Geochemical stability of fine-grained silicic Holocene tephra in Iceland and Scotland

This paper tests two assumptions fundamental to the use of fine-grained silicic tephras from Iceland for creating chronological frameworks in northwest Europe. It is shown firstly, that glass shards can retain their overall chemical integrity on at least a four millennial time-scale in contrasting depositional environments in Iceland and Scotland, and secondly, that an acid digestion process, the most practical method for extracting tephra from peat, does not significantly bias the results of major element analysis by electron microprobe. The implication is that there is great potential and an appropriate method for developing both the resolution and the spatial coverage of chronologies based on silicic Icelandic tephras in northwest Europe.     

Towards a theory for type III solar radio bursts

The procedure developed in Smith (1974) to model the radiation source for type III bursts is modified to include scattering of radiation in the source itself. Since the inhomogeneities in the source must have the same statistical properties as the inhomogeneities used in tracing radiation from the source to the observer, these two parts of the type III problem are no longer uncoupled. Thus we use inhomogeneities consistent with the scattering inhomogeneities of Steinberg et al. (1971) and Riddle (1974) and apply the procedure to an archetype ‘fundamental-harmonic’ pair observed at Culgoora on 28 September, 1973 at 0319 UT. We find that it is impossible to model this burst with a source which is homogeneous in the sense that every part of the source has the same energy density in plasma waves. The density inhomogeneities in the source severely hamper amplification of the supposed fundamental. Possible ways out of this dilemma are discussed, including second harmonic pairs and a source with an inhomogeneous distribution of plasma waves. It is concluded that none of the possibilities are completely satisfactory to explain present observations and suggested that critical observations are missing.     

NEW APPROACH TO ESTIMATING SOLAR RADIATION FROM SATELLITE IMAGERY*

A significantly less expensive but comparatively accurate means of estimating solar radiation from satellite imagery is demonstrated. Opaque cloud cover is visually extracted from nondigitized, photographic forms of GOES satellite imagery and solar radiation is estimated using this information as input into a relatively simple solar model. Daily root mean square, mean absolute and mean bias errors were 13.2, 8.6 and 1.1 percent, respectively. Maps of the spatial distribution of solar radiation for Arizona are included.     

Dynamics and transport from the boundary Northern Current toward the Toulon Bay: multi-platform observations and downscaling modelling approaches

Ocean Dynamics - Coastal regions are vulnerable areas with often high population density, as well as tourism and maritime activities that may have negative impact on the environment. From a...     

Assessment of spatial distribution of contaminants and their levels in soil and water resources of Calabar,Nigeria using geophysical and geological data

The contamination levels of soils and water resources in Calabar, Nigeria have been investigated using resistivity (vertical electrical sounding and electrical resistivity tomography), geochemical analyses of soil and water resources and textural analysis. Sixty randomly sited VES sites were investigated in two seasons while ERT investigations were performed along four profiles. The geochemical investigations were spread across seasons in order to track seasonal changes in physico-chemical parameters: hydrogen ion concentration (pH), electrical conductivity, total dissolved solids, chloride ion (Cl^?), nitrate ion (\( {\text{NO}}_{ 3}^{ - } \)), bicarbonate (\( {\text{HCO}}_{ 3}^{ - } \)), sulphate ion (\( {\text{SO}}_{ 4}^{2 - } \)), calcium ion (Ca²⁺), sodium ion (Na⁺), potassium ion (K⁺) and magnesium ion (Mg²⁺). Additionally, concentrations of ammonium, aluminium and nitrite ions in soils were determined. Results show that ionic concentrations in the sand-dominated soils and water are within permissible limits and baseline standards. The resistivities follow known trends in the area. However, at the central waste disposal site, a localised thin (< 5 m), low resistivity (< 15 Ωm) anomaly suspected to be due to contamination by leachates was observed. Comparatively, the contaminated area is also characterised by marginal increase in ionic concentrations. Strong attenuation capacities of overlying and adjoining clay/lateritic sediments and optimal design of the waste dump site probably reduced the spread of contaminants. The contaminated zone need to be closely monitored so that it does not extend to the aquifers. Hence, all strategies presently being used in managing wastes in Calabar should be sustained.     

Endogenous growth in channelized komatiite lava flows: evidence from spinifex-textured sills at Pyke Hill and Serpentine Mountain,Western Abitibi Greenstone Belt,Northeastern Ontario,Canada

Spinifex-textured sills (i.e., veins) characterized by komatiitic magmas that have intruded their own volcanic-piles have long been recognized. For instance, in the early 1970s, Pyke and coworkers, in their classic work at Pyke Hill in Munro Township, noted that not all spinifex-bearing ultramafic rocks formed as lava flows, rather some were clearly emplaced as small dikes and sills. Several hypotheses have been proposed to explain spinifex-textured sills: intrusion into a cold host, filter pressing, or drainage of residual liquid. However, these do not satisfactorily explain the phenomenon. Field and petrographic observations at Pyke Hill and Serpentine Mountain demonstrate that spinifex-bearing komatiite sills and dikes were emplaced during channel inflation processes when new magma was intruded into a cooler, semi-consolidated but permeable cumulate material. Komatiitic liquids were intruded into the olivine cumulate rocks near the boundary between the spinifex and the cumulate zones of well-organized to organized komatiite flows. Spinifex-textured sills are generally tabular in morphology, stacked one above another, with curviplanar contacts sub-parallel to stratigraphy. Some sills exhibit complex digitated apophyses. Thinner sills typically have a random olivine spinifex texture similar, though generally composed of coarser crystals, to that of komatiite lava flows. Thicker sills exhibit more complex organization of their constituent crystals characterized by zones of random olivine spinifex, overlying zones of organized coarse spinifex crystals similar to those found in lava flows. They have striking coarse dendritic spinifex zones composed of very large olivine crystals, up to several centimetres long and up to 1 cm wide that are not observed in lava flows. Typically, at the sill margins, the cumulate material of the host flow is composed of euhedral to subhedral olivine crystals that are larger than those distal to the contact. Many of these margin-crystals have either concentric overgrowth shells or dendritic olivine overgrowths that grew from the cumulate-sill contact toward the sill interior. The dendrites grew on pre-existing olivine cumulate at the contact in response to a sharp temperature gradient imposed by the intrusion of hot material, whereas the concentric overgrowths formed as new melt percolated into the unconsolidated groundmass of the host-flow cumulate material. Spinifex-textured sills and dikes occur in well-organized to organized flows that are interpreted to have formed by “breakouts” above and peripheral to lava pathways (channels/conduits) as a result of inflation that accompanied voluminous komatiitic eruptions responsible for the construction and channelization of komatiitic flow fields. The spinifex-textured dikes and sills represent komatiitic lava that was originally emplaced into the channel roof during periods of episodic inflation that resulted in lava breakouts and was subsequently trapped in the “roof rocks” during periods of channel deflation. Accordingly, the occurrence of spinifex-textured sills and dikes may indicate proximity to, and aid in the identification and delineation of lava channel-ways that could potentially host Ni–Cu–(PGE) mineralization within komatiitic lava flow-fields.     

Understanding Climatic Impacts, Vulnerabilities, and Adaptation in the United States: Building a Capacity for Assessment

Based on the experience of the U.S. National Assessment, we propose a program of research and analysis to advance capability for assessment of climate impacts, vulnerabilities, and adaptation options. We identify specific priorities for scientific research on the responses of ecological and socioeconomic systems to climate and other stresses; for improvement in the climatic inputs to impact assessments; and for further development of assessment methods to improve their practical utility to decision-makers. Finally, we propose a new institutional model for assessment, based principally on regional efforts that integrate observations, research, data, applications, and assessment on climate and linked environmental-change issues. The proposed program will require effective collaboration between scientists, resource managers, and other stakeholders, all of whose expertise is needed to define and prioritize key regional issues, characterize relevant uncertainties, and assess potential responses. While both scientifically and organizationally challenging, such an integrated program holds the best promise of advancing our capacity to manage resources and the economy adaptively under a changing climate.     

Laboratory Research into Permeable Reactive Barriers for Groundwater Remediation

Permeable Reactive Barriers (PRB) is a new technology for groundwater pollution remediation. Contaminants are converted into harmless by products in situ as the polluted water passes through a reactive wall. Experimental results demonstrate how reactive media can be used to remove contaminants from polluted water by laying the reactive wall across the flow direction of the water. The most comprehensively studied and applied reactive barrier type uses granulated Zero Valent Iron (ZVI) particles. In this process elemental iron provides a reducing environment which makes reductive dechlorination of chlorinated organic compounds feasible or changes redox sensitive metals, so that they are immobilized by a precipitation reaction. A reactive wall column which is made up of ZVI, sand and zeolite has shown the highest contaminant removal capacity compared to the other two which have different components. The potentials of ZVI, zeolite and Powdered Activated Carbon (PAC) to remove contaminants are due to their different physico-chemical proper-ties which make them to "sorb"metal contaminants. The results of this experiment show that PRB technology is an efficient method for the treatment of leachate-contaminated groundwater.     

Influence of river channel morphology and bank characteristics on water surface boundary delineation using high‐resolution passive remote sensing and template matching

Accurate mapping of water surface boundaries in rivers is an important step for monitoring water stages, estimating discharge, flood extent, and geomorphic response to changing hydrologic conditions, and assessing riverine habitat. Nonetheless, it is a challenging task in spatially and spectrally heterogeneous river environments, commonly characterized by high spatiotemporal variations in morphology, bed material, and bank cover. In this study, we investigate the influence of channel morphology and bank characteristics on the delineation of water surface boundaries in rivers using high spatial resolution passive remote sensing and a template‐matching (object‐based) algorithm, and compare its efficacy with that of Support Vector Machine (SVM) (pixel‐based) algorithm. We perform a detailed quantitative evaluation of boundary‐delineation accuracy using spatially explicit error maps in tandem with the spatial maps of geomorphic and bank classes. Results show that template matching is more successful than SVM in delineating water surface boundaries in river sections with spatially challenging geomorphic landforms (e.g. sediment bar structures, partially submerged sediment deposits) and shallow water conditions. However, overall delineation accuracy by SVM is higher than that of template matching (without iterative hierarchical learning). Vegetation and water indices, especially when combined with texture information, improve the accuracy of template matching, for example, in river sections with overhanging trees and shadows – the two most problematic conditions in water surface boundary delineation. By identifying the influence of channel morphology and bank characteristics on water surface boundary mapping, this study helps determine river sections with higher uncertainty in delineation. In turn, the most suitable methods and data sets can be selectively utilized to improve geomorphic/hydraulic characterization. The methodology developed here can also be applied to similar studies on other geomorphic landforms including floodplains, wetlands, lakes, and coastlines. Copyright © 2014 John Wiley & Sons, Ltd.