Internal Code: MAS3767 Geology Assignment Help Question 1a. Explain the 14 C method of dating groundwater. Include in your answer an explanation of the age range that 14 C is useful for, the form and origins of C in groundwater systems, the complications and uncertainties inherent in using this technique for dating groundwater, and an example of a study that has used 14 C to date groundwater. Question 1b. You have been asked to carry out a study of recharge in a semi-arid low relief area with little runoff. Existing data include: a) a set of shallow bores with screens close to the water table and hydrograph records for the last 20 years; b) some deeper bores with screens several metres to tens of metres below the water table that also have hydrograph records; and c) basic major ion geochemistry. You also have the opportunity to measure concentrations of 36 Cl, 14 C, and 3 H in the groundwater. Briefly outline how you would use these data to estimate recharge in this area, including the timescales and distance scales over which the various techniques give you information. Question 1c. Explain how 222 Rn allows us to estimate groundwater inflows to a river. Include in your answer an explanation of why Rn is a suitable tracer, the factors that control the 222 Rn activities in a river, the parameters that we need to estimate or measure to calculate the groundwater inflows, and any problems or uncertainties with this technique. Question 1d. Hydrocarbons are common groundwater contaminants. Explain: some of the sources of hydrocarbon contamination, in what state do we find the contaminants, the factors that control the rate of contaminant migration, and how the contaminants might degrade naturally in the environment. Question 1e. The hydrogeology of the Freshwater Lenses along the River Murray was used as an example of a groundwater recharge from a losing stream. Explain how a) the bore hydrograph data; b) the radiogenic isotope data; and c) the stable isotope data were used to determine that recharge occurred largely through the river bank and not via the floodplain Question 1f. Figures 1a and 1b show stable isotope, 14 C, and 3 H data for groundwater from three aquifers from an area of ~10km x 20km. The area has subdued topography and there is little variation in annual rainfall across the area. Modern rainfall has a 3 H activity of 4.2 TU and the soil zone CO 2 has an a 14 C of 105 pMC. The global meteoric water and the stable isotope values of average modern rainfall are also shown. Use these data to explain the relative ages of the groundwater in the different aquifers and hydrological processes that have affected the groundwater. Integrate as much of the data as possible. 23 total views, 2 views today