Suitability of Existing Numerical Model Codes and Thermodynamic Databases for the Prognosis of Calcite Dissolution Processes in Near-Surface Sediments Due to a CO2 Leakage Investigated by Column Experiments

Among the risks of CO₂ storage is the potential of CO₂ leakage into overlaying formations and near-surface potable aquifers. Through a leakage, the CO₂ can intrude into protected groundwater resources, which can lead to groundwater acidification followed by potential mobilisation of heavy metals and other trace metals through mineral dissolution or ion exchange processes. The prediction of pH buffer reactions in the formations overlaying a CO₂ storage site is essential for assessing the impact of CO₂ leakages in terms of trace metal mobilisation. For buffering the pH-value, calcite dissolution is one of the most important mechanisms. Although calcite dissolution has been studied for decades, experiments conducted under elevated CO₂ partial pressures are rare. Here, the first study for column experiments is presented applying CO₂ partial pressures from 6 to 43 bars and realising a near-natural flow regime. Geochemical calculations of calcite dissolution kinetics were conducted using PHREEQC together with different thermodynamic databases. Applying calcite surface areas, which were previously acquired by N₂-BET or calculated based on grain diameters, respectively, to the rate laws according to Plummer et al. (Am J Sci 278:179–216, doi:10.2475/ajs.278.2.179, 1978) or Palandri and Kharaka (US Geol Surv Open file Rep 2004–1068:71, 2004) in the numerical simulations led to an overestimation of the calcite dissolution rate by up to three orders of magnitude compared to the results of the column experiments. Only reduction of the calcite surface area in the simulations as a fitting procedure allowed reproducing the experimental results. A reason may be that the diffusion boundary layer (DBL), which depends on the groundwater flow velocity and develops at the calcite grain surface separating it from the bulk of the solution, has to be regarded: The DBL leads to a decrease in the calcite dissolution rate under natural laminar flow conditions compared to turbulent mixing in traditional batch experiments. However, varying the rate constants by three orders of magnitudes in a field scale PHREEQC model simulating a CO₂ leakage produced minor variations in the pH buffering through calcite dissolution. This justifies the use of equilibrium models when calculating the calcite dissolution in CO₂ leakage scenarios for porous aquifers and slow or moderate groundwater flow velocities. However, the selection of the thermodynamic database has an impact on the dissolved calcium concentration, leading to an uncertainty in the simulation results. The resulting uncertainty, which applies also to the calculated propagation of an aquifer zone depleted in calcite through dissolution, seems negligible for shallow aquifers of approximately 60 m depth, but amounts to 35 % of the calcium concentration for aquifers at a depth of approximately 400 m.     

Chemical Signatures of Middens at a Late Classic Maya Residential Complex,Guatemala

Phosphorus (P) and other chemical elements have been used to identify residential middens at archaeological sites. This study discusses the relationship of soil chemical elements and middens at Group Chispa, a Late Classic residential complex at a commoner village in the Maya lowlands. The complex was extensively excavated and soil sampled. Ceramic sherd densities, which serve as a proxy for artifact densities, correlate only partially with phosphorus and other chemical elements. One of the three middens in Group Chispa coincides with the highest concentration of P while the two others—including the most extensive one—have medium to low P levels. A spectrum of human activities that include the preparation of pigments explains the nontraditional distribution of chemical elements. High P levels remain useful to detect middens but they provide an incomplete picture and need to be contextualized by comprehensive archaeological data.     

What we know about elemental bulk chondrule and matrix compositions: Presenting the ChondriteDB Database

Chondrules and matrix are the major components of chondritic meteorites and represent a significant evolutionary step in planet formation. The formation and evolution of chondrules and matrix and, in particular, the mechanics of chondrule formation remain the biggest unsolved challenge in meteoritics. A large number of studies of these major components not only helped to understand these in ever greater detail, but also produced a remarkably large body of data. Studying all available data has become known as ?big data? analyses and promises deep insights – in this case – to chondrule and matrix formation and relationships. Looking at all data may also allow one to better understand the mechanism of chondrule formation or, equally important, what information we might be missing to identify this process. A database of all available chondrule and matrix data further provides an overview and quick visualisation, which will not only help to solve actual problems, but also enable students and future researchers to quickly access and understand all we know about these components. We collected all available data on elemental bulk chondrule and matrix compositions in a database that we call ChondriteDB. The database also contains petrographic and petrologic information on chondrules. Currently, ChondriteDB contains about 2388 chondrule and 1064 matrix data from 70 different publications and 161 different chondrites. Future iterations of ChondriteDB will include isotope data and information on other chondrite components. Data quality is of critical importance. However, as we discuss, quality is not an objective category, but a subjective judgement. Quantifiable data acquisition categories are required that allow selecting the appropriate data from a database in the context of a given research problem. We provide a comprehensive overview on the contents of ChondriteDB. The database is available as an Excel file upon request from the senior author of this paper, or can be accessed through MetBase.     

The need for data: natural disasters and the challenges of database management

Hundreds of natural catastrophes occur worldwide every year—there were 780 loss events per year on average over the last 10 years. Since 1980, these disasters have claimed over two million lives and caused losses worth US$ 3,000 billion. The deadliest disasters were caused by earthquakes: the tsunami following the Sumatra quake (2004) and the Haiti earthquake (2010) claimed more than 220,000 lives each. The Great East Japan Earthquake of 11 March 2011 was the costliest natural disaster of all times, with total losses of US$ 210 billion. Hurricane Katrina, in 2005, was the second costliest disaster, with total losses of US$ 140 billion (in 2010 values). To ensure that high-quality natural disaster analyses can be performed, the data have to be collected, checked and managed with a high degree of expertise and professionality. Scientists, governmental and non-governmental organisations and the finance industry make use of global databases that contain losses attributable to natural catastrophes. At present, there are three global and multi-peril loss databases: NatCatSERVICE (Munich Re), Sigma (Swiss Re) and EM-Dat (Centre for Research on the Epidemiology of Disasters). They are supplemented by numerous databases focusing on national or regional issues, certain hazards and specific sectors. This paper outlines the criteria and definitions relating to how global and multi-peril databases are operated, and the efforts being made to ensure consistent and internationally recognised standards of data management. In addition, it presents the concept and methodology underlying the NatCatSERVICE database, and points out the many challenges associated with data acquisition and data management.     

Timing of rockfalls in the Mont Blanc massif (Western Alps): evidence from surface exposure dating with cosmogenic <Superscript>10</Superscript>Be

Rockfalls and rock avalanches are a recurrent process in high mountain areas like the Mont Blanc massif. These processes are surveyed due to the hazard they present for infrastructure and alpinists. While rockfalls and rock avalanches have been documented for the last 150 years, we know very little about their frequency since the Last Glacial Maximum (LGM). In order to improve our understanding, it is imperative to date them on a longer timescale. A pilot campaign using Terrestrial Cosmogenic Nuclide (TCN) dating of five samples was carried out in 2006 at the Aiguille du Midi (3842 m a.s.l.). In 2011, a larger scale study (20 samples) was carried out in five other test sites in the Mont Blanc massif. This paper presents the exposure ages of the 2011 TCN study as well as the updated exposure ages of the 2006 study using newer TCN dating parameters. Most of these exposure ages lie within the Holocene but three ages are Pleistocene (59.87?±?6.10 ka for the oldest). A comparison of these ages with air temperature and glacier cover proxies explored the possible relationship between the most active rockfall periods and the warmest periods of the Holocene: two clusters of exposure ages have been detected, corresponding to the Middle Holocene (8.2–4.2 ka) and the Roman Warm Period (c. 2 ka) climate periods. Some recent rockfalls have also been dated (<?0.56 ka).     

Detection,characterization, and analysis of land subsidence in Nairobi using InSAR

Natural Hazards - Himalayan mountains are one of the most seismo-tectonically active zones on the surface of the earth. Recurring moderate and high magnitude earthquakes are not uncommon in this...     

Development of instrumental seismology in Sweden in 1949–1958

Summary A review is given of the present (1959) seismological stations in Sweden, i.e. Uppsala, Kiruna, Skalstugan, and Göteborg, as well as of older stations, which are no longer in operation, i.e. Vassijaure, Abisko, and Lund, including all pertinent information. The disturbing effect of the loose ground at Lund in distinction from the four first-mentioned stations is clearly demonstrated. The very good ground at Uppsala, Kiruna, Skalstugan, and Göteborg, together with the use of modern equipment of high magnification has made these stations, especially Uppsala and Kiruna, very sensitive. This is obvious from the number of recorded earthquakes. The method of time measurements, including direct recording of time signals, is described, and means to reach a high time accuracy are outlined, including the recommendation to use quartz clocks. Long-period (0.5–2 min) disturbances on the long-period Benioff combinations were mainly due to air currents in the seismometer room and were eliminated by providing the seismometers with special covers. The method of ground amplitude determinations is outlined, especially for the Benioff instruments, and typical magnification curves are given. Comparisons of ground amplitudes from simultaneous records of BenioffE, N and WiechertE, N and of BenioffZ and GrenetZ have been made. The amplitude comparison between Benioff and Wiechert has given a new estimate of the effect of friction (especially of the recording pen against the paper) in the Wiechert apparatus.

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Zusammenfassung Eine Übersicht sowohl von den gegenwärtigen (1959) seismologischen Stationen in Schweden, d.h. Uppsala, Kiruna, Skalstugan und Göteborg, als auch von früheren Stationen, die nicht mehr im Betrieb sind, d.h. Vassijaure, Abisko und Lund, wird gegeben. Die störende Wirkung des lockeren Bodens in Lund zum Unterschied gegen die vier erstgenannten Stationen wird deutlich hervorgehoben. Der sehr gute Untergrund in Uppsala, Kiruna, Skalstugan und Göteborg und die Verwendung moderner Apparate hoher Vergrösserung haben diese Stationen, besonders Uppsala und Kiruna, sehr empfindlich gemacht. Dieser Umstand geht aus der Anzahl registrierter Beben hervor. Die Methode der Zeitmessungen (direkte Registrierung der Zeitsignale einbegriffen) wird beschrieben, und Massnahmen eine hohe Zeitgenauigkeit zu erreichen werden erwähnt, die auch die Verwendung von Quarz-Uhren umfassen. Langperiodische Störungen (Perioden 0.5–2 Min) auf den langperiodischen Benioff-Registrierungen waren hauptsächlich durch Luftströmungen im Seismometerraum verursacht und wurden durch spezielle Kappen über den Seismometern eliminiert. Die Methode der Bestimmung von Boden-Amplituden wird beschrieben, hauptsächlich für die Benioff-Instrumente, und typische Vergrösserungskurven sind gegeben. Vergleichungen der Bodenamplituden von parallelen Registrierungen von BenioffE, N und WiechertE, N und von BenioffZ und GrenetZ sind ausgeführt worden. Die Amplitudenvergleichung zwischen Benioff und Wiechert hat eine neue Schätzung des Einflusses der Reibung (speziell vom Schreibfeder gegen das Papier) im Wiechert-Seismographen gegeben.