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Fine Sand (fine + sand)
Selected AbstractsEffectiveness of very thin soil layers in chemical release from bed sedimentENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 2 2001Bryan Talbert The chemical containment effectiveness of both the natural recovery and the "particle broadcasting" processes for remediating contaminated bed-sediments depend upon very thin soil and/or sand layers millimeters in depth. Conventional capping for in situ chemical containment of bed-sediment or dredged material typically involves thick layers of 30 to 90 centimeters in depth. Few studies have been conducted with thin layers of candidate natural materials. A steady-state benzoic acid dissolution test apparatus and procedure, devised to realistically simulate bed-sediment chemo-dynamic conditions, was used to measure chemical flux through thin layers (1 to 8 mm) of soil, sand, and ideal porous media. The thin layers were found to be very effective. Flux reductions ranged from 81 to 96%, with fine sand being slightly better than top soil. Design algorithms developed for the thick layers used in conventional capping design will under predict the flux through very thin layers. Advective flow induced by surface roughness is proposed to explain the higher average measure d-to-predicted flux ratio of 1.67. [source] Investigation of an onsite wastewater treatment system in sandy soil: Site characterization and fate of anionic and nonionic surfactantsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 12 2002Allen M. Nielsen Abstract This study reports on the fate of linear alkylbenzene sulfonate (LAS), alcohol ethoxylate (AE), and alcohol ether sulfate (AES) surfactants in a home septic system near Jacksonville (FL, USA) that has been used since 1976. The drainfield at this site resides in fine sand (<6% silt and clay) with an unsaturated zone that ranges from 0 to 1.3 m. During the wettest times of the year, it is likely that effluent from the septic system passes directly into the groundwater without exposure to an unsaturated zone of soil. Groundwater was collected during two sampling events, representing seasonal high and low groundwater table levels, and analyzed for the surfactants LAS, AES, and AE. During the wet season, the unsaturated zone was approximately 0.01 m beneath the drainfield. During the dry season, the unsaturated zone was about 0.4 m below the drainfield. Alcohol ethoxylate was not detected in any groundwater samples during either sampling. Alcohol ether sulfate was not found in the dry season sampling, but traces of AES had migrated downgradient about 4.7 m horizontally and 1.8 m vertically in the wet season. Linear alkylbenzene sulfonate was detected in some dry season samples and had moved downgradient some 11.7 m horizontally and 3.7 m vertically in the wet season. These observations demonstrate that these surfactants were removed to a great extent; otherwise, they would have traveled more than 260 m downgradient, which is the calculated distance that a conservative tracer like bromide would have moved downgradient over the life of the system. The most likely removal mechanisms for these surfactants were biodegradation and sorption. Therefore, this study indicates that LAS, AE, and AES are readily removed from groundwater in soils below septic system drainfields even in situations with minimal unsaturated soil zones. [source] Distribution of polycyclic aromatic hydrocarbons in particle-size separates and density fractions of typical agricultural soils in the Yangtze River Delta, east ChinaEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 6 2008J. Z. Ni Summary Soil organic matter can be divided into different organic carbon (C) pools with different turnover rates. The organic pollutants in soils associated with these organic C pools may have different bioavailability and environmental risks during the decomposition of soil organic matter. We studied the distribution patterns of 15 USEPA priority polycyclic aromatic hydrocarbons (PAHs) in different particle-size separates (clay, fine silt, coarse silt, fine sand and coarse sand) and density fractions (light and heavy fractions) of nine agricultural topsoils (0,20 cm depth) from a contaminated area in the Yangtze River Delta region of east China. There was a decreasing trend in PAH concentration in particle-size separates with decreasing particle size. However, the different particle-size separates had similar PAH composition. The concentration of PAHs in the light fraction ranged from 13 037 to 107 299 ,g kg,1, far higher than in the heavy fraction, which ranged from 222 to 298 ,g kg,1. Although the light fraction accounted for only 0.4,2.3% of the soils, it was associated with 31.5,69.5% of soil PAHs. The organic matter in coarse silt had the strongest capacity for enrichment with PAHs. Combining the distributions of PAHs and the turnover rates of organic matter in different soil fractions, the environmental risks of PAH-polluted soils may be due mainly to the PAHs associated with sand and the light fraction. [source] Quantifying the effects of aggregation, particle size and components on the colour of Mediterranean soilsEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 3 2004M. SÁnchez-Marañón Summary Aggregation, particle size, and chemical composition affect the colour of the soil. We have attempted to quantify and understand these effects in 12 Mediterranean soils. We measured the CIELAB colour variables hab, L*, and C*ab in aggregated and dispersed soil samples, and also in coarse sand, fine sand, silt, and clay samples before and after sequential removal of organic matter, carbonates, and Fe oxides. Grassmann's colour-mixing equations adjusted by regression analysis described the colour of the dispersed soil from its particle-size fractions with an error of 1% for hab, 4% for L*, and 9% for C*ab. This suggests that the contribution of each fraction to the colour of the dispersed soil can be accurately calculated by its colorimetric data weighted by its content and a regression coefficient, which was greatest for clay. We inferred the influence of a component within each fraction by measuring the colour changes after its removal. Iron oxides reduced hab of the silicated substrate by 19%, reduced L* by 12%, and increased C*ab by 64% in all particle-size fractions. Carbonates and organic matter had little influence: the former because they impart little colour to the silicates and the latter because there was little of it. The CIELAB colour-difference between dispersed and aggregated soil (mean ,E*ab = 15.3) was due mainly to ,L* (,14.7). Aggregation contributed to diminishing L* of dispersed soil by 34%. Scanning electron microscopy showed that Fe oxides and organic coatings cover the surface of aggregates thereby influencing soil colour. [source] Effect of degree of fluid saturation on transport coefficients in disturbed soilsEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 1 2004A. Tuli Summary To improve the predictive capability of transport models in soils we need experimental data that improve their understanding of properties at the scale of pores, including the effect of degree of fluid saturation. All transport occurs in the same soil pore space, so that one may intuitively expect a link between the different transport coefficients and key geometrical characteristics of the pores such as tortuosity and connectivity, and pore-size distribution. To understand the combined effects of pore geometry and pore-size distribution better, we measured the effect of degree of water saturation on hydraulic conductivity and bulk soil electrical conductivity, and of degree of air saturation on air conductivity and gaseous diffusion for a fine sand and a sandy loam soil. To all measured data were fitted a general transport model that includes both pore geometry and pore-size distribution parameters. The results show that both pore geometry and pore-size distribution determine the functional relations between degree of saturation, hydraulic conductivity and air conductivity. The control of pore size on convective transport is more for soils with a wider pore-size distribution. However, the relative contribution of pore-size distribution is much larger for the unsaturated hydraulic conductivity than for gaseous phase transport. For the other transport coefficients, their saturation dependency could be described solely by the pore-geometry term. The contribution of the latter to transport was much larger for transport in the air phase than in the water phase, supporting the view that connectivity dominates gaseous transport. Although the relation between effective fluid saturation and all four relative transport coefficients for the sand could be described by a single functional relation, the presence of a universal relationship between fluid saturation and transport for all soils is doubtful. [source] Loss of phosphorus from soil in semi-arid northern Tanzania as a result of cropping: evidence from sequential extraction and 31P-NMR spectroscopyEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 4 2000D. Solomon Summary In semi-arid northern Tanzania, the native woodland is being rapidly cleared and replaced by low input agriculture. This has resulted in pronounced environmental degradation, and in particular loss of phosphorus (P) from the soil. We have used sequential extraction and 31P-NMR to investigate the effects of land use changes, i.e. native woodland, degraded woodland, cultivation for 3 and 15 years and homestead fields where manure was applied, on the amount and structural composition of P in this soil. Clearing and continuous cultivation reduced both organic and inorganic P in the soil. The difference in the amount of organic P from the bulk soil of the fields cultivated for 3 and 15 years was not statistically significant (P <,0.05), suggesting that most of the depletion in organic P occurred during the first 3 years of cultivation. By contrast, in the homesteads, there was much organic and inorganic P in the soil. The 31P-NMR revealed that cultivation resulted in a 53% depletion of orthophosphate diester P, whereas only a 30% and 39% reduction of orthophosphate monoester P was found in the bulk soil after 3 and 15 years of cultivation, respectively. These results concur with the suggestion that diester P constitutes more easily mineralizable forms of organic P in soil than does monoester P. Our 31P-NMR also showed that 70% of the inorganic orthophosphate P was depleted from the coarse and fine sand separates as a result of cultivation. The influence of clearing and subsequent cropping on the amount and forms of P was more pronounced in the coarse and fine sand than in the silt and clay, stressing the importance of particle size and chemical properties such as organic matter and oxides in the availability of P in this soil. Our results show that the current low input agricultural practice is not sustainable, and that practices must be developed to combat the ongoing degradation of the soil. A combined use of available organic materials such as animal manure with the judicious use of inorganic fertilizers can replenish the soil's fertility. [source] Sequestration and turnover of plant- and microbially derived sugars in a temperate grassland soil during 7 years exposed to elevated atmospheric pCO2GLOBAL CHANGE BIOLOGY, Issue 2 2007MICHAEL BOCK Abstract Temperate grasslands contribute about 20% to the global terrestrial carbon (C) budget with sugars contributing 10,50% to this soil C pool. Whether the observed increase of the atmospheric CO2 concentration (pCO2) leads to additional C sequestration into these ecosystems or enhanced mineralization of soil organic matter (SOM) is still unclear. Therefore, the aim of the presented study was to investigate the impact of elevated atmospheric pCO2 on C sequestration and turnover of plant- (arabinose and xylose) and microbially derived (fucose, rhamnose, galactose, mannose) sugars in soil, representing a labile SOM pool. The study was carried out at the Swiss Free Air Carbon Dioxide Enrichment (FACE) experiment near Zurich. For 7 years, Lolium perenne swards were exposed to ambient and elevated pCO2 (36 and 60 Pa, respectively). The additional CO2 in the FACE plots was depleted in 13C compared with ambient plots, so that ,new' (<7 years) C inputs could be determined by means of compound-specific stable isotope analysis (13C : 12C). Samples were fractionated into clay, silt, fine sand and coarse sand, which yielded relatively stable and labile SOM pools with different turnover rates. Total sugar sequestration into bulk soil after 7 years of exposure to elevated pCO2 was about 28% compared with the control plots. In both ambient and elevated plots, total sugar concentrations in particle size fractions increased in the order sand Optimization of Full-Scale Permanganate ISCO System Operation: Laboratory and Numerical StudiesGROUND WATER MONITORING & REMEDIATION, Issue 4 2008Jeffrey L. Heiderscheidt Laboratory characterization studies, one-dimensional flow-through studies, and numerical model simulations were conducted to examine site conditions and system features that may have adversely affected in situ chemical oxidation (ISCO) performance at the Naval Training Center's (NTC) Operable Unit 4 located in Orlando, Florida, and to identify potential ISCO system modifications to achieve the desired remediation performance. At the NTC site, ISCO was implemented using vertical injection wells to deliver potassium permanganate into a ground water zone for treatment of tetrachloroethylene and its breakdown products. However, oxidant distribution was much more limited than anticipated. Characterization studies revealed that the ground water zone being treated by ISCO was very fine sand with a small effective particle size and low uniformity coefficient, along with a high organic carbon content, high natural oxidant demand (NOD), and a high ground water dissolved solids concentration, all of which contributed to full-scale ISCO application difficulties. These site conditions contributed to injection well permeability loss and an inability to achieve the design oxidant injection flow rate, limiting the actual oxidant distribution at the site. Flow-through experiments demonstrated that more favorable oxidant delivery and distribution conditions are enabled by applying a lower oxidant concentration at a faster delivery rate for a greater number of pore volumes. Numerical simulations, run for a variety of conditions (injection/extraction well flow rates, injected oxidant concentration, amount of NOD present, and NOD oxidation rate), also revealed that low,oxidant concentration injection at a high flow rate is a more effective method to deliver the required mass of oxidant to the target treatment zone. [source] Detailed measurements of thickness and grain size of a widespread onshore tsunami deposit in Phang-nga Province, southwestern ThailandISLAND ARC, Issue 3 2010Shigehiro Fujino Abstract Measurements of thickness and grain size along flow-parallel transects across onshore deposits of the 2004 Indian Ocean tsunami revealed macroscopic horizontal variations and provided new insights into tsunami sedimentation. The tsunami caused severe erosion of beaches, river mouths, and the shallow seafloor along the coast of southwestern Thailand and supplied sufficient sediment to deposit a kilometer-wide blanket of sand on the land surface. The tsunami deposits generally fine landward with some fluctuations caused by local entrainment and settlement of sediments. Sediments of medium and fine sand are restricted to a few hundreds of meters inland from their source, whereas finer grained sediments were suspended longer and deposited 1 km or more inland. Although the thickness of the tsunami deposits is strongly influenced by local topography, they generally thin landward. In areas of low-relief topography, the rate of landward thinning is exponential and reflects the dominance of sediment supply to nearshore areas over that to areas farther inland. [source] Sediment preferences and size-specific distribution of young-of-the-year Pacific halibut in an Alaska nurseryJOURNAL OF FISH BIOLOGY, Issue 3 2002A. W. Stoner A combination of laboratory experiments and field surveys was used to test the hypotheses that responses to sediments change with fish size and that sediment grain-size is the predominant environmental factor affecting small-scale distribution in young-of-the-year (yoy) Pacific halibut Hippoglossus stenolepis. Laboratory tests showed that the smallest fish (31,40 mm LT) chose fine sediments (muddy and fine sands), fish 51,70 mm had high selectivity (primarily medium sand), and the largest fish (80,150 mm) were not selective although they avoided the largest grain-sizes (pebbles and granules). Sediment preferences were correlated with size-dependent burial capabilities. Beam trawl collections were made over a 6 year period in Kachemak Bay, Alaska, to examine the distribution of yoy Pacific halibut (14,120 mm LT) using small size classes (e.g. 10 mm intervals). Canonical correlation analysis showed that the per cent of sand in the sediment was a highly significant variable for all but one size and date combination. Catch per unit of effort (CPUE) for newly settled fish (<30 mm LT) was highest on very fine sand, fish 41,80 mm were most abundant on fine sand, and the largest yoy fish (81,120 mm) were abundant over a range of sediments from fine sand to mud. Except for the smallest fish, Pacific halibut in the field were associated with sediments somewhat finer than predicted from the laboratory experiments; however, virtually all were captured where they could bury easily. The ability of flatfish to bury and shelter in sediment is related to fish size; consequently, habitat associations shift rapidly during the first year of life. Habitat models for yoy flatfishes should consider size-dependent shifts in capabilities and preferences. [source] A flexible sand coating (Conniflex) for the protection of conifer seedlings against damage by the pine weevil Hylobius abietisAGRICULTURAL AND FOREST ENTOMOLOGY, Issue 1 2009Göran Nordlander Abstract 1 A new method for the physical protection of conifer seedlings against feeding damage by Hylobius abietis (L.), is described and evaluated in field trials in Swedish forest plantations. 2 The lower 60% of the stem of the seedling is protected by the Conniflex coating, consisting of fine sand (grain size = 0.2 mm) embedded in an acrylate dispersion that remains flexible after drying. 3 Seedlings are treated in the nursery by a large-scale application procedure involving four steps: (i) spraying the seedlings with water; (ii) application of fixative to the lower sections of the stems, (iii) application of fine sand to the fixative; and (iv) drying of the fixative. 4 A field experiment over three seasons demonstrated a significant increase in survival for coated seedlings compared with untreated seedlings. The survival rate increased from 29% to 97% for Scots pine and from 26% to 86% for Norway spruce. Coating the lower 30% of the stem (instead of 60%) provided inferior protection, resulting in only 64% survival in spruce. 5 Field trials in 11 commercial plantation areas indicated that the Conniflex sand coating was as effective in protecting seedlings as treatment with the insecticide imidacloprid. 6 The new method of coating conifer seedlings with fine sand provides an effective and environmentally sound alternative to insecticide treatment. [source] Transforming powder mechanical properties by core/shell structure: Compressible sandJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 11 2010Limin Shi Abstract Some active pharmaceutical ingredients possess poor mechanical properties and are not suitable for tableting. Using fine sand (silicon dioxide), we show that a core/shell structure, where a core particle (sand) is coated with a thin layer of polyvinylpyrrolidone (PVP), can profoundly improve powder compaction properties. Sand coated with 5% PVP could be compressed into intact tablets. Under a given compaction pressure, tablet tensile strength increases dramatically with the amount of coating. This is in sharp contrast to poor compaction properties of physical mixtures, where intact tablets cannot be made when PVP content is 20% or less. The profoundly improved tabletability of core/shell particles is attributed to the formation of a continuous three-dimensional bonding network in the tablet. © 2010 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 99:4458,4462, 2010 [source] Silicon Suppresses Phytophthora Blight Development on Bell PepperJOURNAL OF PHYTOPATHOLOGY, Issue 7-8 2010Ronald D. French-Monar Abstract The application of silicon (Si) reduces the intensity of diseases in several economically important crops. This study aimed at determining the potential of this element to decrease the symptoms of Phytophthora blight development on bell pepper, caused by Phytophthora capsici. Bell pepper plants (Sakata Hybrid X pp6115) were initially grown in plastic pots with substrate composed of 1 : 1 mixture of sterile fine sand and Fafard No. 2 peat mix amended with calcium silicate (+Si) or calcium carbonate (,Si). Six weeks later, plants were transplanted to new pots that contained the same +Si and ,Si substrate but were infested with finely ground wheat grains (1- to 2-mm diameter) colonized by two isolates of P. capsici, Cp30 (compatibility type A1) and Cp32 (compatibility type A2). At the end of the experiment, roots and stems from plants of each treatment were collected to determine Si concentration. The presence of lesions on crowns and stems and wilting of plants were monitored up to 9 days after transplanting (DAT). Data obtained were used to calculate the area under diseased plants progress curve (AUDPPC) and area under wilting plants progress curve (AUWPPC). Relative lesion extension (RLE) was obtained as the ratio of vertical lesion extension to stem length at 9 DAT. There was a 40% increase in the concentration of Si in the roots but not in the stems of bell pepper plants in the +Si treatment compared to the ,Si treatment. When comparing +Si to ,Si treatments, the AUDPPC was reduced by 15.4 and 37.5%, while AUWPPC was reduced by 29.1 and 33.3% in experiments 1 and 2, respectively. RLE values were reduced by 35% in the +Si treatment. Dry root weights increased by 23.7%, and stem weights were increased by 10.2% in the +Si treatment. Supplying Si to bell peppers roots can potentially reduce the severity of Phytophthora blight while enhancing plant development. [source] Dimensionierung von Vakuumwasserhaltungen im tertiären FeinsandBAUTECHNIK, Issue 7 2004Peter-Michael Mayer Dr.-Ing. Der Entwurf umfangreicher Vakuumwasserhaltungen ist aufgrund fehlender allgemeingültiger analytischer Berechnungsverfahren bisher auf Abschätzungen und Erfahrungen angewiesen. Vorliegende Untersuchungen zeigen exemplarisch für eine 80 m lange und 37 m breite Spundwandbaugrube im tertiären Feinsand, wie mittels räumlicher Finite-Element-Modelle die erforderliche Anzahl und Tiefe von Vakuumtiefbrunnen zur Grundwasserabsenkung berechnet werden kann. Die Auswirkungen von Schichtanisotropien bzw. lokaler Bereiche mit hoher Durchlässigkeit auf das erreichte Absenkziel und die geförderten Pumpmengen werden aufgezeigt. Darüberhinaus wird auch der Wasserdruck auf die Spundwand analysiert. Die Bedeutung zeitabhängiger Strömungsberechnungen wird durch die Verbindung von Aushub und Wasserhaltung deutlich und kann durch instationäre Betrachtungen erfaßt werden. Der Vergleich von in-situ-Messungen und Berechnungsergebnissen zeigt die Leistungsfähigkeit, aber auch die Grenzen numerischer Strömungsmodelle bei der Abschätzung des Ausführungsrisikos und möglicher wirtschaftlicher Optimierungen. Dimensioning of vacuum dewaterings in tertiary fine sand. Because of outstanding valid analytical solutions, the study of extensive dewatering depends actually only on estimations and experiences. This paper show, for a 80 m long and 37 m large excavation in fine sand, how to calculate the requested number and depth of vacuum deep well for the lowering of the groundwater level by Finite-Element-Models. The effects of anisotropic layer and layer with local ranges with high porosity for the achieved lowering and pumping capacity have been showed. Additionally the water pressure on sheet pile wall was also analyzed. The significance of transient flow calculations becomes clearly by the connection of excavation and dewatering. The comparison of in-situ measurements and results of calculations shows the performance but also the limits of the numerical flow models on the estimation of the execution risks and possible improvement on dewatering process. [source] Another diet of worms: the applicability of polychaete feeding guilds as a useful conceptual framework and biological variableMARINE ECOLOGY, Issue 3-4 2005Paulo Roberto Pagliosa Abstract A fundamental question in guild studies is how to separate species into guilds. In a seminal manuscript, Fauchald & Jumars [Oceanography and Marine Biology Annual Review17 (1979) 193] summarized polychaete feeding biology and proposed a conceptual framework to test hypotheses on the sympatric occurrence of congeners with limited morphological differentiation. Twenty-six years after this publication, few studies have tested the validity and practical functioning of this scheme of polychaete feeding guilds and then only using part of the classification. The objective of the present study was to analyze the applicability of polychaete feeding guilds to ecological and environment assessments. Two data sets from Santa Catarina Island Bay, southern Brazil, were used. The first data set deals with spatial distribution of natural polychaete assemblages along the bay. The second data set treats fauna in urbanized versus relatively pristine mangroves. Multivariate analysis showed similar patterns in sample groups formed using guilds or densities and composition data. The role of feeding guilds in benthic systems was assessed through comparison with environmental variables. The polychaete assemblage from the Bay was related to sediment type. Motile and discretely motile carnivores and herbivores with jawed probosces matched coarse sands; surface deposit feeders and filter feeders were found in fine sands; and surface and subsurface deposit feeders and carnivores, all with soft probosces matched silt and clay sediments. The data analyses in mangroves showed surface deposit feeders and filter feeders in undisturbed sites and omnivorous species in disturbed ones. The polychaete feeding guilds appear relevant to assembly rules based on resource availability, to resource partitioning and to interspecific competition. [source] Seabed Morphology and Pollution Along the Bagnoli Coast (Naples, Italy): a Hypothesis for Environmental RestorationMARINE ECOLOGY, Issue 2002Tommaso De Pippo Abstract. The interaction of coastal and submarine morphology with the hydrodynamic regimes exerts a control on coastal dynamic processes, conditioning the dispersion of sediments and potential pollutants existing in the area. Thus, the study of such parameters is useful in order to define environmental threats. Within the submerged sector of the Bagnoli coast and particularly in the southern part of the investigated area, there are sediment groups composed of very fine sands located in low-energy zones due to wave refraction and diffraction; they can also be found on the sea bottom and on the man-made structures typical of this zone. These areas show high pollutant levels of N, P, Cu, Fe, Mn, Ni, Pb, Zn, Cd, polyaromatic hydrocarbons (PAHs) and polychlorinated bi-phenyls (PCBs). The northern area, a place of high-energy hydrodynamic processes, also shows high concentration levels of pollutants due to the presence of secondary cell circulation. Morphological research and analysis of textural characteristics of bottom sediments along the Bagnoli coast allowed the actual processes and their evolution in space and time to be defined. It has also been possible to correlate such processes to the seabed morphology system, the wave formations which affect the coast, the complex system of sediment transport, as well as to the man-made interventions in the area. The results of recent chemical analyses of beach sediments and bottom sediments off the Bagnoli coast were also incorporated. They prove the presence of heavy metals, PAHs and PCBs in high and sometimes very high concentrations. Finally, based on the results of research and analyses, a hypothesis for an intervention for environmental restoration has been formulated in order to renaturalise the coast through dredging and treatment of the sand, both on the seabed and on the emerged beach. [source]
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