2012/13
Chemistry instructions for sampling and analysis onsite. The parameters to measure, in the river water, are: pH, temperature, dissolved oxygen, nitrates and phosphorus (as phosphate). They are part of our syllabus and are well-tested scientifically for water sampling . • pH is the measure of the acid content of a substance (in this case water), it influences chemical processes in the waterbody and indicates how hospitable a waterbody is to aquatic life. • water temperature is also an important factor for determining what will live in a waterbody. It‟s largely determined by the amount of solar energy absorbed by the water, but it can also be indicative of where the water originates and how it is being used, for instance for industrial uses. • the amount of dissolved oxygen in a water body also affects whether a waterbody can provide optimal habitat for fish and other aquatic life. If compared to the maximum allowed by the temperature of the water, it tells more about capacity of self-purification and/or eutrophication • nitrates are a chemical compounds that can dissolve in water, they are some of the major nutrients needed for plant growth. Their overabundance is often related to eutrophication • phosphorus is another plant nutrient. Generally it is suspended in waters in its organic form or found in sediments. It limits the growth of aquatic plants. It‟s the major chemical responsible of eutrophication. There also two additional parameters: Biological oxygen demand (BOD5) and Fecal Coliform bacteria. • Biological oxygen demand (BOD5) is the amount of oxygen necessary to naturally breakdown or biodegrade and cleanse the river of organic matter suspended in the water. It can be related to the nutrient circle and/or to the degree of pollution in the water.
•
Fecal Coliform are microorganisms (bacteria) that indicate fecal contamination in surface waters, and often originate from sewage systems or waste from animals
1) Take water sample Wheaton Sub Surface Grab Sampler® I The Sub Surface Grab Sampler® is ideal for sub-surface sampling (eliminates surface contamination) for water and wastewater sampling. This lightweight unit affords you easy access to samples from spillways, docks, etc., without your having to physically enter the effluent. It is constructed of 72" x 3/4" square aluminum tubing with a golden anodine finish. It comes with a 1000 mL narrowmouth sample bottle with a PTFE-lined cap and clamps for large and small bottles.
2) Measure pH
Purpose To measure the pH of water Overview Students will use a pH-meter to measure the pH of water based upon the students level and equipment availability. If using the pH-meter, the instrument needs to be calibrated with buffer solutions at pH values of 7, and 4 or 10. Three
measurements in agreement with each other are needed to obtain an average value to report on the Data sheet.
Student Outcomes with this activity Students will learn to: • Use either a pH meter in a scientific measurement context; • Understand the differences among acidic, basic and neutral pH values • Examine reasons for changes in the pH of a water body; • Relate the pH to the optimal conditions for aquatic life Time required for pH-measurement 10 – 15 minutes Level of students: they can use a pH-meter, after a little lab training. Materials and Tools For measuring pH with the pH-meter: • Portable pH-meter for field measurements (permits precise measurements from 0,1 to 0,01 pH units). • Batteries for alimentation of pH-meter • Buffer solutions for pH-calibration (usually included by the manufacturer into the portable pH-meter kit) at pH=7, pH= 4, pH=10. • Jars with lids to put in little amounts of buffer solutions (usually included by the manufacturer into the portable pH-meter kit) • Distilled water in a wash bottle • Clean paper towel • 50-mL or 100-mL beaker • Latex gloves • Salt crystals (table salt NaCl in large crystals) to correct the total salinity of the water of your river. NOTE for teachers: This salt is necessary if your river is supposed to have less than 200 mS/cm of total conductivity – in every case, a small amount of salt added doesn‟t change the pH value, it only permits a good functioning of the pH-meter. Preparation (in lab, before field activity) For measuring pH with pH-paper: • Verify that the pH paper was stored in its own box in a dry place. It should not be stored in too hot or wet environments. Discard the paper if it gets wet or damp during storage.
For measuring pH with the pH-meter: • Verify the conditions of the glass-bulb of the electrode of the pH-meter: glass membrane must be hydrated with a fully immersion into stock solution (consult your manual for maintenance and storage instructions) • Verify the conditions of the external reference standard solution and of the porous septum • Verify the conditions of the alimentation batteries – having an extra-set on hand is a good idea! • Read carefully the instructions for calibration and measurement steps that come with the kit. • NOTE: Normally a pH=7 buffer solution is needed as first step. After calibrating with this first buffer, usually another buffer solution can be chosen to complete the calibration (pH=4 for acid range measurements or pH=10 for basic range measurements). So, you can choose the most useful range for your purpose, 4-7 pH units or 7-10 pH units, related with the expected pH of the water of your river. • Verify in the lab with a calibration and a couple of of measurements to ensure the instrument (as described in “Field procedure”) functions correctly. Measurement of the pH with pH-meter Field procedure 1. Switch on the instrument before the measurements for the time recommended by manufacturer‟s directions (for some instruments it could be half an hour before) 2. Put on the latex gloves 3. Remove the protection cap from the electrode-bulb, that is the sensitive part of the instrument. 4. Rinse accurately the electrode, especially the bulb, with the distilled water; Dry it gently with a clean paper towel. NOTE: don‟t rub the electrode or touch it with your fingers 5. Calibrate the pH-meter. NOTE: Calibration is needed before every use. Even if you calibrated the instrument in the lab, you must repeat this step at your observation site as well! Please, follow the instructions that come with your pH-meter. Normal steps foreseen for calibration: a. Submerge the electrode (and the temperature probe together, if supplied) into the jar containing the pH=7 calibration buffer solution b. Gently stir once in the solution with the meter
c. Wait for a stable lecture of pH on the display. NOTE: Don‟t submerge the whole instrument during use! Pay attention that the porous septum is fully merged into the buffer solution and the bulb doesn’t touch the bottom or the sides of the jar! d. Calibrate the instrument according to the manufacturer‟s instructions e. Rinse the electrode again with distilled water f. Gently dry the electrode with a clean paper towel. Repeat all operations from a) to f ) with the second buffer solution. You must choose the buffer at pH=10 if the expected pH value for water is higher than 7, and if the opposite, you‟ll choose the pH=4 buffer. 6. Rinse a 100-mL beaker three times with sample water, and after that collect a 50-mL sample for the measure. Alternatively, you can insert the electrode directly into the river, if it is easy and safe (for you and for the electrode!) and if salinity correction (see point 8) is not required. 7. If you are taking the measurement in a beaker, use the tweezers to place two or three crystals of salt in the sample water, and stir it until they are dissolved. NOTE: This step is necessary to increase the total salt amount in the water to obtain a correct pH-measurement. If you don‟t know the salt level in the waterbody or its hardness, please follow the above step in order to obtain a correct pH value . In salt water or in hard water you can skip to the next step (ask your teacher if you are in doubt). 8. Put the electrode in the water and gently stir it once. NOTE: see note at point 6.c again! 9. Wait until the value of the pH on the display is stable and record the obtained data in your Water Quality data-sheet under “Observation 1”. 10. Without switching off your pH-meter, repeat steps from 7 to 9 twice using new water samples and record the collected data under “Observation 2” and “Observation 3”. 11. Check to see if the three measurements are within 0,2 units each other. If so, record the average on the Data sheet. If one measurement is out of range more than 0,2 from the others, repeat the measurements (if you cannot get three measurements within 0,2 of one another, ask your teacher about possible problems). 12. When finished, rinse the electrode with distilled water, put the cap on to protect the electrode, and add a few drops of stock solution (see manufacturer‟s instructions). 13. Rinse the beaker with distilled water and be sure to put all the materials into the countainer again! Looking at the data
pH is a measure of the acid content of water. The pH of water influences most of its chemical processes. Pure water with no impurities (and not in contact with air) has a pH of 7. Water with impurities will have a pH of 7 when its acid and base content are exactly equal and balance each other out. At pH values below 7 there is excess acid, and at pH levels above 7 there is excess base in the water. The pH scale usually ranges from 0 to 14, with 0 being the most acidic and 14 being the most basic.
A pH range between 6.5 and 8.5 is generally suitable in surface waters. Most lakes and streams have pH values that range between 6.5 and 8.5. Oceans are well buffered and have a constant pH of about 8.2. If stream water has a pH less than 5.5, it may be too acidic for fish to survive in, while stream water with pH higher than 8.6 may be too basic. In fact, most animals are adapted to live near neutral conditions. A shift of pH in either direction may indicate the presence of pollution in the stream. However, since some streams could be naturally lightly acidic, or basic, pH may not necessarily indicate pollution. The pH of clean water depends on several factors, including the types of rock and vegetation within the watershed. One can find waters that are naturally more acidic in areas with certain types of mineral presents (e.g. sulfides or siliceous soils). Naturally occurring basic waters are found typically in areas where soils are rich in carbonate rocks. The level of acidity can be changed by humanâ€&#x;s actions. Acid rain, a result of air pollution and particulate matter emitted from tailpipes and smokestacks affect the pH. When these chemicals combine with water in the atmosphere, they form sulphuric and nitric acids and then fall to the earth as acid rain, snow, hail, and fog. This precipitation mixes with water already on the earth in creeks, rivers, ponds and wetlands. Other pollutants carried by runoff from the land can also change the pH of the water. Changes in pH endanger the lives of the organisms in the water. A change in stream water pH can also affect aquatic life indirectly by altering other aspects of water
chemistry. Salamanders, frogs and other amphibian life, as well as many macroinvertebrates, are particularly sensitive to extreme pH levels. Most insects, amphibians and fish are absent in water bodies with pH below 4 or above 10. pH values in a water stream normally don‟t change a great deal, although you can find some seasonal trends due to changes in temperature, rainfall patterns or land cover.
3) Measure temperature
Purpose To measure the temperature of water in the riverbed
Overview Students will use a temperature probe to measure the temperature of water. Three measurements in agreement with each other are needed to obtain an average value to report on the Preliminary data sheet and on the Water Quality data sheet. Student Outcomes with this activity Students will learn to: • Use a thermometer or a probe for temperature measurements in a scientific measurement context • Relate the temperature to the optimal conditions for aquatic life • Relate the temperature with other parameters like Dissolved Oxygen • Examine reasons for changes in the Temperature of a water body;
Time required for temperature measurement 10 – 15 minutes Level of students: can use a temperature probe (portable pH-meter instruments are often equipped with a temperature probe that can be used for this purpose) Materials and Tools • Temperature probe/meter. The probe that comes with portable pH meter is acceptable. • Batteries for alimentation of the temperature instrument (or pH-meter) • (Possibly) a large bucket equipped with a rope tied securely to the handle in order to collect a representative water sample • Clock or watch • Distilled water in a wash bottle • Latex gloves Calibrating the alcohol-filled thermometer or temperature probe: 1. Stir together 100 mL of distilled water and 400 mL of crushed ice in a big beaker or other equivalent bowl, and let it sit for 10 minutes so that it reaches zero degrees 2. Put the temperature probe into the ice-water bath, gently moving it around 3. After two or three minutes, read the temperature without removing the bulb from the ice-water bath 4. Let the thermometer stay in the bath for one more minute and read the value again. 5. The read values should be between –0,5 °C and 0,5°C. If not, notify to your teacher. Temperature probe/meters may have adjustments for calibration. In this case, follow the manufacturer‟s instructions. Measurement of the water temperature. Field procedure 1. If you can easily reach the water surface at your observation site safely, submerge the thermometer or probe 10 cm into the water and make the readings without removing the thermometer from the water. If you can take the temperature safely by inserting the thermometer directly into the water, then go directly to step 3. If not, go to step 2. 2. Alternatively, put your latex gloves on and collect a large amount of water with a bucket attached to a rope. Throw the bucket out to a well-mixed area, a little distance from the shore. If the bucket floats, jostle the rope until some water enters the bucket. You should always take a sample from
the top surface water, without letting the bucket sink to the bottom or stiring up bottom sediment. Allow the bucket to fill about 2/3 to ¾ full. If possible bring the bucket to a shady place and quickly go to the next step. 3. Slip the rubber band or string around your wrist so that the thermometer is not accidentally lost or dropped in the water. Put the temperature probe into the water (10 cm under water surface) 4. Leave the probe in the water for two minutes and read the temperature on the meter without removing it from the water. 5. Let the probe stay in the water one more minute and read the temperature again. If the temperature has not changed, go to step 6. If not, repeat from step 4 until the temperature stays the same. NOTE: if you are measuring the temperature of water collected in the bucket, be sure that the water temperature doesn‟t change due to the different temperature conditions of the air, and dio all the steps as quickly as possible. In case of doubt, ask the teacher. 6. Record the temperature on the Preliminary data sheet 7. Have two other students repeat the measurements in the same place or collect new water samples and mark the read values. 8. If the three measurements are within 1,0°C of each other, calculate the average and report the data on the Preliminary data sheet. If the three measurements are not in agreement within 1.0°C of each other, repeat the observations. Take care to leave the instrument in the water long enough for it to stabilise and do not remove the thermometer from the water so that the temperature changes before it can be read. 9. At last, rinse the probe with distilled water. Looking at the data Water temperature is largely determined by the amount of solar energy absorbed by the water as well as the surrounding soil and air. More solar heating leads to higher water temperatures. Water evaporating from the surface of a water body can lower the temperature of water but only for a very thin layer at the surface. Water temperature can sometimes be colder and sometimes warmer than the air temperature, because it has a higher specific heat than air, this means it takes water longer to heat up and longer to cool down than air does. Water temperature can be indicative of where the water originates. Water temperature near the source will be similar to the temperature of the source (e.g., snowmelt will be cool whereas some ground water is warm). Water temperature farther from the source is influenced largely by atmospheric temperature. Temperature affects the oxygen content of water (oxygen levels become lower as temperature increases). It is also an important factor for life in a water body, because the rates of biological and chemical processes depend on temperature.
Warm water can be fatal for sensitive species, such as trout or salmon, which require cold, oxygen-rich conditions.
Fish-life temperature guide-values Lower T (째C)
Higher T (째C)
SALMONIDES
10 (during reproduction)
21,5
CIPRINIDES
-
28
Causes of temperature change include weather, removal of shad providing streambank vegetation, impoundment (a body of water confined by a barrier, such as a dam), discharge of cooling water, urban storm water, and groundwater inflows to the stream. Thermal pollution is an increase in water temperature caused by adding relatively warm water to a water body. Thermal pollution can come from stormwater running off warmed urban surfaces (streets, sidewalks, parking lots) and industries that discharge warm water from their facilities that was used to cool machinery.
4) Measure Dissolved oxygen
Purpose To measure the amount of dissolved oxygen (DO) in water and to relate it with the maximum amount of oxygen permitted by the temperature and pressure (% of saturation). Overview Students will use a dissolved oxygen probe to measure the dissolved oxygen in the water at their observation site. Student Outcomes with this activity Students will learn to:
• Use a dissolved oxygen probe in a scientific measurement context; • Understand the concept of maximum value for dissolved oxygen (saturation depending upon temperature and pressure conditions) • Transform the absolute value of dissolved oxygen, expressed in mg O2/liter, in a relative measurement related to the maximum amount of oxygen permitted by the temperature (% of saturation), using appropriate mathematics to analyze data • Examine reasons for changes in the dissolved oxygen of a water body; • Examine reasons for % of saturation lower or higher than 100 % • Relate the dissolved oxygen level to the optimal conditions for aquatic life Time required for dissolved oxygen measurement 20 minutes Level of students: they can easily make the measurements with a readily available probe. Measurement of the Dissolved Oxygen Field procedure 1. Put on the latex gloves. 2. Rinse the sample bottle and your hands with sample water three times. 3. Place the cap on the empty sample bottle and submerge the sample bottle in the sample water, partially inclined (directly into the river, if possible, or from a fresh sample taken in a bucket, if the river is not directly accessible). 4. Remove the cap and let the bottle fill with water. Submerge the bottle for several minutes so that the water that first ran in and mixed with the air in the bottle is exchanged with water that has not been exposed to air. Move the bottle gently or tap it to get rid of air bubbles. IMPORTANT: Put the cap on the bottle while it is still under the water. 5. Remove the sample bottle from the water. Turn the bottle upside down to check for air bubbles. If you see air bubbles, discard this sample. Collect another sample. 6. Follow the directions in your Dissolved Oxygen probe to test your water sample. 7. Record your value in your Water Quality data-sheet under “Observation 1”. 8. If possible, have two other students repeat the measurement using a new water sample each time. Record the data under “Observation 2” and “Observation 3”. 9. Calculate the average of the three measurements, only if the observations are within 1 mg/L of each other. If not, find the average of the other two measurements. If you cannot get measurements within 1 mg/L of one another, ask your teacher about possible problems.
10. Dissolved oxygen is measured in mg/litre but you can turn it into percentage of saturation by a scheme of transformation according to water temperature. Using the graph in Table 3 convert this value in percentage of saturation, and report this value on your Data Sheet.
Table 3 – Conversion table between mgO2/L values and % saturation, at different temperatures How to read the graph: 1. Mark the DO value in the scale at the bottom 2. Mark the temperature value in the scale at the top of the graphic 3. Connect the two points with a straight line. Read the % of saturation at the intersection on the diagonal scale. BE CAREFUL: 1. Oxygen solubility is dependent on temperature. It‟s therefore important to collect water temperature data along with dissolved oxygen data. 2. The amount of dissolved oxygen in the water can change rapidly after the sample has been collected. It is therefore important to do this test soon after the sample is collected. The water sample for the dissolved oxygen test should be „fixed‟ at the water site. After the sample is fixed, the sample may be taken back to the school to finish the test. 3. Make sure there is no air in the bottle that contains the water you will test. To check for air bubbles in the sample bottle, turn the bottle upside down while it is capped and look for bubbles. 4. Hold bottles and droppers vertically when adding drops of reagent to your water sample so that all of the drops of reagents are the same size. Looking at the data
Dissolved oxygen analysis measure the amount of gaseous oxygen (O2) dissolved in an aqueous solution. A small amount of oxygen is normally dissolved in water. The amount of dissolved oxygen you measure depends on your water site. Dissolved oxygen is added to water through aeration (water running or splashing), diffusion, and by photosynthesis of aquatic plants. It is used up by respiration. The maximum amount of dissolved oxygen your water can hold (saturated solution) depends on elevation (atmospheric pressure) at your site, water temperature, and salinity of your sample. Dissolved oxygen in natural waters may vary from 0.0 mg/L to around 16.0 mg/L. Distilled water at 0.0 C has a solubility of 14.6 mg/L at sea level. Warm, still waters might have dissolved oxygen levels of about 4 or 5 mg/L. Cold, running waters might have oxygen levels at 13 or 14 mg/L. Higher levels are possible due to photosynthesis by plants and lower levels are possible due to oxygen consumption by respiration of biota (fish, bacteria, etc). Since dissolved oxygen levels are dependent on water temperature as well as other variables such as photosynthesis and respiration in the water, it is helpful to look for seasonal trends. Oxygen is important to all life. Aquatic life needs oxygen to live. Aquatic life uses oxygen that is dissolved in the water even if is in much smaller quantities than in the air. If more oxygen is consumed than is produced, dissolved oxygen levels decline and dissolved oxygen levels below 3 mg/L are stressful to most aquatic organisms. Some sensitive organisms will not live in oxygen levels less than 7.5 mg/L. Dissolved oxygen levels that drop to low levels (i.e., less than 5 mg/L) are a reason for concern. Excess nutrients (e.g., fertiliser, organic-rich wastewater) added to the water body can cause an overgrowth of vegetation and algae which can cause increased biological decay in the water. Observing land cover in your watershed can be useful to understand this aspect. The living biota of water systems makes up only a very small portion of the total organic matter of the system. Most organic matter in aquatic systems is non-living and it‟s collectively referred as “detritus”. The bacteria that decompose the organic matter respire and use oxygen: in that way if water is not sufficiently and fast re-oxygenated, it becomes quickly poor of oxygen, so that fishes and other sensitive animals may move away, weaken, or die. Running water, because of its churning, dissolves more oxygen than still water. In addition to looking at the amount of dissolved oxygen in the water, it is also interesting to compare the amount of measured dissolved oxygen with a calculated value for saturation. This can tell us about the productivity of the water body. In a productive water body, plants will be producing oxygen through photosynthesis. Dissolved oxygen values will vary throughout the day, with maximum value occurring in the early afternoon and lowest levels occurring during the night (when respiration is not balanced by photosynthesis). Cloud cover may result in a decrease of photosynthesis during the day. Some water
bodies may actually have a dissolved oxygen measurement above the saturation level, indicating that more oxygen is being produced by photosynthesis than is being consumed by respiration. Water bodies that are highly turbid have low light penetration typically low dissolved oxygen levels and thus low productivity. Percentages of about 100 % of saturation are ideal for supporting life. Values less then 80% are below the critical threshold. Extremely high values (over 140%) suggest an excessive presence of algae (eutrophication).
5) Measure conductivity Conductivity is a measure of the ability of water to pass an electrical current. Conductivity in water is affected by the presence of inorganic dissolved solids such as chloride, nitrate, sulfate, and phosphate anions (ions that carry a negative charge) or sodium, magnesium, calcium, iron, and aluminum cations (ions that carry a positive charge). Organic compounds like oil, phenol, alcohol, and sugar do not conduct electrical current very well and therefore have a low conductivity when in water. Conductivity is also affected by temperature: the warmer the water, the higher the conductivity. For this reason, conductivity is reported as conductivity at 25 degrees Celsius (25 C). Conductivity in streams and rivers is affected primarily by the geology of the area through which the water flows. Streams that run through areas with granite bedrock tend to have lower conductivity because granite is composed of more inert materials that do not ionize (dissolve into ionic components) when washed into the water. On the other hand, streams that run through areas with clay soils tend to have higher conductivity because of the presence of materials that ionize when washed into the water. Ground water inflows can have the same effects depending on the bedrock they flow through. Discharges to streams can change the conductivity depending on their make-up. A failing sewage system would raise the conductivity because of the presence of chloride, phosphate, and nitrate; an oil spill would lower the conductivity. The basic unit of measurement of conductivity is the mho or siemens. Conductivity is measured in micromhos per centimeter (µmhos/cm) or microsiemens per centimeter (µs/cm). Distilled water has a conductivity in the range of 0.5 to 3 µmhos/cm. The conductivity of rivers in the United States generally ranges from 50 to 1500 µmhos/cm. Studies of inland fresh waters indicate that streams supporting good mixed fisheries have a range between 150 and 500 µhos/cm. Conductivity outside this range could indicate that the water is not suitable for certain species of fish or macroinvertebrates. Industrial waters can range as high as 10,000 µmhos/cm.
Sampling and equipment Considerations
Conductivity is useful as a general measure of stream water quality. Each stream tends to have a relatively constant range of conductivity that, once established, can be used as a baseline for comparison with regular conductivity measurements. Significant changes in conductivity could then be an indicator that a discharge or some other source of pollution has entered a stream. Conductivity is measured with a probe and a meter. Voltage is applied between two electrodes in a probe immersed in the sample water. The drop in voltage caused by the resistance of the water is used to calculate the conductivity per centimeter. The meter converts the probe measurement to micromhos per centimeter and displays the result for the user. Conductivity can be measured in the field or the lab. In most cases, it is probably better if the samples are collected in the field and taken to a lab for testing. In this way several teams of volunteers can collect samples simultaneously. If it is important to test in the field, meters designed for field use can be obtained for around the same cost mentioned above. If samples will be collected in the field for later measurement, the sample bottle should be a glass or polyethylene bottle that has been washed in phosphate-free detergent and rinsed thoroughly with both tap and distilled water. How to sample The procedures for collecting samples and analyzing conductivity consist of the following tasks: TASK 1 Prepare the sample containers TASK 2 Prepare before leaving for the sampling site. In addition to the standard sampling equipment and apparel, when sampling for conductivity, include the following equipment: Conductivity meter and probe (if testing conductivity in the field) Conductivity standard appropriate for the range typical of the stream Data sheet for conductivity to record results Be sure to let someone know where you are going and when you expect to return. TASK 3 Collect the sample (if samples will be tested in the lab) TASK 4 Analyze the sample (field or lab) The following procedure applies to field or lab use of the conductivity meter.
1. Prepare the conductivity meter for use according to the manufacturer's directions. 2. Use a conductivity standard solution (usually potassium chloride or sodium chloride) to calibrate the meter for the range that you will be measuring. The manufacturer's directions should describe the preparation procedures for the standard solution. 3. Rinse the probe with distilled or deionized water. 4. Select the appropriate range beginning with the highest range and working down. Read the conductivity of the water sample. If the reading is in the lower 10 percent of the range, switch to the next lower range. If the conductivity of the sample exceeds the range of the instrument, you may dilute the sample. Be sure to perform the dilution according to the manufacturer's directions because the dilution might not have a simple linear relationship to the conductivity. 5. Rinse the probe with distilled or deionized water and repeat step 4 until finished. TASK 5 Return the samples and the field data sheets to the lab/drop-off point. Samples that are sent to a lab for conductivity analysis must be tested within 28 days of collection. Keep the samples on ice or refrigerated.
Table of Aqueous Conductivities ÂľS/cm Solution Totally pure water
ppm
0.055
Typical DI water
0.1
Distilled water
0.5
RO water
mS/cm
50-100
25-50
Domestic "tap" water
500-800
0.5-0.8
250-400
Potable water (max)
1055
1.055
528
56,000
56
28,000
100,000
100
50,000
Sea water Brackish water