CEU Electronic Theses and Dissertations, 2009
| Author | Bello, Musbau Adeoye |
|---|---|
| Title | Demonstrating the utility of Continuous Monitoring to remedy the flaws in Spot sampling of grpund gases |
| Summary | Ground gas risk assessment is required in order to determine the true subsurface gas concentration and to predict how this concentration might change in the future. These requirements are currently being met by periodic discrete measurement of gases from which gas regime is inferred. Two fundamental flaws have been identified in this approach; i) data insufficiency due to low sampling frequency, resulting in failure to account for variability in gas concentration, ii) the techniques only measure gas concentration and not flux, thereby neglecting the time-dimension in the gas regime. With the combination of field and laboratory work, this study demonstrates the utility of continuous data to remedy these flaws through the use of GasclamŪ In-borehole Gas Monitor. The study revealed that the variability in gas concentration is greater than the sampling frequency of spot sampling, and that the frequency of this variation changes at different time scale. Time series data was also shown to allow understanding of processes that control ground gas migration through the correlation of different environmental parameters. However, the study also found that the widely reported relationships between parameters do not always exist, and therefore there is need to characterise migration and /or production rates in each borehole. Model outcome from the laboratory revealed that the use of pump test for characterising gas production and/or migration rate is reproducible thereby allowing inference of gas flux from the resulting recovery profile. As a result, the study recommends that each site and each borehole be characterised on the basis of their gas production and / or migration rates rather than the conventional data extrapolation. Also, the new application in continuous monitor allowed a successful demonstration of PID sensor for continuous measurement in borehole environment thereby providing a novel application in ground VOC monitoring. |
| Supervisor | Dr. Steve Boult |
| Department | Environment Sciences and Policy MSc |
| Full text | https://www.etd.ceu.edu/2009/bello_musbau.pdf |
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