No abstract

AbstraetA geochemical model of an urban environment is presented in which multielemental tracers are used to characterise the circulation of trace elements in particulate matter (atmospheric aerosol, street dust and urban soil) within a city.

a b s t r a c tFrom the end of 2013 and during the following two years, 20 kt of CO 2sc are planned to be injected in a saline reservoir (1500 m depth) at the Hontomín site (NE Spain). The target aquifers are Lower Jurassic limestone formations which are sealed by Lower Cretaceous clay units at the Hontomín site (NE Spain). The injection of CO 2 is part of the activities committed in the Technology Development phase of the EC-funded OXYCFB300 project (European Energy Program for Recovery -EEPR, http://www.compostillaproject.eu), which include CO 2 injection strategies, risk assessment, and testing and validating monitoring methodologies and techniques.Among the monitoring works, the project is intended to prove that present-day technology is able to monitor the evolution of injected CO 2 in the reservoir and to detect potential leakage. One of the techniques is the measurement of CO 2 flux at the soil-atmosphere interface, which includes campaigns before, during and after the injection operations.In this work soil CO 2 flux measurements in the vicinity of oil borehole, drilled in the eighties and named H-1 to H-4, and injection and monitoring wells were performed using an accumulation chamber equipped with an IR sensor. Seven surveys were carried out from November 2009 to summer 2011. More than 4000 measurements were used to determine the baseline flux of CO 2 and its seasonal variations.The measured values were low (from 5 to 13 g m −2 day −1 ) and few outliers were identified, mainly located close to the H-2 oil well. Nevertheless, these values cannot be associated to a deep source of CO 2 , being more likely related to biological processes, i.e. soil respiration. No anomalies were recognized close to the deep fault system (Ubierna Fault) detected by geophysical investigations. There, the CO 2 flux is indeed as low as other measurement stations. CO 2 fluxes appear to be controlled by the biological activity since the lowest values were recorded during autumn-winter seasons and they tend to increase in warm periods. Two reference CO 2 flux values (UCL 50 of 5 g m −2 d −1 for non-ploughed areas in autumn-winter seasons and 3.5 and 12 g m −2 d −1 for in ploughed and non-ploughed areas, respectively, in spring-summer time, and UCL 99 of 26 g m −2 d −1 for autumn-winter in not-ploughed areas and 34 and 42 g m −2 d −1 for spring-summer in ploughed and not-ploughed areas, respectively) were calculated. Fluxes higher than these reference values could be indicative of possible leakage during the operational and post-closure stages of the storage project.

No abstract

a b s t r a c tNatural analogs offer a valuable opportunity to investigate the long-term impacts associated with the potential leakage in geological storage of CO 2 .Degassing of CO 2 and radon isotopes ( 222 Rn-220 Rn) from soil, gas vents and thermal water discharges was investigated in the natural analog of Campo de Calatrava Volcanic Field (CCVF; Central Spain) to determine the CO 2 -Rn relationships and to assess the role of CO 2 as carrier gas for radon. Furthermore, radon measurements to discriminate between shallow and deep gas sources were evaluated under the perspective of their applicability in monitoring programs of carbon storage projects.CO 2 flux as high as 5000 g m −2 d −1 and 222 Rn activities up to 430 kBq m −3 were measured; 220 Rn activities were one order of magnitude lower than those of 222 Rn. The 222 Rn/ 220 Rn ratios were used to constrain the source of the Campo de Calatrava soil gases since a positive correlation between radon isotopic ratios and CO 2 fluxes was observed. Thus, in agreement with previous studies, our results indicate a deep mantle-related origin of CO 2 for both free and soil gases, suggesting that carbon dioxide is an efficient carrier for Rn. Furthermore, it was ascertained that the increase of 222 Rn in the soil gases was likely produced by two main processes: (i) direct transport by a carrier gas, i.e., CO 2 and (ii) generation at shallow level due to the presence of relatively high concentrations of dissolved U and Ra in the thermal aquifer of Campo de Calatrava.The diffuse CO 2 soil flux and radon isotopic surveys carried out in the Campo de Calatrava Volcanic Fields can also be applicable to geochemical monitoring programs in CCS (Carbon Capture and Storage) areas as these parameters are useful to: (i) constrain CO 2 leakages once detected and (ii) monitor both the evolution of the leakages and the effectiveness of subsequent remediation activities. These measurements can also conveniently be used to detect diffuse leakages.