Publications (4)0 Total impact
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Article: Effects of rainfall events on waste-rock surface-water conditions and CO2 effluxes across the surfaces of two waste-rock piles
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ABSTRACT: The influence of rainfall events on the surface-water conditions of waste rock and the resultant CO2 gas effluxes from waste-rock piles are of value in the development of a long-term management plan for these piles. However, data for the direct measurement of CO2 effluxes through field-scale waste-rock piles are lacking. This study investigated the influence of a short-term, multi-day (29 July to 5 August 2002) heavy rainfall event on waste-rock water conditions and CO2 effluxing from two large waste-rock piles at the Key Lake uranium mine in northern Saskatchewan. The study also investigated spatial and temporal variation in CO2 effluxes in these waste-rock piles over a 2-year period (summer 2000 – summer 2002). Results showed that the impact of a heavy rainfall event on surface-water conditions and CO2 effluxes from these waste-rock piles is of relatively short duration. Results also showed that the CO2 effluxes were relatively uniform, both spatially and temporally (average covariance (CV) is 28%–39%), over the 2-year test period. This information can provide an important tool in the development of a long-term management plan for mine waste-rock piles. Key words: CO2 efflux, waste-rock piles, rainfall events, unsaturated zone.Journal of Environmental Engineering and Science. 02/2011; 4(6):469-480. -
Article: Characterizing spatial and temporal variations in CO2 fluxes from ground surface using three complimentary measurement techniques
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ABSTRACT: Fluxes of CO 2 from non-agricultural soil ecosystems, though globally important, are poorly characterized. Previously, we tested a dynamic closed chamber (DCC) method that was shown to accurately measure CO 2 fluxes from ground surface to the atmosphere in mesocosms. In the current study, the DCC method was used to measure the CO 2 efflux at a field site where conditions were similar to those used in the mesocosm tests. Fluxes measurements also were obtained using static closed chamber (SCC) and eddy covariance (EC) methods. The study site consisted of a large, flat-topped, waste pile at the Key Lake uranium mine, in northern Saskatchewan. The pile was constructed of uniform, fine to medium grain sand and was devoid of a soil zone and vegetative cover. Chamber-based measurements were used to characterize the spatial variability associated with the CO 2 flux; whereas the EC method was used to characterize temporal variability. Results showed that the chamber-based (DCC and SCC) methods yielded comparable data, with a time-averaged CO 2 flux of 171G54 mg CO 2 m K2 h K1 . Spatial variability associated with the flux was relatively small and no distinct spatial pattern was observed. Fluxes measured using the EC method tended to underestimate those measured using the chamber-based methods, with a time-averaged CO 2 flux (150G35 mg CO 2 m K2 h K1) that was about 12% lower than the average flux calculated from the chamber data. The greater temporal resolution provided by the EC method demonstrated that the CO 2 flux exhibited a distinct diurnal pattern, but that long-term variations in the flux were relatively small (CVZ23%). When used together, the chamber-based and EC methods provide information of a complementary nature that can greatly improve our understanding of the processes at work in unsaturated media. q 2005 Elsevier B.V. All rights reserved. -
Article: Quantifying CO2 fluxes from soil surfaces to the atmosphere
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ABSTRACT: Measurements of CO2 fluxes from ground surface of the atmosphere (soil respiration) are needed to quantify biotic and abiotic reaction rates in unsaturated zones and to gain insight into the importance of these processes on global warming. The use of three techniques (dynamic closed chambers, static chambers, and gradient calculations) to determine soil respiration was assessed by measuring fluxes of microbially produced CO2 from an unsaturated mesocosm (2.4 m dia.×3.2 m thick) and two unsaturated minicosms (0.58 m dia.×1.2 m thick), one maintained at 18–23 °C (HT) and the other at 5 °C (LT). By injecting known and constant CO2 fluxes into the bottom of the HT minicosm and measuring the resulting fluxes, it was shown that the dynamic closed chamber (DCCS) technique yielded accurate measurements of fluxes over the range observed from natural unsaturated media. Over this same range, results showed that the concentration gradient method yielded reasonable estimates of fluxes but its accuracy was limited by uncertainties in both the concentration gradient and the gaseous diffusion coefficient in the soil atmosphere. The static chamber method underestimated the actual flux at higher CO2 fluxes and when adsorption times of >24 h were used.Journal of Hydrology. -
Article: Characterizing spatial and temporal variations in CO2 fluxes from ground surface using three complimentary measurement techniques
[show abstract] [hide abstract]
ABSTRACT: Fluxes of CO2 from non-agricultural soil ecosystems, though globally important, are poorly characterized. Previously, we tested a dynamic closed chamber (DCC) method that was shown to accurately measure CO2 fluxes from ground surface to the atmosphere in mesocosms. In the current study, the DCC method was used to measure the CO2 efflux at a field site where conditions were similar to those used in the mesocosm tests. Fluxes measurements also were obtained using static closed chamber (SCC) and eddy covariance (EC) methods. The study site consisted of a large, flat-topped, waste pile at the Key Lake uranium mine, in northern Saskatchewan. The pile was constructed of uniform, fine to medium grain sand and was devoid of a soil zone and vegetative cover. Chamber-based measurements were used to characterize the spatial variability associated with the CO2 flux; whereas the EC method was used to characterize temporal variability. Results showed that the chamber-based (DCC and SCC) methods yielded comparable data, with a time-averaged CO2 flux of 171±54 mg CO2 m−2 h−1. Spatial variability associated with the flux was relatively small and no distinct spatial pattern was observed. Fluxes measured using the EC method tended to underestimate those measured using the chamber-based methods, with a time-averaged CO2 flux (150±35 mg CO2 m−2 h−1) that was about 12% lower than the average flux calculated from the chamber data. The greater temporal resolution provided by the EC method demonstrated that the CO2 flux exhibited a distinct diurnal pattern, but that long-term variations in the flux were relatively small (CV=23%). When used together, the chamber-based and EC methods provide information of a complementary nature that can greatly improve our understanding of the processes at work in unsaturated media.Journal of Hydrology.
