Wet Soil Samples Research Articles

Groundwater-induced redox-gradients control soil properties and phosphorus availability across four headwater wetlands, New York, USA

Hydrochemical patterns across groundwater-fed wetlands, especially carbonate and redox gradients, can influence phosphorus (P) availability by controlling its distribution among different soil pools. We explored these linkages by comparing shallow (5–20 cm) soil properties along groundwater flowpaths in two rich fens, a marl fen, and a poor fen. Organic matter content, bulk density, and total elemental content varied more with depth to underlying drift materials than with water table fluctuation, but also were influenced by groundwater discharge, which stabilized water table elevations and controlled redox conditions. Total sulfur and calcium content increased where pore-water chemistry indicated active iron and sulfate reduction. Calcium mineral dynamics, however, did not appear to influence P availability: first, calcium carbonate (CaCO3) accounted for <2% of the soil composition, except in the marl fen where it accounted for 20–25% of the soil composition. Second, Ca-bound P pools, determined from hydrochloric extraction of wet soil samples, accounted for <25% of the inorganic soil P pool. In contrast, iron-bound P determined from bicarbonate-buffered dithionite solution, accounted for 50–80% of the inorganic soil P, and increased where there was evidence of groundwater mixing, as did P release rates inferred from incubated anion resin bags. The total carbon and phosphorus content of organic-rich soils as well as available and labile P pools were strongly correlated with pore-water iron and alkalinity concentrations. Groundwater discharge and resulting hydrochemical gradients explained significant variation in soil composition and P availability across each site. Results highlight the importance of conducting biogeochemical studies in the context of a site’s shallow geologic setting and suggest mechanisms supporting the diverse plant species unique to groundwater wetlands.

Orthogonal array optimization of a multiresidue method for cereal herbicides in soils

Nearly 40 herbicides, commonly used for barley, were selected for analysis in soils of this crop. The primary objective was to develop a multiresidue method taking into account that herbicides belonged to different chemical families. Some preliminary experiments with different solvents in combination with water, acetic acid and ammonium hydroxide, were developed in order to design the predefined region covered by the orthogonal array design used for optimization. Final extracts were splitted in two aliquots, one of them was directly analyzed by gas chromatography–mass spectrometry (GC–MS), and the other one was derivatized before the acidic analyte analysis. Principal component analysis (PCA) was applied to the data generated in the preliminary experiments, in order to clarify the relationships among the different variables studied. According to the obtained results, the following variables were selected: solvent type and ratio, amount of acetic acid and extraction time. The statistical analysis revealed that all the factors were significant being the most important, the type and ratio of solvent for basic and neutral herbicides and the acetic acid percentage for acid herbicides. The final optimized method consisted of shaking previously wet soil samples for 30 min with 30 ml of acetone acidified with 1% acetic acid. Method validation was evaluated following the EU guidelines.

Environmentally Friendly Nitrogen Fertilizers Appplication for Winter Cereals Considering the Mineral Nitrogen Content in Soil

In order to improve nitrogen fertilizers application recommendations for cereals, the soil mineral nitrogen (Nmin) investigations (1995 – 2000) were carried out on sod – podzolic and brown – lesssive loamy sand and loamy soils in co-operation with other research institutions. The soil samples for determination of NO3 – N and NH4 – N were taken in depth 0 - 20, 21 – 40 and 41 – 60 cm in spring before the start of growth on winter cereals fields, but in 2001,2002- also in autumn before the sowing of winter cereals. Data on soil properties, the amount of precipitation in autumn (August 1 until the first decade with the average temperature below 5 oC), preceding crops and the use of organic fertilizers at sites of investigations were considered. The determination of NO3 – N and NH4 – N content was carried out in wet soil samples using for extraction 1 M KCl. Statistical analysis of data obtained in spring has been carried out using MS EXCEL function CORREL, CORRELATION, REGRESSION and SPSS 8.0 for Windows (GLM procedure). According to this analysis the following model (R2 = 0,527) was elaborated: y = 103.513 – 13.515|X1=1 – 0.247·X3 – 27.069|X2=0 – 42.945|X2=1 – 39.044|X2=2 – 16.022|X2=3 – 44.212|X2=4 + 0.104·X3|X2=0 + 0.181·X3|X2=1+ 0.187·X3|X2=2 +0.117·X3|X2=3+0.175·X3|X2=4, where y- predicted Nmin content in spring in 0- 40 cm soil layer, kg ha-1; 103.513 – intercept; X3 – amount of precipitation in autumn, mm; X1 – soil texture; X1=1 – loamy sand soils, X2 – predecessor; X2=0 – cereals; X2=1 – perennial grass; X2=2 – tilled crops; X2=3 – legumes; X2=4 – green manure crops; X2=5- fallow. On the basis of this model and data on meteorological conditions at different sites of Latvia the recommendations on correction N top - dressing application rates for winter cereals in spring were prepared.

Káliumföldpát, savkezelés és száradás-nedvesedés hatása a talajoldat káliumkoncentrációjára

Experiments were carried out on an acidic, clay loam soil (Ragály) to study the release of potassium into the soil solution as affected by soil acidification and soil water content. Two replicates of air-dried samples were acidified with HCl solutions to various water contents: soil suspensions (at 1:10, 1:5, 1:2.5 and 1:1 soil:water ratios) and wet soil samples having water potentials of -0.1 kPa, -20 kPa and -100 kPa were prepared. Constant acid loads, corresponding to 0, 5, 12.5, 25, 37.5, 50 and 62.5 mmol H+/kg soil were applied to each soil water content series. At field capacity acid loads of 75, 87.5 and 100 mmol H+/kg soil were also applied. After one week of incubation the liquid phases were extracted by centrifugation with a rotor speed corresponding to -1500 kPa (equal to the conventional wilting point of plants). At constant soil water content, the potassium concentration in the liquid phase of the soil (cK) increased with decreasing pH according to an exponential relationship (cK = a e-bpH). The slope (b) was higher at low soil water contents. At constant acid load, the potassium concentration in the liquid phase increased with decreasing soil water content (q) according to a hyperbolic relationship cK = a' + b' {1 / (qq-qq')}, where q' denotes the gravimetric soil water content at -1500 kPa water potential. The slope (b') was higher at lower pH values. The combined effect of the matrix of changing acid load and soil water content gave a three-dimensional surface characterizing the plant available potassium concentration over a wide range of these parameters: ln cK (mg/L) = 4.79 - 0.66 pH + 9.79 {1/(qq-qq'); R2 = 0.87. A finely ground (&lt;100 mmm) feldspar mixture (80% orthoclase + 20% albite) was added as potassium source to the air-dried samples of a slightly acidic sandy soil in 0:1, 1:3 and 1:1 feldspar:soil ratios (Somogysárd). Two replicates of the control and feldspar-enriched soil samples were moistened to field capacity with HNO3 solutions of 0, 0.25, 0.50, 0.75 and 1.0 mol/L concentrations (equal to acid loads of 0, 50, 100, 150 and 200 mmol H+/kg soil). The soil solution was extracted with the above centrifugation method. After feldspar application, the potassium concentration in the soil solution increased many times as compared with the control. Due to acid treatment the soil pH decreased by three units and the potassium concentration in the soil solution increased according to a saturation curve. Due to a two-unit decrease in soil pH, the potassium concentration increased threefold in the control and sixfold in feldspar-enriched (1:3) soil. This decrease in pH may take place due to root activity, promoting the dissolution of potassium minerals, and increasing potassium availability in the rhizosphere. The impact of drying-rewetting was also studied at the above feldspar:soil ratios. After one week of incubation the samples were kept in open vessels for one year, irrigated weekly with distilled water to field capacity, then the soil solution was extracted by centrifugation. The concentrations were compared to those measured in a soil solution obtained from soil not subjected to the drying-rewetting procedure. The potassium concentration decreased in the liquid phase of the soil with no added feldspar: presumably it entered more strongly bounded forms during the drying-rewetting cycles. In the feldspar-enriched soil, however, the potassium concentration in the soil solution increased, which may be the consequence of the slow dissolution of the feldspar mineral.

Photostability of methidathion in wet soil amended with biosolid and a surfactant under solar irradiation

Photodegradation studies of the organophosphorous insecticide methidathion in thin layers of wet soil samples have been carried out under solar irradiation. Soil samples consisted of an agricultural soil added with two amendments: a municipal biosolid and the cationic surfactant TDTMA (tetradecyl trimethyl ammonium bromide). Dark controls of the different soil treatments were also considered. Soil and biosolid samples were previously autoclaved to eliminate biotic degradation. In this study we investigated the role of these amendments in methidathion photodegradation which is a rapid (<7 days) and indirect process. Although scarce differences were found between non-amended and amended samples, methidathion from soil exposed under sunlight is degraded more quickly than in dark conditions. Photodegradation products (methidathion oxon GS 13007 and GS 12956) were not detected.

A New Calibration Free pH‐Probe for In Situ Measurements of Soil pH

AbstractA new pH‐probe was developed for in situ determination of soil pH. It consists of a stainless steel tube with a plastic inset containing the indicator electrode, the reference electrode and a temperature sensor at the end of the tube. The indicator electrode is a quinhydrone composite electrode that does not need to be calibrated, because it acquires almost the theoretical predicted potential and has a constant formal potential and slope under all fabrication conditions. The pH‐probe has a low standard deviation (±4 mV or 0.07 pH units). The response time is short (5 s). To characterize its function the soil pH‐probe was used to analyse pond and arable soil samples. The results were compared with those obtained with a conventional combined glass electrode. To evaluate the results, measurements were performed (i) in natural wet soil samples (in situ conditions), (ii) after drying and moistening the soil samples (moistened samples) and (iii) after drying the soil samples and mixing with bidistilled water (soil solutions; generally accepted method in laboratories). The minimum water content required to obtain stable potentials in soil samples was 10%. The influence of S2−, NO$\rm{ {_{3}^{-}}}$ and Fe3+ as naturally available reducing and oxidising agents on the potential response of the pH‐probe was investigated. All the obtained results demonstrate that the developed pH‐probe is a powerful tool to measure the pH of a soil sample under in situ conditions without a calibration step.

Influence of and correction for moisture in rocks, soils and sediments on in situ XRF analysis

AbstractThis paper discusses the influence of water contained in rocks, soils and sediments on in situ XRF analysis with a portable XRF analyzer. Water in natural rocks, soil and sediments absorbs the characteristic x‐rays from the elements and also causes the primary radiation from the excitation sources to scatter, which results in a decrease in the intensity of characteristic x‐rays and an increase in the intensity of scattered x‐rays in a fluorescence spectrum. A method for correcting for the influence of the water on the analysis of wet samples is proposed, based on the fact that the intensity of scattered radiation is directly proportional to the water content of wet samples. Tests on a set of wet soil samples showed that the method can effectively correct for the influence of the water in wet samples up to a 20% water content. The method was also applied to the analysis of soil with an IED‐2000P XRF analyzer in a copper prospecting area in Yunnan, China. The results show satisfactory agreement of the results for Cu, Zn and Sr analyses before and after rain. Copyright © 2004 John Wiley &amp; Sons, Ltd.

An Improved Method for Determining the Fineness Value of Agricultural Limestone for Aquaculture

AbstractThe original method for determining the fineness of agricultural limestone was modified for the greater contribution of particles less than 0.25 mm in diameter that is found in the modern agricultural limestone used in aquaculture. Crusher‐run limestone was screened to give nine particle size separates. Systems containing 3.0 kg of soil (pH = 5.21) and 23.5 L of water (total alkalinity = 0.39 mg/L) were treated with 8.0 g of each separate, and total alkalinity and pH were monitored. After 70 d, total alkalinity equilibrated at 55 mg/L in systems treated with particles less than 0.106 mm. The total alkalinity in systems treated with other particle size separates were as follows: control, 0.52 mg/L; greater than 2.0 mm, 2.28 mg/L; 2.0–0.85 mm, 5.75 mg/L; 0.85–0.42 mm, 12.25 mg/L; 0.42–0.25 mm, 26.8 mg/L; 0.25–0.15 mm, 45.62 mg/L; and 0.15–0.106 mm, 49.30 mg/L. Water pH exceeded 7.36 after 2 weeks for systems treated with particles less than 0.25 mm. Wet soil samples (2.5 kg) of pH 5.04 were placed in trays and treated with 6.7 g of limestone of different particle size separates. After 1 week, pH was 6.9–7.1 in soil treated with particles less than 0.106 mm. By 10 weeks, a pH greater than 6.5 was attained in soils treated with particles less than 0.25 mm. The pH of soil treated with particles greater than 0.25 mm was similar to the control pH. Efficiency factors were assigned to particle size‐classes as follows: less than 0.106 mm, 100%; 0.25–0.106 mm, 86.7%; 0.42–0.25 mm, 49.06%; 0.85–0.42 mm, 22.4%; and greater than 0.85 mm, 7.3%. The sum of the products of the proportion of each particle size‐class and the corresponding efficiency factor gave the fineness value. Fineness values usually were smaller when determined by the new method instead of the old method.

Salmonella in gut and droppings of three pest lizards in Nigeria

The carriage rate of Salmonella in the gut of three lizard species, namely the Agama lizard (Agama agama) (64), the wall gecko (Geckonidae) (60), the ‘snake lizard’ (Ameiva ameiva) (52), and 60 samples of lizard dropping; and their survival under various environmental conditions was investigated. A gastrointestinal Salmonella carriage rate of 32, 39 and 48% were observed for the wall gecko, the Agama and ‘snake’ lizards respectively. An isolation rate of 35% was also recorded for pooled lizard droppings. Salmonella survived in the droppings for 4 weeks in tap water and wet sand, 6 weeks in direct contact with air and up to 8 weeks when mixed with dry sand. An inoculum of 106 c.f.u./g of a pure Salmonella isolate obtained from the lizard droppings proliferated extensively in sterile wet and dry soil samples, but decreased rapidly in the other environments. Salmonella was still detectable after 3 weeks in non-sterile wet and dry soil samples, up to 2 weeks in tap water, and approximately 8 days in powdered milk and ‘gari’. The potential public health significance of the observations is discussed.

Shrinkage and drainage in aggregates of volcanic soils: a new approach combining mercury porosimetry and vacuum drying kinetics

Summary The topsoils of Andisols in the wet high altitude grasslands (paramos) of Ecuador have shrunk after recent changes from permanent grassland to agriculture. The question arises as to whether all Andisols in the region behave in the same way. We have therefore studied the shrinkage on drying of topsoils from four representative types of Andisol in the paramos using a combination of drying kinetics and mercury porosimetry. We aimed to identify and quantify the pore volumes that participate in either drainage or shrinkage or both. The key concept of hierarchical dual porosity of soils used to interpret the shrinkage curves was partly validated, but we also identified more complex relations between drainage, shrinkage and structure. We found that the older was the soil, the more weathered it was, and, consequently, the greater its aggregation and porosity. In turn, the total volumetric shrinkage was controlled by the initial void ratio of the wet soil samples. Our results also show that the solid–pore interfaces of the volcanic soil aggregates were less accessible after shrinkage than before.

Comparison between fractionation and bioavailability of trace elements in rhizosphere and bulk soils

Rhizosphere is a microbiosphere and has quite different chemical, physical and biological properties from bulk soils. A greenhouse experiment was performed to compare the difference of fractionation and bioavailability of trace elements Cr, Ni, Zn, Cu, Pb and Cd between rhizosphere soil and bulk soil. In the meantime, the influence of air-drying on the fractionation and bioavailability was also investigated by using wet soil sample as a control. Soils in a homemade rhizobox were divided into four zones: rhizosphere, near rhizosphere, near bulk soil and bulk soil zones, which was designated as S 1, S 2, S 3 and S 4. Elemental speciations were fractionated to water soluble, exchangeable and carbonate bound (B1), Fe–Mn oxide bound (B2), and organic and sulfide bound (B3) by a sequential extraction procedure. Speciation differences were observed for elements Cr, Ni, Zn, Cu, Pb and Cd between the rhizosphere and bulk soils, and between the air-dried and wet soils as well. The concentrations of all six heavy metals in fraction B1 followed the order of S 2>S 3>S 1>S 4 and for B2, the order was S 2>S 3≈S 4>S 1. For B3, the order was S 1>S 3≈S 4>S 2, while for Cd the order was S 2>S 3≈S 4>S 1. The air-drying increased elemental concentration in fractions B1 and B2 by 20–50% and decreased in fraction B3 by about 20–100%. Correlation analysis also indicated that the bioavailability correlation coefficient of fraction B1 in rhizosphere wet soil to plants was better than that between either air-dried or nonrhizosphere soils. Therefore, application of rhizosphere wet soils should be recommended in the future study on the speciation analysis of trace elements in soils and bioavailability.

Atmospheric movements of lindane (gamma-hexachlorocyclohexane) from canola fields planted with treated seed.

Lindane (gamma-hexachlorocyclohexane [gamma-HCH]) is used as an insecticide in many countries. Concentrations of gamma-HCH have been found in air, water, soil, snow, and tissue samples throughout the world and concerns have been raised for its potential effects on human and ecosystem health. In Canada, gamma-HCH is primarily used as a treatment on canola (Brassica napus L) seed with an estimated 455.3 Mg applied in 1997 and 510.4 Mg in 1998. The purpose of this study was to measure gamma-HCH volatilization from fields planted with treated canola seed. Atmospheric dry and wet deposition and soil samples were collected for two growing seasons (1997 and 1998) from a canola field planted with treated seed. Atmospheric concentrations as high as 16.1 and 7.4 ng m(-3) were measured at 1 m above the canola field compared with maximum concentrations of 2.9 and 2.7 ng m(-3) measured above a grass field located 2 km away (1997 and 1998, respectively). On the basis of measurements made in this study it was estimated that between 12 and 30% of the gamma-HCH applied as canola seed treatment may volatilize and be released to the atmosphere. This would create an atmospheric loading of 66.4 to 188.8 Mg for the 6-wk period following planting, estimated from the quantity of seed sown on the Canadian prairies in 1998. Dry deposition rates and rain concentrations as high as 2,203 ng m(-2) d(-1) and 170 ng L(-1) were measured adjacent to the canola field.

Rill Erosion Dependence on Soil Water Content, Aging, and Temperature

Soil shear strength and cohesion at high water content and low bulk density determine rill erosion. Aging of wet soil samples at different temperatures may increase the cohesion forces between soil particles. The effects of soil water content (200-500 g kg -1 ), aging (15 min, 4 and 24 h) and temperature (25, 40, and 60°C) on rill erosion of three soils, a grumusol (Typic Chromoxerert), a loess (Calcic Haploxeralf), and a hamra (Typic Rhodoxeralf), were studied in the laboratory using a small hydraulic flume. For water contents above air dried, rill erodibility (RE) decreased with increased aging. Optimum water contents for development of cohesion differed for the grumusol and loess. The effect of aging on RE depended on soil type. At no aging, RE was the highest in the clay grumusol (3.26 x 10 -3 s m -1 ) and the lowest in the loamy sand (0.52 x 10 -3 s m -1 ). With increased aging to 4 and 24 h, RE of the grumusol decreased to 0.24 x 10 -3 s m -1 but the RE of the hamra was not affected. Development of biological and chemical cohesion forces determine RE changes with aging. At 60°C the biological mechanism diminished and the chemical mechanism predominated. High water content and high temperature (high Brownian motion) during aging enhance clay-to-clay contacts and cementation of soil particles into a cohesive structure that resists rill erosion.

Fast screening of contaminated soil samples using thermal desorption mass spectrometry

A fast analysis technique for the determination of oil concentrations in soil and sediment samples is described and validated. The so-called thermal desorption mass spectrometry combination (TD-MS) proved to be a very rapid analytical method for mineral oil in soil. When compared to a soxhlet extraction and to the standard method of analysis, the latter yielded significantly different results compared to the other two methods, while the results from TD-MS and soxhlet extraction did not differ significantly from each other. Of the three methods TD-MS yielded the lowest variance for multiple analyses. Total time for the analysis of a wet soil sample was 20 min, including sample preparation.

Mineralization pattern of soil organic n of several soils in the tropics

Abstract The kinetics of mineralization of soil organic nitrogen (N) in samples of several air-dried and fresh soils in the tropics was studied. Four different paddy soil samples in the IRRI lowland field were used. Parameters for mineralization of soil organic N were computed by using Arrhenius' law and Michaelis-Menten's equation. The following results were obtained: 1. The mineralization pattern of organic N in the wet soil samples were represented by an exponential equation as a function of reference days, which were determined by the duration of the incubation period and apparent activation energy. Although significant differences in the mineralization rate and mineralization potential among the soils were observed, there was no appreciable difference in the value of apparent activation energy, which were relatively low compared with those of Japanese paddy soils.2. The mineralization pattern of the dried soil samples was represented by an equation consisting of two exponential equations. When a large amount of extractable carbon was detected by diluted sulfate or hot water in the soils, the mineralization pattern was represented by an equation which consisted of three exponential equations.3. The difference in the amount of inorganic N between the dried and wet soil samples increased rapidly up to 5 weeks after the start of incubation and then became almost constant. The mineralization pattern of the decomposable organic N which appeared with the changes of the soil conditions from wet to dry (DON) could also be represented by an exponential function of reference days.4. There was no appreciable difference in the mineralization rate and apparent activation energy between the organic N of the fresh soil samples and slowly mineralizable organic N of the dried soil samples, and between DON and the rapidly mineralizable organic N of the dried soil samples.

A method for characterizing the state of compactness of the plough layer

A method for characterizing the state of compactness of the plough layer is described. The “degree of compactnes” is defined as the ratio (%) of the dry bulk density of the soil and the dry bulk density of the same soil in a compacted reference state. The bulk density in the field is determined by a frame-sampling technique. The reference state is determined by a drained, uniaxial compression test using wet soil samples which are loosely filled in an oedometer and loaded with a pressure of 200 kPa until drainage ceases. In a series of 100 field experiments with spring barley this method was method was used for characterizing the state of compactness of the annually tilled soil layer. On mineral soils, maximum crop yield was obtained at the same degree of compactness irrespective of soil type, which was the main goal of the method. For organic soils a modification of the procedure for determining the reference bulk density is required.

Image analysis of soils - present and future

With the present state of technology it is possible to impregnate and prepare thin sections from dry or wet soil samples. Thus we can measure the size, shape and distribution patterns of voids and pedological features at different moisture contents. Automated section polishing equipment makes it feasible to produce successive planes at varying intervals (e.g., as narrow as 10 μm) in impregnated blocks. Recent advances in computer software, hardware and imaging technology make it feasible to store the information from successive soil planes for integrated analysis. These advances can be readily adapted for use with SEM-EDXRA and STEM-EDXRA equipment. Thus it is now possible to physically locate and chemically analyse many soil components in three-dimensional soil space. These advances will help soil scientists develop quantitative models of complex soil processes within real soil space. In the future, we foresee improvements in image analysis equipment that will allow the use of spectral data in order to distinguish features in soil samples. In addition, we foresee the need to integrate all levels of imagery, from global to submicroscopic, allowing for the extrapolation of data from the microscope to landscapes and vice versa.

Effect of water content on the fabric of a soil material: an experimental approach

SUMMARYTo characterize the fabric of a wet soil sample two sets of experiments were performed. In one, water retention and shrinkage curves were determined with samples stored at the field water content, and in the other, pore size distribution curves and microscopic observations were made as samples progressively dried. The experiments were performed with soil samples of different aggregate sizes to determine the contribution of each class of pores to porosity.Data were analysed by comparing (i) the amount of water extracted from the sample, (ii) the air‐filled porosity of the sample and (iii) the accumulated pore volume by mercury injection, each in relation to the equivalent pore radius. This gives information on the geometry of pores developed during the drying process. It has shown that micrometric cracks in dried soils are not artefacts but the result of a more severe drying never reached by the material in the field.

A method to impregnate wet soil samples, producing high-quality thin sections.

[120.031]Mineral soils with different moisture content and texture were impregnated successfully by the method described. The water present in the soil sample is replaced by acetone and the acetone-saturated sample is impregnated by FitzPatrick's method (1970) (using acetone as thinner of the polyester resin Synolith 544). Shrinkage is minimal and the thin sections are of high quality. It should be possible to correlate thin section data obtained by this method with physical data obtained from undisturbed material. Micromorphologically, a better understanding of the plasmic fabrics should be possible. (Abstract retrieved from CAB Abstracts by CABI’s permission)