Reactive transport simulations to study groundwater quality changes in response to CO2 leakage from deep geological storage

AbstractAs an effort to evaluate risks associated with geologic sequestration of CO2, this work assesses the potential effects of CO2 leakage on groundwater quality. Reactive transport simulations are performed to study the chemical evolution of aqueous Pb and As after the intrusion of CO2 from a storage reservoir into a shallow confined groundwater resource. The simulations use mineralogies representative of shallow potable aquifers in the USA; both 2D (depth-averaged) and 3D simulations are conducted. Sensitivity studies are also conducted for variation in hydrological and geochemical conditions, as well as several other critical parameters. Model results suggest that a significant increase of aqueous lead (Pb) and arsenic (As) may occur in response to CO2 intrusion, but in most sensitivity cases their concentrations remain below the EPA specified maximum contaminant levels (MCLs). Adsorption/desorption from mineral surfaces significantly impacts the mobilization of Pb and As. Results from the 3D model agree fairly well with the 2D model in cases where the rate of CO2 intrusion is relatively small (so that the majority of CO2 readily dissolves in the groundwater), whereas discrepancies between 2D and 3D models are observed when the CO2 intrusion rate is comparably large

The California Planet Survey II. A Saturn-Mass Planet Orbiting the M Dwarf Gl649

We report precise Doppler measurements of the nearby (d = 10.34 pc) M dwarf Gl649 that reveal the presence of a planet with a minimum mass Msini = 0.328 Mjup in an eccentric (e = 0.30), 598.3 day orbit. Our photometric monitoring reveals Gl649 to be a new variable star with brightness changes on both rotational and decadal timescales. However, neither of these timescales are consistent with the 600-day Doppler signal and so provide strong support for planetary reflex motion as the best interpretation of the observed radial velocity variations. Gl649b is only the seventh Doppler-detected giant planet around an M dwarf. The properties of the planet and host-star therefore contribute significant information to our knowledge of planet formation around low-mass stars. We revise and refine the occurrence rate of giant planets around M dwarfs based on the California Planet Survey sample of low-mass stars (M* < 0.6 Msun). We find that f = 3.4^{+2.2}_{-0.9}% of stars with M* < 0.6 Msun harbor planets with Msini > 0.3$ Mjup and a < 2.5 AU. When we restrict our analysis to metal-rich stars with [Fe/H] > +0.2 we find the occurrence rate is 10.7^{+5.9}_{-4.2}%.Comment: 8 pages, 4 figures, 3 tables, PASP accepte

M2K: I. A Jovian mass planet around the M3V star HIP79431

Doppler observations from Keck Observatory reveal the presence of a planet with Msini of 2.1 Mjup orbiting the M3V star HIP79431. This is the sixth giant planet to be detected in Doppler surveys of M dwarfs and it is one of the most massive planets discovered around an M dwarf star. The planet has an orbital period of 111.7 days and an orbital eccentricity of 0.29. The host star is metal rich, with an estimated [Fe/H] = +0.4. This is the first planet to emerge from our new survey of 1600 M-to-K dwarf stars.Comment: 5 figure

Numerical modeling of injection and mineral trapping of CO2 withH2S and SO2 in a Sandstone Formation

Carbon dioxide (CO{sub 2}) injection into deep geologic formations could decrease the atmospheric accumulation of this gas from anthropogenic sources. Furthermore, by co-injecting H{sub 2}S or SO{sub 2}, the products respectively of coal gasification or combustion, with captured CO{sub 2}, problems associated with surface disposal would be mitigated. We developed models that simulate the co-injection of H{sub 2}S or SO{sub 2} with CO{sub 2} into an arkose formation at a depth of about 2 km and 75 C. The hydrogeology and mineralogy of the injected formation are typical of those encountered in Gulf Coast aquifers of the United States. Six numerical simulations of a simplified 1-D radial region surrounding the injection well were performed. The injection of CO{sub 2} alone or co-injection with SO{sub 2} or H{sub 2}S results in a concentrically zoned distribution of secondary minerals surrounding a leached and acidified region adjacent to the injection well. Co-injection of SO{sub 2} with CO{sub 2} results in a larger and more strongly acidified zone, and alteration differs substantially from that caused by the co-injection of H{sub 2}S or injection of CO{sub 2} alone. Precipitation of carbonates occurs within a higher pH (pH &gt; 5) peripheral zone. Significant quantities of CO{sub 2} are sequestered by ankerite, dawsonite, and lesser siderite. The CO{sub 2} mineral-trapping capacity of the formation can attain 40-50 kg/m{sup 3} medium for the selected arkose. In contrast, secondary sulfates precipitate at lower pH (pH &lt; 5) within the acidified zone. Most of the injected SO{sub 2} is transformed and immobilized through alunite precipitation with lesser amounts of anhydrite and minor quantities of pyrite. The dissolved CO{sub 2} increases with time (enhanced solubility trapping). The mineral alteration induced by injection of CO{sub 2} with either SO{sub 2} or H{sub 2}S leads to corresponding changes in porosity. Significant increases in porosity occur in the acidified zones where mineral dissolution dominates. With co-injection of SO{sub 2}, the porosity increases from an initial 0.3 to 0.43 after 100 years. However, within the CO{sub 2} mineral-trapping zone, the porosity decreases to about 0.28 for both cases, because of the addition of CO{sub 2} mass as secondary carbonates to the rock matrix. Precipitation of sulfates at the acidification front causes porosity to decrease to 0.23. The limited information currently available on the mineralogy of naturally occurring high-pressure CO{sub 2} reservoirs is generally consistent with our simulations

M2K: I. A Jupiter-Mass Planet Orbiting the M3V Star HIP 79431

Doppler observations from Keck Observatory reveal the presence of a planet with M sin i of 2.1 M_(Jup) orbiting the M3V star HIP 79431. This is the sixth giant planet to be detected in Doppler surveys of M dwarfs and it is one of the most massive planets discovered around an M dwarf star. The planet has an orbital period of 111.7 days and an orbital eccentricity of 0.29. The host star is metal rich, with an estimated [Fe/H] = +0.4. This is the first planet to emerge from our new survey of 1600 M-to-K dwarf stars

Love and Taxes – And Matching Institutions

We study a setting with search frictions in the marriage market and with incomplete contracting inside the family. Everyone prefers a partner that has high income and is a perfect emotional match, but compromises must often be struck. A high income earner may abstain from marrying a low-income earner even though they would be a perfect match emotionally, because the highincome earner may dislike the implicit income redistribution implied by the marriage. Redistributive income taxation may ease this problem. Income matching institutions that secure that people largely from the same income groups meet each other can substitute for redistribution, so that optimal redistribution is reduced. We also introduce a divorce option. Redistributive taxation is shown both to further and stabilize marriage.Wenn Menschen mit unterschiedlichem Einkommen heiraten, führt dies zu einer Umverteilung innerhalb der Ehe von der wirtschaftlich stärkeren zur wirtschaftlich schwächeren Person. Zwei Personen, die zufällig aufeinander treffen und aufgrund ähnlicher Interessen und Neigungen gut zueinander passen, werden auch die finanziellen Folgen einer Heirat berücksichtigen. Falls die Person mit hohem Einkommen diese Umverteilung als zu stark empfindet, kommt die Ehe nicht zustande. Die Rente, die z.B. dadurch entsteht, dass das Paar ähnliche Interessen hat oder gemeinsamen Hobbys nachgehen kann, geht in diesem Fall verloren. Progressive Besteuerung führt zu einer Angleichung der Einkommensverteilung und verringert daher die Wahrscheinlichkeit, dass Ehen aufgrund hoher Einkommensunterschiede nicht zustande kommen. Aus wohlfahrtstheoretischer Sicht ist dies ein positiver Aspekt umverteilender Besteuerung, der bisher in der Literatur nicht berücksichtigt wurde. Die optimale Höhe der Besteuerung hängt von den Matching-Institutionen ab, d.h. davon wer wen auf dem Heiratsmarkt trifft. Treffen vorwiegend Personen mit unterschiedlichem Einkommen und ähnlichen Interessen aufeinander, ist der positive Effekt der Besteuerung besonders wirksam. In diesem Fall ist der optimale Steuersatz umso höher, je ähnlicher die Interessen der potentiellen Partner ist. Umgekehrt kann progressive Besteuerung in einer Gesellschaft, in der vorwiegend Personen mit ohnehin ähnlichem Einkommen aufeinandertreffen, kaum etwas bewirken. Daher fällt in diesem Fall der optimale Steuersatz umso geringer aus, je ähnlicher die Einkommen der potentiellen Paare auf dem Heiratsmarkt sind

The California Planet Survey. I. Four New Giant Exoplanets

We present precise Doppler measurements of four stars obtained during the past decade at Keck Observatory by the California Planet Survey (CPS). These stars, namely, HD 34445, HD 126614, HD 13931, and Gl 179, all show evidence for a single planet in Keplerian motion. We also present Doppler measurements from the Hobby-Eberly Telescope (HET) for two of the stars, HD 34445 and Gl 179, that confirm the Keck detections and significantly refine the orbital parameters. These planets add to the statistical properties of giant planets orbiting near or beyond the ice line, and merit follow-up by astrometry, imaging, and space-borne spectroscopy. Their orbital parameters span wide ranges of planetary minimum mass (M sin i = 0.38-1.9 M(Jup)), orbital period (P = 2.87-11.5 yr), semimajor axis (a = 2.1-5.2 AU), and eccentricity (e = 0.02-0.41). HD 34445 b (P = 2.87 yr, M sin i = 0.79 MJup, e = 0.27) is a massive planet orbiting an old, G-type star. We announce a planet, HD 126614 Ab, and an M dwarf, HD 126614 B, orbiting the metal-rich star HD 126614 (which we now refer to as HD 126614 A). The planet, HD 126614 Ab, has minimum mass M sin i = 0.38 MJup and orbits the stellar primary with period P = 3.41 yr and orbital separation a = 2.3 AU. The faint M dwarf companion, HD 126614 B, is separated from the stellar primary by 489 mas (33 AU) and was discovered with direct observations using adaptive optics and the PHARO camera at Palomar Observatory. The stellar primary in this new system, HD 126614 A, has the highest measured metallicity ([ Fe/ H] = + 0.56) of any known planet-bearing star. HD 13931 b (P = 11.5 yr, M sin i = 1.88 MJup, e = 0.02) is a Jupiter analog orbiting a near solar twin. Gl 179 b (P = 6.3 yr, M sin i = 0.82 M(Jup), e = 0.21) is a massive planet orbiting a faint M dwarf. The high metallicity of Gl 179 is consistent with the planet-metallicity correlation among M dwarfs, as documented recently by Johnson & Apps.NSF AST-0702821NASA NNX06AH52GMcDonald Observator

Vertebrate pheromones and other semiochemicals: the potential for accommodating complexity in signalling by volatile compounds for vertebrate management

The interaction between volatile and non-volatile, e.g. proteinaceous, components of pheromone and other semiochemical-based signalling systems presents a daunting set of problems for exploitation in the management of vertebrates, good or bad. Aggravating this is the complexity of the mixtures involved with pheromones, not only by definition associated with each species, but also with individual members of that species and their positions within their immediate communities. Nonetheless, already in some contexts, particularly where signals are perceived at other trophic levels from those of the vertebrates, e.g. by arthropods, reductionist approaches can be applied whereby the integrity of complex volatile mixtures is maintained, but perturbed by augmentation with individual components. In the present article, this is illustrated for cattle husbandry, fish farming and human health. So far, crude formulations have been used to imitate volatile semiochemical interactions with non-volatile components, but new approaches must be developed to accommodate more sophisticated interactions and not least the activities of the non-volatile, particularly proteinaceous components, currently being deduced

M2K: II. A Triple-Planet System Orbiting HIP 57274

Doppler observations from Keck Observatory have revealed a triple planet system orbiting the nearby mid-type K dwarf, HIP 57274. The inner planet, HIP 57274b, is a super-Earth with \msini\ = 11.6 \mearth (0.036 \mjup), an orbital period of 8.135 $\pm$ 0.004 d, and slightly eccentric orbit $e=0.19 \pm 0.1$. We calculate a transit probability of 6.5% for the inner planet. The second planet has \msini\ = 0.4 \mjup\ with an orbital period of 32.0 $\pm 0.02$ d in a nearly circular orbit, and $e = 0.05 \pm 0.03$. The third planet has \msini\ = 0.53 \mjup\ with an orbital period of 432 $\pm 8$ d (1.18 years) and an eccentricity $e = 0.23 \pm 0.03$. This discovery adds to the number of super Earth mass planets with \msini < 12 \mearth\ that have been detected with Doppler surveys. We find that 56 $\pm 18$% super-Earths are members of multi-planet systems. This is certainly a lower limit because of observational detectability limits, yet significantly higher than the fraction of Jupiter mass exoplanets, $20 \pm 8$%, that are members of Doppler-detected, multi-planet systems.Comment: 11 figures, submitte to ApJ on Sept 10, 201

Dynamics of direct inter-pack encounters in endangered African wild dogs

Aggressive encounters may have important life history consequences due to the potential for injury and death, disease transmission, dispersal opportunities or exclusion from key areas of the home range. Despite this, little is known of their detailed dynamics, mainly due to the difficulties of directly observing encounters in detail. Here, we describe detailed spatial dynamics of inter-pack encounters in African wild dogs (Lycaon pictus), using data from custom-built high-resolution GPS collars in 11 free-ranging packs. On average, each pack encountered another pack approximately every 7 weeks and met each neighbour twice each year. Surprisingly, intruders were more likely to win encounters (winning 78.6% of encounters by remaining closer to the site in the short term). However, intruders did tend to move farther than residents toward their own range core in the short-term (1 h) post-encounter, and if this were used to indicate losing an encounter, then the majority (73.3%) of encounters were won by residents. Surprisingly, relative pack size had little effect on encounter outcome, and injuries were rare (<15% of encounters). These results highlight the difficulty of remotely scoring encounters involving mobile participants away from static defendable food resources. Although inter-pack range overlap was reduced following an encounter, encounter outcome did not seem to drive this, as both packs shifted their ranges post-encounter. Our results indicate that inter-pack encounters may be lower risk than previously suggested and do not appear to influence long-term movement and ranging