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Underlying Soil (underlying + soil)
Selected AbstractsExpressing sand supply limitation using a modified Owen saltation equation ,EARTH SURFACE PROCESSES AND LANDFORMS, Issue 12 2008Dale A. Gillette Abstract An analysis of saltation data led us to modify the theory of P. R. Owen using a soil-related parameter ,A' that gave us the possibility of expressing limitation of sand grains of saltation-size in the underlying soil. The value of ,A' was set equal to the ratio of the horizontal flux of saltating particles to Owen's function of wind, times air density divided by gravitational acceleration. Values of A can be used to: (1) characterize the efficiency of the wind to move sand by saltation for different soil textures and aggregations; and (2) to make practical predictions of sand movement based on the condition of the surface soil. Values for A in a range from 1 to 10 are usually associated with supply-unlimited saltation and are usually associated with loose, sandy-textured soils. Values for A in a range from 0·25 to 1 are associated with finer soils that contain more silt and clay. The range of A values between 0 and 0·25 usually reflects finer textured soils that are packed, aggregated, or crusted. A decrease of A to a smaller value is a sign of supply limitation and usually to the soil changing from a looser state to a more aggregated state or more depleted state. Likewise, an increase of A usually corresponds to soil changing from an aggregated state to a looser state. Copyright © 2008 John Wiley & Sons, Ltd. [source] Addressing soil gas vapor intrusion using sustainable building solutionsREMEDIATION, Issue 4 2009Ellen Moyer Soil gas vapor intrusion (VI) emerged in the 1990s as one of the most important problems in the investigation and cleanup of thousands of sites across the United States. A common practice for sites where VI has been determined to be a significant pathway is to implement interim building engineering controls to mitigate exposure of building occupants to VI while the source of contamination in underlying soil and groundwater is assessed and remediated. Engineering controls may include passive barriers, passive or active venting, subslab depressurization, building pressurization, and sealing the building envelope. Another recent trend is the emphasis on "green" building practices, which coincidentally incorporate some of these same engineering controls, as well as other measures such as increased ventilation and building commissioning for energy conservation and indoor air quality. These green building practices can also be used as components of VI solutions. This article evaluates the sustainability of engineering controls in solving VI problems, both in terms of long-term effectiveness and "green" attributes. Long-term effectiveness is inferred from extensive experience using similar engineering controls to mitigate intrusion of radon, moisture, mold, and methane into structures. Studies are needed to confirm that engineering controls to prevent VI can have similar long-term effectiveness. This article demonstrates that using engineering controls to prevent VI is "green" in accelerating redevelopment of contaminated sites, improving indoor air quality, and minimizing material use, energy consumption, greenhouse gas emissions, and waste generation. It is anticipated that engineering controls can be used successfully as sustainable solutions to VI problems at some sites, such as those deemed technically impracticable to clean up, where remediation of underlying soil or groundwater contamination will not be completed in the foreseeable future. Furthermore, green buildings to be developed in areas of potential soil or groundwater contamination may be designed to incorporate engineering controls to prevent VI. © 2009 Wiley Periodicals, Inc. [source] Ground-penetrating radar survey over bronze age circular monuments on a sandy soil, complemented with electromagnetic induction and fluxgate gradiometer dataARCHAEOLOGICAL PROSPECTION, Issue 3 2009L. Verdonck Abstract This paper presents a ground-penetrating radar (GPR) survey over two circular structures originally surrounding Bronze Age burial mounds at the site of Koekelare (western Belgium). The region is characterized by sandy soils. Their low water storage capacity and the consequent moisture contrasts in dry summers played an important role in the detection of over 1000 Bronze Age funeral monuments through aerial archaeology in the past few decades. At Koekelare, low attenuation of GPR waves resulted in the detection of a double and single circular ditch. A fluxgate gradiometer survey and electromagnetic induction (EMI) measurements did not clearly reveal the ditches. For the GPR wave velocity analysis, constant velocity migration tests were combined with time-domain reflectometry (TDR). The TDR measurements were made at different depths within the ditches and in the adjacent undisturbed soil, so that the differences in the physical soil parameters could be assessed. At a depth of approximately 0.45 to 0.8,m, the relatively homogeneous ditch fill produces few GPR reflections compared with the undisturbed soil, and is visible as a weak negative anomaly on the horizontal slices. At this depth, the grey or brownish black ditch fill was found in augering samples, clearly distinguishable from the yellowish brown sandy soil outside the ditches. The transition between the ditch and the underlying soil caused a gradual reflection of radar energy at a depth of approximately 0.8 to 1.2,m, although TDR showed no marked differences in relative permittivity between the ditches and the surrounding soil, and no clear steps as a function of depth. Copyright © 2009 John Wiley & Sons, Ltd. [source] Survival and spread of Shiga toxin-producing Escherichia coli in alpine pasture grasslandsJOURNAL OF APPLIED MICROBIOLOGY, Issue 4 2010B. Fremaux Abstract Aims:, To determine the fate of Shiga toxin-producing Escherichia coli (STEC) strains defecated onto alpine grassland soils. Methods and Results:, During the summers of 2005 and 2006, the field survival of STEC was monitored in cowpats and underlying soils in four different alpine pasture units. A most probable number (MPN)-PCR stx assay was used to enumerate STEC populations. STEC levels ranged between 3·9 and 5·4 log10 CFU g,1 in fresh cowpats and slowly decreased until their complete decay (inactivation rates k < 0·04 day,1). PFGE typing of STEC strains isolated from faecal and soil samples assessed the persistence of various clonal types for at least 2 months in cowpats and their vertical dispersal down through the soil at a depth up to at least 20 cm. STEC cells counts in soil were always below 2 log10 CFU g,1, regardless of the pasture unit investigated. The soil became rapidly free of detectable STEC once the cowpat had decomposed. The eight STEC strains isolated during this study belonged to six distinct serotypes and tested positive for the gene(s) stx2, including the stx2g and stx2 NV206 variants. Conclusions:, STEC were able to persist in cowpats and disseminate down through the soil but were unable to establish. Significance and impact of the Study:, This study provides useful information concerning the ecology of STEC in alpine pasture grasslands and may have implications for land and cattle management. [source] | ||||||||||