Fluoroquinolones in soil—risks and challenges

Fluoroquinolones (FQs) are among the most important antibacterial agents used in human and veterinary medicine. Because of the growing practice of adding manure and sewage sludge to agricultural fields these drugs end up in soils, where they can accumulate and have adverse effects on organisms. This paper presents an overview of recent developments in the determination of FQs in solid environmental matrices and describes the risks and challenges (persistence, fate, effects, and remediation) which result from their presence in soil. Figure Pathways into the environment for FQs     

A fast method for monitoring of organic explosives in soil: a gas temperature gradient approach in LC–APCI/MS/MS

A novel, fast liquid chromatography atmospheric pressure chemical ionization mass spectrometry (LC–APCI–MS/MS) screening method was developed to determine the trace amounts of TNT (trinitrotoluene), RDX (1,3,5-trinitroperhydro-1,3,5-triazine), HMX (cyclotetramethylene-tetranitramine), PETN (pentaerythritoltetranitrate), TETRYL (2,4,6-trinitrophenyl-N-methylnitramine), picric acid (2,4,6 trinitrophenol), 2,6-DNT (2,6-dinitrotoluene), and TMETN (trimethylolethane-trinitrate) which contaminate the soil after explosion. A gradient of 2.00 mM ammonium nitrate aqueous solution-methanol mobile system, C18 column, and atmospheric pressure chemical ionization (APCI) (?) ionization mode was used after a single-step solid–liquid extraction procedure from soil matrix. Phenytoin was used as the internal standard. As an extraordinary application, gas temperature gradient in an APCI ionization was used. Analytes were selectively eluted from the system within 10 min. Average recovery obtained from the soil was between 93.01 and 104.20% at 250.0, 500.0, and 1000.0 ngg^?1 concentration levels. Limit of detection (LOD) and limit of quantification (LOQ) values obtained from the analysis of the soil samples including explosive mix were between 8.9–161.2 and 13.2–241.5 ngg^?1, respectively.     

Surveying selenium speciation from soil to cell—forms and transformations

The aim of this review is to present and evaluate the present knowledge of which selenium species are available to the general population in the form of food and common supplements and how these species are metabolized in mammals. The overview of the selenium sources takes a horizontal approach, which encompasses identification of new metabolites in yeast and food of plant and animal origin, whereas the survey of the mammalian metabolism takes a horizontal as well as a vertical approach. The vertical approach encompasses studies on dynamic conversions of selenium compounds within cells, tissues or whole organisms. New and improved sample preparation, separation and detection methods are evaluated from an analytical chemical perspective to cover the progress in horizontal speciation, whereas the analytical methods for the vertical speciation and the interpretations of the results are evaluated from a biological angle as well.     

Extraction and determination of the potato glycoalkaloid α -solanine in soil

The toxic glycoalkaloids α-solanine and α-chaconine are produced in all parts of the potato plant, and post-harvest potato tubers may represent a source of soil and water contamination. A new method was developed for extraction and purification of α-solanine in soil samples. Soil samples were extracted with THF?:?H₂O?:?ACN?:?CH₃COOH (50?:?30?:?20?:?1) and the extract purified by SPE before HPLC determination of α-solanine. The limit of detection was 2.4?mg of α-solanine?kg^?1 soil. The new procedure was used for determination of α-solanine in spiked soils with varying content of organic matter and texture. Recovery for soil samples spiked with α-solanine 1?h before extraction was 61–68% for soils low in organic carbon (<2.2% C), and to 47% for soil high in organic carbon. Similar recoveries were obtained for α-chaconine. The reproducibility of the method shown by the relative standard deviation varied from 1.7 to 10.1%, depending on the soil type. No decrease in extractable α-solanine was observed until day 17 for soil samples spiked with pure α-solanine kept at 5°C, while the content in samples spiked with potato materials showed a faster decline. This indicates that the degradation and/or ageing processes proceed relatively slowly for glycoalkaloids in soil matrices. This is the first method reported for determination of potato glycoalkaloids in soil.     

Solid-phase microextraction–gas chromatographic determination of volatile monoaromatic hydrocarbons in soil

Benzene, toluene, ethylbenzene, three isomers of xylene, and cumene have been isolated and enriched from soil samples by a combination of water extraction at room and elevated temperature and headspace–solid-phase microextraction before their gas chromatographic–mass spectrometric (GC–MS) determination. The conditions used for all stages of sample preparation and chromatographic analysis were optimized. Analytes sampled on a polydimethylsiloxane-coated solid-phase microextraction fiber were thermally desorbed in the split/splitless injector of a gas chromatograph (GC) coupled with a mass spectrometer (MS). The desorption temperature was optimized. The GC separation was performed in a capillary column. Detection limits were found to be of the order of ca. 1 ng g^–1. Relative recoveries of the analytes from soils were found to be highly dependent on soil organic-matter content and on compound identity; they ranged from ca 92 to 96% for sandy soil (extraction at room temperature) and from ca 27 to 55% for peaty soil (extraction at elevated temperature). A few real-world soil samples were analyzed; the individual monoaromatic hydrocarbon content ranged from below detection limits to 6.4 ng g^–1 for benzene and 8.1 for the total of p- + m-xylene.     

Ammonoxidised lignins as slow nitrogen-releasing soil amendments and CO₂-binding matrix

Nitrogen (N) is a major nutrient element controlling the cycling of organic matter in the biosphere. Its availability in soils is closely related to biological productivity. In order to reduce the negative environmental impact, associated with the application of mineral N-fertilizers, the use of ammonoxidised technical lignins is suggested. They can act as potential slow N-release fertilisers which concomitantly may increase C sequestration of soils by its potential to bind CO?. The idea of our study was to combine an improved chemical characterisation of ammonoxidised ligneous matter as well as their CO?-binding potential, with laboratory pot experiments, performed to enable an evaluation of their behaviour and stability during the biochemical reworking occurring in active soils.     

Exchange of carbonyl sulfide (COS) between wheat soil and atmosphere

The exchange of COS between wheat soil and atmosphere was investigated by using a dynamic enclosure. The investigated soil type acted as a significant sink for the trace gas COS. Atmospheric COS mixing ratios and temperature were found to be the physicochemical parameters controlling the uptake. The uptake reached maximum about 0.6×10~(-12) mol ?g~(-1) ?h~(-1) at 15-20℃ under natural ambient atmospheric conditions. The measured uptake values agree well with that calculated by Guenther algorithm.     

Hydroxypropyl-β-cyclodextrin-based extraction for diuron bioaccessibility in an artificially contaminated soil

Different extraction techniques are presented here to determine whether their extraction abilities correlate with the bioaccessible diuron fraction in an aged contaminated soil. Diuron bioaccessibility was tested establishing correlations between the amount of diuron biodegraded after different aging periods, using a specific diuron biodegrader microorganism consortium, and the amount of diuron extracted by 50 mM hydroxypropyl-β-cyclodextrin (HPBCD), 10 mM CaCl₂, hexane, or butanol. HPBCD extraction procedure correlated better than the other extraction techniques tested with diuron measured microbial biodegradation for all aging times (1, 30, 60, 90, and 120 days). The results obtained with this soil indicate that the aqueous HPBCD extraction technique has potential to become a valuable tool for estimating the bioaccessible fraction of soil-associated diuron at different aging times, and it could be applicable in the assessment of risk and contaminated land bioremediation potential.     

Fruit Tree model for uptake of organic compounds from soil and air†

The current European risk assessment for chemicals considers only tap water, while in reality other beverages play an important role. A good part of beverages are made from fruits, for example apple juice and vine. A mathematical model was developed to predict uptake of neutral organic chemicals from soil and air into fruits. The new fruit tree model considers eight compartments, i.e. two soil compartments, fine roots, thick roots, stem, leaves, fruits, and air. Chemical equilibrium, advective transport in xylem and phloem, diffusive exchange to soil and air and growth dilution are the main processes. The parameterization is for a square-meter of an apple orchard. The model predicts that polar, non-volatile compounds will effectively be transported from soil to fruits, while lipophilic compounds will preferably accumulate from air into fruits. Results from various experiments show no disagreement with the model predictions.     

A method for analyzing the δ18O of resin-extractable soil inorganic phosphate

Improved tools for tracing phosphate transformations in soils are much needed, and can lead to a better understanding of the terrestrial phosphorus cycle. The oxygen stable isotopes in soil phosphate are still not exploited in this regard. Here we present a method for measuring the oxygen stable isotopes in a fraction of the soil phosphate which is rapidly available to plants, the resin-extractable P. This method is based on extracting available phosphate from the soil with anion-exchange membranes, soil organic matter removal by a resin, purification by precipitation as cerium phosphate, and finally precipitation as silver phosphate. The purified silver phosphate samples are then measured by a high-temperature elemental analyzer (HT-EA) coupled in continuous flow mode to an isotope ratio mass spectrometer. Testing the method with Mediterranean and semi-arid soils showed no artifacts, as well as good reproducibility in the same order as that of the HT-EA analytical uncertainty (0.3‰).     

Occurrence of neonicotinoids in guttation liquid of maize – soil mobility and cross-contamination

Movement of clothianidin (CLO) and thiamethoxam (TMX) applied as maize seed dressing or pre-emergence spray application was determined in different soil types. Uptake of these neonicotinoids in plants emerging from coated or non-coated seeds was characterised via guttation liquid measurements. Applied in spray at a recommended dosage of 16.5 µmol/L, TMX and CLO occurred in the guttation liquid at peak concentrations of 1.82 and 1.63 mg/L, respectively, in plants in sandy soil and at 20–40% lower levels in plants in clay or loam soils. Peak emergence was substantially higher (above 100 mg/L) in the guttation liquid of plants emerging from neonicotinoid-coated seeds at dosages of 4.87 and 2.07 µmol per seed for CLO and TMX, respectively, strongly influenced by soil type. CLO and TMX levels in plants emerging from non-coated seeds in the proximity of neonicotinoid-coated seeds were demonstrated: cross-contamination may occur by uptake through soil from neighbouring plants. CLO appeared in the guttation liquid of plants emerging from non-coated seeds in proximity to coated ones at a peak concentration (approximately 53 mg/L) in 15 days corresponding to one-fifth of the levels in plants emerging from CLO-coated seeds; CLO concentrations gradually decreased to the same levels (6.6 ± 0.3 mg/L) after 24 days. A similar trend was observed for non-coated seeds near TMX-coated ones, with a gradual increase of TMX in 17–18 days, the levels in the guttation liquid of plants emerged from non-coated seeds (approximately 123 mg/L) corresponding to two-thirds of the levels in plants emerging from TMX-coated seeds. TMX concentrations dropped to the same levels in plants emerging from non-coated and coated seeds by day 20, and CLO occurred as a metabolite. To our knowledge, this is the first scientific record of neonicotinoid levels in guttation liquid of plants emerged from non-coated maize seeds.     

Application of DSC–TG and NMR to study the soil organic matter

The environmental concern on soil exploitation, linked to global warming by the Kyoto protocol, is responsible for increasing interest in the understanding of the role of the composition and structure of the soil organic matter (SOM) on soil carbon, C, dynamics. Thermal analysis and nuclear magnetic resonance (NMR) are applied to study the thermal properties, the structure and composition of the SOM of six samples with different C contents in order to improve the interpretation of results given by thermal analysis. Results showed that the direct integral of the combustion peaks obtained by DSC and the percentage of SOM given by TG were both directly related to the quantity of total soil C. Thus, soils with higher C content showed higher energy content too. The combustion temperatures of the curves given by DSC are those reported for labile OM. NMR results indicated the presence of aliphatic C, carbohydrates, and a weak signal in the aromatic C band in all the samples that was not detected in the DSC curves. Only two samples showed carboxyl/carbonyl C which was not detected by DSC also.     

δ-Lactam derivative from thermophilic soil fungus exhibits in vitro anti-allergic activity

From cultures of thermophilic soil fungus Humicola grisea var thermoidea, a δ-lactam derivative (3-(2-(4-hydroxyphenyl)-2-oxoethyl)-5,6-dihydropyridin-2(1H)-one) that displayed anti-allergic activity was isolated, which was predicted by in silico computational chemistry approaches. The in?vitro anti-allergic activity was investigated by β-hexosaminidase release assay in rat basophilic leukaemia RBL-2H3 cells. The δ-lactam derivative exhibited similar anti-allergic activity (IC(50)?=?18.7?±?6.7?μM) in comparison with ketotifen fumarate (IC(50)?=?15.0?±?1.3?μM) and stronger anti-allergic activity than azelastine (IC(50)?=?32.0?μM). Also, the MTT cytotoxicity assay with RBL-2H3 cells showed that δ-lactam does not display cytotoxicity at concentrations lower than 50?μM. This study suggests that the δ-lactam derivative has the potential to be used as a lead compound in the development of anti-allergic drugs for clinical use in humans.     

Challenges in measuring the δ13C of the soil surface CO2 efflux

The δ13C of the soil surface efflux of carbon dioxide (δ13CRS) has emerged as a powerful tool enabling investigation of a wide range of soil processes from characterising entire ecosystem respiration to detailed compound-specific isotope studies. δ13CRS can be used to trace assimilated carbon transfer below ground and to partition the overall surface efflux into heterotrophic and autotrophic components. Despite this wide range of applications no consensus currently exists on the most appropriate method of sampling this surface efflux of CO2 in order to measure δ13CRS. Here we consider and compare the methods which have been used, and examine the pitfalls. We also consider a number of analysis options, isotope ratio mass spectrometry (IRMS), tuneable diode laser spectroscopy (TDLS) and cavity ring-down laser spectroscopy (CRDS). δ13CRS is typically measured using chamber systems, which fall into three types: closed, open and dynamic. All are imperfect. Closed chambers often rely on Keeling plots to estimate δ13CRS, which may not be appropriate without free turbulent air mixing. Open chambers have the advantage of being able to maintain steady-state conditions but analytical errors may become limiting with low efflux rates. Dynamic chambers like open chambers are complex, and controlling pressure fluctuations caused by air movement is a key concern. Both open and dynamic chambers in conjunction with field portable TDLS and CRDS analysis systems have opened up the possibility of measuring δ13CRS in real time permitting new research opportunities and are on balance the most suited to this type of measurement.     

Urease–glutamic dehydrogenase biosensor for screening heavy metals in water and soil samples

A screen-printed three-electrode amperometric biosensor based on urease and the nicotinamide adenine dinucleotide hydrogen (NADH)–glutamic dehydrogenase system was developed and applied to the screening of heavy metals in environmental samples. The development of an amperometric sensor for the monitoring of urease activity was feasible by coupling the urea breakdown reaction catalysed by urease to the reductive ammination of ketoglutarate catalysed by glutamic dehydrogenase (GLDH). The ammonia provided by the urea conversion is required for the conversion of ketoglutarate to glutamate with the concomitant oxidation of the NADH cofactor. NADH oxidation is monitored amperometrically at 0.3 V (vs. Ag/AgCl) after urease immobilization onto the screen-printed three-electrode configuration. Immobilization of urease on the surface of screen-printed electrodes was performed by entrapment in alginate gel and adsorption on the electrode in a nafion film. Low sensitivity to inactivation by metals was recorded after urease entrapment in alginate gel with detection limits of 2.9 and 29.8 mg L^–1 for Hg(II) and Cu(II), respectively. The use of the negatively charged nafion film created a more concentrated environment of cations in proximity to the enzyme, thus enhancing the urease inhibition when compared to gel entrapment. The calculated detection limits were 63.6 and 55.3 g L^–1 for Hg(II) and Cu(II), respectively, and 4.3 mg L^–1 for Cd(II). A significant urease inactivation was recorded in the presence of trace amounts of metals (g L^–1) when the enzyme was used free in solution. Analysis of water and soil samples with the developed nafion-based sensor produced inhibition on urease activity according to their metal contents. The obtained results were in agreement with the standard methods employed for sample analysis. Nevertheless, the use of the amperometric assay (with free urease) proved more feasible for the screening of trace amounts of metals in polluted samples.     

Miniaturized liquid–liquid extraction coupled with ultra-performance liquid chromatography/tandem mass spectrometry for determination of topramezone in soil,corn, wheat,and water

A rapid and simple miniaturized liquid–liquid extraction method has been developed for the determination of topramezone in soil, corn, wheat, and water samples using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-electrospray ionization (ESI)/MS/MS). The established method for the extraction and purification procedure was based on liquid–liquid partitioning into an aqueous solution at a low pH (pH ≈ 2.5), followed by back-partitioning into water at pH > 9. Two precursor, product ion transitions for topramezone were measured and evaluated to provide the maximum degree of confidence in the results. Under negative ESI conditions, quantitation was achieved by monitoring the fragment at m/z = 334 and the qualitative fragment at m/z = 318, whereas also collecting the corresponding parent ion at m/z = 362. Chromatographic separation was achieved using gradient elution with a mobile phase consisting of methanol and a 0.01% aqueous ammonium hydroxide solution. Recovery studies for soil, corn, wheat, and water were conducted at four different topramezone concentrations (5 or 10, 50, 100, and 1,000 μg kg⁻¹); the overall average recoveries ranged from 79.9% to 98.4% with intra-day relative standard deviations (RSD) of 3.1~8.7% and inter-day RSD of 4.3~7.5%. Quantitative results were determined from calibration curves of topramezone standards containing 1–500 μg L⁻¹ with an R ² ≥ 0.9994. Method sensitivities expressed as limits of quantitation were typically 6, 8, 9, and 1 μg kg⁻¹ in soil, corn, wheat, and water, respectively. The results of the method validation confirmed that this proposed method was convenient and reliable for the determination of topramezone residues in soil, corn, wheat, and water.     

Assessment of the determination of heavy metals in organic soil improvers by ICP–OES

Directive 86/278/EEC sets maximum levels of heavy metals in sewage sludge used in agriculture to regulate the risk of using these organic soil improvers. The assessment of the compliance of soil improvers with this legislation should be supported on measurements with adequately low uncertainty. This work presents a strategy for assessing the performance of the determination of aqua regia extractable Cu, Zn and Cr in organic soil improvers and urban sewage sludges following EN 13650 standard. The measurement procedure validation involves checking the adequacy of the linear weighted regression model for ICP–OES calibration, the determination of the limit of quantification, the assessment of measurement repeatability, intermediate precision and trueness, and the evaluation of the measurement uncertainty using the differential approach. Routine tests quality control, including the estimated measurement uncertainty, is checked through the analysis of control standards, equivalent to calibrators, and reference materials from proficiency tests. Since the estimated relative expanded uncertainty is smaller than the defined target value (40 %), measurements are fit for assessing compliance of the mass fraction of heavy metals in organic soil improvers with the council directive.     

Ultra-high-pressure liquid chromatography–tandem mass spectrometry method for the determination of alkylphenols in soil

A novel method has been developed for the determination of alkylphenols in soil by ultra-high-pressure liquid chromatography employing small particle sizes, combined with tandem mass spectrometry. Soil samples were extracted with pressurized liquid extraction (PLE) and then cleaned with solid-phase extraction (SPE). The extracts were separated on C18 column (1.7 μm, 50 mm × 2.1 mm) with a gradient elution and a mobile phase consisting of water and acetonitrile, and then detected by an electrospray ionization tandem mass spectrometry in negative ion mode with multiple reaction monitoring (MRM). Compared with traditional liquid chromatography, it took ultra-high-pressure liquid chromatography much less time to analyze alkylphenols. Additionally, the ultra-high-pressure liquid chromatography/tandem mass spectrometry method produces satisfactory reliability, sensitivity, and accuracy. The average recoveries of the three target analytes were 74.0–103.4%, with the RSD < 15%. The calibration curves for alkylphenols were linear within the range of 0.01–0.4 μg/ml, with the correlation coefficients greater than 0.99. When 10 g soil sample was used for analysis, the limits of quantification (LOQs) of the three alkylphenols were all 1.0 μg/kg.     

Are physico-chemical soil characteristics key factors to select the polycyclic aromatic hydrocarbons extraction procedure?

The aim of this work was to assess the impact of soil characteristics and constituents in the total extraction of hydrophobic organic pollutants, such as polycyclic aromatic hydrocarbons (PAH), in real polluted soil samples from different sources. Soil samples were obtained from a wood creosote treatment plant, in the vicinity of a metallurgy industry and coal thermal power stations. Soils showed a wide diversity of textures, organic matter (OM) and CaCO₃ content, pH and electrical conductivity to assure representativeness of multiple situations. Two extraction procedures with soft (solid–liquid extraction, SLE) and intense (pressurised liquid extraction, PLE) extraction power were used to determine the total concentration of PAH in soils. Results obtained showed that soil properties affect the effectiveness of the extraction procedures tested. The validation of PAH extraction procedure with a reference soil did not confirm that the procedure was adequate for all kinds of soil. Results showed that OM content and clay were the main soil characteristics that should be taken into account to select the most adequate PAH extraction procedure for any given polluted soil.     

GC–MS–MS analysis of bacterial fatty acids in heavily creosote-contaminated soil samples

Phospholipid fatty acid profiles of soil samples enable rapid and reproducible measurement and characterization of the dominant soil microbial communities. When extensive polycyclic aromatic hydrocarbon (PAH) pollution is present in the soil it is very difficult, or even impossible, to distinguish specific fatty acids in GC–MS chromatograms in full-scan mode, because of the PAHs which, because of their lipophilic character, are co-extracted with the lipids. Selected ions in the samples were scanned in MS–MS mode to eliminate the aromatic hydrocarbon signals and obtain clear chromatograms of the fatty acids. By using this technique it was possible to clearly distinguish at least eleven fatty acids in heavily creosote-contaminated soil samples (PAH concentration approximately 15 g kg⁻¹ dry weight of soil).