Diploma thesis in Physics submitted by Florian Freundt born in ...

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5.5. Noble gases 5 Results 5.5.3 Soil atmosphere samples from Site A A total of 23 noble gas depth profiles were sampled at Site A and measured, the entire dataset can be found in Table B.9. A few readings (marked red in Table B.9) were omitted from analysis as they scatter unreasonably strong. Except for the 36 Ar reading of sample A01-I, all these outliers were connected to technical problems that occurred during the measurement in the mass spectrometer. The 36 Ar reading of sample A01-I is the only isotope of that sample showing such elevated readings and is therefore regarded as an artifact of an undiscovered problem during that single measurement. The sampling frequency was increased during the irrigation period. Samples were taken right before irrigation (A21), within one hour after irrigation (A22) and days after irrigation events. The noble gas sample that is accompanied by the lowest sum of O2 and CO2 (16.7 Vol%) is A19 2 m depth. Figure 5.9 shows the measured concentrations of the four isotopes 20 Ne, 22 Ne, 36 Ar and 40 Ar standardized to literature data on atmospheric composition, plotted over time. The plots for the remaining isotopes can be found in Figure C.17. It is quite clear that most of the noble gas data is located above or at 100 % relative to atmospheric air composition. A significant drop below 100 %, consistent in all isotopes, was never observed. Only the heavy noble gas isotopes 84 Kr and 132 Xe showed such reduced noble gas concentrations, though suffering from low accuracy and strong scattering their reliability is questionable. The data can be separated into two different time frames based on the differing visible trends. The first interval is August 2010 – April 2011, when all noble gases show a decline from initial values well above 100 % at the beginning to values scattering closely around 100 % within the data’s accuracy. This trend is visible at all three depths, however it is most pronounced at 6 m, where the initial values are between 104 – 106 %, depending on the isotope. The shallower depths both start at 102 – 105 % and reach 100 % earlier than at 6 m. Between December 2010 and April 2011, the noble gas concentrations scattered around 100 % at all depths. The second interval is May – June 2011, marking the artificial irrigation of Site A. The reaction of the noble gases at a depth of 2 m is immediate and strong, concentrations jump from 100 % to 104 – 107 % (depending on the noble gas isotope) at the last measured noble gas sample (A23), taken eleven days after the first irrigation (see Figure 6.1). At depths 4 and 6 m noble gas concentrations show no reaction at all, remaining at around 100 %. The noble gas isotope ratios 3 He/ 4 He, 4 He/ 20 Ne, 20 Ne/ 22 Ne and 40 Ar/ 36 Ar were calculated, however a specific evaluation of the mass spectrometer data focused on these ratios was not done. The ratios displayed no irregularities or significant deviations from literature values (see Table B.9). The change of O2 and CO2 concentrations had no effect on these ratios, as shown exemplarily in Figures C.20 and C.21 for 4 He/ 20 Ne and 20 Ne/ 22 Ne. 60
5 Results 5.5. Noble gases 20 Ne (2m) [% atm. air] 20 Ne (4m) [% atm. air] 20 Ne (6m) [% atm. air] 36 Ar (2m) [% atm. air] 36 Ar (4m) [% atm. air] 36 Ar (6m) [% atm. air] Aug Sep Oct Nov Dec Jan Feb Mar Apr May 115 110 105 100 95 90 110 105 100 95 90 110 105 100 95 90 115 110 105 100 95 90 110 105 100 95 90 110 105 100 95 90 Aug Sep Oct Nov Dec Jan Feb Mar Apr May Date 22 Ne (2m) [% atm. air] 22 Ne (4m) [% atm. air] 22 Ne (6m) [% atm. air] 40 Ar (2m) [% atm. air] 40 Ar (4m) [% atm. air] 40 Ar (6m) [% atm. air] Aug Sep Oct Nov Dec Jan Feb Mar Apr May 115 110 105 100 95 90 110 105 100 95 90 110 105 100 95 90 115 110 105 100 95 90 110 105 100 95 90 110 105 100 95 90 Aug Sep Oct Nov Dec Jan Feb Mar Apr May Figure 5.9: Concentrations of 20 Ne, 22 Ne, 36 Ar and 40 Ar in soil atmosphere samples from the different depths of Site A over time, relative to atmospheric literature values from Porcelli et al. [2002]. 61 Date
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Faculty of Physics and Astronomy He
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Measuring annual variation of soil
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CONTENTS CONTENTS 3.1 Setup of the
Page 11 and 12: Chapter 1 Introduction Understandin
Page 13: 1 Introduction Molins and Mayer [20
Page 16 and 17: 2.1. Noble gas temperatures 2 Theor
Page 24 and 25: 2.2. Physical processes and propert
Page 26 and 27: 2.2. Physical processes and propert
Page 28 and 29: 2.3. Soil atmosphere composition 2
Page 35 and 36: Chapter 3 Sampling sites and method
Page 37 and 38: 3 Sampling sites and methods 3.1. S
Page 43 and 44: Chapter 4 Measuring methods 4.1 Mas
Page 45 and 46: 4 Measuring methods 4.1. Mass spect
Page 47: 4 Measuring methods 4.2. On site me
Page 50 and 51: 5.2. Temperature profiles 5 Results
Page 52 and 53: 5.3. O2 and CO2 profiles 5 Results
Page 54 and 55: 5.4. Borehole sealing 5 Results 5.4
Page 56 and 57: 5.4. Borehole sealing 5 Results Fig
Page 58 and 59: 5.5. Noble gases 5 Results 8 days,
Page 62 and 63: 5.5. Noble gases 5 Results 5.5.4 So
Page 64 and 65: 6 Discussion This rather extreme am
Page 66 and 67: )! )! *+,-./-01234*-56-20301.7*38*9
Page 68 and 69: 6 Discussion Table 6.1: Synthetic d
Page 71: Chapter 7 Summary The results of th
Page 74 and 75: 8 Outlook Considering the manifold
Page 76 and 77: A.1. Gas sample size A Calculations
Page 78 and 79: A.3. Fractionation-Values A Calcula
Page 80 and 81: Table B.3: Noble gas volume mixing
Page 82 and 83: Table B.5: Calculated values of rel
Page 84 and 85: Table B.8: Precipitation record of
Page 86 and 87: Table B.10: Complete dataset of nob
Page 89 and 90: Appendix C Additional plots and fig
Page 91 and 92: C Additional plots and figures Figu
Page 93 and 94: C Additional plots and figures �
Page 97 and 98: C Additional plots and figures O 2
Page 99 and 100: C Additional plots and figures 4 He
Page 101 and 102: C Additional plots and figures 20 N
Page 105 and 106: C Additional plots and figures 10 1
Page 107 and 108: Appendix D Datasheets 107
Page 109 and 110: D Datasheets LogTag TREX-8 Technica
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Bibliography [Aeschbach-Hertig 1994
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BIBLIOGRAPHY BIBLIOGRAPHY [Friedric
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BIBLIOGRAPHY BIBLIOGRAPHY [Riveros-
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Acknowledegment At the end of this
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