutes to dilute salts and acids.
• As previously stated, most reagents are harmless. However, one of the nitrate reagents contains cadmium, and Nessler's Reagent in the ammonia kit contains mercury. These elements are present in very small quantities, but both are heavy metals and are listed as hazardous materials. It is recommended that the solutions that result from the nitrate and ammonia tests be kept separate for disposal in an appropriate facility. There is no cause for concern regarding the mixing of these reagents. Pour them together in a plastic container. A full year of testing will produce less than one half gallon of liquids which can easily be stored in a milk jug. If you have a secure area, you can reduce the volume further by leaving the container cap loose and allowing evaporation to occur. You should label the container and indicate that the solution contains cadmium (Cd). If you test for ammonia, it should also be labeled for mercury (Hg).
• Another option is to return your spent reagents to the volunteer program by bringing them to a Level I or Level II workshop scheduled for your area.
• Another issue regarding reagent disposal is a concern about reinforcing the idea that pouring chemicals down the drain is acceptable. Regardless of the benign nature of most of the reagents, you may want to retain all of your reagents for disposal by the volunteer monitoring program. This will reinforce the concept that care should be taken in deciding what is disposed of in wastewater treatment systems and streams. Again, the volume of waste solution can be reduced through evaporation if there is a secure area available.

Always use clean sample containers and equipment.

Containers and equipment can be washed using a non-phosphate soap and rinsing with tap water or deionized water. Allow to air dry or dry with paper towels. Follow this procedure after each monitoring event.

Rinse sample containers three times with water to be tested.

This helps to assure an unaltered sample by rinsing out any residues that may be present from a previoius sampling event or from the washing procedure.

Reproduced from the "Volunteer Water Quality Monitoring Program", Chapter 8, pages 7-11.