Fate and Transport of Naproxen in a Sandy Aquifer Material: Saturated Column Studies and Model Evaluation

Naproxen-C14H14O3 is a nonsteroidal anti-inflammatory drug which has been found at detectable concentrations in wastewater, surface water, and groundwater. Naproxen is relatively hydrophilic and is in anionic form at pH between 6 and 8. In this study, column experiments were performed using an unconsolidated aquifer material from an area near Barcelona (Spain) to assess transport and reaction mechanisms of Naproxen in the aquifer matrix under different pore water fluxes. Results were evaluated using HYDRUS-1D, which was used to estimate transport parameters. Batch sorption isotherms for Naproxen conformed with the linear model with a sorption coefficient of 0.42 (cm3 g−1), suggesting a low sorption affinity. Naproxen breakthrough curves (BTCs) measured in soil columns under steady-state, saturated water flow conditions displayed similar behavior, with no apparent hysteresis in sorption or dependence of retardation (R, 3.85-4.24) on pore water velocities. Soil sorption did not show any significant decrease for increasing flow rates, as observed from Naproxen recovery in the effluent. Sorption parameters estimated by the model suggest that Naproxen has a low sorption affinity to aquifer matrix. Most sorption of Naproxen occurred on the instantaneous sorption sites, with the kinetic sorption sites representing only about 10 to 40% of total sorption.

Efeito da associação do herbicida clomazone a nanoesferas de alginato/quitosana na sorção em solos

Agrochemicals constitute the class of products most commonly found in water resources. Their high level of concentration is due to the fact that less than 0.1% of pesticides applied to crops reach their target. The present work aims to study the sorption of clomazone herbicide (associated or not with nanoparticles). The sorption tests, performed with the 2(4) factorial design, showed that the form of herbicide is the main factor for sorption of clomazone. The application of nanoparticles as delivery system for agrochemicals is a pressing area of study and can contribute for decrease in effects of clomazone in the environment.

Poly(epsilon-caprolactone)nanocapsules as carrier systems for herbicides: Physico-chemical characterization and genotoxicity evaluation

The toxicity of herbicides used in agriculture is influenced by their chemical stability, solubility, bioavailability, photodecomposition, and soil sorption. Possible solutions designed to minimize toxicity include the development of carrier systems able to modify the properties of the compounds and allow their controlled release. Polymeric poly(epsilon-caprolactone) (PCL) nanocapsules containing three triazine herbicides (ametryn, atrazine, and simazine) were prepared and characterized in order to assess their suitability as controlled release systems that could reduce environmental impacts. The association efficiencies of the herbicides in the nanocapsules were better than 84%. Assessment of stability (considering particle diameter, zeta potential, polydispersity, and pH) was conducted over a period of 270 days, and the particles were found to be stable in solution. In vitro release kinetics experiments revealed controlled release of the herbicides from the nanocapsules, governed mainly by relaxation of the polymer chains. Microscopy analyses showed that the nanocapsules were spherical, dense, and without aggregates. In the infrared spectra of the PCL nanocapsules containing herbicides, there were no bands related to the herbicides, indicating that interactions between the compounds had occurred. Genotoxicity tests showed that formulations of nanocapsules containing the herbicides were less toxic than the free herbicides. The results indicate that the use of PCL nanocapsules is a promising technique that could improve the behavior of herbicides in environmental systems. (C) 2012 Elsevier B.V. All rights reserved.

The bioconcentration factor of pesticides in potatoes.

We presented a model that estimates the bioconcentration factor (BCF) of pesticides in potatoes supposing that the pesticide in the soil solution is absorbed by the potato by passive diffusion, following Fick?s second law. The pesticides in the model are nonionic organic substances, traditionally used in potato crops that degrade in the soil according to a first order kinetic equation. This presents an expression that relates BCF with the pesticide elimination rate by the potato, with the pesticide accumulation rate within the potato, with the rate of growth of the potato and with the pesticide degradation rate in the soil. BCF was estimated supposing steady state equilibrium of the quotient between the pesticide concentration in the potato and the pesticide concentration in the soil solution. It is suggested that a negative correlation exists between the pesticide BCF and the soil sorption partition coefficient. The model was built based on the work of Trapp et al. (2007), [Diffusion of PAH in Potato and Carrot Slices and Applications for a Potato Model] in which an expression to calculate the diffusivity of persistent organic substances in potatoes is presented. The model consists in adding to the expression of Trapp et al. (2007) the hypothesis that the pesticide degrades in the soil. The value of BCF suggests which pesticides should be monitored in potatoes.

Linear solvation energy relationships regarding sorption and retention properties of hydrophobic organic compounds in soil leaching column chromatography

The capacity factors of a series of hydrophobic organic compounds (HOCs) were measured in soil leaching column chromatography (SLCC) on a soil column, and in reversed-phase liquid chromatography on a C-18 column with different volumetric fractions (phi) of methanol in methanol-water mixtures. A general equation of linear solvation energy relationships, log(XYZ) = XYZ(0) + mV(1)/100 + spi* + bbeta(m) + aalpha(m), was applied to analyze capacity factors (k'), soil organic partition coefficients (K-oc) and octanol-water partition coefficients (P). The analyses exhibited high accuracy. The chief solute factors that control log K-oc, log P, and log k' (on soil and on C-18) are the solute size (V-1/100) and hydrogen-bond basicity (beta(m)). Less important solute factors are the dipolarity/polarizability (pi*) and hydrogen-bond acidity (alpha(m)). Log k' on soil and log K-oc have similar signs in four fitting coefficients (m, s, b and a) and similar ratios (m:s:b:a), while log k' on C-18 and log P have similar signs in coefficients (m, s, b and a) and similar ratios (m:s:b:a). Consequently, log k' values on C-18 have good correlations with log P (r > 0.97), while log k' values on soil have good correlations with log K-oc (r > 0.98). Two K-oc estimation methods were developed, one through solute solvatochromic parameters, and the other through correlations with k' on soil. For HOCs, a linear relationship between logarithmic capacity factor and methanol composition in methanol-water mixtures could also be derived in SLCC. (C) 2002 Elsevier Science Ltd. All rights reserved.

Re-inoculation of autoclaved soil as a non-sterile treatment for xenobiotic sorption and biodegradation studies

Autoclaved soil is commonly used for the study of xenobiotic sorption and as an abiotic control in biodegradation experiments. Autoclaving has been reported to alter soil physico-chemical and xenobiotic sorption characteristics such that comparison of autoclaved with non-autoclaved treatments in soil aging and bioavailability studies may yield misleading results. Experiments could be improved by using autoclaved soil re-inoculated with indigenous microorganisms as an additional or alternative non-sterile treatment for comparison with the sterile, autoclaved control. We examined the effect of autoclaving (3 x 1 h, 121°C, 103.5 KPa) on the physico-chemical properties of a silt loam soil (pH 7.2, 2.3% organic carbon) and the establishment of indigenous microorganisms reintroduced after autoclaving. Sterilisation by autoclaving significantly (p ≤ 0.05) decreased pH (0.6 of a unit) and increased concentrations of water-soluble organic carbon (WSOC; nontreated = 75 mg kg^-1; autoclaved = 1526 mg kg^-1). The initial first-order rate of ¹⁴C-2,4-dichloro-UL-phenol (2,4-DCP) adsorption to non-treated, autoclaved and re-inoculated soil was rapid (K₁ = 16.8-24.4 h^-1) followed by a slower linear phase (K₂). In comparison with autoclaved soil (0.038% day^-1), K₂ values were higher for re-inoculated (0.095% day^-1) and nontreated (0.181% day^-1) soil. This was attributed to a biological process. The Freundlich adsorption coefficient (K(f)) for autoclaved soil was significantly (p ≤ 0.05) higher than for re-inoculated or non-treated soil. Increased adsorption was attributed to autoclaving-induced changes to soil pH and solution composition. Glucose-induced respiration of autoclaved soil after re-inoculation was initially twice that in the non-treated control, but it decreased to control levels by day 4. This reduction corresponded to a depletion of WSOC. 2,4-DCP mineralisation experiments revealed that the inoculum of nonsterile soil (0.5 g) contained 2,4-DCP-degrading microorganisms capable of survival in autoclaved soil. The lag phase before detection of significant 2,4-DCP mineralisation was reduced (from 7 days to ≤3 days) by pre-incubation of re-inoculated soils for 7 and 14 days before 2,4-DCP addition. This was attributed to the preferential utilisation of WSOC prior to the onset of 2,4-DCP mineralisation. Cumulative ¹⁴CO₂ evolved after 21 days was significantly lower (p ≤ 0.05) from non-treated soil (25.3%) than re-inoculated soils (ca 45%). Experiments investigating sorption-biodegradation interactions of xenobiotics in soil require the physico-chemical properties of sterile and non-sterile treatments to be as comparable as possible. For fundamental studies, we suggest using re-inoculated autoclaved soil as an additional or alternative non-sterile treatment.

Biochar alteration of the sorption of substrates and products in Soil Enzyme Assays

Pine wood and barley straw biochar amendments to Kettering and Cameroon sandy silt loam soils (15, 30, or 150 mg biochar g−1 soil) caused significant reductions (up to 80%,

Influence of sugar cane vinasse on the sorption and degradation of herbicides in soil under controlled conditions

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Sorption and desorption of phosphate on biochar and biochar-soil mixtures

The term biochar refers to materials with diverse chemical, physical and physicochemical characteristics that have potential as a soil amendment. The purpose of this study was to investigate the P sorption/desorption properties of various slow biochars and one fast pyrolysis biochar and to determine how a fast pyrolysis biochar influences these properties in a degraded tropical soil. The fast pyrolysis biochar was a mixture of three separate biochars: sawdust, elephant grass and sugar cane leaves. Three other biochars were made by slow pyrolysis from three Amazonian tree species (Lacre, Ingá and Embaúba) at three temperatures of formation (400 °C, 500 °C, 600 °C). Inorganic P was added to develop sorption curves and then desorbed to develop desorption curves for all biochar situations. For the slow pyrolysis, the 600 oC biochar had a reduced capacity to sorb P (4-10 times less) relative to those biochars formed at 400 °C and 500 °C. Conversely, biochar from Ingá desorbed the most P. The fast pyrolysis biochar, when mixed with degraded tropical mineral soil, decreased the soil's P sorption capacity by 55% presumably because of the high soluble, inorganic P prevalent in this biochar (909 mg P/kg of biochar). Phosphorus desorption from the fast pyrolysis biochar/soil mixture not only exhibited a common desorption curve but also buffered the soil solution at a value of ca. 0.2 mg/L. This study shows the diversity in P chemistry that can be expected when biochar is a soil amendment and suggests the potential to develop biochars with properties to meet specific objectives. © 2013 British Society of Soil Science.

Soil, Clay, and caustic soda effects on solubility, sorption, and mobility of hexachlorocyclopentadiene /

Bibliography: p. 51-54.

Sorption and desorption behaviour of acetochlor in surface, subsurface and size-fractionated soil

Pesticides leaching through a soil profile will be exposed to changing environmental sorption and desorption conditions as different horizons with distinct physical and chemical properties are encountered. Soil cores were taken from a clay soil profile and samples taken from 0.0 to 0.3 m (surface), 1.0-1.3 m (mid) and 2.7-3.0 m (deep) and treated with the chloroacetanilide herbicide, acetochlor. Freundlich isotherms revealed that sorption and desorption behaviour varied with each depth sampled. As soil depth increased, the extent and strength of sorption decreased, indicating that the potential for leaching was increased in the subsoils compared with the surface soil. Hysteresis was evident at each of the three depths sampled, although no significant correlations between soil properties and the hysteresis coefficients were evident. Desorption studies using soil fractions with diameters of > 2000, 250-2000, 53-250, 20-53, 2-20, 0-2 and 0-1 mum separated from each of the three soil depths showed that differential desorption kinetics occurred and that the retention of acetochlor significantly correlated (R-2 = 0.998) with organic matter content. A greater understanding of the influence of soil components on the overall sorption and desorption potential of surface and subsurface soils is required to allow accurate prediction of acetochlor retention in the soil. In addition, it is likely that the proportion of each size fraction in a soil horizon would influence acetochlor bioavailability and movement to groundwater.

Sorption characteristics of a nonionic surfactant during remediation of contaminated soil with different organic content

Surfactant enhanced subsurface remediation has gained importance in soil remediation. Since surfactants can be sorbed on soils, the concentration of free surfactant could drop below the critical micelle concentration, CMC, which may reduce the ability of the surfactant to solubilize the contaminants in soils. ^ The main goal of this research was to study the factors affecting the surfactant sorption on soil such as surfactant concentration, soil organic content, and organic contaminants in soil and to determine the organic contaminants removed from soils by surfactant. The results would be served as the basis for the implementation of a future study in the pilot scale and field scale for surfactant enhanced subsurface remediation. ^ This research study investigated the relationship between the organic content of soils and the sorption characteristics of a nonionic surfactant, Triton X-100. The experiments were performed using uncontaminated soils and soil contaminated with naphthalene and decane. The first part of the experiments were conducted in batch mode utilizing surface tension technique to determine the CMC of surfactant Triton X-100 and the effective CMC in the soil/aqueous system. The sorption of Triton X-100 was calculated from the surface tension measurements. The second part of the experiments utilized the SPME/GC/FID technique to determine the concentration of the contaminants solubilized from the soils by the surfactant Triton X-100 at different concentrations. ^ The results indicated that when the concentration of surfactant was lower than the CMC, the amount of surfactant sorbed on soil increased with the increasing surfactant concentration and the surfactant sorption characteristics of the uncontaminated soils could be modeled by the Freundlich isotherm. For the contaminated soils, the amount of surfactant sorbed was higher than those for the uncontaminated soils. The amount of surfactant sorbed on soils also depends on the organic content in the soils. The higher the organic content in the soil, higher is the amount of surfactant sorbed onto the soil. When the concentration of surfactant was higher than the CMC, the amount of surfactant added into the soil/aqueous system will increase the number of micelle and it increase the solubilization of organic contaminant from the soils. The ratio of the moles of organic contaminant solubilized to the moles of surfactant present as micelles is called the molar solubilization ratio (MSR). MSR value for naphthalene was about 0.16 for the soil-water systems. The organic content of soil did not appear to affect MSR for naphthalene. On the other hand, the MSR values for decane were 0.52, 0.39 and 0.38 for soils with 25%, 50% and 75% organic content, respectively. ^

Biochar increases the sorption and reduces the potential leaching the diuron in sandy soil.

2016