Extraction of Residues of Dyfonate-ring-14C from Soil

Abstract

Residues of Dyfonate-ring-¹⁴C were extracted from a clay loam soil with various solvents under a variety of conditions. Recovery of radioactivity from the soil was not related to the polarity (dipole moment) or the dielectric constant of the solvents. Commonly used solvents such as acetone, methanol, ethanol, and hexane/acetone (1:1) extracted only 28, 44, 27, and 25%, respectively, of the residues from the air-dried soil. The extraction efficiencies were increased to 46, 60, 54, and 49%, respectively, when 20% water was added to the soil prior to extraction with these solvents. The amount of water added to the soil and time of contact with water also affected the recovery of radioactivity from the soil. Any of the solvents or methods investigated failed to recover more than 60% of the radioactivity in the soil, indicating that residues of Dyfonate were strongly bound to the soil and were difficult to recover.     

Determination of fatty acids in soil samples by gas chromatography with mass spectrometry coupled with headspace solid‐phase microextraction using a homemade sol–gel fiber†

Through the use of a homemade sol–gel‐derived fiber, a headspace solid‐phase microextraction technique coupled to gas chromatography with mass spectrometry was developed for the determination of fatty acids with long, even‐numbered carbon chains (C₁₂–C₂₄) in soil samples. The experimental parameters such as reaction time, temperature, and ionic strength that might affect derivatization, extraction, and desorption were investigated. Under the optimized conditions, the linearity of the method ranged from 0.1 to 100 mg/L with a correlation coefficient >0.997. The limit of detection values based on a signal‐to‐noise ratio of 3:1 were determined with the concentration from 0.39 to 39.4 μg/L. The recoveries of the method for the soil samples were from 91.15 to 108.1%. This developed method using a homemade fiber showed a higher sensitivity than that using a commercial polydimethylsiloxane fiber and was also for the analysis of real soil samples from the Paomaling geological park of China.     

Ionic liquids as stationary phases in gas chromatography: Determination of chlorobenzenes in soils

The present research focuses on the evaluation of different ionic liquid (IL) stationary phases in gas chromatography. The different IL columns were evaluated in terms of peak resolution (R_s) and peak symmetry for the separation of the chlorobenzenes. The determination of chlorobenzenes in soil samples by means of the optimal IL stationary phase (SLB‐IL82) is proposed as an application. Soil pretreatment was based on a simplified quick, easy, cheap, effective, rugged, and safe extraction procedure and a large injection volume via a programed temperature vaporizer working in solvent vent mode. The retention time of the chlorobenzenes increased as the polarity of the IL column decreased. SLB‐IL82 is the stationary phase that provides the best values as regards R_s and asymmetry factor. Soil sample blanks were spiked with the analytes before subjecting the sample to the extraction process. The existence of a matrix effect was checked and the analytical characteristics of the method were determined in a fortified garden soil sample. The method provided good linearity, good repeatability and reproducibility values, and the LODs were in the 0.1–4.7 μg/kg range. Two fortified soil samples were applied to validate the proposed methodology.     

The fate and behavior of glufosinate-enantiomers and their metabolites in open-field soil and weeds

In this study, a chiral method based on high performance liquid chromatography–Q-Exactive Orbitrap Mass Spectrometry was developed to determine glufosinate stereoisomers and three metabolites in weed. Fortified recoveries in weed and soil samples were from 78.6 to 94.3 %, with relative standard deviations of less than 9.8 % and fortified values ranging from 0.04 to 40 mg/kg for the glufosinate enantiomers and 0.08–8 mg/kg for three metabolites. When glufosinate was given at the peak of weed growth in three orchards, it was mostly distributed and degraded in the weeds, with little remaining in the soil. The two glufosinate enantiomers degraded rapidly in the weeds and soils, with half-lives ranging from 0.7 to 3.1 days. The degradation of glufosinate enantiomers in Guizhou and Hunan weeds was enantioselective, with l-glufosinate being preferentially degraded. In Hainan weed, the degradation rate of the two enantiomers was nearly the same. In open field soils, glufosinate enantiomers were almost non-enantioselective. 3-methylphosphinico-propionic acid (MPP) was the primary glufosinate metabolite in weeds and soils, accounting for up to 14 % of the parent. N-acetyl-glufosinate (NAG) was relatively low, with less than 1 % of the parent glufosinate metabolized into 2-methylphosphinico-acetic acid (MPA).     

Relevance of gaseous flows in electrochemically assisted soil thermal remediation

Treatment of polluted soil is one of the priorities in the search of a more sustainable planet. Electrochemically assisted soil remediation has been considered a good option for removing organic contaminants contained in soil, including the removal of volatile organic compounds, associated with gaseous streams produced during the treatment. Also, recently, electrochemical gas treatment technologies have been appointed as promising for the treatment of volatile organic compounds. In this work, we review the current opinion about the most recent studies in both areas. The first section focuses on the production of gaseous compounds during soil remediation by conventional and electrochemical systems. The second section describes the recent progress in the integration of adsorption and absorption with electrochemical processes. Finally, we discuss the holistic application of assisted electrochemical technologies in soil remediation, considering also emerging processes recently published in the literature.     

New green process to increase the solubility of soil fertilizer based on Potassium Nitrate (KNO3)

Fertilization is the set of operations that consists of fertilizing the soil so that the plant finds all these mineral nutrition needs, among these nutrients is found potassium nitrate (KNO₃), as an important source of two elements which are nitrogen (N) and potassium (K). The need for potassium nitrate for plants will increase dramatically as its demand for nutrition growing up. However, the application of this potassium in fertilization is limited by a physicochemical parameter which is solubility. The availability of potassium and nitrogen in ionic form, which can be assimilated by the plant, is closely related to its solubility in irrigation water. Herein, we have chosen three experimental parameters such as the KNO₃ content, the magnetization time, and the type of water, to optimize the factors which have the maximum effect on KNO₃ solubility.We adopted a model from nine experiments performed with Minitab software, which informed us that the solubility of KNO₃ in irrigation water is strongly influenced by water type, magnetization time and KNO₃ content. The best conditions which allow the best solubility of potassium nitrate are 24% KNO₃, 30 ​min of water magnetization, and salt water (SW).     

[Hmim]PF6 enhanced the extraction of polycyclic aromatic hydrocarbons from soil with the QuEChERS method

To detect, identify, and quantify the polycyclic aromatic hydrocarbons (PAHs) released into the environment, the PAHs need to be isolated from the soil matrix. In this work, a modified quick, easy, cheap, efficient, rugged and safe (QuEChERS) method with ionic liquid was combined with liquid chromatography to identify 16 selected PAHs in soil. Ionic liquid 1-hexyl-3-methylimidazolium hexafluorophosphate ([Hmim]PF₆) was applied as an extractant component to enhance the process. The [Hmim]PF₆ content in acetonitrile (ACN) was optimized. The [Hmim]PF₆ modified QuEChERS method has the advantages defined by its name and a similar recovery to other extraction methods reported in the literature. Adding [Hmim]PF₆ may eliminate the co-extract proportion and achieve a more effective extraction. Compared with ACN alone, the matrix effect (ME) of ACN containing 5% [Hmim]PF₆ was reduced by approximately 35%. Additionally, the ME of using ACN containing [Hmim]PF₆ without a clean-up procedure was similar to that of using ACN followed by a clean-up procedure. The recoveries of the QuEChERS method implemented with [Hmim]PF₆ ranged from 75.19% to 100.98%. The limits of detection (LOD) and limits of quantification (LOQ) ranged from 0.86 to 4.51 µg/kg and from 2.87 to 15.13 µg/kg, respectively.     

The removal of Cu,Ni, and Zn in industrial soil by washing with EDTA-organic acids

In order to improve the heavy metal removal ability of traditional single washing agents and explore the removal mechanism of heavy metals. Then, the washing reagents that mixed by low-molecular weight organic acids (citric acid, oxalic acid, and tartaric acid) and artificial chelating compound ethylenediaminetetraacetic acid disodium (EDTA) were selected. Furthermore, the effect of soil washing parameters, the variation of leaching toxicity, mobility, stability and speciation of heavy metals were also considered. The results of soil washing experiments showed that mixing an equal volume of 0.05 M EDTA and 0.2 M organic acids (citric acid, oxalic acid, and tartaric acid) could remove more than about 80% heavy metals from soil under the optimal conditions. In addition, the soil leaching toxicity was decreased and the stability of remaining heavy metals was increased, indicating that EDTA-organic acid washing reagents could effectively reduce the ecological risk of contaminated soil. EDTA had a stronger chelating ability with heavy metals than the organic acids, and the organic acids could not only chelate heavy metals but also decrease the pH of the mixture for promoting the desorption of heavy metals. Thus, mixing EDTA and organic acids was advisable method to improve soil washing technology.     

Rapid assessment of the impact of microwave heating coupled with UV-C radiation on the degradation of PAHs from contaminated soil using FTIR and multivariate analysis

The presence and fate of polyaromatic hydrocarbons (PAHs) in the environment are receiving a great concern. In this study, three oil-contaminated soils (industrial area, Dukhan city, and artificial soils) were utilized to examine the effect of microwave (MW) heating and UV-C irradiation on the PAHs degradation. A rapid assessment of the impact was evaluated using Fourier transform infrared (FTIR) and multivariate analysis. The total organic matter values for the maximum PAHs reduction were evaluated based on the FTIR spectra of the contaminated soils followed with the principal component analysis (PCA). The results showed that the highest total organic carbon reduction was achieved for the industrial soil sample that required a high MW power and long MW exposure time. On the other hand, the Dukhan city soil sample, which has the lowest total organic carbon, required a high MW power and short MW exposure time followed by UV-C treatment for 20 min to reach the maximal FTIR transmittance reduction. The cluster analysis was also used to evaluate the impact of MW heating, and MW heating followed by UV-C irradiation on the degradation of PAHs. The PCA results of the industrial city sample showed that neither MW treatment (100% MW, 15 min exposure time) followed by UV-C treatment for 20 min nor 10 min is significantly different from the MW treatment (100% MW, 15 min exposure time). However, for the Dukhan sample, the UV-C treatment at 10 min after high MW power and long exposure time (100% MW, 15 min exposure time) was the most efficient treatment.     

The Space of Inextensional Displacements for a Partially Clamped Linearly Elastic Shell with an Elliptic Middle Surface

We consider a linearly elastic shell with an “elliptic” middle surface, clamped along a portion of its lateral face and subjected to body forces. Under weak regularity assumptions on the middle surface, we prove that the space of linearized inextensional displacements is reduced to zero, by using unique continuation results. Consequently, when the thickness of the shell goes to zero, the limit of the average with respect to the thickness of the three-dimensional displacement vector solves the “generalized membrane” shell model, according to the terminology introduced by P.G. Ciarlet and the first author. This revised version was published online in August 2006 with corrections to the Cover Date.