983 resultados para Humidity of soil
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Bibliography: p. 28.
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Subtitle varies slightly.
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Includes bibliographical references (p. 82).
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Literature cited: p. 38-44.
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"The greater part of the material used was selected from the files of the Work Projects Administration Erosion history project, 701-2-240, Columbia, S.C."--Foot-note, p. 1.
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"August 1981."
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Riley J. Wilson, chairman.
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Mode of access: Internet.
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Mode of access: Internet.
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Mode of access: Internet.
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From October 2014 to March 2015, I provided excavation oversight services at a property with substantial environmental concerns. The property in question is located near downtown Seattle and was formerly occupied by the Washington’s first coal gasification plant. The plant operated from 1888 to 1908 and produced coal gas for municipal use. A coal tar like substance with a characteristically high benzene concentration was a byproduct of the coal gasification process and heavily contaminated at or below the surface grade of the plant as shown in previous investigations on the property. Once the plant ceased operation in 1908 the property was left vacant until 1955 when the site was filled in and a service station was built on the property. The main goal of the excavation was not to achieve cleanup on the property, but to properly remove what contaminated soil was encountered during the redevelopment excavation. Areas of concern were identified prior to the commencement of the excavation and an estimation of the extent of contamination on the property was developed. “Hot spots” of contaminated soil associated with the fill placed after 1955 were identified as areas of concern. However, the primary contaminant plume below the property was likely sourced from the coal gasification plant, which operated at an approximate elevation of 20 feet. We planned to constrain the extents of the soil contamination below the property as the redevelopment excavation progressed. As the redevelopment excavation was advanced down to an elevation of approximately 20 feet, soil samples were collected to bound the extents of contamination in the upper portion of the site. The hot spots, known pockets of carcinogenic polycyclic aromatic hydrocarbons (cPAH) located above 20 feet elevation, were excavated as part of the redevelopment excavation. Once a hot spot was excavated, soil samples were collected from the north, south, east, west and bottom sidewalls of the hot spot excavation to check for remaining cPAH. Additionally, four underground storage tanks (USTs) associated with the service station were discovered and subsequently removed. Soil samples were also collected from the resulting UST excavation sidewalls to check for remaining petroleum hydrocarbons. Once the excavation reached its final excavation depth of 20 to 16 feet in elevation, bottom of excavation samples were collected on a 35 foot by 35 foot grid to test for concentrations of contaminants remaining onsite. Once the redevelopment excavation was complete, soils observed from borings drilled for either structural elements, geotechnical wells, or environmental wells were checked for any evidence of contamination using field screening techniques. Evidence of contamination was used to identify areas below the final excavation grade which had been impacted by the operation of the coal gasification plant. Samples collected from the excavation extents of hot spots and USTs show that it was unlikely that any contamination traveled from the post-1955 grade down to the pre-1955 grade. Additionally, the lack of benzene in the bottom of excavation samples suggests that a release from the coal gasification plant occurred below the redevelopment excavation final elevations of 20 to 16 feet. Qualitative data collected from borings for shoring elements and wells indicated that the spatial extent of the subsurface contaminant plume was different than initially estimated. Observations of spoils show that soil contamination extends further to the southwest and not as far to the east and north than originally estimated. Redefining the extent of the soil contamination beneath the property will allow further subsurface investigations to focus on collecting quantitative data in areas that still represent data gaps on the property, and passing over areas that have shown little signs of contamination. This information will help with the formation of a remediation plan should the need to clean up the site arise in the future.
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Four sites located in the north-eastern region of the United States of America have been chosen to investigate the impacts of soil heterogeneity in the transport of solutes (bromide and chloride) through the vadose zone (the zone in the soil that lies below the root zone and above the permanent saturated groundwater). A recently proposed mathematical model based on the cumulative beta distribution has been deployed to compare and contrast the regions' heterogeneity from multiple sample percolation experiments. Significant differences in patterns of solute leaching were observed even over a small spatial scale, indicating that traditional sampling methods for solute transport, for example the gravity pan or suction lysimeters, or more recent inventions such as the multiple sample percolation systems may not be effective in estimating solute fluxes in soils when a significant degree of soil heterogeneity is present. Consequently, ignoring soil heterogeneity in solute transport studies will likely result in under- or overprediction of leached fluxes and potentially lead to serious pollution of soils and/or groundwater. The cumulative beta distribution technique is found to be a versatile and simple technique of gaining valuable information regarding soil heterogeneity effects on solute transport. It is also an excellent tool for guiding future decisions of experimental designs particularly in regard to the number of samples within one site and the number of sampling locations between sites required to obtain a representative estimate of field solute or drainage flux.
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Soil properties that influence water movement through profiles are important for determining flow paths, reactions between soil and solute, and the ultimate destination of solutes. This is particularly important in high rainfall environments. For highly weathered deep profiles, we hypothesize that abrupt changes in the distribution of the quotient [QT = (silt + sand)/clay] reflect the boundaries between textural units or textural (TS) and hydrologic (HS) stratigraphies. As a result, QT can be used as a parameter to characterize TS and as a surrogate for HS. Secondly, we propose that if chloride distributions were correlated with QT, under non-limiting anion exchange, then chloride distributions can be used as a signature indicator of TS and HS. Soil cores to a depth of 12.5 in were taken from 16 locations in the wet tropical Johnstone River catchment of northeast Queensland, Australia. The cores belong to nine variable charge soil types and were under sugarcane (Saccharun officinarum-S) production, which included the use of potassium chloride, for several decades. The cores were segmented at I m depth increments and subsamples were analysed for chloride, pH, soil water content (theta), clay, silt and sand contents. Selected bores were capped to serve as piezometers to monitor groundwater dynamics. Depth incremented QT, theta and chloride correlated, each individually, significantly with the corresponding profile depth increments, indicating the presence of textural, hydrologic and chloride gradients in profiles. However, rapid increases in QT down the profile indicated abrupt changes in TS, suggesting that QT can be used as a parameter to characterize TS and as a surrogate for HS. Abrupt changes in chloride distributions were similar to QT, suggesting that chloride distributions can be used as a signature indicator of QT (TS) and HS. Groundwater data indicated that chloride distributions depended, at least partially, on groundwater dynamics, providing further support to our hypothesis that chloride distribution can be used as a signature indicator of HS. Copyright (c) 2005 John Wiley & Sons, Ltd.
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The appropriate use of wastes is a significant issue for the pig industry due to increasing pressure from regulatory authorities to protect the environment from pollution. Nitrogen contained in piggery pond sludge ( PPS) is a potential source of supplementary nutrient for crop production. Nitrogen contribution following the application of PPS to soil was obtained from 2 field experiments on the Darling Downs in southern Queensland on contrasting soil types, a cracking clay ( Vertosol) and a hardsetting sandy loam (Sodosol), and related to potentially mineralisable N from laboratory incubations conducted under controlled conditions and NO3- accumulation in the field. Piggery pond sludge was applied as-collected ( wet PPS) and following stockpiling to dry ( stockpiled PPS). Soil NO3- levels increased with increased application rates of wet and stockpiled PPS. Supplementary N supply from PPS estimated by fertiliser equivalence was generally unsatisfactory due to poor precision with this method, and also due to a high level of NO3- in the clay soil before the first assay crop. Also low recoveries of N by subsequent sorghum ( Sorghum bicolor) and wheat ( Triticum aestivum) assay crops at the 2 sites due to low in-crop rainfall in 1999 resulted in low apparent N availability. Over all, 29% ( range 12 - 47%) of total N from the wet PPS and 19% ( range 0 - 50%) from the stockpiled PPS were estimated to be plant-available N during the assay period. The high concentration of NO3- for the wet PPS application on sandy soil after the first assay crop ( 1998 barley, Hordeum vulgare) suggests that leaching of NO3- could be of concern when high rates of wet PPS are applied before infrequent periods of high precipitation, due primarily to the mineral N contained in wet PPS. Low yields, grain protein concentrations, and crop N uptake of the sorghum crop following the barley crop grown on the clay soil demonstrated a low residual value of N applied in PPS. NO3- in the sandy soil before sowing accounted for 79% of the variation in plant N uptake and was a better index than anaerobically mineralisable N ( 19% of variation explained). In clay soil, better prediction of crop N uptake was obtained when both anaerobically mineralisable N (39% of variation explained) and soil pro. le NO3- were used in combination (R-2 = 0.49).