Sulfadimethoxine and sulfaguanidine: their sorption potential on natural soils

Sulfonamides (SAs) are one of the oldest groups of veterinary chemotherapeutic agents. As these compounds are not completely metabolized in animals, a high proportion of the native form is excreted in feces and urine. They are therefore released either directly to the environment in aquacultures and by grazing animals, or indirectly during the application of manure or slurry. Once released into the environment, SAs become distributed among various environmental compartments and may be transported to surface or ground waters. The physicochemical properties of SAs, dosage and nature of the matrix are the factors mainly responsible for their distribution in the natural environment. Although these rather polar compounds have been in use for over half a century, knowledge of their fate and behavior in soil ecosystems is still limited. Therefore, in this work we have determined the sorption potential of sulfadimethoxine and sulfaguanidine on various natural soils. The influence on sorption of external factors, such as ionic strength and pH, were also determined. The sorption coefficients (K_d) obtained for the sulfonamides investigated were quite low (from 0.20 to 381.17 mL g⁻¹ for sulfadimethoxine and from 0.39 to 35.09 mL g⁻¹ for sulfaguanidine), which indicated that these substances are highly mobile and have the potential to run off into surface waters and/or infiltrate ground water. Moreover, the sorption of these pharmaceuticals was found to be influenced by OC, soil solution pH and ionic strength, with higher K_d values for soils of higher OC and lower K_d values with increasing pH and ionic strength.     

Sorption comparison between phenanthrene and its degradation intermediates, 9,10-phenanthrenequinone and 9-phenanthrol in soils/sediments

The degradation intermediates of phenanthrene (PHE) may have increased health risks to organisms than PHE. Therefore, environmental fate and risk assessment studies should take into considerations of PHE degradation products. This study compared the sorption properties of PHE and its degradation intermediates, 9,10-phenanthrenequinone (PQN) and 9-phenanthrol (PTR) in soils, sediments and soil components. A relationship between organic carbon content (f_OC) and single-point sorption coefficient (log K_d) was observed for all three chemicals in 10 soils/sediments. The large intercept in the log f_OC − log K_d regression for PTR indicated that inorganic fractions control PTR sorption in soils/sediments. No relationship between specific surface area and K_d was observed. This result indicated that determination of surface area based on gas sorption could not identify surface properties for PHE, PQN, and PTR sorption and thus provide limit information on sorption mechanisms. The high sorption and strong nonlinearity (low n values) of PTR in comparison to PHE suggested that the mobility of PTR could be lower than PHE. Increased mobility of PQN compared with PHE may be expected in soils/sediments because of PQN lower sorption. The varied sorption properties of the three chemicals suggested that their environmental risks should be assessed differently.     

Sorption of 17α-ethinyl estradiol, bisphenol A and phenanthrene to different size fractions of soil and sediment

The potential for negative effects caused by endocrine disrupting chemicals (EDCs) release into the environment is a prominent concern and numerous research projects have investigated possible environmental fate and toxicity. However, their sorption behavior by size fractions of soil and sediment has not been systematically represented. The sorption of bisphenol A (BPA), 17α-ethinyl estradiol (EE2) and phenanthrene (Phen) by different size fractions of soil and sediment were investigated. Sorption isotherms of EE2, BPA, and Phen by size fractions of soil (SL) and sediment (ST) were well fitted to the Freundlich model. The positive correlation between EE2, BPA and Phen sorption capacity (log K_d) of size fractions and their organic carbon (OC) content suggests that OC of size fractions in SL and ST should regulate sorption, while the surface area (SA) of size fractions may not account for sorption of EE2, BPA and Phen. Each size fraction of ST had higher sorption capacity (K_d or K_OC) of EE2 and BPA than that of SL due to their difference in the polarity of organic matter (OM) between terrestrial and aquatic sources. Sorption capacity logK_d for size fractions of SL and ST did not follow the order: clay > silt > sand due to the difference in OM abundance and composition between the size fractions. Large particle fractions of ST contributed about 80% to the overall sorption for any EE2, BPA, and Phen. This study was significant to evaluate size fractions of soil and sediment as well as their associated OM affecting EE2 and BPA sorption processes.     

Migration and leaching risk of extraneous antimony in three representative soils of China: Lysimeter and batch experiments

Antimony (Sb) distribution, solubility and mobility onto natural soils of China were studied in lysimeter and batch experiments as a function of physicochemical properties of the soil. An outdoor lysimeter experiment investigated the leaching and migration of Sb in the soils with Sb-polluted topsoil and unpolluted subsoil over a 5 month period. Soil solutions were collected by suction cups installed at different depth of lysimeters, and leachates were regularly collected and analyzed for Sb concentrations. The majority of the added Sb was retained in the topsoil layers, but small portions were moved to the sub-layers. Sb concentrations in the soil solutions and leachates ranged from 0–755.5 (6.38 ± 54 on average) μg l⁻¹ and 0–0.45 (smaller than the detection limit) μg l⁻¹ respectively, indicating the low solubility of Sb in the soils. Batch experiments were performed in order to determine the sorption capacity and the partition coefficient (K_d). Freundlich isotherm described properly the equilibrium experimental data and results show that the K_d values for Primosol, Isohumosol, Ferrosol equal to 22.5, 87.8, 704 L kg⁻¹, respectively. These results showed the strong capacity of the soils to retain Sb, and prevent it being leached down the profile. The mobilizable Sb was in the order: Primosol > Isohumosol > Ferrosol. Sb migration in the soils was mainly associated with the exchangeable, carbonate-bound, and metal–organic complex-bound fractions. Health risk assessment indicates that Sb leaching from Ferrosol will not harm to human health through groundwater under the test conditions, while it has certain health risks from the Isohumosol and Primosol.     

Enhancement of chlorophenol sorption on soil by geophagous earthworms (Metaphire guillelmi)

Earthworms are the dominant soil biomass of many terrestrial ecosystems and markedly influence the physico-chemical and biological properties of soil; however, little is known about the effects of earthworm activities on the environmental behavior of micropollutants in soil. We studied the sorption and desorption of 2,4-dichlorophenol, 2,4,6-trichlorophenol, and pentachlorophenol on geophagous earthworm (anecic Metaphire guillelmi) casts of various aging times and on the parent soil. The casts were characteristic of lower pH and higher content of fine particles (silt and clay) than the parent soil. The sorption of the chlorophenols on the soil and casts were well fitted to linear isotherms, with sorption capacity in the order of pentachlorophenol > 2,4-dichlorophenol > 2,4,6-trichlorophenol. The sorption on the cast with different aging time was quite similar and was higher than on the parent soil. The sorption on the soil did not change between pH 7.07 of the soil and pH 6.76 of the casts. The desorption hysteresis of the chlorophenols on the soil and casts was compound specific and 2,4,6-trichlorophenol showed the highest hysteresis. The higher sorption capacity of the casts was not owing to the lowered pH of the casts, but mainly to the higher fine particles in the casts and the possible changes of nature of the soil organic matter through the earthworm gut passage. Our results indicate that geophagous earthworms may change sorption behavior and thus the bioavailability and transport of chlorophenols in soil. Earthworm effects should be considered when evaluating the environmental behavior and risk of organic pollutants in the ecosystems where earthworms are abundant.     

Sorption and transport of trichloroethylene in caliche soil

Sorption of TCE to the caliche soil exhibited linear isotherm at the high TCE concentrations (Co = 122-1300 mg L⁻¹) but Freundlich isotherm at the low concentration range (1-122 mg L⁻¹). Sorption strength of the carbonate fraction of the soil was about 100-fold lower than the sorption strength of soil organic matter (SOM) in the caliche soil, indicating weak affinity of TCE for the carbonate fraction of the soil. Desorption of TCE from the caliche soil was initially rapid (7.6 × 10⁻⁴ s⁻¹), then continued at a 100-fold slower rate (7.7 × 10⁻⁶ s⁻¹). Predominant calcium carbonate fraction of the soil (96%) was responsible for the fast desorption of TCE while the SOM fraction (0.97%) controlled the rate-limited desorption of TCE. Transport of TCE in the caliche soil was moderately retarded with respect to the water (R = 1.75-2.95). Flow interruption tests in the column experiments indicated that the rate-limited desorption of TCE controlled the non-ideal transport of TCE in the soil. Modeling studies showed that both linear and non-linear nonequilibrium transport models provided reasonably good match to the TCE breakthrough curves (r² = 0.95-0.98). Non-linear sorption had a negligible impact on both the breakthrough curve shape and the values of sorption kinetics parameters at the high TCE concentration (Co = 1300 mg L⁻¹). However, rate-limited sorption/desorption processes dominated at this concentration. For the low TCE concentration case (110 mg L⁻¹), in addition to the rate-limited sorption/desorption, contribution of the non-linear sorption to the values of sorption kinetics became fairly noticeable.     

Sorption of 1-hydroxy-2-naphthoic acid to goethite, lepidocrocite and ferrihydrite: batch experiments and infrared study

The adsorption of naphthoic acids to iron oxides and hydroxides influences strongly their mobility in soils and sediments. Sorption of 1-hydroxy-2-naphthoic acid (HNA) to three iron oxides was examined over a wide range of conditions (pH, ionic strength, sorbate and sorbent concentrations). In the examination of HNA sorption, Tempkin model was performed to fit sorption data of HNA onto all iron oxides. The adsorption in the Henry law range increases in the order: goethite相似文献   

Passive dosing: an approach to control mutagen exposure in the Ames fluctuation test

By using dialysis equilibrium experiments, the sorption of a branched nonylphenol isomer [4-(1-ethyl-1,3-dimethylpentyl)-phenol] (NP111) on various humic acids (HAs) isolated from river sediments and two reference HAs was studied. The HAs were characterized by solid-state ¹³C direct polarization/magic angle spinning nuclear magnetic resonance (¹³C DP/MAS NMR) spectroscopy. Sorption isotherms of NP111 on HAs were described by a linear model. The organic carbon-normalized sorption coefficient (K_OC) ranged from 2.3 × 10³ to 1.5 × 10⁴ L kg⁻¹. Interestingly, a clear correlation between K_OC value and alkyl C content was observed, indicating that the aliphaticity of HAs markedly dominates the sorption of NP111. These new mechanistic insights about the NP111 sorption indicate that the fate of nonylphenols in soil or sediment depends not only on the content of HA, but also on its structural composition.     

Sorption of polycyclic aromatic hydrocarbons (PAHs) on glass surfaces

Sorption of polycyclic aromatic hydrocarbons (PAHs) to glass commonly used in laboratories was studied. Sorption coefficients (K_d) of five selected PAHs to borosilicate glass surfaces were measured using column chromatography. A linear relationship between log K_d and the corresponding water solubility of the subcooled liquid (log S_w) of the investigated PAHs was observed. Based on the determined sorption coefficients our data revealed that mass loss caused by sorption on glass walls strongly depends on the ratio of solution volume to contacted surface area (V/S). The influence of solution chemistry such as ionic strength, solution pH, presence of cosolvent, and the influence of temperature on the sorption process were investigated. In the presence of ionic strength, sorption coefficients concurrently increased but less than a factor of 2 up to 0.005 M calcium chloride concentration. However, further increasing ionic strength had no influence on K_d. The cosolvent reduced sorption at a concentration of methanol in water above 0.5% (v/v); however, for benzo[a]pyrene even with 10% (v/v) methanol the mass loss would be still higher than 10% (with a V/S ratio less than 0.25). Significant effects of the solution pH and temperature were not observed. These results suggest that van der Waal’s forces dominate the sorption process. In the analysis of highly hydrophobic PAHs in aqueous samples, mass loss due to sorption on glass walls should be accounted for in the final result if untreated glass is used. The presented relationship between log K_d and log S_w may help to decide if such a correction is necessary. Furthermore, the frequently used silanization of glass surfaces may not be sufficient to suppress sorption for large PAHs.     

Adsorption and breakdown of penicillin antibiotic in the presence of titanium oxide nanoparticles in water

The fate and transport of antibiotics in natural water systems is controlled in part by interactions with nanometer (10⁻⁹ m) metal oxide particles. Experiments were performed by mixing solutions of ampicillin (AMP), a common, penicillin-class human and veterinary antibiotic, with 25 nm-TiO₂ (anatase) nanoparticles at different pH conditions. Both sorption and degradation of AMP were observed in the AMP-nanoparticle solutions. For AMP concentrations from ∼3 μM to 2.9 mM the overall AMP removal from solution can be described by linear isotherms with removal coefficients (K_r) of 3028 (±267) L kg⁻¹ at pH 2, 11,533 (±823) L kg⁻¹ at pH 4, 12,712 (±672) L kg⁻¹ at pH 6, and 1941 (±342) L kg⁻¹ at pH 8. Mass spectral analysis of AMP solutions after removal of the solid nanoparticles yielded ions that indicate the presence of peniclloic acid, penilloic acid and related de-ammoniated by-products as possible compounds resulting from the degradation of AMP at the TiO₂ surface.     

Sorption, desorption, and degradation of (4-chloro-2-methylphenoxy)acetic acid in representative soils of the Danubian Lowland, Slovakia

Herbicide leaching through soil into groundwater greatly depends upon sorption-desorption and degradation phenomena. Batch adsorption, desorption and degradation experiments were performed with acidic herbicide MCPA and three soil types collected from their respective soil horizons. MCPA was found to be weakly sorbed by the soils with Freundlich coefficient values ranging from 0.37 to 1.03 mg^1−1/n kg⁻¹ L^1/n. It was shown that MCPA sorption positively correlated with soil organic carbon content, humic and fulvic acid carbon contents, and negatively with soil pH. The importance of soil organic matter in MCPA sorption by soils was also confirmed by performing sorption experiments after soil organic matter removal. MCPA sorption in these treated soils decreased by 37-100% compared to the original soils. A relatively large part of the sorbed MCPA was released from soils into aqueous solution after four successive desorption steps, although some hysteresis occurred during desorption of MCPA from all soils. Both sorption and desorption were depth-dependent, the A soil horizons exhibited higher retention capacity of the herbicide than B or C soil horizons. Generally, MCPA sorption decreased in the presence of phosphate and low molecular weight organic acids. Degradation of MCPA was faster in the A soil horizons than the corresponding B or C soil horizons with half-life values ranging from 4.9 to 9.6 d in topsoils and from 11.6 to 23.4 d in subsoils.     

Influence of Suwannee River humic acid on particle properties and toxicity of silver nanoparticles

Adsorption of natural organic matter (NOM) on nanoparticles can have dramatic impacts on particle dispersion resulting in altered fate and transport as well as bioavailability and toxicity. In this study, the adsorption of Suwannee River humic acid (SRHA) on silver nanoparticles (nano-Ag) was determined and showed a Langmuir adsorption at pH 7 with an adsorption maximum of 28.6 mg g⁻¹ nano-Ag. It was also revealed that addition of <10 mg L⁻¹ total organic carbon (TOC) increased the total Ag content suspended in the aquatic system, likely due to increased dispersion. Total silver content decreased with concentrations of NOM greater than 10 mg TOC L⁻¹ indicating an increase in nanoparticle agglomeration and settling above this concentration. However, SRHA did not have any significant effect on the equilibrium concentration of ionic Ag dissolved in solution. Exposure of Daphnia to nano-Ag particles (50 μg L⁻¹ and pH 7) produced a linear decrease in toxicity with increasing NOM. These results clearly indicate the importance of water chemistry on the fate and toxicity of nanoparticulates.     

The pH-dependent adsorption of tributyltin to charcoals and soot

Widespread use of tributyltin (TBT) poses a serious environmental problem. Adsorption by black carbon (BC) may strongly affect its behavior. The adsorption of TBT to well characterized soot and two charcoals with specific surface area in the range of 62-111 m² g⁻¹ have been investigated with main focus on pH effects. The charcoals but not soot possess acidic functional groups. TBT adsorption reaches maximum at pH 6-7 for charcoals, and at pH > 6 for soot. Soot has between 1.5 and 15 times higher adsorption density (0.09-1.77 μmol m⁻²) than charcoals, but charcoals show up to 17 times higher sorption affinities than soot. TBT adsorption is successfully described by a new pH-dependent dual Langmuir model considering electrostatic and hydrophobic adsorption, and pH effects on TBT speciation and BC surface charge. It is inferred that strong sorption of the TBTOH species to BC may affect TBT toxicity.     

Sorption of ionic liquids onto soils: experimental and chemometric studies

Chemometric analyses are a great tool to support typical experimental studies of the interactions of xenobiotics with natural environment. Such interpretations are able to determine statistically significant correlations and finally lead to identification of the major sorption factors. However, to effectively use chemometrics a bigger data set is required. Even though the ionic liquids are intensively studied, their complete fate or prediction of their behavior in the natural environment is still unclear. Therefore, to evaluate and distinguish the patterns of interactions of ILs in soil environment by chemometrics, sorption of nine ionic liquids (imidazolium and pyridinium chlorides) on 11 types of various soils was tested. Experimental studies indicated that compounds with longer alkyl side chains were sorbed far more strongly than weakly lipophilic ones. Moreover, salts with short and/or hydroxylated derivatives were more mobile in soils/sediments and thus, might cause a danger of contamination of surface or ground waters. Cluster analysis revealed that ionic liquids form two major clusters according to interaction with soil surface - one grouping compounds with short and hydroxylated alkyl side chains and the second with the rest of compounds. Pairwise scatterplots for correlations between soil variables and sorption coefficients indicated that the main soil parameter responsible for the sorption was cation exchange capacity. Correlation of sorption coefficients, K(d), with pH indicated the existence of lower sorption potency in lower pH values.     

Linear and non-linear relationships between soil sorption and hydrophobicity: model, validation and influencing factors

The hydrophobic parameter represented by the octanol/water partition coefficient (log P) is commonly used to predict the soil sorption coefficient (K_oc). However, a simple non-linear relationship between log K_oc and log P has not been reported in the literature. In the present paper, soil sorption data for 701 compounds was investigated. The results show that log K_oc is linearly related to log P for compounds with log P in the range of 0.5-7.5 and non-linearly related to log P for the compounds in a wide range of log P. A non-linear model has been developed between log K_oc and log P for a wide range of compounds in the training set. This model was validated in terms of average error (AE), average absolute error (AAE) and root-mean squared error (RMSE) by using an external test set with 107 compounds. Nearly the same predictive capacity was observed in comparison with existing models. However, this non-linear model is simple, and uses only one parameter. The best model developed in this paper is a non-linear model with six correction factors for six specific classes of compounds. This model can well predict log K_oc for 701 diverse compounds with AAE = 0.37. The reasons for systemic deviations in these groups may be attributed to the difference of sorption mechanism for hydrophilic/polar compounds, low solubility for highly hydrophobic compounds, hydrolysis of esters in solution, volatilization for volatile compounds and highly experimental errors for compounds with extremely high or low sorption coefficients.     

Dissolution of mimetite Pb5(AsO4)3Cl in low-molecular-weight organic acids and EDTA

Due to its relatively low solubility, mimetite Pb₅(AsO₄)₃Cl may control Pb and As(V) solution levels at a low value in contaminated soils. The time-dependent dissolution of mimetite by low-molecular-weight organic acids (LMWOAs) such as acetic, lactic, citric, and ethylene diamine tetra-acetic acid (EDTA) was determined. At pH 3.5, the presence of citric acid or EDTA significantly increases the solubility of mimetite while acetic or lactic acids show little effect. The effect of all organic anions on the dissolution of mimetite increased with the increase in solution pH. The rate of mimetite dissolution depended on the kind and concentration of organic solvents in the sequence r_EDTA > r_lactate > r_acetate > r_citrate. Soluble Pb and As(V) released in LMWOAs and EDTA were higher than the WHO guideline value for these elements in drinking water (10 μg As(V) L⁻¹, 10 μg Pb L⁻¹). This suggests that soil organic acids in rhizosphere can potentially liberate Pb and As(V) from mimetite in contaminated soils.     

Estimating the spatial scale of herbicide and soil interactions by nested sampling, hierarchical analysis of variance and residual maximum likelihood

An unbalanced nested sampling design was used to investigate the spatial scale of soil and herbicide interactions at the field scale. A hierarchical analysis of variance based on residual maximum likelihood (REML) was used to analyse the data and provide a first estimate of the variogram. Soil samples were taken at 108 locations at a range of separating distances in a 9 ha field to explore small and medium scale spatial variation. Soil organic matter content, pH, particle size distribution, microbial biomass and the degradation and sorption of the herbicide, isoproturon, were determined for each soil sample. A large proportion of the spatial variation in isoproturon degradation and sorption occurred at sampling intervals less than 60 m, however, the sampling design did not resolve the variation present at scales greater than this. A sampling interval of 20-25 m should ensure that the main spatial structures are identified for isoproturon degradation rate and sorption without too great a loss of information in this field.     

Enhanced sorption of perfluorooctane sulfonate (PFOS) on carbon nanotube-filled electrospun nanofibrous membranes

Multi-walled carbon nanotube-filled electrospun nanofibrous membranes (MWCNT-ENFMs) were prepared by electrospinning. The addition of MWCNTs (0.5 wt.% vs. ENFMs) doubled the specific surface area and tensile strength of the ENFMs. The MWCNT-ENFMs were used to adsorb perfluorooctane sulfonate (PFOS) in aqueous solutions. The sorption kinetics results showed that the sorption rate of PFOS onto the MWCNT-ENFMs was much higher than the sorption rate of PFOS onto the pure ENFMs control, and the pseudo-second-order model (PSOM) described the sorption kinetics well. The sorption isotherms indicated that the sorption capacity of the MWCNT-ENFMs for PFOS (16.29 ± 0.26 μmol g⁻¹) increased approximately 18 times, compared with the pure ENFMs (0.92 ± 0.06 μmol g⁻¹). Moreover, the solution pH significantly affected the sorption efficiency and sorption mechanism. The MWCNT-ENFMs were negatively charged from pH 2.0–10.0, but the electrostatic repulsion between the MWCNT-ENFMs and PFOS was overcome by the hydrophobic interactions between PFOS and the MWCNTs or nanofibers. The strong hydrophobic interactions between PFOS and the MWCNTs played a dominant role in the sorption process. For the pure ENFMs, the electrostatic repulsion was conquered by the hydrophobic interactions between PFOS and the nanofibers at pH > 3.1. In addition to the hydrophobic interactions, an electrostatic attraction between PFOS and the pure ENFMs was involved in the sorption process at pH < 3.1.