Search Results (34)

High levels of pesticide use are associated with intensive crop production. Pesticides are increasingly prevalent in surface and groundwater, which is a major environmental concern. Various methods have been proposed to improve the retention and/or degradation of pesticides in soils. These methods are mainly based on soil adaptation with organic wastes to mitigate soil and water pollution. In addition, there has recently been increased interest in assessing the influence of organic waste additions on pesticide movement in soils with low contents of organic matter. Agriculture and related industries generate large amounts of waste each year. Because of their components, they have the great ability to produce high-value products for environmental restoration. This study reports on the influence of four different agro-industrial wastes (orange peel, beer bagasse, grape pomace, and gazpacho waste) used as organic amendments on the leaching of metobromuron and chlorbromuron (phenylurea herbicides) on a silty clay loam soil (gypsic–calcaric regosol) with low organic matter contents from a semiarid area (southeastern Spain). The adsorption, leaching, and dissipation processes of these herbicides were evaluated on a laboratory scale in amended and unamended soils. In addition, the main leaching indices (GUS, LIX, LEACH, M LEACH, LIN, GLI, HI, and ELI) commonly used to assess groundwater protection against pesticide pollution were evaluated. The sorption coefficients (K_OC) increased in the amended soils. Metobromuron was found in leachates in all cases, although a marked reduction was observed in amended soils, while chlorbromuron was mainly retained in soils, especially in the top layer. The disappearance time (DT₅₀) for metobromuron and chlorbromuron in soil ranged from 11 to 56 d and 18 to 95 d, respectively. All indices except GLI categorize metobromuron as mobile or very mobile in unamended soil. For chlorbromuron, GUS, LIX, LEACH, MLEACH, and Hornsby classify this compound as a medium-to-high leache, while GLI and ELI classify it as having low mobility. In amended soils, most indices classify metobromuron as transitioning to mobile, while most indices catalog chlorbromuron as immobile/transition. Full article

In the context of contaminated site remediation, the fate of chlorinated solvents in the subsurface and subsequent groundwater contamination is influenced by soil properties governing sorption. The solid–water distribution coefficient (K_d) is a key parameter for modeling contaminant distribution and transport, essential for risk assessment and remediation planning. This study evaluated tetrachloroethene sorption isotherms in 34 low-organic-carbon soils from the Czech Republic, assessing the influence of soil properties on K_d. Soil samples exhibited variability in organic carbon content (˂0.05–0.81%), with clay ranging from 0% to 64.9%, silt 5.1% to 71.2%, and sand 5.2% to 88.9%, specific surface area (0.41–64.39 m² g⁻¹), particle density (2.05–4.09 g cm⁻³), and porosity (43.5–67.3%). Batch experiments were conducted using standard procedures, with K_d values ranging from 0.379 to 2.272 L kg⁻¹. Statistical analysis grouped the soils into three textural classes: sandy, clayey fine, and silty loam. The findings reveal that organic carbon content and specific surface area are the primary predictors of K_d, while clay and sand also play a significant role in shaping sorption behavior. Multivariate regression models explained 63.6% to 98.5% of K_d variability with high accuracy, as indicated by low root means square error (0.070–0.329) and mean absolute percentage error (3.8–28.8%) values. These models offer reliable predictions of sorption behavior, providing valuable tools for risk assessment and remediation strategies. Full article

The impact of chain length on the sorption of anionic PFAS by soils and sediments was investigated by aggregating and synthesizing data sets from the literature. Quantitative structure/property relationship (QSPR) analysis was applied to characterize the influence of molecular size and soil properties on sorption. The log of the organic carbon-normalized equilibrium sorption coefficient (K_oc) exhibited a biphasic relationship with molar volume, wherein the log K_oc values for the short-chain PFAS were generally greater than would be predicted using the QSPR correlation determined for the long-chain PFAS. This enhanced differential sorption is observed to different degrees for all studies, which are compiled and synthesized for the first time. The results reveal remarkable congruency across a wide array of soils comprising a large range of properties and indicate that the observed enhanced differential sorption of short-chain PFAS is a prevalent phenomenon. Aggregating the long-chain PFAS data for all soils and sediments with organic carbon contents > 1% produced a strong correlation, indicating that the resultant QSPR model can produce representative log K_oc values irrespective of the other properties of the medium. Silt+clay content was shown to be an important soil component for the short-chain PFAS for most soils, as well as the long-chain PFAS for soils with organic carbon contents < 1%. The results indicate that while the simple K_oc-f_oc approach may produce reasonable estimates of K_d values for long-chain anionic PFAS, particularly for soils and sediments with larger organic carbon contents, it is unlikely to do so for short-chain anionic PFAS. Full article

Sustainable solutions are increasingly being sought in the containment and remediation of contaminated soil and groundwater, and the use of fibers is promising. In this context, polyvinylidene fluoride fibers (PVDF) have potential applications in various fields due to their mechanical and hydraulic properties, highlighting the sorption capacity due to their hydrophobic nature and large surface area. This study aimed to evaluate the sorption capacity, adsorption, and diffusion of atrazine by PVDF fibers with a concentration of 555.63 ppm in diffusion cells containing sandy soil and a composite of the fibers in blanket format at different contents (2% and 4%) relative to the dry mass of the soil. The diffusion and determination coefficients for each cell were calculated using Wolfram Mathematica software by means of a 3D model (Space × Time × c_w/c₀). The absorption results showed a mass gain, with and without prior drying of the fibers, of 70% and 60%, respectively, while the adapted adsorption tests showed retained amounts of atrazine of 0%, 11.4%, and 21.8%, respectively, for the samples without fiber, with 1.5 g of fiber, and with 4 g of fiber. And finally, the diffusion coefficients resulted in 6.25 × 10⁻¹³ m²/s, 6.03 × 10⁻¹³ m²/s, and 3.64 × 10⁻¹³ m²/s, respectively, for the sample without fibers, with 1.5% fiber, and with 4% fiber. This suggests that the use of PVDF fibers may be a viable solution for the containment of contaminated soil and groundwater. Full article

In this study, a two-dimensional contaminant transport model with time-varying axial input sources subject to non-linear sorption, decay, and production is numerically solved to find the concentration distribution profile in a heterogeneous, finite soil medium. The axial input sources are assigned on the coordinate axes of the soil medium, with background sources varying sinusoidally with space. The groundwater velocities are considered space-dependent in the longitudinal and transversal directions. Various forms of axial input sources are considered to study their transport patterns in the medium. The alternating direction implicit (ADI) and Crank-Nicolson (CN) methods are applied to approximate the two-dimensional governing equation, and the obtained algebraic system of equations in each case is further solved by MATLAB scripts. Both approximate solutions are illustrated graphically for various hydrological input data. The influence of various hydrogeological input parameters, such as the medium’s porosity, density, sorption conditions, dispersion coefficients, etc., on the contaminant distribution is analyzed. Further, the influence of constant and varying velocity parameters on groundwater contaminant transport is studied. The stability of the proposed model is tested using the Peclet and Courant numbers. Substantial similarity is observed when the approximate solution obtained using the CN method is compared with the finite element method in a special case. The proposed approximate solution is compared with the existing numerical solutions, and an overall agreement of 98–99% is observed between them. Finally, the stability analysis reveals that the model is stable and robust. Full article

Pharmaceutically active compounds (PhACs) enter soil with organic waste materials such as manure. Such complex substrates differently affect PhACs’ soil sorption. For the first time, batch experiments were conducted using five selected chemicals as model constituents to elucidate the effects. Urea, phosphate (KH₂PO₄), acetic acid, phenol and nonadecanoic acid (C:19) altered the sorption strength and/or nonlinearity of sulfadiazine, caffeine, and atenolol in an arable Cambisol topsoil. The nonlinear Freundlich model best described sorption. Overall, the PhACs’ Freundlich coefficients (sorption strength) increased in the sequence urea < phosphate < phenol < C:19 < acetic acid, while the Freundlich exponents largely decreased, indicating increasing sorption specificity. The effects on sulfadiazine and caffeine were rather similar, but in many cases different from atenolol. Phosphate mobilized sulfadiazine and caffeine and urea mobilized sulfadiazine, which was explained by sorption competition resulting from specific preference of similar sorption sites. Soil sorbed phenol strongly increased the sorption of all three PhACs; phenolic functional groups are preferred sorption sites of PhACs in soil. The large increase in sorption of all PhACs by acetic acid was attributed to a loosening of the soil organic matter and thus the creation of additional sorption sites. The effect of C:19 fatty acid, however, was inconsistent. These results help to better understand the sorption of PhACs in soil–manure mixtures. Full article

The soil sorption coefficient (K_d) of glyphosate mainly controls its transport and fate in the environment. Laboratory-based analysis of K_d is laborious and expensive. This study aimed to test the feasibility of visible near-infrared spectroscopy (vis–NIRS) as an alternative method for glyphosate K_d estimation at a country scale and compare its accuracy against pedotransfer function (PTF). A total of 439 soils with a wide range of K_d values (37–2409 L kg⁻¹) were collected from Denmark (DK) and southwest Greenland (GR). Two modeling scenarios were considered to predict K_d: a combined model developed on DK and GR samples and individual models developed on either DK or GR samples. Partial least squares regression (PLSR) and artificial neural network (ANN) techniques were applied to develop vis–NIRS models. Results from the best technique were validated using a prediction set and compared with PTF for each scenario. The PTFs were built with soil texture, OC, pH, Fe_ox, and P_ox. The ratio of performance to interquartile distance (RPIQ) was 1.88, 1.70, and 1.50 for the combined (ANN), DK (ANN), and GR (PLSR) validation models, respectively. vis–NIRS obtained higher predictive ability for K_d than PTFs for the combined dataset, whereas PTF resulted in slightly better estimations of K_d on the DK and GR samples. However, the differences in prediction accuracy between vis–NIRS and PTF were statistically insignificant. Considering the multiple advantages of vis–NIRS, e.g., being rapid and non-destructive, it can provide a faster and easier alternative to PTF for estimating glyphosate K_d. Full article

In the present study, the adsorption of zinc (Zn), lead (Pb), copper (Cu), and cadmium (Cd) was studied in two already polluted urban soil samples with different pH values, an acidic and an alkaline one. The Langmuir and Freundlich adsorption isotherm equations were used to thoroughly study the adsorption of the metallic elements on the solid surface of the soils. Langmuir equation described the adsorption of each metal satisfactorily, with a slight predominance over Freundlich, in both soils, as the R² value approached almost unity. Even though Zn and Cu were adsorbed on the soil phase, their adsorption was minimal compared to the adsorption of more harmful metals such as Pb and Cd. Using the values of the coefficients obtained from the equations of the mathematical models, we concluded that in alkaline soils, the retention of metals was much greater than in acidic soils. The simultaneous presence of metals during the addition of the single-element solutions of the metals to the already metal-contaminated soils caused competitive adsorption increasing the retention of the more toxic metals on the solid surface of the alkaline soil. Factors affecting soil sorption (such as soil pH and CaCO₃ content) were studied to provide theoretical support for understanding the laws and causes of metal sorption in the soils of the survey. Full article

Using the mixture of carbonized rice husk and shungite from the Kazakhstan Koksu deposit and the experimentally determined oil sorption capacity from contaminated soil with oil originating in the Karazhanbas oil field, a set of Artificial Neural Network (ANN) models were built for sorption predictions. The ANN architecture design, training, validation and testing methodology were performed, and the sorption capacity prediction was evaluated. The ANN models were successfully trained for capturing the sorption capacity dependence on time and on a carbonized rice husk and shungite mixture ratio for the 10% and 15% oil-contaminated soil. The best trained ANNs revealed a very good prediction capability for the testing data subset, demonstrated by the high coefficient of the determination values of R² = 0.998 and R² = 0.981 and the mean absolute percentage errors ranging from 1.60% to 3.16%. Furthermore, the ANN sorption models proved their interpolation ability and utility for predicting the sorption capacity for any time moments in the investigated time interval of 60 days and for new values of the shungite and rice husk mixture ratios. The ANN developed models open opportunities for planning new experiments, maximizing the sorption performance and for the design of dedicated equipment. Full article

In soils, cadmium (Cd) and its compounds, originating from industrial activities, differ both in mobility as well as in their ability to permeate the soil solution from naturally occurring cadmium compounds (native Cd). Therefore, the determination of the parameters of cadmium mobility in soils and its accumulation by plants in the soil–soil solution–plant system is very important from both scientific and practical viewpoints. ¹⁰⁹Cd was used as a radioactive tracer to study the processes of the transition of Cd into the aqueous phase and its uptake by plants over the course of a vegetative lysimeter experiment. Using sequential extraction according to the Tessier–Förstner procedure and modified BCR schemes, certain patterns were determined in the distribution of Cd/¹⁰⁹Cd among their forms in various compounds in the soil, along with the coefficients of the enrichment of native stable Cd with radioactive ¹⁰⁹Cd. It was shown that the labile pool of stable Cd compounds (29%) was significantly smaller than that of radioactive ¹⁰⁹Cd (69%). The key parameters characterizing the migration capacity of Cd in the soil–soil solution–plant system were determined. It was found that the distribution coefficient of native Cd between the soil and the quasi-equilibrium lysimeter solution exceeded the similar value for the ¹⁰⁹Cd radionuclide by 2.2 times, and the concentration coefficients of Cd and ¹⁰⁹Cd in the barley roots were 9 times higher than in its vegetative parts. During the experiment, the average removal of Cd (¹⁰⁹Cd) from the soil by each barley plant was insignificant: 0.002 (0.004)%. Based on the results of ¹³C nuclear magnetic resonance (NMR) spectroscopy of a lyophilized sample of the high-molecular-weight dissolved organic matter (HMWDOM) of the soil solution, its components were determined. It transpired that the isolated lyophilized samples of HMWDOM with different molecular weights had an identical structural and functional composition. The selective sorption parameters of the HMWDOM and humic acid (HA) with respect to Cd²⁺ ions were determined by the isotope dilution method. Full article

Sulfonamides (SAs) and tetracyclines (TCs) are two classes of widely used antibiotics. There is a lack of easy models for estimating the parameters of antibiotic sorption in soils. In this work, a dataset of affinity coefficients (K_f and K_d) of seven SA/TC antibiotics (i.e., sulfachlorpyridazine, sulfamethazine, sulfadiazine, sulfamethoxazole, oxytetracycline, tetracycline, and chlortetracycline) and associated soil properties was generated. Correlation analysis of these data showed that the affinity coefficients of the SAs were predominantly affected by soil organic matter and cation exchange capacity, while those of the TCs were largely affected by soil organic matter and pH. Pedotransfer functions for estimating K_f and K_d were built by multiple linear regression analysis and were satisfactorily validated. Their performances would be better for soils having higher organic matter content and lower pH. These pedotransfer functions can be used to aid environmental risk assessment, prioritization of antibiotics and identification of vulnerable soils. Full article

Pharmaceuticals are known for their great effects and applications in the treatment and suppression of various diseases in human and veterinary medicine. The development and modernization of science and technologies have led to a constant increase in the production and consumption of various classes of pharmaceuticals, so they pose a threat to the environment, which can be subjected to the sorption process on the solid phase. The efficiency of sorption is determined by various parameters, of which the physicochemical properties of the compound and the sorbent are very important. One of these parameters that determine pharmaceutical mobility in soil or sediment is the soil–water partition coefficient normalized to organic carbon (K_oc), whose determination was the purpose of this study. The influence of organic matter, suspended in an aqueous solution of pharmaceutical (more precisely: cefdinir, memantine, and praziquantel), was studied for five different types of soil and sediment samples from Croatia. The linear, Freundlich, and Dubinin–Raduskevich sorption isotherms were used to determine specific constants such as the partition coefficient K_d, which directly describes the strength of sorbate and sorbent binding. The linear model proved to be the best with the highest correlation coefficients, R² > 0.99. For all three pharmaceuticals, a positive correlation between sorption affinity described by K_d and K_oc and the amount of organic matter was demonstrated. Full article

Increasing prevalence of cyanotoxins in surface water bodies worldwide threatens groundwater quality when contaminated water recharges an aquifer through natural or artificial means. The subsurface fate of anatoxin-a (ATX) is not well studied. Laboratory batch experiments were performed to expand the current knowledge of ATX sorption affinities to geologic media, with a focus on natural soil (Vertisol, Ultisol, Alfisol, and Inceptisol) and physical, chemical, and mineralogical characteristics. For a range of aqueous ATX concentrations (0.3–14 μg/L), linear, Freundlich, and Langmuir isotherms fit observed data well (r² = 0.92–1.00, RMSE = 0.4–6.3 μg/kg). Distribution coefficient (K_d) and retardation factor (R_f) values were computed for the linear isotherm, giving K_d of 22.3–77.1 L/kg and R_f of 62–256. Average percent removals were 85.0–92.2%. The strongest predictors of K_d were kaolinite and smectite group mineral abundances and for R_f were smectite group and silt and clay abundances. Results indicate that loamy, silty, or clayey soils—particularly Vertisols—tend to substantially slow migration of ATX through natural soil systems. Where implemented as a functionalized amendment in an engineered pollution control media, such soils may enhance natural ATX attenuation processes, thereby supporting the protection of in situ and extracted groundwater during irrigation, natural and managed aquifer recharge, or riverbank filtration. Full article

Perfluorinated and polyfluoroalkyl substances (PFASs) are known for their long-distance migration, bioaccumulation, and toxicity. The transport of PFASs in the environment has been a source of increasing concerned. The organic carbon normalized sorption coefficient (K_oc) is an important parameter from which to understand the distribution behavior of organic matter between solid and liquid phases. Currently, the theoretical prediction research on log K_oc of PFASs is extremely limited. The existing models have limitations such as restricted application fields and unsatisfactory prediction results for some substances. In this study, a quantitative structure–property relationship (QSPR) model was established to predict the log K_oc of PFASs, and the potential mechanism affecting the distribution of PFASs between two phases from the perspective of molecular structure was analyzed. The developed model had sufficient goodness of fit and robustness, satisfying the model application requirements. The molecular weight (MW) related to the hydrophobicity of the compound; lowest unoccupied molecular orbital energy (E_LUMO) and maximum average local ionization energy on the molecular surface (ALIE_max), both related to electrostatic properties; and the dipole moment (μ), related to the polarity of the compound; are the key structural variables that affect the distribution behavior of PFASs. This study carried out a standardized modeling process, and the model dataset covered a comprehensive variety of PFASs. The model can be used to predict the log K_oc of conventional and emerging PFASs effectively, filling the data gap of the log K_oc of uncommon PFASs. The explanation of the mechanism of the model has proven to be of great value for understanding the distribution behavior and migration trends of PFASs between sediment/soil and water, and for estimating the potential environmental risks generated by PFASs. Full article

The use of soil conditioners in conjunction with brackish water irrigation is critical for the efficient development and use of brackish water as well as the enhancement of the structure of saline soil and stimulating crop growth. This study investigated the effects of different polyacrylamide (PAM) dosages (0, 0.02%, 0.04%, and 0.06%) on the water flow properties of sandy loam during brackish water infiltration using one-dimensional vertical and horizontal soil column infiltration experiments. The results showed that: (1) PAM could lower the soil infiltration rate and increase soil water retention performance under brackish water infiltration conditions. (2) PAM had a significant effect on the parameters of the Philip and Kostiakov infiltration models. The soil sorption rate S and the empirical coefficient λ were the smallest, and the empirical index β was the largest when the PAM dosage was 0.04%. (3) PAM dosage displayed a quadratic polynomial connection with the soil saturated water content and the saturated hydraulic conductivity. The soil saturated water content was highest when the PAM dosage was 0.04%, the intake suction h_d of the Brooks-Corey model increased by 15.30%, and the soil water holding capacity was greatly improved. (4) Soil treated with PAM could absorb more water under the same soil water suction, whereas the soil unsaturated hydraulic conductivity and its growth rate decreased. The soil saturated diffusion rate D_s, as well as the soil water diffusion threshold, rose. Finally, the 0.04% PAM dosage could improve soil hydrodynamic characteristics under brackish water infiltration, which is beneficial for the efficient utilization of brackish water. Full article