Soil-water Partition Coefficient Research Articles

Fluoranthene slow down sulfamethazine migration in soil via π-π interaction to increase the abundance of antibiotic resistance genes

Sulfonamide antibiotics and polycyclic aromatic hydrocarbons (PAHs) often coexist in soil, leading to compound pollution through various pathways. This study focuses on sulfamethazine (SMZ) and PAHs (fluoranthene) as the subject for compound pollution research. Using a soil-groundwater simulation system, we investigated the migration characteristics of SMZ under coexistence with fluoranthene (Fla) and observed variations in the abundance of antibiotic resistance genes (ARGs). Through molecular docking simulations and isothermal adsorption experiments, we discovered that Fla bound with SMZ via π−π interactions, resulting in a 20.9% increase in the SMZ soil-water partition coefficient. Under compound conditions, the concentration of SMZ in surface soil could reach 1.4 times that of SMZ added alone, with an 13.4% extension in SMZ half-life. The deceleration of SMZ's vertical migration rate placed additional stress on surface soil microbiota, leading to a proliferation of ARGs by 66.3%–125.8%. Moreover, under compound pollution, certain potential hosts like Comamonadaceae and Gemmatimonas exhibited a significant positive correlation with resistance genes such as sul 1 and sul 2. These findings shed light on the impact of PAHs on sulfonamide antibiotic migration and the abundance of ARGs. They also provide theoretical insights for the development of technologies aimed at mitigating compound pollution in soil.

Bioremediation experiments and dynamic model of petroleum hydrocarbon contaminated soil

Clarifying the occurrence and morphological characteristics of petroleum hydrocarbons (PHs) in soil can facilitate a comprehensive understanding of their migration and transformation patterns in soil/sediment. Additionally, by establishing the dynamic transformation process of each occurrence state, the ecological impact and environmental risk associated with PHs in soil/sediment can be assessed more precisely. The adsorption experiments and closed static incubation experiments was carried out to explore the PHs degradation and fraction distribution in aged contaminated soil under two remediation scenarios of natural attenuation (NA) and bioaugmentation (BA) by exogenous bacteria through a new sequential extraction method based on Tenax-TA, Hydroxypropyl-β-cyclodextrin and Rhamnolipid (HPCD/RL), accelerated solvent extractor (ASE) unit and alkaline hydrolysis extraction. The adsorption experiment results illustrated that bioaugmentation could promote the desorption of PHs in the adsorption phase, and the soil-water partition coefficient Kd decreased from 0.153 L/g to 0.092 L/g. The incubation experiment results showed that compared with natural attenuation, bioaugmentation could improve the utilization of PHs in aged soil and promote the generation of non-extractable hydrocarbons. On the 90th day of the experiment, the concentrations of weakly adsorbed hydrocarbons in the natural attenuation and bioaugmentation experimental groups decreased by 46.44% and 87.07%, respectively, while the concentrations of strongly adsorbed hydrocarbons and non-extractable hydrocarbons increased by 77.93%, 182.14%, and 80.91%, and 501.19%, respectively, compared their initial values. We developed a novel dynamic model and inverted the kinetic parameters of the model by the parameter scanning function and the Markov Chain Monte Carlo (MCMC) method based on the Bayesian approach in COMSOL Multiphysics® finite element software combined with experimental data. There was a good linear relationship between experimental interpolation data and model prediction data. The R2 for the concentrations of weakly adsorbed hydrocarbons ranged from 0.9953 to 0.9974, for strongly adsorbed hydrocarbons from 0.9063 to 0.9756, and for non-extractable hydrocarbons from 0.9931 to 0.9982. These extremely high correlation coefficients demonstrate the high accuracy of the parameters calculated using the Bayesian inversion method.

Insights into the pH-dependent interactions of sulfadiazine antibiotic with soil particle models

Sulfonamide antibiotics (SAs) are widely used as a broad-spectrum antibiotic, leading to global concerns due to their potential soil accumulation and subsequent effects on ecosystems. SAs often exhibit remarkable environmental persistence, necessitating further investigation to uncover the ultimate destiny of these molecules. In this work, molecular dynamics simulations combined with complementary quantum chemistry calculations were employed to investigate the influence of pH on the behavior of sulfadiazine (SDZ, a typical SAs) in soil particle models (silica, one of the main components of soil). Meanwhile, the quantification of SDZ molecules aggregation potential onto silica was further extended. SDZ molecules tend to form a monolayer on the soil surface under acidic conditions while forming aggregated adsorption on the surface under neutral conditions. Due to the hydrophilicity of the silica, multiple hydration layers would form on its surface, hindering the further adsorption of SDZ molecules on its surface. The calculated soil-water partition coefficient (Psoil/water) of SDZ+ and SDZ were 9.01 and 7.02, respectively. The adsorption evaluation and mechanisms are useful in controlling the migration and transformation of SAs in the soil environment. These findings provide valuable insights into the interactions between SDZ and soil components, shedding light on its fate and transport in the environment.

Uptake, accumulation, and translocation of organophosphate esters by watermifoil (Myriophyllum aquaticum) in an aquatic ecosystem: effects of chemical structure and concentrations

In order to explore the environmental behavior of organophosphate esters (OPEs) in aquatic environment, the accumulation and distribution of OPEs in water, sediment, and plant were investigated. In this study, watermifoil (Myriophyllum aquaticum) were exposed with ten OPEs for concentrations of 200ng/g, 500ng/g, 1000ng/g, and 2000ng/g, respectively. The concentrations of Σ10OPEs in rhizosphere sediment were higher than those in non-rhizosphere sediment, demonstrating that rhizosphere processes tend to transport OPEs into the rhizosphere sediment. Most of the selected OPEs were not in equilibrium between water and sediment, and trend to retain in sediment. In addition, OPEs with relatively higher hydrophobicity had trend to retained in Myriophyllum aquaticum roots, whereas OPEs with lower hydrophobicity were more likely transported to shoots. In this study, octanol-water partition coefficient (KOW) had significantly positive correlations with organic carbon-normalized soil-water partition coefficients (KOC) and root-water concentration factors (RWCFs), but KOW was negatively correlated with translocation factors (TFs). Moreover, the substituent types and initial levels of OPEs also have impacts on the plant uptake and accumulation. These observations will improve our understanding of the distribution and translocation of OPEs in aquatic environment.

Influence of Organic Matter on the Sorption of Cefdinir, Memantine and Praziquantel on Different Soil and Sediment Samples.

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 (Koc), 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 Kd, 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 Kd and Koc and the amount of organic matter was demonstrated.

Modeling pesticide residue uptake by leguminous plants: a geocarpic fruit model for peanuts.

Pesticide residues are frequently found in leguminous plants; however, no modeling approaches predict residue concentrations in edible legume seeds. In this study, a geocarpic fruit model, simplified for neutral organic compounds, was proposed for high-throughput simulations (over 700 pesticides) of the residue uptake by peanut plants, which characterized three scenarios, namely (i) pesticide foliar application during the pre-seed development stage, (ii) foliar application during the seed development stage, and (iii) soil contamination before plant germination. In the foliar application scenario, in general, lipophilic pesticides have high simulated residue unit doses (RUDs, residue concentrations in plants per 1.0kg ha-1 of pesticide application) in peanut leaves owing to intensified uptake via surface deposition, whereas hydrophilic pesticides have high simulated RUDs in peanuts because the uptake of residues via diffusion is enhanced. For the soil-contamination scenario, organic compounds with moderate lipophilicity have a high bioconcentration potential (i.e. the soil-plant system) in leaves and peanuts, due to large transpiration stream concentration factors (TSCFs) that boost the uptake via transpiration. The simulation results have some degrees of agreement with field measurements, indicating that the proposed model can be used as a screening tool for dietary risk assessment of pesticides in peanuts. In future research, pH-dependent physicochemical properties (e.g. soil-water partition coefficient and TSCF) and degradation rate constants of chemicals need to be refined to improve the simulation analysis. © 2022 Society of Chemical Industry.

Immobilized artificial membrane-chromatographic and computational descriptors in studies of soil-water partition of environmentally relevant compounds

Chromatographic retention factor log kIAM obtained from immobilized artificial membrane (IAM) HPLC with buffered, aqueous mobile phases and calculated molecular descriptors (molecular weight — log MW; molar volume — VM; polar surface area — PSA; total count of nitrogen and oxygen atoms -(N + O); count of freely rotable bonds — FRB; H-bond donor count — HD; H-bond acceptor count — HA; energy of the highest occupied molecular orbital — EHOMO; energy of the lowest unoccupied orbital — ELUMO; dipole moment — DM; polarizability — α) obtained for a group of 175 structurally unrelated compounds were tested in order to generate useful models of solutes’ soil-water partition coefficient normalized to organic carbon log Koc. It was established that log kIAM obtained in the conditions described in this study is not sufficient as a sole predictor of the soil-water partition coefficient. Simple, potentially useful models based on log kIAM and a selection of readily available, calculated descriptors and accounting for over 88% of total variability were generated using multiple linear regression (MLR) and artificial neural networks (ANN). The models proposed in the study were tested on a group of 50 compounds with known experimental log Koc values by plotting the calculated vs. experimental values. There is a good close similarity between the calculated and experimental data for both MLR and ANN models for compounds from different chemical families (R2 ≥ 0.80, n = 50) which proves the models’ reliability.

Soil properties affect vapor-phase adsorption to regulate dimethyl disulfide diffusion in soil

Dimethyl disulfide (DMDS) is efficacious against nematodes and other soil-borne pathogens known to reduce crop quality and yield. Previous studies reported inconsistent efficacy and suggested that the diffusion of DMDS varied with different soil types. The effect of soil adsorption on gaseous DMDS diffusion through different soil types is poorly understood. To clarify the role and mechanism of soil adsorption in the diffusion of gaseous DMDS in soil, we have studied the diffusion rate constant (Rt) of gaseous DMDS in soils using a soil column experiment. The adsorption of DMDS at each gas-soil, soil-water and gas-water partition was measured by a batch-equilibrium headspace method. The results showed the DMDS adsorption equilibrium was well-described by the nonlinear Freundlich isotherm and the linear Henry isotherm. Rt values were strongly negatively correlated with the Henry coefficient (Kd) values. The Kd values of dry soil were several orders of magnitude higher than those observed in moist soil within each moisture content range. The Kd values in dry soil were strongly positively correlated with soil pore size (<2 nm). However, when the soil moisture content ranged from 3 to 12% (w/w), the Kd values were strongly correlated with specific surface area (SSA). Elevated temperatures promoted the gaseous phase of DMDS (consistent with Henry's Law) and its diffusion through soil. The soil-water partition coefficient (K'f) ranged from 1.83 to 2.20 μg11/n mL1/n g−1 in tested soils. Our results suggest that the DMDS vapor-phase diffusion in soil was significantly affected by soil adsorption, which in turn depended on the soil's properties especially the SSA and soil moisture content. These findings suggest applicators can reduce the risk of unsatisfactory and inconsistent efficacy results against soil-borne pests by adjusting the DMDS dose and fumigation period according to soil type, moisture conditions, and other environmental factors.

Agricultural application of digestates derived from agricultural and municipal organic wastes: a health risk-assessment for heavy metals

A Human-health Risk Assessment was performed for an agricultural site in North-East Italy undergone digestate application to (i) check the compliance of digestate land spreading with the Italian and European regulations on contaminated agricultural soils and (ii) evaluate how resulting risk estimations can be influenced by the applied modeling assumptions. The assessment estimated the risk related to adults and children intake of Heavy Metals (HM) contained in crops at concentrations estimated by a soil-plant transfer model based on the substance-specific soil-water partition coefficients. Eight different scenarios were investigated, according to different digestate type (from biowaste and agro-industrial byproducts), digestate application techniques and soil background concentrations. Non-risky situations resulted in all scenarios involving digestate application. The totality of calculated non-carcinogenic Hazard Indexes () and carcinogenic total risk () resulted below 0.02 and 3E10−9, respectively. In contrast with the definition, non-carcinogenic risks were associated with the considered soil background concentrations, with s up to 1.7 for child receptors, while carcinogenic risk was calculated below the concern threshold (i.e., < 10−5). Accordingly, this study highlighted (i) non-concerning situations related with lawful application of digestates and (ii) the need to improve the modeling of bioavailability to plant of HMs background content of soil.

Comparative study of Cadmium adsorption on three contrasting soils from a highly industrialized region

Evaluation of natural soils potentiality to effectively immobilize heavy metals is a fundamental tool for a sustainable management of an industrialized region. Three soil textures from Bahía Blanca Citýs industrial zone (Argentina) were analyzed to quantify Cd adsorption and assess its applicability for industrial land use. Soils textural classes corresponded to sandy loam (M1), sand (M2) and silt loam (M3). Batch adsorption kinetics and isotherms were carried out with a 1:10 soil:solution ratio. Adsorption kinetics was conducted for 240 min at constant initial Cd concentration (250 mg l−1) and varying pH (4–8 range). Adsorption isotherm was done for twenty Cd concentrations (range 0.5 mg l−1 to 460 mg l−1) and contact time of 24 h. Kinetics showed a fast instantaneous initially adsorption. Soil-water partitioning coefficient (Kd) was calculated for each concentration supplied to soils, showing a direct relationship between pH and Kd. Adsorption isotherms plots showed a nonlinear shape for M1 and M2 and a linear shape for M3. The affinity of Cd for soils is in the order: M3 > M1 > M2. Metal retention in M3 was upper than 97.8%. Langmuir, Freundlich and Dubinin-Radushkevich (DRK) adsorption models correctly reproduced experimental data. However, M1 (R2 = 0.992) and M3 (R2 = 0.985) fitted better to Freundlich model. Otherwise, M2 (R2 = 0.981) fitted better to Langmuir adsorption model. M3 presented the highest buffer and Cd retention capacity, possibly related to its clay content. Based on desorption studies, M3 presented the strongest binding site as 95% of metal removal was attributed to specific sorption. Silt loam is the most suitable soil coverage for industrial land of all analyzed soils.

RP-18 TLC retention data and calculated physico-chemical parameters as predictors of soil-water partition and bioconcentration of organic sunscreens

RP-18 TLC chromatography was used to evaluate the impact on the environment (mobility in soil expressed as soil-water partition coefficient, log Koc; bioconcentration factor in aquatic organisms, log BCF) of several cosmetic raw materials - sunscreens, preservatives and vitamins. The retention parameters RM0 (RM extrapolated to zero concentration of an organic modifier in a mobile phase), S (slope), PC1 (1st principal component) and RM75% (single TLC run parameter for mobile phases containing 75% (v/v) of an organic modifier) obtained for six organic modifiers (methanol, acetonitrile, THF, acetone, dioxane, DMF) were used as the sole descriptors or combined with calculated physico-chemical properties (PSA – polar surface area; MW – molecular weight; VM – molar volume) of studied compounds.The chromatographic parameters considered in this study are, generally speaking, good predictors of the compounds’ mobility in soil or the affinity for aquatic organisms. The parameters RM0, S and RM75% obtained for THF, dioxane and acetone may be used to investigate even very lipophilic compounds. RM75% is of a little bit limited use but it should be considered a time- and cost-effective alternative to the chromatographic parameters obtained by extrapolation or interpolation methods. In the case of some environmental parameters investigated in this study additional descriptors (PSA) have a significant influence on the quality of correlations.

Laboratory-scale and pilot-scale stabilization and solidification (S/S) remediation of soil contaminated with per- and polyfluoroalkyl substances (PFASs)

Remediation of soil contaminated with per- and polyfluoroalkyl substances (PFAS) is critical due to the high persistence and mobility of these compounds. In this study, stabilization and solidification (S/S) treatment was evaluated at pilot-scale using 6 tons of soil contaminated with PFAS-containing aqueous film-forming foam. At pilot-scale, long-term PFAS removal over 6 years of precipitation (simulated using irrigation) in leachate from non-treated contaminated reference soil and S/S-treated soil with 15 % binder and 0.2 % GAC was compared. PFAS removal rate from leachate, corresponding to reduction in leaching potential after 6 years, was >97 % for four dominant PFASs (perfluorohexanoic acid (PFHxA), perfluorooctanoic acid (PFOA), perfluorohexanesulfonic acid (PFHxS) and perfluorooctanesulfonic acid (PFOS)), but low (3%) for short-chain perfluoropentanoic acid (PFPeA). During the pilot-scale experiment, PFAS sorption strength (i.e., soil-water partitioning coefficient (Kd)) increased 2- to 40-fold for both reference and S/S-treated soil, to much higher levels than in laboratory-scale tests. However, PFAS behavior in pilot-scale and laboratory-scale tests was generally well-correlated (p < 0.001), which will help in future S/S recipe optimization. In addition, seven PFASs were tentatively identified using an automated suspect screening approach. Among these, perfluorohexanesulfonamide and 3:2 fluorotelomer alcohol were tentatively identified and the latter had low removal rates from leachate (<12 %) in S/S treatment.

Per- and polyfluoroalkyl substances in water and soil in wastewater-irrigated farmland in Jordan.

The Zarqa river (ZR) in Jordan receives >300,000m3day -1 of wastewater effluent from Assamra wastewater treatment plant (WWTP) and is a major source of irrigation water for vegetable crops and fodder downstream. ZR water quality is therefore highly important and directly influences crop and soil quality in irrigated fields. This study investigated the occurrence and concentration of 20 per- and polyfluoroalkyl substances (PFASs) in Assamra wastewater, ZR water, soils and crop plants (alfalfa (Medicago sativa), mint (Mentha spicata) and lettuce (Lactuca sativa)) along the ZR flow path between Assamra WWTP and Jerash spring. The combined PFAS concentration (∑PFASs) in Assamra WWTP effluent (14-24ngL-1) was comparable to that in influent (10-15ngL-1), indicating poor removal of PFASs. The dominant PFAS in influent was perfluorodecanoate (PFDA), while perfluorooctanoate (PFOA) and perfluoropentanoate (PFPeA) dominated in effluent. ∑PFASs in an unaffected upstream tributary (Sukhna station) was 4.7-5.4ngL-1. Farther downstream, ZR water contained 16-27ngL-1, with PFPeA, PFOA and PFDA dominating, and these levels did not change along the flow path to Jerash spring. ∑PFASs in soil was generally low, 340±150pgg-1 dry weight (dw) in alfalfa soil (mainly PFOA and PFDA) and 710±420pgg-1 dw in mint soil and 970±800pgg-1 dw in lettuce soil (mainly linear perfluorooctane sulfonate (L-PFOS) in both cases). Soil-water partitioning coefficient (Kd) was generally low in all soils (range 24-62Lkg-1, 20-46Lkg-1 and 28Lkg-1 for PFOA, PFDA and L-PFHxS, respectively). No PFASs were detected in alfalfa and mint plants. Overall, this investigation demonstrated that PFAS contamination in wastewater, surface water and soil in the ZR basin is very low in a global comparison, and that there is no accumulation of PFASs in the food and feed crops studied.

Sorption behaviors of antimicrobial and antiparasitic veterinary drugs on subtropical soils

Brazil is one of the world's largest producers of animal protein, requiring the large-scale use of veterinary drugs. The administration of antimicrobials and antiparasitics is a common practice. However, there is a lack of information on how these drugs impact the environment. Antimicrobials are capable of altering the soil microbial population and are responsible for the development of multidrug-resistant microbial strains. Therefore, it is important to evaluate the fate and transport of these compounds in the environment, and one parameter used for this purpose is the soil-water partition coefficient. In this work, an assessment was made of the soil sorption behaviors of 18 drugs from seven different families, including antimicrobials (sulfonamides, fluoroquinolones, amphenicols, and macrolides) and antiparasitic drugs (milbemycin, avermectins, and benzimidazoles). Seven subtropical soils of different textural classes were tested. The Freundlich sorption coefficients, expressed as μg1−1/n (cm3)1/n g−1, were in the following ranges: 0.45 to 19 (sulfonamides), 72 to 2410 (fluoroquinolones), 9 to 58 (thiabendazole), 0.03 to 0.48 (florfenicol), 105 to 424 (moxidectin), 14 to 184 (avermectins), and 1.5 to 74 (macrolides). The results showed that the drugs belonging to the same family, with chemical structures in common, presented similar behaviors regarding sorption and desorption, for the different soils tested and are generally in agreement with soils from temperate regions. The data set obtained in this work give an overview of the fate of the veterinary drugs in Brazilian subtropical soils with different textures and composition and can be very helpful for exposure risk assessments.

Per- and polyfluoroalkyl substances (PFASs) in water, soil and plants in wetlands and agricultural areas in Kampala, Uganda

Occurrence and concentrations of 26 per- and polyfluoroalkyl substances (PFASs) were evaluated in wastewater, surface water, soil and crop plants (yam (Dioscorea spp.), maize (Zea mays) and sugarcane (Saccharum officinarum)) in Nakivubo wetland and Lake Victoria at Kampala, Uganda. ∑PFAS concentrations in effluent from Bugolobi wastewater treatment plant (WWTP) were higher (5.6–9.1ngL−1) than in the corresponding influent (3.4–5.1ngL−1), indicating poor removal of PFASs within the WWTP. ∑PFAS concentrations decreased by a factor of approximately five between Nakivubo channel (8.5–12ngL−1) and Lake Victoria (1.0–2.5ngL−1), due to dilution, sorption to sediment and uptake by plants in the wetland. ∑PFAS concentrations were within the range 1700–7900pgg−1 dry weight (dw) in soil and 160pgg−1 dw (maize cobs) to 380pgg−1 dw (sugarcane stems) in plants. The dominant PFASs were perfluorohexanesulfonate (PFHxS) in wastewater, perfluorooctanoate (PFOA) in surface water, perfluorooctanesulfonate (PFOS) in soil and perfluoroheptanoate (PFHpA) and PFOA in different plant tissues, reflecting PFAS-specific partitioning behaviour in different matrices. Soil-water partitioning coefficient (log Kd) in wetland soil under yam was lowest for short-chain PFHxA (1.9–2.3Lkg−1) and increased with increasing chain length to 2.8–3.1Lkg−1 for perfluoroundecanoate (PFUnDA) and 2.8–3.1Lkg−1 for perfluoroctanesulfonate (PFOS). The log Koc values ranged between 2.2 and 3.6Lkg−1, with the highest log Koc estimated for long-chain perfluorocarbon PFASs (i.e. PFUnDA 3.2–3.5Lkg−1 and PFOS 3.2–3.6Lkg−1). The concentration ratio (CR) between plants and soil was <1 for all PFASs and plant species, with the highest CR estimated for PFHpA (0.65–0.67) in sugarcane stem and PFBS (0.53–0.59) in yam root. Overall, this investigation demonstrated PFASs entry into the terrestrial food chain and drinking water resources in Kampala, Uganda. Source identification, assessment of impacts on human health and the environment, and better wastewater treatment technologies are needed.

Azithromycin sorption and biodegradation in a simulated California river system

Azithromycin (AZ) is a widely-used macrolide antibiotic that is continually deposited into natural waterways by sewage effluent. Though recognized as an emerging contaminant of concern, little is known about its fate and transport in aquatic systems. American River soils and water were used to determine degradation of AZ in microcosms simulating flooded (anaerobic) and non-flooded (aerobic) California watershed conditions. Under aerobic conditions the degradation rate constant (k=0.0084 ± 0.0039 day−1) and DT50 (82.52 ± 56.54 days) were calculated, as AZ disappearance indicated potential degradation. However, based on concurrent product appearance, less than one percent of the parent degraded over 150 days. Throughout the experiment microbial growth was observed by culturing in tryptic soy broth despite antibiotic addition and soil being autoclaved. Sorption likely contributes to AZ recalcitrance, thus the soil-water partition coefficient (log Kd = 2.18 Lkg−1), Freundlich sorption and desorption coefficients (log Kf = 1.90 ± 0.14 and log Kfd = 2.51 ± 0.30, respectively), and organic-carbon-normalized distribution coefficient (log Koc = 4.25 Lkg−1) were also calculated. Based on these results, AZ degradation in aquatic systems will likely be very limited and transport will fluctuate based on the extent of soil-water saturation or bulk movement of sediment.

Development of a predictive model for lead, cadmium and fluorine soil–water partition coefficients using sparse multiple linear regression analysis

In this study, we applied sparse multiple linear regression (SMLR) analysis to clarify the relationships between soil properties and adsorption characteristics for a range of soils across Japan and identify easily-obtained physical and chemical soil properties that could be used to predict K and n values of cadmium, lead and fluorine. A model was first constructed that can easily predict the K and n values from nine soil parameters (pH, cation exchange capacity, specific surface area, total carbon, soil organic matter from loss on ignition and water holding capacity, the ratio of sand, silt and clay). The K and n values of cadmium, lead and fluorine of 17 soil samples were used to verify the SMLR models by the root mean square error values obtained from 512 combinations of soil parameters. The SMLR analysis indicated that fluorine adsorption to soil may be associated with organic matter, whereas cadmium or lead adsorption to soil is more likely to be influenced by soil pH, IL. We found that an accurate K value can be predicted from more than three soil parameters for most soils. Approximately 65% of the predicted values were between 33 and 300% of their measured values for the K value; 76% of the predicted values were within ±30% of their measured values for the n value. Our findings suggest that adsorption properties of lead, cadmium and fluorine to soil can be predicted from the soil physical and chemical properties using the presented models.

Sorption and Leaching Potential of Isoproturon and Atrazine in Low Organic Carbon Soil of Pakistan Under a Wheat-Maize Rotation

Pesticide leaching is a great threat in low organic carbon soils when subjected to improper irrigation scheduling. Limited data are available on the sorption and leaching potential of pesticides in agricultural soils of Pakistan with low soil organic carbon (SOC). Lysimeter and field studies were conducted with and without manure application at two irrigation levels in a wheat-fallow-maize rotation in Faisalabad, Punjab, Pakistan. Isoproturon was applied to wheat 55 d after sowing at 1 kg active ingredient (a.i.) ha−1, while atrazine was sprayed on maize 30 d after sowing at 0.774 kg a.i. ha−1. Soil was sampled from three depths (0–35, 35–70, and 70–110 cm) for the field study and four depths (0–35, 35–70, 70–115, and 115–160 cm) for the lysimeter study, 280 and 65 d after application of isoproturon and atrazine, respectively. The soil-water partition coefficients (Kd) of isoproturon and atrazine ranged from 0.3 to 1.2 and 0.4 to 1.5 L kg−1, respectively, and increased linearly with increase in SOC contents. The organic carbon-normalized soil-water partition coefficient (Koc) of isoproturon and atrazine averaged 246.1 and 184.9 L kg−1, respectively, being higher with low spiking concentration. Isoproturon residues measured 280 d after application ranged from 2.1% to 3.6% of the applied mass in the lysimeter study and from 1.5% to 3.1% under field conditions. Atrazine residues 65 d after application ranged from only 0.62% to 0.78% and from 0.88% to 0.82% in the lysimeter and field studies, respectively. The lowest levels of residues for both pesticides were observed with frequent irrigation applied to manure-amended soil. A pesticide leaching risk screening tool, the ground water ubiquity score (GUS), indicated that in the absence of manure under both irrigation levels, isoproturon has a leaching potential (GUS = 2.8), while with the application of manure it has a very low leaching risk. Atrazine GUS ranged from 1.7 to 1.9, indicating a very low risk of leaching.

New insight into advection of organic contaminate plume at drain outlet areas

To provide insight to optimize organic contaminants treatment at the drain outlet areas due to the discharge from the industrial plants, the fate and transport of variety kinds of organic contaminants were investigated. By taking the chemical properties (molecular weight (MW), Henry’s law constant (H), vapor pressure (Pv), organic carbon normalized soil-water partition coefficient for organic compounds (Koc), water solubility (S), air diffusivity (Da), and water diffusivity (Dw)) of 56 kinds of organic chemical into account, we studied the general transport equation (GTE) regarding the mass balance for the steady-state analysis of the accumulation of a chemical over time by the plume advection. We found that Koc has significant relationship with S and MW of the chemicals. Furthermore, higher organic carbon-water partitioning coefficient of the chemical will make it easier to stay at the drain outlet area, which gives us hints for next research of nanoscale particles for in situ remediation.

Geochemical characteristics of heavy metal contamination induced by a sudden wastewater discharge from a smelter

Metal contaminations from smelting have been widely reported, however, the study on metal mobility or transfer characteristics in soil profiles after a sudden wastewater overflow is far limited. This study was undertaken to investigate distribution and potential mobility of heavy metals in soils flooded by smelting wastewater in Hechi, China. Total heavy metal/metalloid levels were measured in topsoil, profile and profile pore-water taken in-situ. Enrichment factor (EF) and nemero synthesis index (PN) were used to detect the contribution of anthropogenic emissions to trace element fluxes and pollution levels, respectively. Soil-water partition coefficient (Kd) was used to reflect the fate and the mobility of elements. Results showed topsoil were seriously contaminated with Sb (289–3100mgkg−1), Pb (444–6388mgkg−1), Zn (294–923mgkg−1), Cu (59–192mgkg−1), Cd (12–34mgkg−1), and As (32–405kg−1), and PN values indicated this area was in severe or strongly pollution level. Higher EF values of Sb, Zn, Cd and As were found in the flooded soils, and PN in flooded area was 5 times of that in the unflooded sites, indicating wastewater flooding aggregated pollution in the low-lying area. The Sb, Pb, and Cd concentrations declined drastically with profile but dropped to constant levels below a depth of about 20cm. In contrast, Zn and Cu in flooding soils declined first and then increased to another extreme value even at depth of 50cm. Pore-water profiles exhibited the similar declining trends of vertical metal/metalloid distribution pattern. The Kd values ranged from 102–106Lkg−1, and the mobility and bioavailability of the six elements in the profiles declined in the following order: Sb>Zn>Cu>Cd>As>Pb. The relatively low Kd values for some depth intervals may reflect adsorption decrease or migration increase of metal/metalloid. However, it is worth to further study and assess their potential risk to environment in longer period.