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Lab1: Water Chemistry Study: Stiff, Ternary, and Piper Diagrams This lab introduces you how to use Rockware software Piper-Stiff to generate (1) a stiff diagram for comparing the ion concentration of groundwaters, (2) a termary diagram which illustrates a closed data set in which three variables add to a fixed total as 1, and (3) a Piper (trilinear) diagram which illustrates the percentage composition of major ions. Stiff Diagram In the first part of the lab, we will use Stiff/W to create Stiff diagram for groundwater ion concentration analysis. On Stiff diagram, the values are plotted as milliequivalents on a horizontal axis extending on each side of a zero vertical axis. Cations concentrations are plotted to the left of zero, while anion concentrations are plotted on the right. The points representing the values are connected to produce a distinctive shape or pattern. The patterns help identify water-quality differences. To start up the program, double-click the RockWare group icon from the Window's Program Manager. Double-click Stiff/W program icon. An untitled Spreadsheet window appear. Now select the Open command from the File menu to open (by double-clicking) a demo data file "stiff.atd". There are ten columns of data in this file. The first column is the sample ID (alphabetic or numeric character). The second column represents symbol number. This column is actually ignored by this program (but will be used in the companion program Piper/W). Columns 3-6 represent cation concentrations in the order: Na+, K+, Ca++, Mg++. Columns 7-10 are anion concentrations in the order: Cl-, HCO3-, CO3-, SO4--. Again, comments lines are noted with a colon (":") as the first entry on the row. The first nine rows contain comments that the program will ignore. Now let's try out the stiff plot for this file. 1. Display the Toolbar by selecting the Toolbar command from the Options menu. 2. Click on the Generate Diagram icon (the first icon on the right) on the Toolbar, or select the Generate Stiff Diagram command from the Compute menu, to make a ternary diagram. The program will display a dialog box from which you can change the diagram setting. Don't change the default setting for this exercise. Choose the OK box. The program will work like this. First, it will read data for the four cations (columns 3-6, combine Na and K values, convert the ppm (mg/l) to meq/l (milliequivalents per liter), and plot a point for each component on the left side of the Stiff diagram. Each ion will be represented by a dot of a different color and label. Anions will be plotted on the right hand side. Lines are then drawn between the ion dots, to generate a polygon with 6 corner points. Each sample will be labeled with its ID below the polygon shape. The completed diagram will be displayed in an Image window. Now let us learn a few tricks about modifying the image. _ Double-click on the Image window to bring up the Image Controls _ Click on the "Actual Size" button and select OK, which allows you to resize the plot. _ Hold down the <Shift> key while you double-click the left mouse button and you can zoom into the image. _ Hold down the <Shift> key while you double-click the right mouse button and you can zoom back out the image. 3. Select Print from the File Menu to print the image. Select Best Fit in the Image Window before printing. Ternary Diagram To start up the program, double-click the RockWare group icon from the Window's Program Manager. Double-click Ternary/W program icon. An untitled Spreadsheet window appear. Now select the Open command from the File menu to open (by double-clicking) a demo data file "ternary.atd". There are three columns of data in this file, representing measured values of three oxides. The first two rows contain "comments" (denoted as ":") that the program will ignore. Now let's try out the ternary plot for this file. 1. Display the Toolbar by selecting the Toolbar command from the Options menu. 2. Click on the Generate Diagram icon (a triangle, the first icon on the right) on the Toolbar, or select the Generate Ternary Diagram command from the Compute menu, to make a ternary diagram. 3. A dialog box appears. Enter CaO for Left Title, Na2O for Center Title, and K2O for Right Title. The Left, Center, and Right Col # are entered as 1, 2, 3 automatically by default. The program will read the data from columns 1, 2, and 3 of the file and plot the data at the lower-left (CaO), upper (Na2O), and lower-right (K2O) vertices of the ternary diagram, respectively. This means that the components equal 100% at their respective corners and decrease in value towards the other corners. 4. Then a Diagram Options dialog box appears. Click on the Contour box to remove the check-mark. By doing this, the diagram will be drawn without contours. 5. Choose the OK box to create the diagram. Piper Diagram Use Piper/W (double-click the Piper/W icon in the RockWare group window) to generate Piper diagram for the demo file piper.atd. The data structure of piper.atd is the same as stiff.atd. You can follow the same procedure used in generating Stiff diagram to create a Piper diagram. Note that you can resize the image as you do in the Stiff diagram. Exercise 1.1 Plot ternary diagrams for the following data of benzene (C6H6)-toluene (C7H8)-xylene (C8H10), or BTX composition (%) in a oil spill in Kansas. Hydrocarbons such as gasolines are a mixture of different organic compounds. These organic compounds can partition into the vapor phase and a soluble phase in groundwater. The proportional constant between the concentration dissolved in solution and the vapor pressure and is called a Water-Air Partition Coefficient. The water-air partition coefficients for benzene, toluene, and xylene are 5.88, 3.85, and 3.80. The compounds with low partition coefficient favor the vapor phase, whereas those with high partition coefficient favors the aqueous phase. The following data shows the composition (%) of BTX in vadose zone (unsaturated zone) (1) 10 days and (2) 100 days after bioremediation of the oil plume. Use ternary diagrams to explain the change in BTX composition as a function of time. Which compounds partition at a high rate into the groundwater? data set 1 (10 days after spill) data set 1 (100 days after spill) benzene toluene xylene benzene toluene xylene 30 35 35 68 20 12 28 39 33 60 25 15 21 37 42 72 18 10 20 40 40 65 27 8 25 41 34 59 28 13 32 23 45 70 21 9 Exercise 1.2 Given the following chemical analysis of groundwater (locations show distance in feet between wells and regional recharge point) from the Floridan aquifer in central Florida: Well locations mg/L Ca2+ Mg2+ Na+ K+ HCO3- SO42- Cl- 1 0 34 5.6 3.2 0.5 124 2.4 4.5 2W 190 54 14 6.9 1.0 253 3.6 8.5 2S 350 58 17 6.1 0.7 163 71 9.0 3S 678 66 29 8.3 2.0 168 155 10 4S 1020 106 60 21 3.7 206 344 28 A. Convert all values to meq/L and %, using a spreadsheet program if possible (5 pts). B. Plot a Piper diagram of water analysis by hand and by computer (10 pts). C. Comment on how the chemical composition of groundwater is shifting along the flow path (with increasing distance from the recharge area). It has known that both dolomite (CaMg(CO3)2) and gypsum (CaSO4.2H2O) saturation increase along the flow path. How do the Mg2+/Ca2+ and SO42-/HCO3- ratios change with increasing distance from the recharge area?. (5 pts).