Caliche Soils as a Filter Medium for Treatment and Disposal of Wastewater

Through support from the Texas On-Site Wastewater Treatment Research Council, a project to search the literature relative to caliche materials as a medium for treatment and disposal of wastewater has been conducted. It was hypothesized before undertaking this effort that there would be a dearth of published and unpublished information on this subject. Specifically, the goals of the project were to: Provide a working definition of “caliche” in relation to treatment of wastewater. Perform a comprehensive literature review on the effectiveness of caliche soils as a bioremediation filter media in the treatment and disposal of wastewater. Develop recommendations for future research that would address issues identified above

Wetness conditions and redoximorphic features in a microtoposequence on the Texas Coast Prairie

The purpose of this study was to investigate the relationship between wetness conditions and redoximorphic features in three soils that occur on adjacent microtopographic landform positions. The landform positions included a closed, seasonally ponded depression, and intermound, and a pimple mound. Aquic conditions as defined by the Keys to Soil Taxonomy (Soil Surv. Staff, 1996) were assessed by: (i) redoximorphic features, and (ii) measurement of saturation and reduction to verify morphological features used to infer aquic conditions. Taxonomic classification of the three pedons representing the toposequence were: (i) mound (fine-loamy, siliceous, thermic Oxyaquic Paleudalfs), (ii) intermound (coarse-loamy, siliceous, thermic Typic Natraqualfs, and (iii) depression (fine-loamy, siliceous, thermic Typic Endoaqualfs). The soil sites were located northwest of Houston near the city of Cypress in Harris County on the Katy Prairie portion of the central Texas Gulf Coast Prairie. The three sites represent the upper, middle, and lower topographic positions on this landscape. During a 19-mo period, each of the different landform positions exhibited different perched and groundwater piezometric surfaces within the upper 200 cm. During periods of saturation, low oxidation-reduction potentials (≤ 120 mV in the intermound and \u3c240 mV in the depression) suggested that Fe reduction occurred in the soils. The intermound was saturated at the surface and below 100 cm that corresponded closely with decreased water movement within the portion of the soil profile where a natric horizon occurred between 26 and 136 cm. The depression site exhibited saturation during the fall to spring and Fe reduction in the profile, so redox features were associated with current and possibly with relict aquic conditions

Water and Solute Flow in a Highly-Structured Soil

Prevention of groundwater contamination by agricultural activities is a high priority in the United States. Water and contaminants often follow particular flow paths through the soil that lead to rapid movement of pesticides out of the rootzone. An improved understanding of why water and solute follow particular flow paths is needed to identify soils that allow agricultural chemicals to move rapidly to groundwater. The rate that water and contaminants are transferred from the soil surface to groundwater may be related to the degree of flow path channelization (convergence or divergence of water flow paths). This project was designed to test the feasibility of measuring the degree of channelization as water percolates through structured soils. A flow interceptor device consisting of 98 individual 25 by 25 mm cells operating under tension was constructed for this purpose. Water flux probability density distributions (pdd's) were measured at 0.3, 0.6 and 0.9 m depth in Ships clay (very-fine, mixed, thermic, Chromic Udic Haplusterts). Water flux and solute travel time pdd's were measured at 0.3, 0.9 and 1.2 m in Silawa loamy fine sand (fine-loamy, siliceous, thermic, Ustic Haplusterts). Both probability distributions were fitted with log-normal functions. In Ships clay, water flow paths converged as water moved from 0.3 to 0.9 m depth, while in Silawa loamy fine sand flow paths converged from 0.3 to 0.9 and diverged from 0.9 to 1.2 m depth. This convergence and divergence of water flux in the soil was related to changes in structural definition with depth. Convergence of water and solute flow is expected to increase the pollution potential of the soil because of increased bypassing of soil matrix and increased pore water velocities. Solute travel time pdd's for Silawa at 0.9 and 1.2 m depth were predicted with a stochastic transfer function model calibrated at 0.3 and 0.9 m depth, respectively, and compared to the actual measured travel time pdd's at 0.9 and 1.2 m. From this it was concluded that water flux measurements at the surface alone are, in general, not a suitable way to predict water and solute fluxes at lower depths. Spatial variability of water fluxes and bromide fluxes were highly correlated, and the coefficient of variation of both depended on the horizon in which the measurements were taken

Evidence for the formation of Luvisols/Alfisols as a response to coupled pedogenic and anthropogenic influences in a clay soil in Finland

Kuivatus muuttaa maan ominaisuuksia monin tavoin. Savisedimentin kuivuminen saa aikaan kutistumista ja rakenteen muodostumista. Rakenteellisen kutistumisen seurauksena syntyvät makrohuokoset toimivat ilman ja veden sekä siihen liuenneiden ja suspendoituneiden aineiden kulkureitteinä. Suomen ilmasto-oloissa kuivatus vaikuttaakin merkittävällä tavalla viljelymaiden pedogeneesiin. Maankuivatuksen vaikutuksia Jokioisilla sijaitsevan savimaan ominaisuuksiin tutkittiin tarkastelemalla maan makro- ja mikromorfologiaa horisonteittain 150 cm:n syvyyteen saakka. Peltoa on viljelty 1700-luvulta lähtien, ja se on salaojitettu 1930-luvulla. Tilavuuspainon määritystä varten maakokkareet tasapainotettiin vakiokosteuteen ylipainemenetelmällä (33 kPa). Kutistumiskerroin (Coefficient of Linear Extensibility, COLE) laskettiin kosteiden ja kuivien (105 °C) maakokkareiden tilavuudenmuutoksen perusteella. Pohjavesihavainnot osoittivat, että yhdeksän vuoden jaksolla pohjaveden pinta oli laskenut useana kesänä salaojien tasoa syvemmälle mahdollistaen rakenteen muodostumisen ja aineiden liikkumisen makrohuokosia pitkin myös syvimpiin tutkittuihin maahorisontteihin. Maankuivatus oli johtanut rakenteen muodostumiseen koko tutkittuun syvyyteen. Tilavuuspaino pieneni syvemmälle mentäessä, vaikka hiilipitoisuus oli suurin ylimmässä horisontissa. Tulos heijastelee peltomaan kuivumisen aiheuttamaa maan huokostilan irreversiibeliä pienenemistä, kun maasta on poistunut vettä.Varsinkin syvempien horisonttien maa kutistui kuivuessaan melko paljon ja täytti maannosluokittelussa käytettävän Vertic-attribuutin vaatimukset (COLE > 6%). Ohutleikkeissä havaittiin paljon maaprofiilissa alaspäin kulkenutta savesta, ja saveksen kertymistä huokosten seinämiin esiintyi vielä salaojien alapuolellakin. Maannos oli Vertic Luvisol (World Reference Base-järjestelmä) ja Vertic Cryaqualf (Soil taxonomy). Näitä maannoksia ei Suomessa ole aiemmin dokumentoitu.Clayey soils with a cryic soil temperature regime and an aquic soil moisture regime are extensive in southern Finland but they have rarely been pedogenically described. A pedon in a field that has been in agricultural use since the 17th century was characterized and features indicative of human-influenced pedogenic processes were identified. Owing to intensified agriculture, the soil has become drier than ever before. Natural shrink-swell and anthropogenic turbation processes had destroyed the rock structure to a depth of 72 cm. Groundwater monitoring during nine years proved that in several years the soil had a chance to desiccate down to 150 cm, resulting in wedge-shaped prisms and desiccation joint planes. The cracks and root channels serve as routes for clay translocation. Illuvial clay, observed in thin sections, had the maxima (>1%) in the Btg (38 72 cm) and BCtg2 (112 140 cm) horizons, corresponding to the effective drainage depths during ditch drainage until 70 years ago and subsequent subsurface tile drainage, respectively. Seventy years of improved drainage seems to be sufficient to give rise to an argic/argillic horizon. This feature is likely manmade but, being irreversible, it must be taken into account in soil classification. In this climate, agriculture seems to influence pedogenesis strongly throughout the solum far below the plough layer. Luvisols (WRB) or Cryaqualfs (Soil Taxonomy) have not been documented in a clay soil in Finland or Sweden before.v2009okMaankuivatus vaikuttaa savimaan maannostumisee

Physical and chemical changes induced by agricultural use of boreal clay soils

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A simple method of fabricating mask-free microfluidic devices for biological analysis

We report a simple, low-cost, rapid, and mask-free method to fabricate two-dimensional (2D) and three-dimensional (3D) microfluidic chip for biological analysis researches. In this fabrication process, a laser system is used to cut through paper to form intricate patterns and differently configured channels for specific purposes. Bonded with cyanoacrylate-based resin, the prepared paper sheet is sandwiched between glass slides (hydrophilic) or polymer-based plates (hydrophobic) to obtain a multilayer structure. In order to examine the chip’s biocompatibility and applicability, protein concentration was measured while DNA capillary electrophoresis was carried out, and both of them show positive results. With the utilization of direct laser cutting and one-step gas-sacrificing techniques, the whole fabrication processes for complicated 2D and 3D microfluidic devices are shorten into several minutes which make it a good alternative of poly(dimethylsiloxane) microfluidic chips used in biological analysis researches