STATE OF OHIO DEPARTMENT OF TRANSPORTATION SUPPLEMENT 1122 DETERMINING SULFATE CONTENT IN SOILS 1122.01 Scope 1122.02 Definitions 1122.03 Equipment 1122.04 Procedure 1122.05 Report July 17, 2015 1122.01 Scope. This supplement describes the test procedure for the determination of the sulfate content of soils using a turbidimetric method. 1122.02 Definitions. A. Turbidimetric Method The process of measuring the cloudiness of a liquid and translating it into concentration. A reagent is combined with a sample, which causes cloudiness or turbidity in the sample. For sulfate testing, barium chloride is the reagent and, in the presence of sulfates, the addition of barium chloride causes a white cloud of barium sulfate to form. The darker or more intense the cloud, the higher the amount of sulfate present. B. Filtrate Soil and water mixture that has passed through a filter. 1122.03 Equipment. A. Colorimeter and associated accessories, as necessary: 1. Glass sample vials. 2. Sulfate reagent chemicals (tablets or powder). 3. Mixing rod. 4. Calibration blank. Note: Department uses the CHEMetrics V-2000 Photometer and their associated Sulfate Vacu-vial Kit, K-9203, that includes: Vacu-vial ampoules; Acidifier Solution (HCl); Activator Powder (Barium Chloride); 25mL sample cup; and an ampoule blank. B. Filtration system, either: 1. Gravimetric filtering system that includes: a. Funnel, short stem, glass or plastic, approximately 80 mm diameter. 1
b. Filter paper, qualitative, fine porosity, 2.5 to 1.0 μm. (For example, Whatman Grade 5, VWR Grade 410.) c. Beakers, glass or plastic, 600 ml. 2. Vacuum filtering system (Note: Department uses a system from EMD Millipore) that includes: a. All-glass filter holder assembly (90 mm) with funnel, fritted base, cap, and clamp. b. Filter membrane, Hydrophilic, 0.45 μm, 90 mm. (For example, Durapore Membrane Filter (PVDF), #HVLP09050.) c. Vacuum filtering flask (1 L), vacuum pump, and vacuum hose. C. Balance and pans. D. Fine aggregate sample splitter. E. Mortar and pestle. F. Sieves, U.S. Standard No. 4 and No. 40 with pan. G. Bottles, 500 ml, polyethylene. H. Distilled or deionized water. I. Disposable pipettes, 2 ml. J. Graduated cylinder, 10 ml. 1122.04 Procedure. A. Preparing the sample. 1. For a bulk sample from the field, select a representative 1,500 g soil sample. For soil boring samples, select a representative 300 g soil sample. 2. Air-dry the soil sample to a constant mass. Low heat (less than 100 F) may be used to help dry the soil sample. 3. Crush and grind the soil sample to pass the No. 4 sieve. Discard any rock material that will not pass the sieve. 4. Using the fine aggregate sample splitter, split the material passing the No. 4 sieve to obtain three representative samples of about 100 grams (±20 grams) each. Note: The replicate samples are to check the sulfate content variability found within the collected soil sample. 5. Pulverize each 100 g sample to pass the No. 40 sieve. Discard any materials that cannot be pulverized to pass the sieve. 2
6. Weigh 20.0 g (±0.1 g) of the material passing the No. 40 sieve and place into a 500 ml polyethylene bottle. 7. Add 400 ml of distilled or deionized water to each bottle. This provides an initial dilution ratio of 1:20. 8. Vigorously shake the bottles of soil/water mixture by hand for 1 minute and then let the bottles sit for a period of 16 to 24 hours. Record the start and elapsed soaking times. 9. After the soaking period has elapsed, assemble the filtration system by placing one filter sheet into the funnel and placing the funnel into the collection container (e.g., 600 ml beaker). Shake the bottle of soil/water mixture for 1 minute and pour the mixture into the filtration system. Collect the filtrate. Repeat the filtering process for each replicate sample using clean, uncontaminated equipment and new filter papers. Note: Use gravimetric filtering when calibration of the colorimeter is zeroed for each test with the filtrate. Use vacuum filtering when the colorimeter is zeroed daily with a distilled water blank (i.e., nonturbid water). B. Measuring the sulfate content. Use one of the following alternative procedures to measure the sulfate content based on the liquid used to calibrate the colorimeter. Use the procedure in Step B.1., when filtrate is used for calibration. Use the procedure in Step B.2., when nonturbid distilled water is used for calibration. 1. Colorimeter calibration with filtrate. Repeat these steps for the three filtrate replicates. (Note: The following instructions are applicable to the Thermo Scientific's Orion Aquafast AQ3700 colorimeter and sulfate test kit.) a. Turn on the colorimeter using the power button. Select the sulfate test program according to the manufacturer's instruction. b. Measure 10 ml of the filtrate from Step A.9 (1:20 dilution ratio) into a graduated cylinder using a clean, uncontaminated pipette. Transfer the 10 ml of filtrate from the cylinder into a clean sample vial. c. Wipe the vial with a lint free towel to remove any fingerprints or dirt. Place the vial into the colorimeter chamber, and align with device reference marks. d. Press the "ZERO/TEST" button. The method symbol flashes for three seconds and confirms the zero calibration. e. Remove the vial from the device. Add one sulfate test tablet (barium chloride) to the vial without touching the tablet and crush immediately with the plastic mixing rod provided. Tamp the sulfate test tablet with the rod until it is completely dissolved. f. Cap the vial, wipe the outside of the vial clean again, and immediately place it in the colorimeter chamber, and align with the reference marks. g. Press the "ZERO/TEST" button. The method symbol flashes for three seconds and a sulfate content reading is displayed. 3
h. If an error message is displayed, go to Step B.1.j. i. Multiply the sulfate content reading by the dilution ratio. Report the concentration in parts per million (ppm). Example: 100 (reading) x 20 (1:20 dilution ratio) = 2000 ppm j. Take the corresponding action below for the type of error message displayed: (1) If the message indicates that the result is below the device's measuring range limit (e.g., ' Err message...'), report the concentration as "< 100 ppm sulfate". (2) If the message indicates that the result is above the device's measuring range limit (e.g., ' Err message...'), dilute the filtrate with more distilled water to bring the reading within the measuring range. Measure 5 ml of the filtrate from Step A.9 into a graduated cylinder and add 5 ml of distilled or deionized water using a clean pipette. This provides a new solution with a dilution ratio of 1:40. Transfer the 10 ml of solution from the cylinder into a clean sample vial. Repeat Steps B.1.c through B.1.i. Multiply the reading by 40 in Step B.1.i. If the above range error message is displayed again (e.g., ' Err message...'), report the concentration as "> 8,000 ppm sulfate". 2. Colorimeter calibration with distilled water. Repeat these steps for the three filtrate replicates. (Note: The following instructions are specific to the Department's CHEMetrics colorimeter and sulfate test kit.) a. Turn on the device using the power button. Select the sulfate test program according to the manufacturer's instruction. b. Wipe the ampoule blank from the test kit with a lint free towel to remove any fingerprints or dirt, and then insert it into the colorimeter. Place the light shield over the ampoule, and then press the "0" button. After displaying "Wait" during a short period, the results will be displayed as "0.000". c. Fill the sample cup from the sulfate sample kit to the 20 ml mark with the filtrate from Step A.9 (1:20 dilution ratio). d. Add 7 drops of Acidifier Solution to the sample cup. With the tip of a new Vacu-vile ampoule, stir to mix the contents of the cup. e. Add 1 scoop of Activator Powder to the sample cup and stir for 10 seconds. All of the crystals do not have to dissolve. f. Place the Vacu-vile ampoule, tip first, into the sample cup. Snap the ampoule tip on the side of the cup. The ampoule will fill and leave a bubble at the top for mixing. g. To mix the ampoule, invert it several times, allowing the bubble to travel from end to end. 4
h. Dry the ampoule with a lint free towel to remove any fingerprints or dirt. Insert the ampoule into the colorimeter, place the light shield over the ampoule, and press the "meas" button to obtain a sulfate content reading. i. If an error message is displayed, go to Step B.2.k. j. Multiply the sulfate content reading by the dilution ratio. Report the concentration in parts per million (ppm). Example: 50 (reading) x 20 (1:20 dilution ratio) = 1000 ppm k. Take the corresponding action below for the type of error message displayed: (1) If the display shows "UNDRRNG", report the concentration as "< 100 ppm sulfate". (2) If the display shows "OVRRNG" and the dilution ration is 1:20, dilute the filtrate with more distilled water to bring the reading within the measuring range. Empty and clean the sample cup. Measure 10 ml of the filtrate from Step A.9 into the sample cup. Add 10 ml of deionized or distilled water into the sample cup. The solution in the sample cup is now at a 1:40 dilution ratio. Repeat Steps B.2.d through B.2.j. Multiply the reading by 40 in Step B.2.j. (3) If the display shows "OVRRNG" and the dilution ration is 1:40, dilute the filtrate again with more distilled water to bring the reading within the measuring range. Empty and clean the sample cup. Measure 5 ml of the filtrate from Step A.9 into the sample cup. Add 15 ml of deionized or distilled water into the sample cup. The solution in the sample cup is now at a 1:80 dilution ratio. Repeat Steps B.2.d through B.2.j. Multiply the reading by 80 in Step B.2.j. (4) If the display shows "OVRRNG" and the dilution ration is 1:80, report the concentration as "> 8,000 ppm sulfate". 1122.05 Test Report. Use a test report similar to the Department s Sulfate Content Form at the end of this supplement. Report the sample location by ID number, Station, Offset, geographic coordinates, and elevation. Report all three replicate sample sulfate content readings or sulfate content results, and the averaged sulfate content result as ppm sulfate to two significant digits. Report the soaking time that elapsed during Step A.8. Provide the geographic coordinate location where the soil samples where obtained by either decimal degrees or Ohio State Plane (NAD 83). Note: The reporting of the sample coordinates allows the department to track all sulfate content results statewide. 5
OHIO DEPARTMENT OF TRANSPORTATION DETERMINING SULFATE CONTENT IN SOILS SUPPLEMENT 1122 Project C-R-S: PID No: Report Date: Consultant: Technician: Sample or Boring ID Station Offset Latitude & Longitude or State Plane Coordinates Elevation Soaking Time (hr) Dilution Ratio Replicate Sample Readings 1 2 3 Average Reading Sulfate Content (ppm) B-001 3414+00 50' LT N39.958953 W83.054347 785.2 23.0 1:40 46.21 30.03 31.32 35.85 1400