Soil Water Sorption Research Articles

A sorption isotherm model for soil incorporating external and internal surface adsorption, and capillarity

Soil water sorption isotherm is governed by soil–water interactions of adsorption and capillarity, depending on particle surface properties and pore size distribution, respectively. Recent studies have separated soil particle surfaces into two categories in terms of distinct adsorption behaviors, i.e., external and internal surfaces, identifying three independent sorption processes with varying energy levels, namely external adsorption, internal adsorption, and capillarity. Here, an isotherm model is developed to describe water sorption on soils in the full relative humidity ( RH) range by incorporating the three physical processes. The internal and external adsorptions are represented by an augmented-Brunauer–Emmett–Teller (A-BET) equation, and capillarity is described by Kosugi’s model. Two scaling factors are introduced to expand A-BET equation’s application RH range from 0%−40% to 0%−100%—one for the reduction of available adsorption area in restricted pores and another for the disparity between heats of adsorption and liquefaction. Experimental validation demonstrates that the proposed model excellently matches the isotherm data for a wide array of soils in the full RH range. Further, the proposed model performs well in capturing soil water retention data in the full matric potential range, providing a seamless linkage between soil sorption isotherm and water retention behaviors.

Determination of physicochemical properties of small molecules by reversed-phase liquid chromatography.

The physicochemical properties of small molecules that can be determined by retention measurements in reversed-phase liquid chromatography include solvent-based properties inferred from equilibrium processes occurring predominantly in the mobile phase and sorption properties for materials which can be used as stationary phases inferred from solute-stationary phase interactions. In addition, physicochemical properties can be estimated from correlation models based on surrogate chromatographic systems with a similar capability for intermolecular interactions to the chemical or biological system. Examples of properties determined by direct methods include molecular descriptors (solvation parameter model), acid dissociation constants, formation constants, and surface properties of solids determined by inverse liquid chromatography. Examples of properties estimated by indirect methods include hydrophobicity, lipophilicity, n-octanol-water partition constant, soil-water sorption constant, non-specific toxicity to fish and microorganisms, and permeation coefficients for the blood-brain and skin-water barriers. Since all approaches depend on an accurate measurement of chromatographic retention parameters typical operational and mechanistic problems are discussed from the perspective of data quality. Fundamentally the accuracy of direct methods is limited by stationary phase heterogeneity and indirect methods by the limited number of suitable surrogate chromatographic models.

Predictive ion-electrostatic model of disjoining pressure of synthetic gel structures in coarse-dispersed soil substrates

The mechanism of disjoining pressure controlling the swelling and water absorption of gel structures for soil conditioning is discussed. Its quantitative description is based on the fundamental ion-electrostatic model of soil water sorption isotherms containing the phase variable of gel swelling degree and specific surface area index of the soil substrate. The model adequately reproduces the s-shape of soil water sorption isotherms in a wide range of water activity from 0.05 to 0.999 depending on the working doses of hydrogels in the range of 0.05-0.3 mass%. Reinforcement of gel structures with amphiphilic dispersed particles increases the effect of disjoining pressure and water absorption.

Comparing Visible–Near‐Infrared Spectroscopy and a Pedotransfer Function for Predicting the Dry Region of the Soil‐Water Retention Curve

Core Ideas The Campbell–Shiozawa (CS) model was fitted to dry region data. The CS model was anchored to soil water content at −106 cm H2O matric potential. The model's parameters were well predicted from vis‐NIR spectra or a PTF. Both the vis‐NIRS and PTF models gave good predictions of dry region water retention. The soil‐water retention curve (SWRC) at the dry end, also known as soil water vapor sorption isotherms, is essential for the modeling of water vapor transport, microbial activity, and biological processes such as plant water uptake in the vadose zone. Measurement of detailed soil water vapor sorption isotherms (WSIs) can be time consuming. Therefore, we propose rapid, inexpensive methodologies (visible–near‐infrared spectroscopy [vis–NIRS] and a pedotransfer function [PTF]) to predict the Campbell–Shiozawa (CS) model parameters to obtain the WSIs. Water vapor sorption isotherms were measured on 144 soil samples with a vapor sorption analyzer. The CS semi‐logarithmic‐linear function anchored at a soil‐water matric potential of −106 cm H2O (log|−106| = pF 6) was fitted to the measured data because it accurately characterizes the WSIs. Thereafter, a vis–NIRS calibration model and a PTF, based on clay and organic C contents, were developed and used to predict the two reference CS model parameters (α and W6). Both parameters were predicted with a reasonable degree of accuracy using vis–NIRS and the PTF (for α, RMSE values of 0.0041 and 0.0025, and for W6, RMSE values of 0.0042 and 0.0034 for vis–NIRS and the PTF, respectively). Based on the predicted α and W6 values, the predicted WSIs compared closely with the measured isotherms for individual soil samples from each field. At the field scale, the vis–NIRS model performed marginally better than the PTF. Thus, it is evident that the use of vis–NIRS or PTFs provides a relatively inexpensive approach to predicting soil water sorption isotherms.

Short communication: Predicting cation exchange capacity from hygroscopic moisture in agricultural soils of Western Europe

Soil cation exchange capacity (CEC) depends on the extent and negative charge density of surfaces of soil mineral and organic components. Soil water sorption also depends on the extent of such surfaces, giving thus way to significant relationships between CEC and hygroscopic moisture (HM) in many soils. In this work, we explored whether CEC could be accurately predicted from HM in agricultural soils of Mediterranean and humid temperate areas in Western Europe. For this purpose, we examined 243 soils across a wide variation range of their intrinsic properties. Soil CEC was determined using 1 M ammonium acetate at pH 7 and HM at an equilibrium air relative humidity (RH) of 43% (HM43). Most of the variation of soil CEC was explained by HM43 through a linear function (CEC = 1.4 + 0.78HM43; R2 = 0.962; standard deviation = 2.30 cmolc/kg). Coefficients of the regression equation were similar for subgroups of soils differing in moisture regime, clay mineralogy, carbonate content and organic carbon content. Therefore, soil hygroscopic moisture measurements at a fixed RH level provided a simple, robust, inexpensive method for predicting soil CEC.

Determination of soil-water sorption coefficients of volatile methylsiloxanes.

The sorption behaviors of 4 cyclic and linear volatile methyl siloxane (VMS) compounds between water and organic matter in 3 United Kingdom soils were studied by a batch equilibrium method using13C-enriched sorbates. Sorption and desorption kinetics and isotherms were determined for octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), octamethyltrisiloxane (L3), and decamethyltetrasiloxane (L4). Concentrations of [13C]-VMS in the soil and aqueous phases were measured directly by extraction and gas chromatography–mass spectrometry techniques. All VMS compounds were sorbed rapidly, reaching constant distributions in all soils by 24 h. Desorption kinetics were very rapid, with reattainment of equilibrium within 1 h. In the main, linear isotherms were observed for aqueous concentrations at or below 4% of the solubility limits. The average sorption organic carbon partition coefficient (log KOC) values across soils were 4.23 for D4, 5.17 for D5, 4.32 for L3, and 5.13 for L4, with standard deviations of 0.09 to 0.34. Desorption KOC values were systematically greater by 0.1 log units to 0.3 log units. The linear isotherms and low variation in KOC values across soils suggested partitioning-dominated sorption of the VMS. Compared with traditional hydrophobic organic compounds, KOC values for the VMS compounds were significantly lower than expected on the basis of their octanol–water partition coefficients. A linear free energy relationship analysis showed that these differences could be rationalized quantitatively in terms of the inherent characteristics of the VMS compounds, combined with the differences in solvation properties of organic matter and octanol. Environ Toxicol Chem 2014; 33:1937–1945.

Water Vapor Transport in Soils from a Pervaporative Irrigation System

AbstractA novel method for irrigation with saline water uses a polymer membrane, formed into a tube, to treat and distribute the water simultaneously. The flux of water across the membrane occurs by the process of pervaporation, during which a phase change from liquid to vapor occurs. Thus, water arrives in the soil in the vapor phase. The experimental results presented in this paper demonstrate that, contrary to previous assumptions, soil vapor flows are a significant transport mechanism during pervaporative irrigation in dry soils. The soil water sorption properties affect the rate of condensation in the soil, which in turn affects both the water distribution in the soil and the loss of water vapor to the atmosphere. The flux from the tube becomes limited by high humidities adjacent to the external surface of the membrane. Thus, enhancing condensation in the soil or increasing diffusion through the soil increases flux from the system. These findings highlight the need to consider how plants might intera...

Performance of chromatographic systems to model soil–water sorption

A systematic approach for evaluating the goodness of chromatographic systems to model the sorption of neutral organic compounds by soil from water is presented in this work. It is based on the examination of the three sources of error that determine the overall variance obtained when soil–water partition coefficients are correlated against chromatographic retention factors: the variance of the soil–water sorption data, the variance of the chromatographic data, and the variance attributed to the dissimilarity between the two systems. These contributions of variance are easily predicted through the characterization of the systems by the solvation parameter model. According to this method, several chromatographic systems besides the reference octanol–water partition system have been selected to test their performance in the emulation of soil–water sorption. The results from the experimental correlations agree with the predicted variances. The high-performance liquid chromatography system based on an immobilized artificial membrane and the micellar electrokinetic chromatography systems of sodium dodecylsulfate and sodium taurocholate provide the most precise correlation models. They have shown to predict well soil–water sorption coefficients of several tested herbicides. Octanol–water partitions and high-performance liquid chromatography measurements using C18 columns are less suited for the estimation of soil–water partition coefficients.

EDTA Leaching of Cu Contaminated Soils Using Ozone/UV for Treatment and Reuse of Washing Solution in a Closed Loop

Ozone and UV irradiation were used for oxidative decomposition of EDTA-Cu complexes in washing solution obtained during multi-step leaching of Cu (344,1 ± 36.5 mg kg−1) contaminated vineyard soil with EDTA as a chelant. The released Cu was absorbed from the washing solution on a commercial mixture of metal absorbing minerals, and the treated washing solution then reused for removal of soil residual Cu-EDTA complexes in a closed-loop process. Six consecutive leaching steps (6 × 2.5 mmol kg−1 of EDTA) removed 38.8 % of Cu from soils, and reduced Cu soil mobility, determined using the toxicity characteristic leaching test (TCLP), by 28.5%. The final washing solution obtained after soil remediation was colourless, with a pH close to neutral (7.5 ± 0.2) and with low concentrations of Cu and EDTA (0.51 ± 0.22 mg L−1 and 0.083 mM, respectively). The proposed remediation method has therefore potential not just to recycle and save process water, but also not to produce toxic wastewaters. Soil treatment did not substantially alter the soil properties determined by pedological analysis, and had relatively little impact on soil hydraulic conductivity and soil water sorption capacity.

Sorção do herbicida imazaquin em Latossolo sob plantio direto e convencional

O objetivo deste trabalho foi avaliar o efeito da variabilidade do pH e da matéria orgânica de um Latossolo Vermelho distrófico, textura argilosa, sob diferentes manejos na retenção do herbicida imazaquin. A retenção deste herbicida foi medida pelo coeficiente de partição solo-água (Kd) em amostras de solos coletados na camada superficial (0-15 cm) em área de 38 ha, sob irrigação com pivô central e plantio direto e convencional. A retenção do imazaquin foi maior nas áreas com menores valores de pH e altos teores de matéria orgânica, ou seja, nas áreas onde o plantio direto foi utilizado por longo tempo. O pH afetou a retenção do imazaquin por controlar tanto a natureza iônica dos componentes do solo, matéria orgânica e minerais de argila, quanto a sua especiação. O teor de argila não apresentou variação na área estudada, ou seja, não afetou a retenção do imazaquin. O modelo de predição da sorção do imazaquin no solo pela análise de regressão multivariada com duas variáveis independentes (teor de matéria orgânica e pH) apresentou boa correlação (R² = 0,91).

Influence of a biodegradable ([S,S]-EDDS) and nondegradable (EDTA) chelate and hydrogel modified soil water sorption capacity on Pb phytoextraction and leaching

Synthetic chelates, such as ethylene diamine tetraacetic acid (EDTA), have been shown to enhance phytoextraction of Pb from contaminated soil but also cause leaching of heavy metal-chelate complexes, posing a groundwater contamination threat. In a soil column study, we examined the effect of EDTA and a biodegradable chelate [S,S] isomere of ethylene diamine disuccinate ([S,S]-EDDS), newly introduced in phytoextraction research, on the uptake of Pb by the Chinese cabbage (Brassica rapa) and Pb leaching through the soil profile. Soil water sorption characteristics were modified by acrylamide hydrogel. The addition of 0.1 and 0.2% (w/w) of hydrogel amendments increased soil field water capacity from initial 24.6% to 28.5% and 31.3%, respectively. The additions of 2.5, 5 and 10 mmol EDTA kg−1 soil were more effective in enhancing Pb plant uptake than comparable [S,S]-EDDS treatments, but caused (as also 10 mmol kg−1 [S,S]-EDDS additions) unacceptably high Pb leaching in treatments with any soil water sorption conditions tested. The most efficient level of EDTA (10 mmol kg−1) enhanced plant Pb uptake by 97 times compared to the control. Shoots Pb concentrations reached 500 mg kg−1 of dry biomass. However, in this treatment 36.2% of total initial Pb was leached from the soil during the first four weeks after chelate addition. Hydrogel soil amendments were more effective in treatments with [S,S]-EDDS than with EDTA. In treatments with 10 mmol kg−1[S,S]-EDDS hydrogel amended soils, plant Pb uptake was significantly reduced and Pb leach was as high as 44.2% of total initial soil Pb. At lower [S,S]-EDDS concentrations, the effect of hydrogel soil amendment on Pb leaching was the opposite. The addition of 5 mmol kg−1 [S,S]-EDDS soil to the soil amended with 0.2% hydrogel increased Pb uptake by 18 times while only 0.2% of total initial Pb was leached. In all treatments, the concentrations of Pb in dry plant biomass were far from concentrations required for efficient soil remediation within a reasonable time span.

SORPTION OF HERBICIDES IN RELATION TO SOIL VARIABILITY AND LANDSCAPE POSITION

Using the soil-water sorption partitioning coefficient (Kd), this study quantified the spatial variation of 2,4-D sorption by soil in an undulating-to-hummocky terrain landscape near Minnedosa, MB, Canada. Herbicide sorptionwas most strongly related to soil organic matter content and slope position, with greatest sorption occurring in lower landscape positions with greater soil organic matter content. The relation between sorption and slope position was more pronounced under conventional tillage (CT) than under long-term zerotillage (ZT). Using multivariate regression and three independent variables (soil organic matter content, soil clay content and soil pH), the prediction of herbicide sorption by soil was very good for CT (R2 = 0.89) and adequately for ZT (R2 = 0.53).

Polychlorinated biphenyl sorption by soils: Measurement of soil-water partition coefficients at equilibrium

The sorption of PCB congeners 24′ (lUPAC number 8), 22′55′ (52) and 22′44′55′ (153) by eight soils differing in their organic carbon content (2.3 to 0.2% by Wt.) and expandable clay mineral content (17 to 53 % by wt.) has been investigated for 0.1 g/L soil-water suspensions. The time to reach sorption equilibrium, i.e. sorption-diffusion equilibrium, for a highly aggregated montmorillonitic soil containing 0.9% organic carbon for congeners 8, 52, 153 was determined to be 3, 5, and 10 months, respectively, using a gas-purge technique. For these sorbate-sorbent contact times soil-water sorption equilibrium partition coefficients on a soil-organic carbon basis (K oc) were measured and for these congeners ranged varied from 2.4 × 10 4 to 6.8 × 10 6 mL/g. Based on these data a correlation relation was derived, log K oc = 1.07 log K ow − 0.98, for estimating K oc from known values of octanol-water partition coefficient (K ow). From literature K ow values this regression equation was used to estimate K oc for 46 of the major PCB congeners in Aroclor 1242, 1254 and 1260.

Model for the sorption of organic compounds by soil from water

The solvation parameter model successfully accounts for the factors that determine the uptake of organic compounds by soil from water. Wet soil is significantly less cohesive than water, is less dipolar, has roughly similar hydrogen-bond basicity, and substantially weaker hydrogen-bond acidity. By analogy to other distribution systems it has similar extraction power to isobutanol and retention properties that resemble those of sodium taurodeoxycholate micelles in micellar electrokinetic chromatography. The possible use of chromatographic systems for the surrogate estimation of the soil–water sorption coefficient (KOC) is discussed.