Show all your work for credits. Question #1. You have collected 100 g of a soil sample from the nearby farm and the following data is obtained. Calculate the percent base saturation assuming the...

see attached file. answer all 20 questions


Show all your work for credits. Question #1. You have collected 100 g of a soil sample from the nearby farm and the following data is obtained. Calculate the percent base saturation assuming the following are the only cations present in the soil. Cation H+ Ca2+ Mg2+ K+ Na+ [meq] 9.4 14 3 0.5 0.1 Question #2. Identify what is the point of zero charge for this unknown sample. Will this material react with Cl-at pH 6? Will it react with Ca2+ at pH 6? Explain your logic. Question #3. If a soil contains 5% organic matter and 10% kaolinite clay, what is a reasonable estimate of its CEC per 100 g? Question #4.  A soil has a CEC of 24 meq/100 g.  How many grams of Na+ will it take to saturate the CEC?  (Atomic weight of Na+ = 23) Question #5. If a soil can hold 50 mg of Mg2+ per 100 g, how many mg of K+ could it hold? (Atomic weight of Mg2+ = 24; K+ = 39) Question #6. Explain difference between unconfined and confined aquifer. Which one is associated with surface water? Ground water? Which aquifer will be more difficult to clean up and why? Question #7. Explain how oxbow lakes form. Diagrams and labeling will help. Question #8. Explain what residence time for lake and why it is important. Question #9. Average cation exchange capacity for organic matter is 200 meq/100g. Average cation exchange capacity of clay is 50 meq/100g. Your soil contains about 10% organic matter and 20% clay. 100 g of soil sample contains the following ions. Calculate the base saturation percentage for this soil. (Hint: Make sure you include only the base cations) (25 pts). Ions Ca Mg K Na Al Concentration 100 ppm 30 ppm 78 ppm 23 ppm 52 ppm Molecular Weight 40 mg/mmol 24 mg/mmol 39 mg/mmol 23 mg/mmol 26 mg/mmol Question #10. An aquifer is 2045 m wide and 28 m tall. Its hydraulic gradient is .05 and its hydraulic conductivity is 145 m/day. Calculate the velocity of the groundwater as well as the amount of water that passes through the end of the aquifer its day if the porosity of the aquifer is 32%. Question #11. An aquifer has a cross section with a horizontal width of 265 m and a vertical thickness below the water table of 42 m. The water table is 36 m below the ground surface. Each day, 3340 m3 of water is discharged through the cross section. The aquifer rock has an effective porosity of 27.1%. Find (a) the Darcy speed, and (b) the actual speed of the water as it passes through the aquifer. Question #12. Cations from solution are more likely to replace weakly-held cations first. The clay mineral sample has been submerged in an excess amount of ammonium (NH4+) solution. Identify series of ions that will be replaced from the clay minerals, i.e. list which ions will be first replaced followed by the next one, and so forth. Use the provided table to justify your answer. Question #13. In pot A, B and C the soil is sterilized. In pot A nothing has been added. In pot B, nitrogen and phosphorus have been added and in pot C nitrogen has been added. Pot D has neither been sterilized nor fertilized. a. Why did the plant in pot D grow so well compared to the plant in pot A? b. Why did the plant in pot B grow as well as the plant in pot D? c. Why did the plant in pot C grow better than the plant in pot A but not as well as either the plant in pot B or D? Question #14. A certain soil has a bulk density of 1.28 g cm-3 and an organic carbon content of 1%. The porosity of the soil is 30%, of which 50% is occupied by water and 50% by air. Find the percentages of trichloroethene contained within the solid, liquid and gas phases for this soil. Kow of trichloroethene = 195 and KH of trichloroethene = 0.397 Question #15. Fish (5.0 % body fat) taken from a particular lake were tested and found to contain 200 ppm DDT in their tissues. Determine the concentration of DDT (pKOW = 6.2) in this lake. Question #16. Mineralization, nitrification, denitrification, nitrogen fixation and nitrogen uptake are important processes that N undergoes in the N-cycle. Explain the meaning of each term. Question #17. Explain how soils develop negative charges. Question #18. Nitrification is carried out in two steps, first to nitrite, then to nitrate, by different chemautotrophs NH4+ + 3/2 O2 NO2- + 2H+ + H2O: Reaction A NO2- + 1/2 O2 NO3-: Reaction B What organisms are responsible for step A and step B? Does nitrification typically occur quickly after addition of ammonium to soil? Question #19. Why don't 1:1 minerals expand when these are exposed to water? Question #20. Of these general types of layer silicate minerals, only certain 2:1 minerals expand. Name the three general types of 2:1 minerals. Which is expanding? Which is limited-expanding? Which is non-expanding? Why? 3