Pressurized liquid extraction of six tetracyclines from agricultural soils

Veterinary antibiotics used in agriculture can be introduced into the environment through land application of animal manure, accumulating in soils and groundwaters and posing a significant risk to human health and animal well-being. As the analysis of tetracyclines in soil is challenging due to their strong interaction with soil minerals and organic carbon, the objective of this study was to develop a reliable and reproducible method for quantitative analysis of chlortetracycline and oxytetracycline, and their respective metabolites in soils. A method based on pressurized liquid extraction (PLE) with in-cell clean-up was developed for the extraction of chlortetracycline and oxytetracycline and four likely metabolites from a set of four soils. Optimized conditions included a cell size of 22?mL, soil loading of 5?g, pH of 8.0, methanol:water ratio of 3:1, 50?°C, and two cycles. Soil extracts were analysed by high-performance liquid chromatography (HPLC) coupled with ion trap mass spectrometry (MS). Recoveries of seven tetracyclines from soil ranged from 41% to 110%. The limits of detection for tetracyclines were 0.08–0.3 µg g^?1 soil, and intra- and inter-day variation ranged from 0.12–0.34%. The proposed PLE method is suitable for quantification of tetracyclines in agricultural soils at typical concentrations expected in contaminated environments.     

Influence of modified soils on the removal of diesel fuel oil from water and the growth of oil degradation micro-organism

Three soils were modified with two kinds of cationic surfactants in order to increase their sorptive capabilities for organic contaminants. Sorption of diesel fuel oil in water by these modified soils had been investigated. Modified soils can effectively sorb diesel fuel oil from water. The sorption capability of modified soils is: HDTMA-black soil > HDTMA-yellow brown soil > HDTMA-red soil > TMA-black soil > TMA-yellow brown soil > TMA-red soil. Sorption of diesel fuel oil by natural soils and HDTMA modified soils is via partition, the sorption isotherms can be expressed by Henry equation, and logK(SOM) is 2.42-2.80, logK(HDTMA) is 3.37-3.60. Sorption isotherms of TMA modified soils can be expressed by Langmuir equation, the saturation sorption capacities are 1150 (TMA-black soil), 750 (TMA-yellow-brown soil), 171 mg/kg (TMA-red soil), respectively. A diesel fuel oil degradation micro-organism (Pseudomonas sp.) was isolated in the lab. To test the influence of the modified soils on the micro-organism, various growth curves of Pseudomonas in different conditions were drawn. Pseudomonas can grow very well with natural soils and TMA modified soils. The acclimation period of Pseudomonas is reduced. As to HDTMA modified soils, HDTMA loading amount is very important. When HDTMA loading amount is no higher than 0.5 CEC, the micro-organism can grow very well after a long acclimation period.     

Sorption of 3,4-dichloroaniline on four contrasting Greek agricultural soils and the effect of liming

Sorption of 3,4-dichloroaniline (3,4-DCA) on four typical Greek agricultural soils, with distinct texture, organic matter content and cation exchange capacities, was compared by using sorption isotherms and the parameters calculated from the fitted Freundlich equations. The sorption process of 3,4-DCA to the soil was completed within 48-72 h. The 3,4-DCA sorption on all soils was well described by the Freundlich equation and all sorption isotherms were of the L-type. The sandy clay loam soil with the highest organic matter content and a slightly acidic pH was the most sorptive, whereas the two other soil types, a high organic matter and neutral pH clay and a low organic matter and acidic loam, had an intermediate sorption capacity. A typical calcareous soil with low organic matter had the lowest sorption capacity which was only slightly higher than that of river sand. The 3,4-DCA sorption correlated best to soil organic matter content and not to clay content or cation exchange capacity, indicating the primary role of organic matter. The distribution coefficient (K(d)) decreased with increasing initial 3,4-DCA concentration and the reduction was most pronounced with the highly sorptive sandy clay loam soil, suggesting that the available sorption sites of the soils are not unlimited. Liming of the two acidic soils (the sandy clay loam and the loam) raised their pH (from 6.2 and 5.3, respectively) to 7.8 and reduced their sorption capacity by about 50 %, indicating that soil pH may be the second in importance factor (after organic matter) determining 3,4-DCA sorption.     

Dissipation of oxytetracycline, chlortetracycline, tetracycline and doxycycline using HPLC-UV and LC/MS/MS under aquatic semi-field microcosm conditions

A mixture of four tetracyclines; oxytetracycline (OTC), chlortetracycline (CTC), tetracycline (TC), and doxycycline (DC) was applied in fifteen 12000l outdoor microcosms at four treatment levels plus controls each with three replicates (n = 3). The dissipation times of parent compounds were monitored and half-lives (DT50) of 1-4 days, depending on treatment level were recorded. This is in accordance with half-lives from previous findings in bench-top experiments. Parent compound DT50, were determined using HPLC-UV. Furthermore, the samples were analyzed for ten different tetracycline products using LC/MS/MS. Two products were found for chlortetracycline; 4-epi-anh-chlortetracyline and the iso-chlortetracycline. Iso-forms were only found for CTC and only at the highest treatment (300 microg l(-1)). The half-lives, trajectories, and relative amounts of the products were analogous for all four tetracyclines. DT50 for products were less than 1.2 days. Formation of 4-epi-anh-tetracyclines, occurred at neutral to weak alkaline conditions.     

Effects of SOM, surfactant and pH on the sorption-desorption and mobility of prometryne in soils

Sorption and desorption of the herbicide prometryne in two types of soil subjected to the changes of pH and soil organic matter and surfactant were investigated. The sorption and desorption isotherms were expressed by the Freundlich equation. Freundlich K_f and n values indicate that soil organic matter was the major factor affecting prometryne behavior in the test soils. We also quantified the prometryne sorption and desorption behavior in soils, which arose from the application of Triton X-100 (TX100), a nonionic surfactant and change in pH. Application of TX100 led to a general decrease in prometryne sorption to the soils and an increase in desorption from the soils when applied in dosages of the critical micella concentration (CMC) 0.5, 1 and 2. At the concentration below the CMC, the non-ionic surfactant showed a tendency to decrease prometryne sorption and desorption. It appeared that TX100 dosages above CMC were required to effectively mobilize prometryne. Results indicate that the maximum prometryne sorption and minimum prometryne desorption in soils were achieved when the solution pH was near its pK_a. Finally, the influence of TX100 on the mobility of prometryne in soils using soil thin-layer chromatography was examined.     

Sorption of lead in soil as a function of pH: a study case in México

Reactions of lead sorption onto soil are largely affected by properties and composition of soil and its solution. In this study, the lead sorption onto regosol eutric soil from Francisco I. Madero, Zacatecas, Mexico is evaluated at different pH values. Soil samples were suspended in lead solutions of 10, 25, 50, 100, 150, 200, 300, and 400 mg/l (as Pb(NO3)2). The pH was adjusted at 2, 3, 4, and 5.5 with nitric acid for each of the lead solution concentrations. In all the cases the ionic strength was I=0.09 M with calcium nitrate. The solid-liquid-ratios were fixed in 1:100 and 1:200 g/ml. The results show that lead sorption increases when pH increases. Experimental isotherms were adjusted by both Langmuir and Freundlich models. The Langmuir affinity parameter, K, indicates that the lead sorption capacity of Francisco I. Madero soils is largely perceptible to pH changes.     

Sorption of 3,4-dichloroaniline on four contrasting Greek agricultural soils and the effect of liming

Sorption of 3,4-dichloroaniline (3,4-DCA) on four typical Greek agricultural soils, with distinct texture, organic matter content and cation exchange capacities, was compared by using sorption isotherms and the parameters calculated from the fitted Freundlich equations. The sorption process of 3,4-DCA to the soil was completed within 48–72 h. The 3,4-DCA sorption on all soils was well described by the Freundlich equation and all sorption isotherms were of the L-type. The sandy clay loam soil with the highest organic matter content and a slightly acidic pH was the most sorptive, whereas the two other soil types, a high organic matter and neutral pH clay and a low organic matter and acidic loam, had an intermediate sorption capacity. A typical calcareous soil with low organic matter had the lowest sorption capacity which was only slightly higher than that of river sand. The 3,4-DCA sorption correlated best to soil organic matter content and not to clay content or cation exchange capacity, indicating the primary role of organic matter. The distribution coefficient (K _d) decreased with increasing initial 3,4-DCA concentration and the reduction was most pronounced with the highly sorptive sandy clay loam soil, suggesting that the available sorption sites of the soils are not unlimited. Liming of the two acidic soils (the sandy clay loam and the loam) raised their pH (from 6.2 and 5.3, respectively) to 7.8 and reduced their sorption capacity by about 50 %, indicating that soil pH may be the second in importance factor (after organic matter) determining 3,4-DCA sorption.     

水中四环素类化合物在不同光源下的光降解

研究了模拟太阳光和实际室外太阳光下四环素类化合物在水溶液中的光降解。结果表明,四环素类化合物(TCs)在模拟太阳光照射下均能发生直接光降解,且其降解速率随pH不同变化很大。四环素(TC)、土霉素(OTC)、金霉素(CTC)和多西环素(DTC)的光降解速率随溶液pH升高明显加快,而米诺环素(MTC)在水中的光降解速率随溶液pH升高略有下降。天然水体pH范围内,模拟太阳光照下四环素类化合物表观光降解速率常数在0.004～0.026 min-1范围内,降解半衰期在26～136 min范围内。在室外实际太阳光照下,四环素类化合物光降解反应速率与太阳光强成正比例关系。晴朗无云天气下,四环素类化合物降解半衰期在春冬季节较长、夏季节较短;四环素在东江实际水体中表观光降解速率很快,在冬季晴天天气下,其平均半衰期仅为8.2 min。     

Production of monoclonal antibody against doxycycline for immunoassay of seven tetracyclines in bovine muscle and milk

The objective of this study was to produce a generic monoclonal antibody for multi-determination of the residues of tetracycline drugs in bovine muscle and milk. Two new immunogens of doxycycline were prepared that were used to produce the monoclonal antibodies. Results showed the obtained antibodies simultaneously recognized seven tetracycline drugs (doxycycline, tetracycline, chlortetracycline, oxytetracycline, minocycline, methacycline, demeclocycline). The obtained antibodies and three coating antigens were arranged into six combinations to optimize the reagents combination. After comparison of the performances of these combinations, a heterologous indirect competitive ELISA was then used to determine the seven tetracyclines in bovine muscle and milk. The crossreactivities to the seven analytes were in the range of 47%–102% and the limits of detection were in the range of 1.5–6.9 ng/mL depending on the compound. The recoveries of the seven drugs from fortified blank samples were in the range of 75.3%–106.8% with coefficients of variation lower than 10.9%. Therefore, this method could be used as a multi-analytes screen tool for routine monitoring of the residues of these tetracycline drugs in bovine muscle and milk.     

Tetracycline resistance in semi-arid agricultural soils under long-term swine effluent application

Annually, millions pounds of antibiotics are released unmetabolized into environment along with animal wastes. Accumulation of antibiotics in soils could potentially induce the persistence of antibiotic resistant bacteria. Antibiotics such as tetracyclines and tetracycline-resistant bacteria have been previously detected in fields fertilized with animal manure. However, little is known about the accumulation of tetracyclines and the development of tetracycline resistance in semi-arid soils. Here we demonstrate that continuous land application with swine effluent, containing trace amounts of chlortetracycline, does not necessarily induce tetracycline resistance in soil bacteria. Based on the testing of more than 3,000 bacteria isolated from the amended soils, we found no significant increase in the occurrence and level of chlortetracycline resistant bacteria in soils after 15 years of continuous swine effluent fertilization. To account for a possible transfer of tetracycline-resistant bacteria originated from the swine effluent to soils, we analyzed two commonly found tetracycline resistant genes, tet(O) and tet(M), in the swine effluent and fertilized soils. Both genes were present in the swine effluent, however, they were not detectable in soils applied with swine effluent. Our data demonstrate that agronomic application of manure from antibiotic treated swine effluent does not necessarily result in the development of antibiotic bacterial resistance in soils. Apparently, concentrations of chlortetracycline present in manure are not significant enough to induce the development of antibiotic bacterial resistance.     

Hydrolysis and soil sorption of insecticide pyraclofos

The hydrolysis of the insecticide pyraclofos in buffered solutions at pH 5.0, 7.0 and 9.0, and its sorption on four soils of different physicochemical properties were investigated. The results showed that the degradation of pyraclofos in buffered solutions followed pseudo-first-order kinetics. At 40 degrees C, the rate constants for the hydrolysis of pyraclofos at pH 5.0, 7.0 and 9.0 were 0.0214, 0.1293, and 2.1656 d(-1), respectively. Pyraclofos was relatively stable under both acidic and neutral conditions, while it was readily hydrolyzed under basic conditions. The sorption of pyraclofos on four soils was well described by the Freundlich equation. The sorption constant, K(f), increased with an increase in soil organic carbon content, suggesting that organic carbon content was an important factor affecting sorption. The K(oc) values for Xiaoshan clay loam soil, Hangzhou I clay loam soil, Hangzhou II soil, and Fuyang silt loam soil were 30.4, 6.7, 5.3, and 7.1, respectively. These results suggest that the sorption of pyraclofos on the tested soils was relatively weak.     

Complexation of the antibiotic tetracycline with humic acid

The effect of solution chemistry and sorbate-to-sorbent ratio on the interaction of the antibiotic tetracycline with Elliott soil humic acid (ESHA) was investigated using equilibrium dialysis and FITEQL modeling. Tetracycline speciation strongly influenced its sorption to ESHA. Sorption was strongly pH-dependent with a maximum around pH 4.3, and competition with H+ and electrolyte cation (Na+) was evident. The pH-dependent trend was consistent with complexation between the cationic/zwitterionic tetracycline species and deprotonated sites in ESHA (mainly carboxylic functional groups). Modification of ESHA by Ca2+ addition increased tetracycline sorption suggesting that ternary complex formation (ESHA-metal-tetracycline) may be important at higher concentrations of multivalent metal cations. The macroscopic data (pH-envelope and sorption isotherms) were successfully modeled using a discrete logK function with the FITEQL 4.0 chemical equilibrium program indicating that ESHA-tetracycline interaction could be reasonably represented as complex formation of a monoacid with discrete sites in humic acid. Sorption-desorption hysteresis was observed; both sorption and desorption isotherms were well described by the Freundlich equation.     

Sorption of imidacloprid and its metabolites on tropical soils

The sorption of imidacloprid (1-[(6-chloro-3-pyridinyl)-methyl]-N-nitro-2-imidazolid-inimine ) (IMI) and its metabolites imidacloprid-urea (1-[(6-chloro-3-pyridinyl)-methyl]-2-imidazol-idinone) (IU), imidacloprid-guanidine (1-[(6-chloro-3-pyridinyl)-methyl]-4,5-dihydro-1H-imidazol-2-amine) (IG), and imidacloprid-guanidine-olefin (1-[(6-chloro-3-pyridinyl)methyl]-1H-imidazol-2-amine) (IGO) was determined on six typical Brazilian soils. Sorption of the chemicals on the soil was characterized using the batch equilibration method. The range and order of sorption (Kd) on the six soils was IG (4.75-134) > or = IGO (2.87-72.3) > IMI (0.55-16.9) > IU (0.31-9.50). For IMI and IU, Kd was correlated with soil organic carbon (OC) content and CEC, the latter due to the high correlation between OC and cation exchange capacity (CEC) (R2 = 0.98). For IG and IGO, there was no correlation of sorption to clay, pH, OC or CEC due to the high sorption on all soils. Average Koc values were IU = 170, IMI = 362, IGO = 2433, and IG = 3500. Although Kd and Koc values found were consistently lower than those found in soils developed in non-tropical climates, imidacloprid and its metabolites were still considered to be slightly mobile to immobile in Brazilian soils.     

Sorption characteristics of cyromazine and its metabolite melamine in typical agricultural soils of China

A myriad of physical, chemical, and biological processes controls the fate of organic contaminants in soils. The knowledge of bioavailability of a contaminant in soil can be useful to conduct environmental risk assessment. We conducted batch equilibrium experiments to investigate the sorption of cyromazine (CA) and its metabolite melamine (MA) onto five typical soils of China belonging to suborders Ali-Perudic Ferrosols, Udic Argosols, Gleyic-Stagnic Anthrosols, Ustic Cambosols, and Udic Isohumosols. Results showed that sorption of CA and MA onto soils was linear, as indicated by the Freundlich and Langmuir models. Different sorption behaviors of CA and MA were observed on the five agricultural soils, with lgK _f values (Freundlich model) of 1.6505–2.6557 and 1.632–2.549, respectively. Moreover, the K _f values for CA and MA were positively correlated with soil organic matter (r?=?0.989, r?=?0.976) and significantly negatively correlated with pH (r?=??0.938, r?=??0.964). The free energy of sorption of CA and MA ranged from ?20.8 to ?23.0 kJ mol^?1 and ?20.8 to ?22.8 kJ mol^?1, respectively, suggesting that the sorption of CA and MA onto the soils is primarily a physical process.     

Long-term tillage effects on soil metolachlor sorption and desorption behavior

Sorption and desorption are two important processes that influence the amount of pesticides retained by soils. However, the detailed sorption mechanisms as influenced by soil tillage management are unclear. This study examined the sorption and desorption characteristics of metolachlor [2-chloro-N-(2-ethyl-6-methyphenyl)-N-(2-methoxy-1-methylethyl)-acetamide] using the soil samples collected from the long-term conservation tillage (CnT) and conventional tillage (CT) research plots established in 1979 in Darlinton, SC. Humic acid (HA) and humin were extracted from the soils and used in the sorption experiments along with the whole soil samples. The sorption experiments were conducted using a batch-equilibration method. Three sequential desorption rinses were carried out following the sorption experiments. By comparing metolachlor sorption and desorption results we observed hysteresis for all soil samples and their organic matter fractions. Sorption nonlinearity (N) and hysteresis were dependent on the structure and composition of soil organic matter (SOM), e.g., Freundlich isotherm exponents (N) of HA and humin from CnT were higher than those of CT treatment, which may be related to high aromaticity of SOM fractions in CT treatment. Sorption capacity (K'f) was positively correlated with soil organic carbon (SOC) content. These results show that long-term tillage management can greatly affect metolachlor sorption and desorption behavior probably by qualitative differences in the structural characteristics of the humic substances.     

Lead sorption in calcareous soils

The sorption of lead by three soils that differed in texture and calcium carbonate content was studied at three different temperatures. Lead sorption was found to conform to both Freundlich and Langmuir isotherms. Soil adsorption maxima were derived from the reciprocal of the slope obtained by a least-squares fit of Langmuir plots for each soil. The highest adsorption capacity was exhibited by CaCO(3)-rich soil (773.55 mmol Pb kg(-1)). Raising the temperature from 298 K to 308 and 318 K increased the sorption capacity of all of the soils.     

Sorption-desorption behavior of metsulfuron-methyl and sulfosulfuron in soils

Sorption of metsulfuron-methyl and sulfosulfuron were studied in five Indian soils using batch sorption method. Freundlich adsorption equation described the sorption of herbicides with K(f) (adsorption coefficient) values ranging between 0.21 and 1.88 (metsulfuron-methyl) and 0.37 and 1.17 (sulfosulfuron). Adsorption isotherms were L-type suggesting that the herbicides sorption decreased with increase in the initial concentration of the herbicide in the solution. The K(f) for metsulfuron-methyl showed good positive correlation with silt content (significant at p = 0.01) and strong negative correlation with the soil pH (significant at p = 0.05) while sorption of sulfosulfuron did not correlate with any of the soil parameter. Desorption of herbicides was concentration dependent and, in general, sulfosulfuron showed higher desorption than the metsulfuron-methyl. The study indicates that these herbicides are poorly sorbed in the Indian soil types and there may be a possibility of their leaching to lower soil profiles.     

Sorption and degradation of imidacloprid in soil and water

Imidacloprid, the major component of many widely used insecticide formulations, is highly persistent in soils. In this study, the sorption of imidacloprid by six soils as well as its photodegradation and hydrolysis in water were studied. The soils differed significantly in organic matter content and other physical and chemical properties. Sorption increased with increasing soil organic matter content but was not significantly correlated with other soil properties. Removal of organic matter via H2O2 oxidation decreased the sorption. By normalizing the Freundlich coefficients (Kf) to organic matter contents, the variability in obtained sorption coefficient (Kom) was substantially reduced. These results indicate that soil organic matter was the primary sorptive medium for imidacloprid. The low heat of sorption calculated from Kom suggests that partition into soil organic matter was most likely the mechanism. The photodegradation and hydrolysis of imidacloprid in water followed pseudo-first-order kinetics; however, the latter process needed a six-time-higher activation energy. While both processes produced the same main intermediate, they occurred via different pathways. The hydrolysis of imidacloprid was not catalyzed by the high interlayer pH in the presence of metal-saturated clays, which appeared to result from the lack of the pesticide adsorption in the interlayers of clays.     

Sorption of imazaquin in soils with positive balance of charges

The herbicide imazaquin has both an acid and a basic ionizable groups, and its sorption depends upon the pH, the electric potential (psi0), and the oxide and the organic carbon (OC) contents of the soil. Sorption and extraction experiments using 14C-imazaquin were performed in surface and subsurface samples of two acric oxisols (an anionic "rhodic" acrudox and an anionic "xanthic" acrudox) and one non-acric alfisol (a rhodic kandiudalf), treated at four different pH values. Imazaquin showed low to moderate sorption to the soils. Sorption decreased and aqueous extraction increased as pH increased. Up to pH 5.8, sorption was higher in subsurface than in surface layers of the acric soils, due to the positive balance of charges resulted from the high Fe and Al oxide and the low OC contents. It favored electrostatic interactions with anionic molecules of imazaquin. For the subsurface samples of these highly weathered soils, where psi0 was positive and OC was low, it was not possible to predict sorption just by considering imazaquin speciation and its hydrophobic partition to the organic domains of the soil. Moreover, if Koc measured for thesurface samples were assumed to represent the whole profile in predictive models for leaching potential, then it would result in underestimation of sorption potential in subsurface, and consequently result in overestimation of the leaching potential.