Sorption Distribution Coefficient Research Articles

Imidacloprid residues in Willapa Bay (Washington State) water and sediment following application for control of burrowing shrimp.

Pesticides have been used in the Willapa Bay estuary in western Washington State to control the exotic invasive plant species Spartina alterniflora (cordgrass) and the native species of burrowing shrimp (Callianassa sp.; Upogebia sp.) that affect oyster production. Carbaryl, the only registered insecticide for control of burrowing shrimp, has not been extensively studied in the Willapa Bay. However, carbaryl use has been severely restricted, and alternatives likely to have less severe environmental impacts are being sought. Imidacloprid applied directly to exposed sediments when the tide is out is efficacious for burrowing shrimp control but lacks studies of its behavior in the estuary. For this study, imidacloprid dissipation was monitored as the tide was rising in Willapa Bay. Over 99% of applied material dissipated from small plots within 24 h, but residues near the analytical detection limit were found in sediments 28 days later. At a distance of 152 m along a transect from the plot in the direction of tidal flow, imidacloprid residues in water peaked within 10 min after initiation of tidal flow. Within 30 min, imidacloprid residues were not detected, nor were residues detected in the water any time over the next month after application. Carbaryl residues in water were also monitored, and they exhibited the same rise and fall at the 152 m distance from the experimental plot as did the imidacloprid residues. However, carbaryl levels significantly above the detection limit were still present in water over the next month after application. The rapid dissipation of imidacloprid from water was hypothesized to be due to extensive dilution by the tide. The hypothesis was tested in batch equilibration sorption studies with radiolabeled imidacloprid and Willapa Bay sediment. Sorption distribution coefficients were <1 mL/g, and hysteresis was not observed during two desorption cycles, suggesting that imidacloprid was widely dispersed to extremely low levels soon after application.

Development of a kinetic basis for bioavailability of sorbed naphthalene in soil slurries

The degradation of naphthalene in soil–slurry systems was studied using four different organisms and two soils. Organisms with zero-order, first-order, and Michaelis–Menten rates were selected. The soils had substantially different sorption distribution coefficients. Sorption and desorption was evaluated in abiotic soil–slurry systems. The desorption process was described by a model that accounts for equilibrium, rate-limited and non-desorbing sites. Biodegradation parameters were measured in soil-extract solutions. Bioavailability assays, inoculated soil slurries, were conducted and both liquid- and sorbed-phase naphthalene concentrations were measured over time. For the less sorptive soil, the results could be explained by sequential desorption and degradation processes. For the other soil, enhanced degradation was clearly observed for the organisms with first-order and Michaelis–Menten rates. Several explanations are explored for these observations including direct sorbed-phase degradation and the development of elevated substrate concentrations at the organism/sorbent interface. No enhancement was found for the organism with zero-order kinetics.

2–D SATURATED–UNSATURATED ZONE IRRIGATION AND DRAINAGE MODEL: PART II. SENSITIVITY ANALYSIS

The modified SWMS_2D model described in the previous article was used to study sensitivity of model output tocritical head, sorption distribution coefficient, initial solute concentration, distal boundaries, plant water uptake parameters,irrigation schedules, and soil type considering a 100 m 9 m transect in the western San Joaquin Valley. Output was foundinsensitive to reductions in minimum soil water suction head (hd) and distal boundaries located 1000 m away from the domainof interest, and was found to be sensitive to values of sorption coefficient (Kd), plant water uptake parameters, irrigationschedules, and soil type. Finally, application of a method to separate evapotranspiration into evaporation and transpirationby deriving the ground shading parameters from crop coefficients was demonstrated. The results suggest that the modifiedSWMS_2D model can be used for irrigation and drainage management.

Impacts of heterogeneous organic matter on phenanthrene sorption: different soil and sediment samples.

Organic petrography has been proposed as a tool for characterizing the heterogeneous organic matter present in soil and sediment samples. A new simplified method is proposed as a quantitative means of interpreting observed sorption behavior for phenanthrene and different soils and sediments based on their organic petrographical characterization. This method is tested under singe solute conditions and at phenanthrene concentration of 1 microg/L. Since the opaque organic matter fraction dominates the sorption process, we propose that by quantifying this fraction one can interpret organic content normalized sorption distribution coefficient (Koc) values for a sample. While this method was developed and tested for various samples within the same aquifer, in the current study the method is validated for soil and sediment samples from different sites that cover a wide range of organic matter origin, age, and organic content. All 10 soil and sediment samples studied had log Koc values for the opaque particles between 5.6 and 6.8. This range of Koc values illustrates the heterogeneity of opaque particles between sites and geological formations and thus the need to characterize the opaque fraction of materials on a site-by-site basis.

Effects of fundamental differences between batch and miscible displacement techniques on sorption distribution coefficient

A circulation-through-column (CTC) technique was developed and employed to evaluate the influence of fundamental differences between batch and miscible displacement (MD) techniques on the value of the sorption distribution coefficient (K). Batch, MD, and CTC experiments were conducted to determine sorption equilibrium parameters for dimethylphthalate (DMP), diethylphthalate (DEP), and dipropylphthalate (DPP) using two natural soil samples with 0.36 and 1.48% organic carbon. Batch sorption isotherms of DMP and DEP were linear while that of DPP was nonlinear. Batch-determined K values for the compounds were 30 to 170% higher than the corresponding values obtained from breakthrough curves (BTCs) generated through MD experiments. Similarities between values of K derived from batch and CTC techniques suggest that underestimation of K determined from BTCs is not due to fundamental differences between batch and MD techniques. The extent of deviation between the K values determined by batch and MD experiments was inversely related to the value of K. This was well explained by a fixed percent reduction in the retardation coefficient determined from solute BTCs, suggesting a possible leftward shift of these curves.

Biodegradation of non-desorbable naphthalene in soils.

The degradation of naphthalene was studied in soil-slurry systems, and a quantitative model was developed to evaluate the bioavailability of sorbed-phase contaminant. Four soils with different organic matter contents were used as sorbents. Two naphthalene-degrading organisms, Pseudomonas putida G7 and NCIB 9816-4, were also selected. Sorption isotherms and single and series dilution desorption studies were conducted to evaluate distribution coefficients, desorption parameters, and the amount of non-desorbable naphthalene. Biodegradation kinetics were measured in soil extract solutions and rate parameters estimated. Bioavailability assays involved establishing sorption equilibrium, inoculating the systems with organisms, and measuring naphthalene concentrations in both sorbed and dissolved phases over time. For all four soils, the sorption isotherms were linear, and desorption could be described by a model involving three types of sites: equilibrium, nonequilibrium, and non-desorption. Enhanced bioavailability, as evidenced by faster than expected degradation rates based on liquid-phase concentrations, were observed in soils with the higher sorption distribution coefficients. These observations could be described using model formulations that included solid-phase degradation. In all soils studied, degradation of non-desorbable naphthalene was observed.

Selection of Conditions for the Dynamic Sorption Preconcentration of a 1,1-Dimethylhydrazine Derivative (4-Nitrobenzaldehyde N,N-Dimethylhydrazone) on Hydrophobized Silica

The type of mass transfer in the sorption of 4-nitrobenzaldehyde N,N-dimethylhydrazone (BDH) on silica chemically modified with hexadecyl groups was determined using the linear model of sorption dynamics, and distribution and mass transfer coefficients of hydrazone were calculated. Optimal conditions of the dynamic sorption preconcentration and desorption of BDH and its subsequent determination by reversed-phase high-performance liquid chromatography were proposed. The detection limit of the compound for preconcentration from a sample of 100 mL was 1 μg/L.

Enhancement of soil–bentonite barrier performance with the addition of natural humus

To assess the performance of a modified slurry wall material, laboratory-scale contaminant transport experiments were conducted with trichloroethylene (TCE) and soil–bentonite (SB) amended with the addition of natural humus. Low-flow column studies were performed using flexible wall permeameters, with the primary emphasis on the measurement of spatial contaminant distributions from columns operated for different durations. Batch experiments were also performed to assess the sorption characteristics of the modified SB. Penetration of TCE into the amended SB was significantly retarded, suggesting that the addition of organic-rich material can be an effective strategy for improving barrier performance. The advective–dispersive–reactive equation (ADRE) gave good predictions of the observed contaminant spatial distributions in the columns provided that nonequilibrium sorption was included in the model formulation. The calibrated TCE diffusion coefficient corresponded to a porosity-corrected hindrance factor of 2.7, which is similar to other studies of barrier materials. However, the sorption distribution coefficient estimated from the column data was approximately one half the value measured in the batch isotherm test. Although the reason for this discrepancy was not identified, the results suggest that caution should be exercised in extrapolating the performance of strongly sorbing barrier materials from batch test data.

Influence of molecular structure on sorption of phenoxyalkanoic herbicides on soil and its particle size fractions.

The sorption and desorption behaviors of four phenoxyalkanoic acid herbicides and their metabolites on four agricultural soils and soil particle size fractions were examined. Generally, there was a trend of increasing adsorption and decreasing desorption in the order mecoprop < MCPA < dichlorprop < 2,4-D. The significant increase in adsorption of the phenolic metabolites can be explained by their lower polarity and enhanced partition in the organic soil matrix. Estimation of sorption distribution coefficients from particle size fraction adsorption data was possible for a sandy soil and a silty Cambisol soil only. It is suggested that increasing steric demand, for example, molecular volume, and slight changes in the polarity of the compounds affect their adsorption properties. Comparison of adsorption and desorption data of structurally similar compounds obtained from a variety of soils allows investigation of structure-induced differences in sorption strength.

Sorption and desorption of Eu and Yb on alumina: mechanisms and effect of fulvic acid

The effects of pH, ionic strength and FA (fulvic acid) on the sorption and desorption of Eu(III) and Yb(III) on alumina were respectively investigated by using batch technique and radiotracers 152+154Eu and 169Yb. The distribution coefficients for sorption and desorption of Eu on alumina at pH 4.4, 4.6 and 5.7 in 1 mol/l NaCl solutions as a function of solid phase concentration were determined in the presence or absence of FA. The effects of pH, FA and ionic strength on the distribution coefficients for sorption and desorption of Yb on alumina were determined in 0.01–2.0 mol/l NaNO 3. It was found that pH and FA influenced the sorption of Eu(III) and Yb(III) on alumina greatly. A surface hydrolysis model can satisfactorily and qualitatively explain the observations on bare alumina. The competition among the complexations of surface free hydroxyl groups, soluble and sorbed fulvic acids can satisfactorily and qualitatively explain the observations on the coated alumina.

Impact of Porosity Heterogeneity in the Diffusion of Some Alkali- and Alkaline Earth-Metals in Crystalline Rock

Data from diffusion experiments using Na+, Ca2+, Sr2+, Cs+ and Ba2+ as tracers in a crystalline rock type (Aspo diorite, originating from the Aspo Hard Rock Laboratory) have been evaluated using a heterogeneity model. The model concept consists of diffusion in a variety of different channels with different porosities. The porosity distribution used has been obtained from independently performed measurements of porosity distributions using the14C-polymethylmethacrylate impregnation method. Breakthrough curves in through-diffusion experiments as well as penetration profiles in the matrix have been evaluated using the porosity distributions. In the calculations only two parameters, the pore diffusivity (D p) and the sorption distribution coefficient (K d) have been varied in order to fit the experimental data to the proposed model. For the penetration profile of more strongly sorbing tracers, i.e., Cs+ and Ba2+, a significantly better explanation of the data is obtained using a heterogeneity model compared to using a uniform porosity distribution model. The data from the through-diffusion experiments gives a better explanation of the shape at the beginning of the breakthrough curve. The implication of the proposed diffusion model is discussed, both from anin situ sorption experiment application and a performance assessment application.

Variability of chlorinated-solvent sorption associated with oxidative weathering of kerogen

The perchloroethylene (PCE) sorption distribution coefficient ( K d, measured at 40–100 μg/l solution concentration in batch experiments) ranged from 4.0 to 134 l/kg over the sampled thickness (1.0–6.0 m depth) of a moderately-low organic carbon (0.002–0.005), fractured and weathered diamict (poorly sorted, glacially deposited) aquitard. The organic carbon-normalized K d ( K oc) for deeper, unoxidized (reduced) samples from this deposit (log K oc=4.4–4.59) were generally consistent with the kerogen in the underlying Devonian-age shale (log K oc=4.57), a likely source rock for these sediments. The similarities between these samples suggest that the sorption capacity of the kerogen was minimally altered during transport and deposition, and that humic substances were not co-deposited with the kerogen in the glacially-deposited sediments. The K oc within the diamict was correlated to the oxidation state of the organic matter, characterized by the H/O ratio through elemental analysis. The K oc for more oxidized samples from shallower depth samples (log K oc=3.35–3.65) were approximately an order of magnitude less than those determined for the reduced samples. The K oc for 1.5- to 2.5-cm thick oxidation haloes surrounding fractures and characterized by visible Fe-oxidation, were approximately 20–30% lower than the adjacent unaltered matrix samples. The linear trend observed between log K oc and log H/O is similar to, but steeper than, the relation reported previously, which represents increasing sorption magnitude with increasing diagenesis in coal and shale samples. The spatial distribution of the K oc within this aquitard, in concert with qualitative geologic observations, suggests that oxidative weathering of the native kerogen exerts an important control on hydrophobic organic compound sorption.

Transport of sequentially decaying reaction products influenced by linear nonequilibrium sorption

Predicting the migration of sequentially degrading reaction products is important for the accurate analysis of subsurface treatment walls and other environmental systems. Recently, it has also been realized that consideration of rate‐limited sorption may be necessary to quantify the transport of contaminants in reactive treatment walls. In this paper, analytical and semianalytical solutions are developed for the one‐dimensional transport of a parent compound and three sequentially decaying reaction products influenced by nonequilibrium sorption. The solutions are based on the Laplace transformation technique and incorporate a different sorption distribution coefficient and mass transfer rate for each reaction product. Two types of exit boundary conditions are considered: semi‐infinite and finite zero‐gradient. The developed solutions are used to simulate the migration of trichloroethylene and its reaction products in a zero‐valent iron treatment wall. The effect of nonequilibrium sorption on the time to reach steady state is investigated, and it is shown that a zero‐valent iron treatment wall may exhibit a significant transient period. However, concentrations reach 80% of the steady state values within the first 100 pore volumes. It is also shown that neglecting dispersion may lead to nonconservative predictions of the effluent contaminant concentrations.

Studies of time-dependent sorption of linuron and isoproturon in soils

Changes in sorption over time were measured for the substituted urea herbicides linuron (3-(3,4-dichlorophenyl)-1-methoxy-1-methyhuea) and isoproturon (3-(4-isopropylphenyl)-1,1-dimethylurea) in three different soils. Studies were made at two incubation temperatures (5°C to restrict degradation and 20°C to promote degradation), with soil moisture contents equivalent to field capacity. Measurements were made of the changes over time in both methanol extractable herbicide residues and in herbicide concentrations in the soil solution. Sorption distribution coefficients of linuron and isoproturon increased with residence time in the soil, and the increases were more pronounced at 20°C than at 5°C, suggesting an interaction between sorption and degradation.With linuron, comparative studies were done with the herbicide applied to soil as either a commercial formulation, or as pure, analytical grade compound. No significant differences were observed between the two treatments.In further experiments with isoproturon, incubations were made at 5°C with initial concentrations of 2, 4, 6, 8 and 10 mg isoproturon kg −1 soil, and total residues and soil solution concentrations were measured after 4 days. Sorption measurements of isoproturon were also made using a standard batch equilibrium method. Initial in-situ isotherms were similar to standard batch equilibrium isotherms, although equilibrium was reached faster in the shaken than in the static systems. These data suggest that the apparent increase in sorption distribution coefficient with time is linked in part to preferential degradation in the soil solution, in part to diffusion to less accessible sorption sites, and is in part an artefact caused by marked curvature in some of the sorption isotherms.

SORPTION OF s-TRIAZINE HERBICIDES IN ORGANIC MATTER AMENDED SOILS: FRESH AND INCUBATED SYSTEMS

Fresh amendment of soil with sewage sludge and composted sewage sludge resulted in increased sorption of three s-triazine herbicides: atrazine, ametryn and terbuthylazine. The extent of increased sorption (as evaluated by sorption coefficients Kd or Kf) was a function of soil type, such that sorption in amended organic carbon-poor soil (0.4% OC) was more enhanced than in amended organic carbon-rich soil (1.55% OC). Despite significant differences between the organic amendments in terms of humic and fulvic acid content, humin content, soluble organic matter content, total organic matter content, and H/C and O/C atomic ratios, organic matter composition had no discernible effect on either sorption distribution coefficients or on isotherm linearity in amended soils. Soils amended with composted sludge had the same sorption potential as did soils amended with the analogous uncomposted sludge. After incubating soil-sludge mixtures for a year at room temperature, organic matter content decreased to original pre-amendment levels. Sorption coefficients for the three compounds similarly decreased to initial pre-amendment values. Organic carbon normalized sorption coefficients (Koc) were essentially identical in the soils, amended soils, and incubated amended soils, indicating that sludge and compost derived organic matter does not have a significantly different sorption capacity as compared with the original soils, despite compositional differences.

Sorption of atrazine and dicamba in Delaware coastal plain soils: a comparison of soil thin layer and batch equilibrium results

The mobility and retention of atrazine and dicamba in six Atlantic Coastal Plain soils were estimated by soil thin-layer chromatography (soil-TLC). The soils studied were representative of the major agricultural regions in Delaware and were sampled, by horizon, to the water table. Four horizons from each profile were leached simultaneously with distilled water on one soil-TLC plate. Two values were obtained from each plate: the ratio of the distance traveled by the herbicide center of mass over that traveled by the solvent front (Rm), and a sorption distribution coefficient (Kd). The Rm values ranged from 0·06 to 0·94 for atrazine and from 0·80 to 0·94 for dicamba. Herbicide mobility was found to be greatest in coarse-textured soil horizons that contained low levels of organic matter, clay, and Fe and Al oxides. Correlation analysis indicated that effective cation exchange capacity, exchangeable acidity, exchangeable aluminum, and clay were useful predictive variables or both atrazine mobility and sorption. Organic matter was not useful for predicting soil-TLC derived sorption estimates; however, it was correlated to Kd-batch estimates. Distribution coefficients calculated from soil-TLC data were found to be in general agreement with Kd values obtained for the same soils by batch equilibrium techniques. The average Kd-soil-TLC values for atrazine and dicamba were 2·09(±2·24) and 0·03(±0·02), respectively. The ratio of the batch Kd to the soil-TLC Kd ranged from 0·1 to 19 (x̄=1·6, SD=3·8) for atrazine and from 2·9 to 38 (x̄=12·6, SD=8·7) for dicamba. Thus, although for some horizons agreement between the two methods was good, for other horizons significant discrepancies existed. It is suggested that the soil-TLC gives results under non-equilibrium conditions, whereas the batch procedure is, by definition, at quasi-equilibrium. These fundamental differences may account for the observed differences between the two methods. It is also suggested that, due to this difference, the soil-TLC procedure can provide additional information relevant to herbicide partitioning in the field environment that is not provided by traditional batch equilibrium techniques. © 1998 Society of Chemical Industry

Sorption of Imidacloprid on Soil Clay Mineral and Organic Components

AbstractSoil clay mineral and organic components have been shown to be responsible for sorption of many pesticides. This study assessed the influence of the different components of the clay fraction of five soils and model sorbents (montmorillonite, Fe oxide, and humic acid) and their binary and ternary associations on sorption of the insecticide imidacloprid (1‐[(6‐chloro‐3‐pyridinyl)‐methyl]‐N‐nitro‐2‐imidazoli‐dinimine). Sorption was very high on a clay fraction containing a high content of low‐laminar‐charge montmorillonite and relatively high organic C content. When organic matter of the soil clays was reduced by H2O2, sorption decreased; however, the sorption coefficient based on organic C (Koc) increased. The increase in Koc was greater on clays whose surface areas substantially increased after H2O2 treatment. This indicates a contribution of the surfaces of mineral components of the soil clay to sorption of imidacloprid. Imidacloprid sorbed on both montmorillonite and humic acid, whereas sorption on Fe oxide was very low. The sorption distribution coefficient, Kd, on montmorillonite increased from 15 to 180 when pH was decreased from 3.5 to 1.0, suggesting protonation of the ‐NH group of the imidazol ring. Sorption on binary and ternary associations of these model sorbents indicated that organic matter is the single most important component affecting sorption of imidacloprid, although there is some contribution of the mineral surfaces.

Sorption of 1,2,4-trichlorobenzene and tetrachloroethene within an authigenic soil profile: Changes in Koc with soil depth

The sorption of 1,2,4-trichlorobenzene and tetrachloroethene was investigated in a series of well-controlled batch experiments, using authigenic soil materials from a profile extending to 2.5 m below ground surface. Batch experiment techniques were verified by study with both pulverized and unpulverized soil at different times of equilibration, using two widely different soil:water ratios, and at a wide range of aqueous concentration. Sorption isotherms were approximately linear, with sorption distribution coefficients ( K d) found to decrease roughly 100-fold down the soil profile. K d decreased with depth to an extent greater than could be predicted on the basis of the only 10-fold decrease in natural solid organic matter (SOM) content and despite significantly higher specific surface area in the lower horizons. All base-extractable SOM in these deeper soil horizons was operationally defined as fulvic acid (FA), although there was also a significant fraction that was not extracted by the standard base technique. The lower K d of the deeper soil horizons is believed to reflect a complex combination of (1) lower SOM content; (2) a more hydrophilic form of SOM; and (3) a more intimate association of the SOM with the mineral fraction, affecting its accessibility, sorptivity, or both. For the deeper horizons, an increase in overall K d by more than 4-fold was observed on solids treated by either base extraction or H 2O 2 treatment, demonstrating that sorption to remaining soil components could be dramatically increased by fractional SOM removal and/or chemical alteration of the soil. A simple regression model that divides SOM into only two types (shallow and deep SOM) provides a reasonably good explanation of sorption in all seven horizons and suggests an order-of-magnitude variability in K oc among surface soil and deeper horizons.

Retardation Coefficients of Nonionic Organic Compounds Determined by Batch and Column Techniques

AbstractBatch and column techniques were utilized to determine retardation coefficients of two nonionic organic compounds: benzene and dimethylphthalate. Three sandy soil materials with medium to high organic C content were used as sorbents. Batch data consistently overestimated retardation coefficients of the two compounds. Several previously reported factors that may cause discrepancy between the two techniques were experimentally investigated. Sorption nonsingularity, sorption nonequilibrium, presence of immobile water regions in the column, and reduction in particle spacing in the column were eliminated as the cause of this discrepancy. Loss of sorbent from the column is unlikely to be the cause of the discrepancy. Although rapidly mixed batch tubes are subjected to soil abrasion, it causes no apparent impact on the value of sorption distribution coefficients. Batch isotherms at two solids concentrations were identical, indicating that differences in solids concentration between batch and column setup is not a significant factor. This was also confirmed by a column study. Sorption nonlinearity was found to have a minor impact. Column residence time had a major impact on one of the cases studied, but no effect on the other cases. When column residence time was accounted for, some differences in sorption distribution coefficients, which seemed to be independent of the organic C content, were noticed. In this study, all previously suggested causes for the discrepancy between batch‐ and column‐determined retardation coefficients were investigated and rejected. It remains unclear why the values determined by the two techniques were different.

Rate of strontium sorption and the effects of variable aqueous concentrations of sodium and potassium on strontium distribution coefficients of a surficial sediment at the Idaho National Engineering Laboratory, Idaho

The rate of strontium sorption and the effects of variable aqueous concentrations of sodium and potassium on strontium sorption were measured as part of an investigation to determine strontium chemical transport properties of a surficial sediment at the Idaho National Engineering Laboratory (INEL), Idaho. Batch experimental techniques were used to determine the rate of strontium sorption and strontium distribution coefficients (Kds) between aqueous and solid phases. Rate experiments indicate that strontium in solution reached an apparent equilibrium with the sediment in 26 h. Kds were derived using the linear isotherm model at initial sodium concentrations from 100 to 5,000 mg/l and initial potassium concentrations from 2 to 150 mg/l. Kds ranged from 56±2 to 62±3 ml/g at initial aqueous concentrations of sodium and potassium equal to or less than 300 and 150 mg/l, respectively. Kds ranged from 4.7±0.2 to 19±1 ml/g with initial aqueous concentrations of sodium between 1,000 and 5,000 mg/l. These data indicate that sodium concentrations greater than 300 mg/l in wastewater increase the availability of strontium for transport beneath waste disposal ponds at the INEL by decreasing strontium sorption on the surficial sediment. Wastewater concentrations of sodium and potassium less than 300 and 150 mg/l, respectively, have little effect on the availability of strontium for transport.