Soil Surface Area Research Articles

Clay mineralogy, specific surface area and micromorphology of polygenetic soils from Eastern Kansas

The objective of this study was to evaluate the relationship between clay mineralogy, specific surface area (SSA) and micromorphology in polygenetic Konza soil series. Physical, chemical and mineralogical analyses were performed on disturbed soil samples, and micromorphological investigations of selected horizons were done on undisturbed soil samples. X-ray diffraction indicated that lower part of each parent materials has more mectite and less clay mica content than that of the upper horizons in each parent material. Greater amounts of smectite can be attributed to transformation product of the clay mica in to smectite, eluviation from upper horizons or originated from parent material. Specific surface area of upper horizons in each parent material tended to increase to lower horizons. Clay content gradually increased from surface (21%) to the lower part (∼48%) of the solum. Clay in Bt horizons had strong birefrengent, sharp boundary, and strong orientation pattern. SSA, clay content increase, clay mineralogy and oriented clay features agreed to one another. Therefore, this relationship gives opportunity to make predictions on extend of SSA and related soil processes by looking at one of these features.

Improving phosphorus availability in two upland soils of Vietnam using Tithonia diversifolia H.

Phosphorus was added to two acidic upland soils (a Cambisol and a Ferralsol) at two rates (9 mg P kg−1 and 145 mg P kg−1) either in an inorganic P form (KH2PO4) or as a green manure (Tithonia diversifolia H. at 2.5 g kg−1 and 40 g kg−1). The effect of P source on the chemical availability of P was assessed in an incubation experiment by measuring resin extractable P, soluble molybdate reactive (DMR-P) and unreactive P (DMU-P). Soil pH and extractable Al were monitored during the incubation period of 49 days. Green manure addition caused an immediate and sustained increase in soil pH and an immediate and sustained decrease in extractable Al. Labile P (resin P + DMR-P + DMU-P) was increased more by P added as a green manure than when added in inorganic form in one soil (Ferralsol), while it decreased or did not differ in the other one (Cambisol). In both soils, the concentrations of soluble DMU-P were frequently higher where Tithonia had been added. The effects of green manure amendment on physical factors governing the phosphorus supply through diffusive transport were also investigated. Aggregate size distribution was substantially changed by green manure amendment due to a shift in the percentage of microaggregates (<250 μm in diameter) to larger sizes. Changes in soil aggregation as a consequence of green manure amendment led to a reduction in specific surface area (SSA) of the whole soil. Coupled with the large increase in effective cation exchange capacity caused by green manure amendment in both soils, and the decrease in SSA, there was an increase in the net negative surface charge density in both soils. In summary, at a large addition rate – and in addition to the well-known effect derived from the extra supply in P, green manure amendment may improve the chemical availability and diffusive supply of P through the following mechanisms: (i) an increase in soil pH increasing the solubility of phosphate sources; (ii) a decrease in extractable Al reducing the fixation of added P; (iii) increased macro-aggregation and reduced specific surface area and porosity leading to fewer sorption sites for P and hence enhanced diffusion rates; and (iv) increased negative charges and reduced positive charges at the soil surface resulting in a net increase in repulsive force for P. The induced changes in most measured soil properties were smaller in the Ferralsol than in the Cambisol.

Eluviation of dissolved organic carbon under wetting and drying and its influence on water infiltration in degraded soils restored with vegetation

SummaryOne mechanism in the restoration of severely degraded soil by vegetation might be the movement of dissolved organic carbon (DOC) to macropore and aggregate surfaces. We propose that this lowers the soil wetting rate and subsequently its slaking resistance by creating a partially hydrophobic surface. In this study, we determined how wetting and drying (w/d) cycles redistribute DOC to soil surfaces, and how DOC affects hydrophobicity where it accumulates, in relation to the soil surface area to volume ratio and to different types of vegetation planted to restore a severely degraded soil. Repacked soil cores that simulate different soil aggregate sizes were tested. The results showed that w/d cycles increase surface DOC concentration through a depletion of DOC in the interior of the soil. Correspondingly, w/d cycles enhanced hydrophobicity, measured as a water repellency index, R, from 1.5–2.3 to 3.6–7.6, the values affected significantly by the type of vegetation. This index (R) did not change for a control soil with no vegetation. The link between the amount of DOC and water repellency was weak (coefficient of determination r2 = 0.06–0.26), indicating that DOC quality was probably more important than its quantity. Although increasing the core size resulted in a greater accumulation of DOC on the drying surface of the core, the impact of this on water repellency was minimal. Incubation caused a decrease in the amount of DOC, but had minimal influence on water repellency. This work improves the understanding of changes in soil wetting and soil stabilization under processes of natural weathering and vegetation restoration.

A NEW IDEA IN MARSH CORING

Standard coring techniques are often ineffective in the unconsolidated and vegetated soils and sediments of marsh environments. In this paper, a novel coring device is presented that minimizes the problems of compaction, core plugging, and root disturbance to allow the collection of intact 35+ cm cores from densely vegetated marsh areas. The simple concept uses a sharpened main body and cover plate that are inserted sequentially to obtain a wedge‐shaped soil or sediment slice. In a typical application, the corer is transferred to the field laboratory where sectioning can occur. Removal of the cover plate exposes a large surface area of soil or sediment for visual inspection and sampling. The advantages of the wedge corer design are described in relation to its use in a Spartina alterniflora salt marsh.

Development of harvester ant colonies alters soil chemistry

Nests of the harvester ant Pogonomyrmex barbatus typically contain higher concentrations of organic matter, nitrogen and phosphorus than surrounding soils. The difference between nest soils and surrounding soils is due, at least in part, to ant foraging behavior. Ants retrieve seeds from the environment and concentrate seed nutrients in the vicinity of the nest. But elevated nutrient concentrations in nests may also reflect initial conditions, if nest-founding queens are more likely to choose or survive in soils with high organic matter and nutrient content. By measuring the soil nutrient content and surface area of P. barbatus nests ranging from 1 to 20 years of age over two sampling periods, we (a) investigated the relationship between nest soil characteristics and colony age, and (b) tested the hypothesis that nest soils differ from background soils when nests are established. Nest surface area increased with colony age until age 5–10 years and leveled off thereafter. Relative to surrounding soils, concentrations of total nitrogen and orthophosphate increased, and pH decreased, with increasing colony age. The difference between nest soils and surrounding soils in total nitrogen, nitrate, and ammonium concentrations also increased over a 9-month interval between sampling bouts. Extrapolations from regressions of soil chemical variables against colony age provided no evidence that nest founding and early colony survival is more likely to occur in high-nutrient soils.

Surface irregularity of soils in molecular domain

Soil surface area does not keep constant and varies with the yardstick. Experimental results show that the amount of molecules absorbed in the surface monolayers is a function of absorbate size. The surface topography of soils from a few up to as many as thousand angstroms is very well described by fractal dimension, D s. The surface fractal dimension, D s is usually used to measure the irregularities of soil surface. The surface fractal dimensions of kaolin, montmorillonite and other six soils are measured using the adsorption method. The surface fractal dimensions of kaolin and montmorillonite are examined by the values measured using the nitrogen/water isotherm adsorption. The relationship between the surface fractal dimension and the content of clay is also discussed in this paper.

Planning of gravimetric investigations on mars

We propose to install a balance at the surface of Mars. In this paper we present a survey on tasks which could be accomplished by means of a balance. The determination of the specific surface area and porosity of Martian soil and other sorption experiments are discussed. Criteria for the choice of a suitable balance type are given.

Modeling the Influence of Water Content on Soil Vapor Extraction

We present a comprehensive model and simulation results to assess the impact of changing water content on nonaqueous phase liquid (NAPL) mass transfer, vapor phase retardation, and slow desorption during soil vapor extraction (SVE). Contaminant mass transfer and water and energy transport processes for a one‐dimensional, nonisothermal, and single contaminant component system are considered. Literature‐derived relationships are used to express the fraction of soil surface area exposed to the vapor phase and the NAPL–gas mass transfer rate expression as a function of water saturation. Simulations are presented for two scenarios: (i) low water saturation, where soil drying is expected and direct vapor sorption to soil may be important, and (ii) high water saturation, where NAPL mass transfer to the gas phase is rate‐limited and the gas flow rate is very low. At low water saturation slow desorption controls long tailing in the effluent concentration and the cleanup time. Also, when dry air is purged through the system, water evaporation occurs, the temperature decreases, and hence, desorption rates decrease. The NAPL mass transfer rates were negligibly affected by water evaporation because time scales of the NAPL volatilization were much smaller than time scales of the water evaporation. At high water saturation, NAPL is trapped by water and NAPL mass transfer to the gas phase is limited by diffusion through water films. For this case, NAPL mass transfer is slow and thus controls concentration tailing and cleanup times.

Modeling the Influence of Water Content on Soil Vapor Extraction

We present a comprehensive model and simulation results to assess the impact of changing water content on nonaqueous phase liquid (NAPL) mass transfer, vapor phase retardation, and slow desorption during soil vapor extraction (SVE). Contaminant mass transfer and water and energy transport processes for a one-dimensional, nonisothermal, and single contaminant component system are considered. Literature-derived relationships are used to express the fraction of soil surface area exposed to the vapor phase and the NAPL–gas mass transfer rate expression as a function of water saturation. Simulations are presented for two scenarios: (i) low water saturation, where soil drying is expected and direct vapor sorption to soil may be important, and (ii) high water saturation, where NAPL mass transfer to the gas phase is rate-limited and the gas flow rate is very low. At low water saturation slow desorption controls long tailing in the effluent concentration and the cleanup time. Also, when dry air is purged through the system, water evaporation occurs, the temperature decreases, and hence, desorption rates decrease. The NAPL mass transfer rates were negligibly affected by water evaporation because time scales of the NAPL volatilization were much smaller than time scales of the water evaporation. At high water saturation, NAPL is trapped by water and NAPL mass transfer to the gas phase is limited by diffusion through water films. For this case, NAPL mass transfer is slow and thus controls concentration tailing and cleanup times.

Reflectance measurement of canopy biomass and nitrogen status in wheat crops using normalized difference vegetation indices and partial least squares regression

Hyperspectral reflectance (438 to 884 nm) data were recorded at five different growth stages of winter wheat in a field experiment including two cultivars, three plant densities, and four levels of N application. All two-band combinations in the normalized difference vegetation index ( λ1− λ2)/( λ1+ λ2) were subsequently used in a linear regression analysis against green biomass (GBM, g fresh weight m −2 soil), leaf area index (LAI, m 2 green leaf m −2 soil), leaf chlorophyll concentration (Chl conc, mg chlorophyll g −1 leaf fresh weight), leaf chlorophyll density (Chl density, mg chlorophyll m −2 soil), leaf nitrogen concentration (N conc, mg nitrogen g −1 leaf dry weight), and leaf nitrogen density (N density, g nitrogen m −2 soil). A number of grouped wavebands with high correlation ( R 2>95%) were revealed. For the crop variables based on quantity per unit surface area, i.e. GBM, LAI, Chl density, and N density, these wavebands had in the majority (87%) of the cases a center wavelength in the red edge spectral region from 680 to 750 nm and the band combinations were often paired so that both bands were closely spaced in the steep linear shift between R red and R nir. The red edge region was almost absent for bands related to Chl conc and N conc, where the visible spectral range, mainly in the blue region, proved to be better. The selected narrow-band indices improved the description of the influence of all six-crop variables compared to the traditional broad- and short-band indices normally applied on data from satellite, aerial photos, and field spectroradiometers. For variables expressed on the basis of soil or canopy surface area, the relationship was further improved when exponential curve fitting was used instead of linear regression. The best of the selected narrow-band indices was compared to the results of a partial least square regression (PLS). This comparison showed that the narrow-band indices related to LAI and Chl conc, and to some extent also Chl density and N density, were optimal and could not be significantly improved by PLS using the information from all wavelengths in the hyperspectral region. However, PLS improved the prediction of GBM and N conc by lowering the RMSE with 22% and 24%, respectively, compared to the best narrow-band indices. It is concluded that PLS regression analysis may provide a useful exploratory and predictive tool when applied on hyperspectral reflectance data.

Non‐Flow‐Through Steady‐State Chambers for Measuring Soil Respiration

Soil respiration estimates obtained from non‐flow‐through steady‐state chambers (also called static, absorption, or alkali trap chambers) are considered by many investigators to be unreliable. We studied the accuracy, functioning, and design requirements of this chamber type using a gas diffusion model validated for this purpose by demonstrating that it matched the empirical relation between alkali‐measured flux and headspace CO2 concentration. Simulated measurement error depended on (i) magnitude of the soil respiration rate, which spawned positive or negative error depending on the algebraic sign of the change in headspace CO2, (ii) absorption efficiency of the alkali trap, which was determined by headspace air mixing rates, the thickness of atmospheric interfacial layers, and especially the ratio of exposed alkali surface area to emitting soil surface area, (iii) the effective diffusivity and storage coefficient of CO2 in underlying soil, which depended on the soil's air‐filled porosity (AFP) and pH, respectively, and (iv) the rate of CO2 leakage between the chamber system and its surroundings. The results also indicated that although no single chamber design is universally applicable, striving for the ideal design in every situation is not required; for example, measurement error associated with the design used in our simulations was usually only ≈5% despite that headspace concentration rose more than 70% within 2 h. Larger errors occurred for chamber designs less well matched to the soil respiration rate they were intended to measure, but if such serious design deficiencies are avoided, the method offers a simple inexpensive means for obtaining multiple reliable time‐integrated estimates of soil respiration, even at remote locations.

Modeling the Influence of Water Content on Soil Vapor Extraction

We present a comprehensive model and simulation results to assess the impact of changing water content on nonaqueous phase liquid (NAPL) mass transfer, vapor phase retardation, and slow desorption during soil vapor extraction (SVE). Contaminant mass transfer and water and energy transport processes for a one-dimensional, nonisothermal, and single contaminant component system are considered. Literature-derived relationships are used to express the fraction of soil surface area exposed to the vapor phase and the NAPL–gas mass transfer rate expression as a function of water saturation. Simulations are presented for two scenarios: (i) low water saturation, where soil drying is expected and direct vapor sorption to soil may be important, and (ii) high water saturation, where NAPL mass transfer to the gas phase is rate-limited and the gas flow rate is very low. At low water saturation slow desorption controls long tailing in the effluent concentration and the cleanup time. Also, when dry air is purged through the system, water evaporation occurs, the temperature decreases, and hence, desorption rates decrease. The NAPL mass transfer rates were negligibly affected by water evaporation because time scales of the NAPL volatilization were much smaller than time scales of the water evaporation. At high water saturation, NAPL is trapped by water and NAPL mass transfer to the gas phase is limited by diffusion through water films. For this case, NAPL mass transfer is slow and thus controls concentration tailing and cleanup times.

Carbon dioxide efflux from a 550 m 3 soil across a range of soil temperatures

Because of scaling problems point measurements of soil CO 2 efflux on a small volume of soil may not necessarily reflect an overall community response. The aim of this study was to test this hypothesis in the Biosphere 2 facility and achieve the following broad goals: (1) investigate soil net CO 2 exchange–temperature relationship at the community level; (2) compare soil net CO 2 exchange at the community level to the traditional sample point estimates of CO 2 efflux scaled up to the community level; (3) evaluate the usefulness of a facility such as Biosphere 2 for conducting community level experiments for studying response to a climatic perturbation under controlled environmental conditions. A 550 m 3 volume of soil with 282, 15 cm tree stumps was enclosed at the Biosphere 2 Center and warmed from 10 to 25 °C over a period of 34 days. Net CO 2 exchange from this community was measured at various points on the soil surface with 78.5 cm 2 chambers and for the whole community using each of the three bays at Biosphere 2 Center as a closed system. Soil CO 2 efflux rates obtained by point measurements showed tremendous variability from location to location. At the community level and with point measurements, net CO 2 exchange increased exponentially with increasing soil temperatures. Q 10 values from both the point and community level measurements ranged from 1.7 to 2.5. Scaling of point measurements by soil surface area and time overestimated community rates by 36% revealing some of the limitations of point measurements. This experiment demonstrates how Biosphere 2 facility could be used to study behavior of individual components and measure responses at the community level and test our capacity to scale point in time and space measures of community processes to the community level.

West Indian Dropseed/Giant Smutgrass (Sporobolus indicus var. pyramidalis) Control in Bahiagrass (Paspalum notatum) Pastures1

Field experiments were conducted in 1997 and 1998 to evaluate the effect of mowing followed by hexazinone for West Indian dropseed/giant smutgrass (Sporobolus indicus var. pyramidalis) (hereafter referred to as dropseed) control. The experimental design was a split plot, with mowing (nonmowed [mature] and 35-cm regrowth) as the whole plot and hexazinone rate (0.0 [control], 0.56, 0.84, 1.12, 1.40, and 1.68 kg ai/ha) as the subplot treatments. The application of 0.84 kg/ha hexazinone provided 94 and 81% dropseed control, 365 d after treatment (DAT) during 1997 and 1998, respectively. Increasing application rate to 1.12 kg/ha hexazinone provided 87 and 88% dropseed control, 365 DAT during 1997 and 1998, respectively. Both the 0.84 and 1.12 kg/ha rates provided the same average control (87.5%); however, the 1.12 kg/ha rate provided consistent control over years. Mowing dropseed, followed by hexazinone application at 35-cm regrowth, provided no additional control when compared with no mowing treatments. Rates of hexazinone at 1.40 and 1.68 kg/ha caused phytotoxicity to bahiagrass and increased bare soil surface area, especially 90 and 120 DAT. Phytotoxic effect on bahiagrass and on bare soil decreased 365 DAT, resulting in 75 to 80% total forage cover. Concentration and yield of total nonstructural carbohydrates were significantly lower for the mowed 35-cm regrowth treatment than for the nonmowed plants; however, even in its weakened condition this reduction had no effect on dropseed control.Nomenclature: Hexazinone; West Indian dropseed/giant smutgrass, Sporobolus indicus (L.) R. Br. var. pyramidalis (P. Beauv.) Veldkamp; S. indicus (L.) R. Br. var. indicus #3 SPZIN; S. jacquemontii Kunth.; S. poiretii (Roem. & Schult.) A. S. Hitchc. # SPZIN; bahiagrass, Paspalum notatum Fluegge # PASNO.Additional index words: Bermudagrass, CYNDA, Cynodon dactylon (L) Pers., hexazinone, pasture weeds, tropical forage.Abbreviations: DAT, days after treatment; GC, percent ground cover; TNC, total nonstructural carbohydrates.

Determination of Surface Area of Fine-Grained Soils by the Ethylene Glycol Monoethyl Ether (EGME) Method

Abstract This paper describes a test procedure for determining the total surface area of fine-grained soils using the Ethylene Glycol Monoethyl Ether (EGME). The test involves saturating a soil sample with EGME and then removing the excess EGME in a vacuum desiccator, until the EGME forms a monomolecular layer on the soil surface. The results of the test are expressed as Specific Surface Area (SSA), which describes the surface area/unit mass of dry soil with units of m2/g. Test results are presented demonstrating the effect of various test parameters on the results. Results for a number of different fine-grained soils are presented. A detailed recommended test procedure is given. The proposed method uses simple and inexpensive laboratory equipment, is relatively simple to perform, and allows for rapid determination of SSA.

Determination of surface area of soil by adsorption methods

SummaryHow significant are estimates of surface areas of soils obtained by adsorption methods? To answer this we tested the applicability of an equation that relates monolayer coverage (N) of an adsorbent with the area (A) of adsorbate, NAz = k, for six soil samples using six adsorbates of different sizes. The data obtained confirm the validity of the equation with the z parameter ranging between 1.25 and 1.41. Hence each soil sample showed preferences towards small‐sized adsorbates for which the product NA (calculated surface area) is inversely related to the size of adsorbate. We also demonstrated that the equation has roots in the Langmuir adsorption equation.

Effect of soil properties on bioavailability and extractability of phenanthrene and atrazine sequestered in soil

Sixteen soils with markedly different properties were analyzed to determine their porosity in the range of 7 nm–10 μm, cation-exchange capacity (CEC), surface area and clay mineralogy. The extent of sequestration of phenanthrene and atrazine has been shown to differ markedly among these soils. Correlations were sought between soil characteristics and four methods of measuring sequestration. Simple correlation analysis showed that some but not all measures of phenanthrene and atrazine sequestration were highly correlated with organic C content, nanoporosity or CEC but not other properties of the soils. Multiple linear-regression analysis suggested an interaction of organic C content with soil texture, CEC or surface area in determining the extent of atrazine or phenanthrene sequestration. We conclude that organic C content, CEC and other properties of soil may be useful predictors of sequestration of some compounds.

Physicochemical properties of a solonetzic toposequence

Surface, charge, and pore properties of three profiles of a solonetzic toposequence: Mollic Solonetz (top), Salic Solonetz (in-between), and Haplic Solonetz (bottom) were studied. A trial of finding relations between the above and other chemical and physical parameters characterizing salt-affected soils was undertaken. Physicochemical soil properties differed among the studied profiles and horizons. Upper, eluvial A horizons differed to the greatest extent among the profiles studied and the lowest C horizons appeared to be most similar. Surface and pore characteristics were mostly governed by organic matter and clay content. Organic matter and clay fraction increased soil surface area and amount of variable charge. The surface area increased also with amount of exchangeable bases and the CEC of the soils. Sodicity and alkalinity, mainly exchangeable sodium percentage and less the pH, appeared to reduce mesopore radii and pore complexity (fractal dimensions).

Tortuosity, Diffusivity, and Permeability in the Soil Liquid and Gaseous Phases

Tortuosity phenomena of pore space influence the transport of water, solutes, and gases in soil. This study presents three analyses linking tortuosity and transport in unsaturated soil. The first is a diffusion‐based analysis of tortuosity in the soil water and soil air phases, related to soil surface area (SA) and pore‐size distribution (PSD) (characterized by Campbell b and content of pores &gt;30 μm). The analysis is based on recent models to predict the diffusion coefficients, Dp, of (i) a solute in soil, (ii) a gas in repacked soil, and (iii) a gas in undisturbed soil, each as a function of fluid‐phase (soil water or soil air) content, α. For use in the analysis, the relation between SA and the threshold water content where solute diffusion ceases due to disconnected water films was measured for eight soils (5–46% clay). The tortuosity analysis supported by measured Dp(α) data shows that SA governs and has a larger impact on liquid‐phase tortuosity than PSD has on gaseous‐phase tortuosity. At the same value of α, the tortuosity is typically larger in the soil water than in the soil air phase, and the difference becomes more pronounced with increasing SA and at low α. In the second analysis air permeability, ka, and gas diffusivity, DP,g, are linked in the Millington and Quirk fluid flow model to describe soil structure‐forming potential and to establish a model platform to describe ka as a function of DP,g and α. Measurements on repacked, nonaggregated soil support the ka(DP,g;α) model platform, while measurements on repacked, aggregated soils and on undisturbed soils show that ka is greatly affected by soil aggregation and structure and DP,g is not. In the third analysis, a constitutive parameter model is applied to gas and solute diffusivities and air and water permeabilities in six soils along a soil texture gradient. This illustrates the different behavior of the four transport parameters with PSD and α. The liquid‐phase transport parameters show a steeper decrease with α compared with the gaseous‐phase parameters, in part due to the higher tortuosity in the liquid phase. Also, ka in undisturbed soil exhibited a less steep decrease with α compared with DP,g, probably due to preferential air flow in larger pores during convective transport. Any attempt to develop a unifying and PSD‐dependent model for transport parameters in the soil liquid and gaseous phases will require careful distinction between repacked and undisturbed soils.

Surface reactivity of A horizons towards polar compounds estimated from water adsorption and water content

The measurement of the specific surface area of soils may be useful for ranking soils in their ability to sorb polar compounds such as some pesticides and pollutants. For A horizons with varied mineralogy, particularly those containing large amounts of soil organic matter, this is problematic. We have estimated the surface area of a range of topsoils from water adsorption using the BET equation. The values obtained were greater than those measured from the adsorption of para-nitrophenol. There was a good relationship between the BET water area and the CEC of the samples (r2 = 0.83). There was a better relationship between the BET surface area and the water content of air-dry topsoils (r 2 = 0.98). We suggest that the air-dry water contents of topsoils could be used as a quick method to rank soils in order of their surface reactivity towards polar molecules, and this is preferable to more complicated methods.