Thermal asymmetry and cross-valley circulation in a small alpine valley

Wind observations from a small Alpine valley are used to investigate the problem of cross-valley winds. The observed daytime windfield is a superposition of dynamically and thermally forced cross-winds. Prevailing cross-winds above the valley result in a recirculation cell above the lee slope. The return flow is strengthened or weakened by thermal effects which induce a wind that blows from the shaded to the sunny side of the valley. The reaction time of the thermally induced cross-winds is only 4 min. The horizontal and vertical motions of the cross-valley circulation transport heat in such a way that the insolation differences between the two sides of the valley are nearly equalized.     

Mixed land use and obesity: an empirical comparison of alternative land use measures and geographic scales

Obesity is a growing epidemic in the United States. Walkable neighborhoods, characterized as having the 3Ds of walkability (population Density, land use Diversity, and pedestrian-friendly Design), have been identified as a potentially promising factor to prevent obesity for their residents. Past studies examining the relationship between obesity and walkability vary in geographic scales of neighborhood definitions and methods of measuring the 3Ds. To better understand potential influences of these sometimes arbitrary choices, we test how four types of alternative measures of land use diversity measured at three geographic scales relate to body mass index for 4960 Salt Lake County adults. Generalized estimation equation models demonstrate that optimal diversity measures differed by gender and geographic scale and that integrating walkability measures at different scales improved the overall performance of models.     

Methane Production and Isotopic Fingerprinting in Ethanol Fuel Contaminated Sites

Biodegradation of organic compounds in groundwater can be a significant source of methane in contaminated sites. Methane might accumulate in indoor spaces posing a hazard. The increasing use of ethanol as a gasoline additive is a concern with respect to methane production since it is easily biodegraded and has a high oxygen demand, favoring the development of anaerobic conditions. This study evaluated the use of stable carbon isotopes to distinguish the methane origin between gasoline and ethanol biodegradation, and assessed the occurrence of methane in ethanol fuel contaminated sites. Two microcosm tests were performed under anaerobic conditions: one test using ethanol and the other using toluene as the sole carbon source. The isotopic tool was then applied to seven field sites known to be impacted by ethanol fuels. In the microcosm tests, it was verified that methane from ethanol (δ¹³C = −11.1‰) is more enriched in ¹³C, with δ¹³C values ranging from −20‰ to −30‰, while the methane from toluene (δ¹³C = −28.5‰) had a carbon isotopic signature of −55‰. The field samples had δ¹³C values varying over a wide range (−10‰ to −80‰), and the δ¹³C values allowed the methane source to be clearly identified in five of the seven ethanol/gasoline sites. In the other two sites, methane appears to have been produced from both sources. Both gasoline and ethanol were sources of methane in potentially hazardous concentrations and methane could be produced from organic acids originating from ethanol along the groundwater flow system even after all the ethanol has been completed biodegraded.     

Assessment of Workforce Demands to Shape GIS&T Education

The Body of Knowledge for Geographic Information Science and Technology (GIS&T BoK) has been the main reference document for curriculum design in the geospatial domain. Today, the BoK is supposed to have fallen short in adequately covering the domain due to significant conceptual and technological advances in the field. Thus, several initiatives around the globe work towards an update of the GIS&T BoK. This research assesses the demands of today's GIS&T workforce across Europe to contribute to the effort of a demand‐oriented update. We assessed the workforce demand by means of a Europe‐wide distributed online questionnaire and complementary expert interviews. The results show that the BoK still is a comprehensive reference base for the geospatial domain that is generally deemed relevant by the European workforce. However, workforce demands point to three main topics that need to be addressed by an update of the BoK: (1) the shift from primary data acquisition to the handling of highly abundant spatial data; (2) a lack of competences in programming and application development; and (3) a poor coverage of web‐related aspects. Future research should complement workforce demands with a review of the scientific literature to identify additional shortcomings related to conceptual advances.     

Annual deformation signals from homogeneously reprocessed VLBI and GPS height time series

The first part of this paper compares homogeneously reprocessed Very Long Baseline Interferometry (VLBI) and Global Positioning System (GPS) long-term height series from 1994 to 2007. The data analysis used fully adapted state-of-the-art models (like VMF1 and a priori zenith delays from ECMWF) for the GPS and VLBI processing. The series are compared in terms of long-term non-linear behaviour, harmonic and mean annual signals (not necessarily of harmonic nature). The similarity between both techniques is very good (especially the mean annual signals), which is assumed to be due to the adapted models and consistent reprocessing of both series. As two almost independent observing techniques see the same annually recurring signals at almost all co-located sites, we expect a good geophysical interpretability as integral vertical deformation. For the second part of this paper, the height time series of 161 suitable GPS sites (of the same solution as before) are used to determine a harmonic and a mean annual signal for each of them. Comparing the annual signals for this big dataset visually to GRACE-determined load deformations described in other publications, we find good agreement. This puts emphasis to the assumption that our height data have a lot of potential to be interpreted as geophysical signals. Out of these 161, 131 are grouped to 55 clusters, if at least two nearby (some thousand kilometres) sites show similar mean annual signals, which are thus confirmed to be real regional deformation, not local or technical artefacts. These 55 signals are presented on a “world map” of regional average mean annual height signals, as easy-to-handle tool to validate geophysical models. The data of these measured regional mean annual signals can be downloaded from a web-page for numerical analysis.     

A 1D Hypoplastic constitutive model for expansive soils

This paper presents a simple hypoplastic constitutive model that describes the essential features of the material behaviour of partially saturated clayey soils observed in oedometric compression tests. The model is formulated in terms of net stress and degree of saturation. The total strain rate is decomposed into a portion related to the changes in saturation and a portion for the evolution of net stress. However, no distinction is made between plastic and elastic strains. With this strain rate decomposition, the maximum swelling strain/stress are obtained by simulating wetting processes under constant stress/strain conditions. In addition to the void ratio, the model includes two scalar variables to track the loading history (preloading). The calibration of the model constants using common laboratory tests is discussed. Confined and unconfined swelling tests under oedometric conditions with subsequent loading and unloading phases carried out on three different materials were satisfactorily simulated by the model. Its promising results call for an extension to a 3D formulation.

     

Preliminary trace element analysis of arsenic in Nepalese groundwater may pinpoint its origin

Arsenic contamination of groundwater used as drinking water in South Asia poses a serious health threat to the inhabitants living on alluvial plains of the Himalayan foreland of countries like Bangladesh, India, Nepal and Myanmar. Although the geological and geochemical conditions favoring the release of the highly poisonous contaminant from the sediments hosting the groundwater are meanwhile quite well understood, there is still a significant debate about the origin of arsenic. The sediments forming a huge proportion of the Terai (lowlands of Nepal) aquifers are derived from two main sources, (i) sediments deposited by large rivers that erode the upper Himalayan crystalline rocks and (ii) weathered meta-sediments carried by smaller rivers originating in the Siwalik foothills adjacent to the Terai. In this article a so far underestimated source of As is discussed: the peraluminous leucogranites found ubiquitously in the Nepal Himalaya. The relationship between the trace elements analyzed in the groundwater in the Terai and trace elements found in such felsic rocks reflect the origin of the arsenic in the high Himalayas of Nepal. In addition to the high concentration of As, a striking feature is the presence of the lithophile trace elements like Li, B, P, Mn, Br, Sr and U in the groundwater. The mentioned elements point to a felsic initial source like metapelites or leucogranites—all rocks showing a high abundance of especially B, P and As as well as Cd and Pb.     

Landforms on Asteroid 25143-Itokawa: A geomorphological perspective on periglacial origin and meltwater history

Asteroid surface geology offers a full range of opportunities for geomorphologists to participate in the analysis of landform distributions, deposit composition, source areas for sediments, age estimations, and the reconstruction of geohydrological records. A recent touchdown (2005) on 25143-Itokawa, a Near Earth Object (NEO), by the Hayabusa Spacecraft provides imagery (released, 2008, by the Japanese Aerospace Agency) that allows the analysis of data relevant to geomorphologists. The abbreviated interpretation of landform distributions on Itokawa discussed below provides a preliminary analysis of landform morphogenesis in a cold climate with near-zero gravity. The analysis generates several questions related to source of water, cause of fluid propagation and explanations of previously unrecognized processes of denudation.