Evaluating impacts of CO2 intrusion into an unconsolidated aquifer: II. Modeling results

Large scale deployment of CO2 geological sequestration requires the assessment of the risks. One of the potential risks is the impact of CO2 leakage on shallow groundwater overlying the sequestration site.The understanding of the key chemical processes and parameters are critical for building numerical models for risk assessment. Model interpretation of laboratory and field tests is an effective way to enhance such understanding. As part of this investigation, column experiments in which the CO2 saturated synthetic groundwater flowed through a column packed with materials from the High Plains aquifer, were conducted. Changes in concentrations of several constituents in the column effluent and pH were determined. In this paper, a reactive transport model was developed to describe and interpret the observed concentration changes, attempting to shed light on the chemical reactions and mechanisms and key parameters that control the changes in effluent chemistry. The reactive transport model described fairly well the changes in pH and the concentration changes of Ca, Mg, Ba, Sr, Cs, As and Pb. Calcite dissolution and Ca-driven cation exchange reactions were the major drivers for the concentration changes of Ca, Ba, Sr, and Cs. The pH-driven adsorption/desorption reactions led to a concentration increase of As and Pb. The volume fraction and reactive surface area of calcite, CEC and sorption capacity were key parameters in controlling the magnitude of concentration increase. Model results also showed that Ba, which is an important chemical element released into the aqueous phase during these experiments, may be incorporated into the calcite crystal structure and the dissolution of Ba-bearing calcite could be an alternative pathway to explain the increase in aqueous Ba concentration when sediments are exposed to the CO2 saturated leaching groundwater

The Bride is Keeping Her Name: A 35-Year Retrospective Analysis of Trends and Correlates

We used data obtained from wedding announcements in the New York Times newspaper from 1971 through 2005 (N=2,400) to test 9 hypotheses related to brides\u27 decisions to change or retain their maiden names upon marriage. As predicted, a trend was found in brides keeping their surname, and correlates included the bride’s occupation, education, age, and the type of ceremony (religious versus nonsectarian). Partial support was found for the following correlates: officiants representing different religions, brides with one or both parents deceased, and brides whose parents had divorced or separated. There was mixed support for the hypothesis that a photograph of the bride alone would signal a lower incidence of name keeping. Results indicated that 14 out of the 30 hypothesized directional planned comparisons were statistically significant after Bonferroni adjustment

Review of the impacts of leaking CO2 gas and brine on groundwater quality

This paper provides an overview of the existing data and knowledge presented in recent literature about the potential leaking of CO2 from the deep subsurface storage reservoirs and the effects on groundwater quality. The objectives are to: 1) present data and discuss potential risks associated with the groundwater quality degradation due to CO2 gas and brine exposure; 2) identify the set of geochemical data required to develop models to assess and predict aquifer responses to CO2 and brine leakage; and 3) present a summary of the findings and reveal future trends in this important and expanding research area. The discussion is focused around aquifer responses to CO2 gas and brine exposure and the degree of impact; major hydrogeological and geochemical processes and site-specific properties known to control aquifer quality under CO2 exposure conditions; contributions from the deep reservoirs (plume characteristics and composition); and the possibility of establishment of a new network of reactions and processes affecting or controlling the overall mobility of major, minor, and trace elements and the fate of the elements released from sediments or transported with brine. This paper also includes a discussion on the development of conceptual and reduced order models (ROMs) to describe and predict aquifer responses and whether or not the release of metals following exposure to CO2 is harmful, which are an essential tool for CO2 sequestration related risk assessment. Future research needs in this area are also included at the end of the paper

An Approach Toward Visual Autonomous Ship Board Landing of a VTOL UAV

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