Rock-magnetic proxies of climate change from loess -paleosol sediments of the Czech Republic

Summary Rock-magnetic characteristics of late Pleistocene loess-paleosol sequences in the Czech Republic show patterns of variation that reflect climate-related depositional and diagenetic processes which acted on the sedimentary profiles. Mass-normalized magnetic susceptibility is high in interglacial and interstadial paleosols, while uniformly low values are measured in unweathered loess horizons. Normalized ferrimagnetic susceptibility and anhysteretic remanent magnetization show an enhancement of ultrafine (superparamagnetic, SP) and fine (single-domain, SD, and pseudo-single-domain, PSD) grains in chernozem paleosols correlated with δ¹⁸O substages 5c and 5a as well as in the Holocene soil. The parabraunerde paleosol associated with peak interglacial conditions, correlated with δ¹⁸O substage 5e, shows evidence of diagenetic loss of fine grained magnetic minerals, although coarse (multidomain, MD) grains appear to be preserved. Low temperature remanence behavior plus high temperature susceptibility measurements of representative samples from each lithologic unit indicate that magnetite and maghemite are the dominant magnetic minerals within the sediments. Variations in concentration-independent rock-magnetic parameters are therefore primarily a function of grain size variations through the profile. It is anticipated that with additional magnetic and non-magnetic sedimentological and geochemical tests, a quantitative rock-magnetic — paleoclimate model can be developed for the central European loess region.     

Estimation and application of near‐surface full waveform redatuming operators

Land seismic data quality can be severely affected by near‐surface anomalies. The imprint of a complex near‐surface can be removed by redatuming the data to a level below the surface, from where the subsurface structures are assumed to be relatively smooth. However, to derive a velocity‐depth model that explains the propagation effects of the near‐surface is a non‐trivial task. Therefore, an alternative approach has been proposed, where the redatuming operators are obtained in a data‐driven manner from the reflection event related to the datum. In the current implementation, the estimation of these redatuming operators is done in terms of traveltimes only, based on a high‐frequency approximation. The accompanying amplitudes are usually derived from a local homogeneous medium, which is obviously a simplification of reality. Such parametrization has produced encouraging results in the past but cannot completely remove the near‐surface complexities, leaving artefacts in the redatumed results. In this paper we propose a method that estimates the redatuming operators directly from the data, i.e., without using a velocity model, in a full waveform manner, such that detailed amplitude and phase variations are included. The method directly outputs the inverse propagation operators that are needed for true‐amplitude redatuming. Based on 2D synthetic data it is demonstrated that the resulting redatuming quality is improved and artefacts are reduced.     

Transport of radionuclides in an unconfined chalk aquifer inferred from U-series disequilibria

U-series disequilibria measured in waters and rocks from a chalk aquifer in France have been used as an analog for long-term radionuclide migration. Drill core samples from a range of depths in the vadose zone and in the saturated zone, as well as groundwater samples were analyzed for ²³⁸U, ²³⁴U, ²³²Th and ²³⁰Th to determine transport mechanisms at the water/rock interface and to quantify parameters controlling the migration of radionuclides. Isotope measurements in rocks were done by TIMS, whereas (²³⁴U/²³⁸U) and (²³⁰Th/²³²Th) activity ratios in water samples were measured by multi-collector-ICP-MS. Both depletion and enrichment in ²³⁴U relative to ²³⁸U were observed in carbonate rock samples resulting from chemical weathering in the unsaturated zone and calcite precipitation in the zone of water-table oscillation, respectively. The correlation between (²³⁰Th/²³²Th) activity ratios and ⁸⁷Sr/⁸⁶Sr ratios found in the chalk samples indicates that thorium is mainly contained in a minor silicate phase whose abundance is variable in chalk samples. Water samples are all characterized by (²³⁴U/²³⁸U) > 1 resulting from α-recoil effect of ²³⁴Th. Groundwaters are characterized by a more radiogenic signature in ⁸⁷Sr/⁸⁶Sr than the rocks. Moreover, (²³⁰Th/²³²Th) activity ratios in the waters are lower than in the rocks, and increase with distance from the water divide, which suggests that Th transport is controlled by colloids formed during water infiltration in the soil. A 1-D transport model has been developed in order to constrain the U-series nuclide transport considering a transient behavior of radionuclides in the aquifer and a time-dependent composition for the solid phase. This model permits a prediction of the time scale of equilibration of the system, and an estimation of parameters such as weathering rate, distribution coefficients and α-recoil fractions. Retardation factors of 10-35 and from 1 × 10⁴ to 2 × 10⁵ were predicted for U and Th, respectively, and can be used to predict the migration of radionuclides released as contaminants in the environment. At the scale of our watershed (∼32 km²), a characteristic migration time from recharge to riverine discharge of 200-600 yr for U and 0.2-3.7 Myr for Th was obtained.     

Global sensitivity analysis of DRAINMOD‐FOREST,an integrated forest ecosystem model

Global sensitivity analysis is a useful tool to understand process‐based ecosystem models by identifying key parameters and processes controlling model predictions. This study reported a comprehensive global sensitivity analysis for DRAINMOD‐FOREST, an integrated model for simulating water, carbon (C), and nitrogen (N) cycles and plant growth in lowland forests. The analysis was carried out for multiple long‐term model predictions of hydrology, biogeochemistry, and plant growth. Results showed that long‐term mean hydrological predictions were highly sensitive to several key plant physiological parameters. Long‐term mean annual soil organic C content and mineralization rate were mainly controlled by temperature‐related parameters for soil organic matter decomposition. Mean annual forest productivity and N uptake were found to be mainly dependent upon plant production‐related parameters, including canopy quantum use efficiency and carbon use efficiency. Mean annual nitrate loss was highly sensitive to parameters controlling both hydrology and plant production, while mean annual dissolved organic nitrogen loss was controlled by parameters associated with its production and physical sorption. Parameters controlling forest production, C allocation, and specific leaf area highly affected long‐term mean annual leaf area. Results of this study could help minimize the efforts needed for calibrating DRAINMOD‐FOREST. Meanwhile, this study demonstrates the critical role of plants in regulating water, C, and N cycles in forest ecosystems and highlights the necessity of incorporating a dynamic plant growth model for comprehensively simulating hydrological and biogeochemical processes. Copyright © 2013 John Wiley & Sons, Ltd.     

Murky waters: Media reporting of marine protected areas in South Australia

Given the public's limited knowledge of marine environments, informing the public about marine protection presents a unique challenge. Studies have shown a well-informed public is more likely to support environmental issues and that newspapers, in particular, are considered a credible media source. This research investigates media representations of current South Australian efforts to establish a marine protected area (MPA). Articles from five newspapers between 1999 and 2006 were examined for content in the following areas: local marine ecology, the policy process of MPA establishment and stakeholder views. The research found that newspapers concentrated their reporting on opposing stakeholders, opinions and were largely ineffective in conveying the significance of the local marine ecology, the economic benefits of the MPA, and the delayed establishment process. These information gaps have left the public poorly informed, and therefore, there is unlikely to be significant pressure to overcome the continued delays in the establishment process.     

A New Population of Radio Quasars

We present a new population of radio quasars whose X-ray band, unlike previously known sources which have (flat) inverse Compton radiation, is characterized by (steep) synchrotron emission, with a broad-band spectral energy distribution similar to that of BL Lacs with high energy synchrotron peaks. We discuss how this new class was discovered, the class properties, and the implications of its existence for our understanding of jets and active galactic nuclei in general.     

Expansion of an invasive coral species over Abrolhos Bank,Southwestern Atlantic

Invasive coral species of the genus Tubastraea have been increasingly recorded in Southwestern Atlantic waters since the 1980s. Their invasion and infestation are mainly related to port and oil exploration activities. For the first time the presence of Tubastraea tagusensis colonies is reported in Espírito Santo State, colonizing a port shore area, and incrusting oil/gas platform structures situated in the southern Abrolhos Bank, which is part of the most important coral reef system of the South Atlantic Ocean. Tubastraea colonies exhibit fast growth and high recruitment rates, and colonized 40% of the analyzed structures in just four years. The projection of port and oil/gas industry growth for the Espírito Santo State (more than 300%) highlights an alert to the dispersal of this alien species to natural areas.     

Impact of tunneling on regional groundwater flow and implications for swelling of clay–sulfate rocks

Tunnels play a key role in many transportation concepts. The swelling of clay–sulfate rocks leads to serious damage to many tunnels crossing such rock, producing great difficulties and high extra costs in tunnel engineering. The swelling is caused by the transformation of the sulfate mineral anhydrite into gypsum, entailing a 60% volume increase. The transformation involves anhydrite dissolution in water, transport of the solution with groundwater flow, and gypsum precipitation at a different location. Therefore, the knowledge of groundwater flow systems at the tunnel and adjacent areas is essential to better understand the swelling processes. The present study investigates the groundwater flow systems at the Chienberg tunnel in Switzerland before and after the tunnel excavation, based on numerical flow modeling. The models include faults and the hydrostratigraphic layering in the subsurface to assess the role of the hydrogeological setting. The results of this study indicate effects on groundwater flow caused by the tunneling, which may trigger rock swelling by favoring anhydrite dissolution and gypsum precipitation, including (1) increase of flow rates around the tunnel, (2) broadened, shifted and more distributed capture zones leading to a change in origin and age of groundwater, (3) access of groundwater from preferential flow paths (e.g. faults) due to the drainage effect of the tunnel, and (4) change in geochemical equilibrium conditions because of decreased pore water pressures in the tunnel area.     

Editorial

Abstract

With the increase in volume of spatial data now available, more effective ways must be found of storing and processing these data. This paper presents a compacted version of the linear quadtree and a spatially-referenced index method that can significantly reduce the storage requirements of a set of images and the time taken to process spatial queries. The index acts as a high-level summary of a regular-sized portion of the underlying image and so can be used to avoid examining areas of the image where none of the required features is present. Some example results are given. A method for the optimization of spatial searches is presented which takes into account the area and distribution of features within an image. Finally, a method for directly associating the edges of features with the individual nodes of a quadtree is reported. This is important since the edges of objects are no longer explicitly present in linear quadtrees and so must be recalculated when they are required for part of a query. Recalculation of object edges or boundaries is expensive; it is best, therefore, to perform the operation once only, and then save the results.