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Alkalinity Protocol PDF

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Alkalinity Protocol Purpose Scientifc Inquiry Abilities To measure the alkalinity of a water sample Use a chemical test kit to measure alkalinity. Overview Identify answerable questions. Students will use an alkalinity kit to measure Design and conduct scientifc the alkalinity in the water at their hydrosphere investigations. study site. The exact procedure depends on Use appropriate mathematics to the instructions in the alkalinity kit used. analyze data. Develop descriptions and explanations Student Outcomes using evidence. Recognize and analyze alternative Students will learn to, explanations. - use an alkalinity kit; Communicate procedures and - examine reasons for changes in the explanations. alkalinity of a water body; - explain the difference between pH Time and alkalinity; 15 minutes - communicate project results with Quality Control Procedure: 20 minutes other GLOBE schools; - collaborate with other GLOBE Level schools (within your country or other Middle and Secondary countries); and - share observations by submitting Frequency data to the GLOBE archive. Weekly Quality Control Procedure: twice a year Science Concepts Earth and Space Science Materials and Tools Earth materials are solid rocks, soils, Alkalinity test kit water and the atmosphere. Hydrosphere Investigation Data Sheet Water is a solvent. Making the Baking Soda Alkalinity Each element moves among different Standard Lab Guide (optional) reservoirs (biosphere, lithosphere/ Alkalinity Protocol Field Guide pedosphere, atmosphere, Distilled water in wash bottle hydrosphere). Latex gloves Physical Sciences Safety goggles Objects have observable properties. For Quality Control Procedure, the above plus: Life Sciences - Alkalinity standard Organisms can only survive in - Hydrosphere Investigation Quality environments where their needs are Control Procedure Data Sheet met. - Quality Control Procedure for Earth has many different environments Alkalinity Lab Guide that support different combinations of organisms. Preparation Humans can change natural Suggested activities: Practicing Your environments. Protocols: Alkalinity All organisms must be able to obtain Prerequisites and use resources while living in a Discussion of safety procedures when using constantly changing environment. chemical test kits GLOBE® 2014 Alkalinity Protocol - 1 Hydrosphere Welcome Introduction Protocols Learning Activities Appendix Alkalinity Protocol – Teacher Support Introduction Advance Preparation Alkalinity and pH are properties of water The Practicing Your Protocols: Alkalinity that are related, but different. Alkalinity is Learning Act iv i ty , wi l l help students the measure of the pH buffering capacity understand the variables that may affect their of the water. pH, on the other hand, is the measurements. acidity of water. (refer to pH Protocol). pH is a very important water quality parameter. Perform the Quality Control Procedure if it has Many plants and animals have very specifc not been done within six months. pH requirements and are harmed by sudden pH changes or extreme pH values. What Measurement Procedures happens to the pH of your water if acid is These kits are based on the technique of added? The answer depends on how much adding a pH sensitive color indicator to the alkalinity is in the water and how much acid sample and then adding an acid titrant solution is added. drop by drop until a color change is observed. Alkalinity is expressed as the amount of There are a number of techniques the students calcium carbonate (CaCO 3) in your water, should follow to take quality data. although other substances can contribute 1. Have the students read the directions to alkalinity as well. The units of alkalinity before they begin to make sure they are either part per million (ppm) or mg/L. understand the procedure. These units are equivalent, as 1 ppm = 2. Measure carefully. Read the volume 1 mg/L. of the sample in the sample bottle at Let us say your water has a high alkalinity. eye level Read at the bottom of the When acid is added to the water, the alkalinity meniscus. neutralizes the acid. Some of the alkalinity will 3. If using a titrator, make sure that the be used up, so that alkalinity will go down. If titrator is being read correctly. Most kits more acid is added, the alkalinity will continue include instructions for the proper use to decrease. Eventually, when the alkalinity of titrators. Make sure the students are is low enough, adding acid will cause the pH familiar with the units on the titrator. to decrease. 4. If the alkalinity kit uses drops, hold the When water has high alkalinity, we say that dropper bottle vertically so that all of the it is well buffered. It resists a decrease in pH drops are the same size. when acidic water, such as rain or snowmelt, 5. During the Quality Control Procedure enters it. Alkalinity comes from dissolved and actual water testing, be sure to rocks, particularly limestone (CaCO ), and note the color change that gives the 3 soils. It is added to the water naturally as correct alkalinity. In many kits, it is an water comes in contact with rocks and soil. intermediate color change that gives the Water dissolves the CaCO , carrying it into correct alkalinity and not the fnal color. 3 streams and lakes. Lakes and streams in For kits with an intermediate color (such areas rich in limestone bedrock will tend to as a LaMotte kit), if you are not sure have a higher alkalinity than those in regions when the intermediate color change with non-carbonate bedrock. occurs, read the titrator or write down the number of drops when you think it If water has an alkalinity below about 100 might be frst occurring. For kits with mg/L as CaCO , it is poorly buffered and pH 3 only one color change during titration, sensitive. A big rainfall or snowmelt event add one more drop to see if the color could add enough acid to lower the pH in a changes further. If it does not, use the sensitive system. This could be harmful to the previous number you wrote down. plants and animals that live there, particularly at certain times of the year (e.g., when fsh or insect larvae are hatching). GLOBE® 2014 Alkalinity Protocol - 2 Hydrosphere Quality Control Procedure Alkalinity Kit Precisions For the Quality Control Procedure, you Different alkalinity test kits have different may make your own baking soda standard precisions. Below are values for the maximum (Making the Baking Soda Alkalinity Standard acceptable differences for some common test Lab Guide). Alternatively, you may purchase kits. a ready-made alkalinity standard solution. Please make sure to note which standard you are using in the Hydrosphere Investigation Kit manufacturer Precision Quality Control Procedure Data Sheet. LaMotte ± 8 mg/L The alkalinity of the baking soda standard is Hach ± 6.8 mg/L approximately 84 mg/L. It is the sum of the (Low Range, 0-10 mg/L) true alkalinity of the baking soda added (70 ± 17 mg/L mg/L) plus the alkalinity of the distilled water (High Range, 0-50 mg/L) used (usually 14 mg/L or less): 70 mg/L + 14 mg/L = 84 mg/L. If your alkalinity test kit is not listed in the The purity of distilled water available table above and you are not certain how to worldwide varies signifcantly. As a result, its determine the precision of your kit, please alkalinity is also variable. Unfortunately, most contact your GLOBE Country Coordinator alkalinity test kits are not capable of producing or the GLOBE Help Desk and provide them accurate measurements for samples of very with the manufacturer and model of your kit. low alkalinities (i.e., less than 30 mg/L). As a result, it is very diffcult to determine the actual Safety Precautions alkalinity of your distilled water and therefore • Students should wear gloves when the alkalinity of your baking soda standard handling chemicals and water that solution. To account for this, the actual may contain potentially harmful measurement of your baking soda standard substances. should be 84 mg/L ±10 mg/L. If the alkalinity • Students should wear goggles when of your baking soda standard is measured working with chemicals. to be less than 74 mg/L or greater than 94 mg/L, prepare a new standard making sure • Local authorities should be consulted your weights and dilutions are accurate. If you on the proper disposal of used are still off by more than ±10 mg/L, you may chemicals. need to replace the reagents of your test kit. Supporting Protocols Ready-made alkalinity standards have pH: Alkalinity is directly related to pH; waters a precisely known alkalinity. During the with higher alkalinity are more resistant to Quality Control Procedure, your resultant changes in pH from the infux of acid. It is, measurement should be the actual alkalinity therefore, important to collect accurate pH of your standard plus or minus the maximum data to compare with your alkalinity data. acceptable difference for your test kit. Atmosphere: Atmosphere measurements, especially precipitation and temperature, are also important for interpreting your alkalinity data. Heavy rain or snowmelt, resulting in an infux of large amounts of freshwater to the system, may decrease your water’s alkalinity. In addition, knowing the geology and soil types of your area may be important for interpreting your alkalinity data. ® GLOBE 2014 Alkalinity Protocol - 3 Hydrosphere Welcome Introduction Protocols Learning Activities Appendix Helpful Hints Questions for Further Investigation • If your students are using multiple What is the relationship between changes kits, mark the items in each kit with a in pH and changes in alkalinity at your site? dot of the same color. Use a different How might the type of rocks and soil in your color for each kit. This will help avoid watershed affect the alkalinity of your water kit contamination by exchanging site? chemicals or titrators between kits. What factors in your environment do you Instrument Maintenance think might cause a change in the alkalinity 1. The alkalinity kit should be kept in a at your site? dry place away from direct heat. Does the alkalinity at your site have a 2. All chemicals should be kept tightly seasonal pattern? Does this same pattern capped. exist at other sites? 3. Chemicals in the kits should last a year if they are not contaminated, and are stored in a dry area away from extreme heat. 4. The alkalinity standard should be kept refrigerated after opening and discarded after one year. 5. Store the titrator with the plunger removed to avoid the rubber end sticking in the tube. ® GLOBE 2014 Alkalinity Protocol - 4 Hydrosphere Making the Baking Soda Alkalinity Standard Lab Guide What You Need o Baking soda (1.9 g) o Stirring rod o Balance o 100-mL graduated cylinder o 500-mL graduated cylinder o Pen or pencil o Distilled water o 500-mL beaker In the Lab 1. Weigh out 1.9 g baking soda and add it to the 500-mL graduated cylinder. 2. Pour distilled water into the cylinder with the baking soda to the 500-mL mark. 3. Pour this baking soda solution into the 500-mL beaker, and stir it with a stirring rod to make sure all of the baking soda has dissolved. 4. Rinse the 500-mL graduated cylinder with distilled water. Measure 15 mL of baking soda solution with the 100-mL graduated cylinder and pour it into the clean 500-mL graduated cylinder. 5. Add distilled water to the solution in the 500-mL graduated cylinder to the 500-mL mark. 6. This solution is your standard and has an alkalinity of approximately 84 mg/L. GLOBE® 2014 Alkalinity Protocol - 5 Hydrosphere Quality Control Procedure for Alkalinity Lab Guide Task Check the accuracy of your alkalinity kit. Practice using the alkalinity test kit correctly. What You Need o Hydrosphere Investigation Quality Control o Goggles Data Sheet o Pen or pencil o Alkalinity test kit o Latex gloves o Alkalinity standard (A standard may be purchased or you can mix a standard o 100-mL graduated cylinder following the Making the Baking Soda Alkalinity Standard Lab Guide.) o Distilled water in wash bottle In the Lab 1. Put on the gloves and goggles 2. Fill in the top part of the Hydrosphere Investigation Quality Control Data Sheet. Make sure to note the type of alkalinity standard you are using, as well as your kit’s manufacturer and model number. 3. Measure the alkalinity of your standard solution following your kit’s directions. Note: Use the alkalinity standard as your water sample. 4. Record the results on the Hydrosphere Investigation Quality Control Data Sheet. 5. Compare your results with the value of your alkalinity standard: - if you using the baking soda standard, your results should be 84 mg/L ± 10 mg/L. - if you are using a ready-made standard, your results should be the actual alkalinity of your standard plus or minus the maximum acceptable difference for your test kit. Maximum acceptable differences for common alkalinity test kits Kit manufacturer Precision LaMotte ± 8 mg/L Hach ± 6.8 mg/L (Low Range, 0-10 mg/L) ± 17 mg/L (High Range, 0-50 mg/L) 6. If your measured values are not within the expected range, try doing the procedure again using a fresh standard sample. 7. If your value is still not within range, discuss possible problems with your teacher. GLOBE® 2014 Alkalinity Protocol - 6 Hydrosphere Alkalinity Protocol Field Guide Task Measure the alkalinity of your water sample. What You Need o Hydrosphere Investigation Data Sheet o Distilled water in wash bottle o Alkalinity test kit o Goggles o Gloves o Pen or Pencil In the Field 1. Fill out the top portion of your Hydrosphere Investigation Data Sheet. 2. Put on the gloves and goggles 3. Follow the instructions in your alkalinity kit to measure the alkalinity of your water. 4. Record your measurement on the Hydrosphere Investigation Data Sheet as Observer 1. 5. Repeat the measurement using fresh water samples. 6. Record as Observers 2 and 3. 7. Calculate the average of the three measurements. 8. Each of your individual measurements should be within the acceptable range of the average. Maximum acceptable differences (precision) for common alkalinity test kits Kit manufacturer Precision LaMotte ± 8 mg/L Hach ± 6.8 mg/L (Low Range, 0-10 mg/L) ± 17 mg/L (High Range, 0-50 mg/L) 9. If one measurement is outside this range, discard that measurement and fnd the average of the other two. 10. If they are still in range, report only the two measurements. 11. If more than two of your measurements are not in range, repeat from Step 3. GLOBE® 2014 Alkalinity Protocol - 7 Hydrosphere Frequently Asked Questions 2. Should I worry if my water site has very low alkalinity? 1. How can I be sure when the color Some areas will naturally have change has happened? low alkalinity. This might be true Become familiar with the color change by in mountain streams. The waters have not doing the Quality Control Procedure. contacted rocks or soil long enough for the rocks to dissolve. This just means that these areas are more sensitive to acid additions. ® GLOBE 2014 Alkalinity Protocol - 8 Hydrosphere Collecting Data Alkalinity Protocol – The student examines the daily data. Three Looking at the Data of the alkalinity data points seem very low. On August 15, 1997 the reported Are the Data Reasonable? alkalinity was 1 mg/L and on September Alkalinity values range from close to 0.0 ppm 15 and September 18 1998 i t was to more than 500 ppm, although most water 9 mg/L. These values seem very low bodies will have values between 40-300 ppm. compared to the rest of the values. However, Discovering unusual values in the data often she decides to go ahead with her analysis and depends on knowledge of typical patterns at a hope the data are correct. site. If a site has been measured with almost She wants to eliminate some of the noise no alkalinity for many months, then suddenly (scatter) in the plot in order to see the has 300 ppm, students should recognize relationship more clearly. She plots the a deviation from the normal pattern and monthly average total rainfall and average investigate further. Other sites may naturally alkalinity for the fve full years of the record, have large swings in alkalinity in response to 1997-2001. See Figure HY-AL-2. She then precipitation, snowmelt, or other inputs into downloads the monthly data (total rainfall, the system. number of days rainfall was measured, average alkalinity and number of days What Do the Scientists Look for in alkalinity was measured) and imports them the Data? into a spreadsheet. Scientists are interested in how well a water Analyzing Data body may be buffered against acid input. Streams with naturally low alkalinity are more The student notices that not all months had sensitive. The pH may drop dangerously low rainfall data recorded every day. Instead of with a relatively small acid input. Scientists looking at total rainfall for each month, she would also be interested in investigating decides it will be more appropriate to look at areas that show large swings in alkalinity. the average rainfall per day. By doing this, These areas may be receiving very large she assumes that any missing days will have amounts of acid. Even though a stream about the same amount of average rainfall has alkalinity to help buffer the acid input, as the rest of the days of the month. She alkalinity will eventually be neutralized by the calculates the average by dividing the total acid, resulting in a lower pH. amount of rainfall (mm) by the number of days the measurement was reported. [For Example of a Student Research example, the total precipitation in April 1997 was 113.4 mm, measurements were reported Project on 30 days, and so the average precipitation Forming a Hypothesis was 3.78 mm/day]. A student is looking at the alkalinity data Then she eliminates months for which there from SWS-02 at Crescent Elk School in is no value for either total precipitation or California. This water body is Elk Creek, a average alkalinity. Six of the 60 months have small freshwater creek. She notices that no average alkalinity data, 3 months have although there is a lot of scatter in the data, no total precipitation data, and 1 month, Oct- the values seem to be highest in the summer, 2001, does not have either. After she does and lowest in the winter. She knows that this, she has 50 months left of data. precipitation can sometimes affect alkalinity, so she plots rainfall and alkalinity, shown She sorts her data by precipitation as shown in Figure HY-AL-1. Precipitation is clearly in Table HY-AL-1 and then calculates the highest from November through March, and average precipitation and alkalinity for lowest in July and August. each 10-month block. The ten months with the highest average rainfall include one She forms her hypothesis: In Elk Creek, November, two Decembers, three Januarys, alkalinity is highest when rainfall is lowest and three Februarys and a March, with an average alkalinity is lowest when rainfall is highest. GLOBE® 2014 Alkalinity Protocol - 9 Hydrosphere Welcome Introduction Protocols Learning Activities Appendix rainfall rate of 12.7 mm/day. Alkalinity ranges Further Thoughts and Future Research from 55 to 72 ppm, with an average of 66 There are some other aspects this student during these months. As rainfall decreases needs to consider. To what extent is the for the next three sets of months (from stream affected by snowmelt? How much 5.5 to 3.3 to 1.4 mm/day), the 10-month does snowfall contribute to total precipitation average alkalinity is in the 70s: 74, 79 and 76 in this watershed? How might the snowmelt mg/L. During the 10 months with the lowest during the spring affect the alkalinity even in precipitation (10-month average only 0.1 mm/ months with little rainfall? day), the alkalinity ranges from 66 to 99, with This site has fairly low alkalinity all year an average of 86 mg/L. These months include long (less than 100 mg/L as CaCO ). Would one June, three Julys, four Augusts, and two 3 a site with higher alkalinity show as much Septembers. So, she is satisfed that, on change? How about a site with more seasonal average, the alkalinity is higher during months precipitation? with very little rainfall than it is during months with high rainfall. Next, she takes the same data and sorts them by alkalinity rather than rainfall, and again calculates 10-month averages in a spreadsheet, as shown in Table HY-AL-2. The sorted 10-month averages show a good trend. For average alkalinities of 94, 81,75, 70 and 61 mg/L, the average rainfall is 1.6, 2.7, 3.5, 6.5 and 8.7 mm/day, respectively. Most of the ten highest alkalinities occur from June through September, although there is one March and one April. Monthly average rainfall associated with the 10 highest transparencies range form 0.0 to 4.4 mm/ day. Eight of the 10 lowest alkalinities were recorded from November to March; the other two months were in May and in August, both of which had low rainfall. Monthly average rainfall ranges from 0.0 to 16.9 mm/day (the lowest and highest values) despite the high 10-month average. The student feels she has enough data to support her hypothesis. She prints out her plots and tables and writes her results as a report and asks her teacher to submit it to the GLOBE Website. ® GLOBE 2014 Alkalinity Protocol - 10 Hydrosphere

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