Accurate prediction bioaccessibility of PAHs in soil-earthworm system by novel magnetic solid phase extraction technique.

Conventional chemical extraction methods may lead to overestimate or underestimate bioaccessibility due to their inability to provide realistic kinetic information regarding PAHs in soils. In this study, we propose the use of magnetic solid phase extraction (MSPE) technique for assessing the bioaccessibility of PAHs in the soil-earthworm system. Firstly, a novel polydopamine-coated magnetic core-shell microspheres (Fe3O4-C16@PDA) was developed by a one-pot sol-gel and self-polymerization method. The PDA coatings not only enhance the hydrophilicity of material surfaces but also exhibit excellent biocompatibility. The maximum adsorption capacity of Fe3O4-C16@PDA for 16 PAHs was 52.72 mg g-1, indicating that the proposed material fulfills the assessment requirements for highly contaminated soil. To compare the measurement of PAHs and their uptake by earthworms (Eisenia fetida), experiments were conducted using four different soils with varying properties. The desorption kinetics data obtained from these experiments demonstrated that the capability of the MSPE in accurately predicting the bioavailable portions of PAHs. After a 28-day exposure, the best predictor of bioavailable PAHs in earthworms was MSPE method exhibited the highest correlation coefficient (R2 > 0.90), and its slopes in the four soils were 0.972, 0.961, 1.012, and 0.962, respectively, all close to 1. These results demonstrate that the MSPE method successfully mimics the conditions encountered in soil-earthworm systems and effectively assess bioaccessibility of PAHs in soils.

Selected pesticidal POPs and metabolites in the soil of five Vietnamese cities: Sources, fate, and health risk implications.

Large quantities of organochlorine pesticides (OCPs) have been used in tropical regions. The fate processes and risks of these legacy contaminants in the tropics are poorly understood. Herein, we investigated the occurrence of three classes of widely used OCPs and their metabolites in surface and core soil from five cities across Vietnam with a prevalent tropical monsoon climate and a long history of OCP application. We aimed to elucidate migration potentials, degradation conditions, and transformation pathways and assess current health risks of these contaminants. Generally, the concentrations of OCPs and metabolites in the soil core were slightly lower than those in surface soil except for hexachlorocyclohexane (HCH) isomers. 2,2-bis(4-chlorophenyl)-1,1,1-trichloroethane (p,p'-DDT), 2,2-bis(4-chlorophenyl)-1,1-dichloroethylene (p,p'-DDE), the sum of dicofol and 4,4'-dichlorobenzophenone (p,p'-DBP), and 2,2-bis(4-chlorophenyl)-1,1-dichloroethane (p,p'-DDD) were the most abundant compounds in both surface and core soils. A uniform distribution of HCHs (the sum of α-, ß-, γ-, and δ-HCH) at trace levels was found in almost all soils, serving as evidence of the lack of recent use of HCH pesticides. Higher concentrations of DDTs (the sum of DDT, DDD, and DDE) were observed in north-central Vietnamese soil, whereas appreciable concentrations of ENDs (the sum of α- and ß-endosulfan and endosulfan sulfate) were only found in southern Vietnamese soils. Empirical diagnostic ratios indicated residuals of DDTs were mainly from technical DDT rather than dicofol, whereas aged HCHs could be explained by the mixture of lindane and technical HCH. Both historical applications and recent input explain DDTs and ENDs in Vietnamese soil. Total organic carbon performs well in preventing vertical migration of more hydrophobic DDTs and ENDs. The dominant transformation pathway of DDT in surface soil followed p,p'-DDE→2,2-bis(4-chlorophenyl)-1-chloroethylene or p,p'-DDMU→1,1-bis(4-chlorophenyl)ethylene or p,p'-DDNU→p,p'-DBP, whereas the amount of p,p'-DDMU converted from p,p'-DDD and p,p'-DDE is similar in soil core. Non-cancer risks of OCPs and metabolites in all soils and cancer risks of those chemicals in core soils were below the safety threshold, whereas a small proportion of surface soil exhibited potential cancer risk after considering the exposure pathway of vegetable intake. This study implied that organic matter in non-rainforest tropical deep soils still could hinder the leaching of hydrophobic organic contaminants as in subtropical and temperate soils. When lands with a history of OCP application are used for agricultural purposes, dietary-related risks need to be carefully assessed.

Preparation of magnetic Janus microparticles for the rapid removal of microplastics from water.

The continuous spread of microplastics in aquatic environments poses a growing concern and a potential risk to human health. To address this concern, this paper presents a novel approach using magnetic Janus microparticles (MJMs) synthesized via a modified Pickering emulsion method with aminated Fe3O4@SiO2 as the raw material. The effectiveness of these MJMs in removing polystyrene (PS) and polyethylene (PE) microplastics from water was investigated. Paraffin was employed as the masking agent, while N-Octadecylphosphosphonic acid (PAC18) was used as the graft material for MJM preparation. The resulting particles exhibited a distinctive asymmetric flower-shaped structure on the surface, which was confirmed through various analytical techniques including FTIR, TGA, SEM, and water phase contact angle analysis. The MJMs demonstrated exceptional efficiency in adsorbing microplastics. With a microplastic suspension concentration of 2 mg/mL and an adsorbent dosage of 1 mg/mL, the MJMs can attain removal efficiencies of 92.08 % for PS and 60.67 % for PE in just 20 min of contact time. The effectiveness of the adsorption process was attributed to several factors, including hydrophobic interactions, cation-π interactions, electrostatic attraction, and the efficient dispersion of particles in water, as revealed by size distribution and zeta potential analysis. Additionally, kinetic and thermodynamic studies confirmed the remarkable adsorption rate and capacity of the MJMs (0.759 min-1 and 2.72 mg/mg for PS, 0.539 min-1 and 2.42 mg/mg for PE), highlighting their potential as a promising method for rapidly removing microplastics from water. This work provides valuable insights into the development of effective strategies for addressing microplastic pollution in aquatic environments.

Magnetic poly(ß-cyclodextrin) combined with solubilizing agents for the rapid bioaccessibility measurement of polycyclic aromatic hydrocarbons in soils.

The rapid determination of the bioaccessibility of polycyclic aromatic hydrocarbons (PAHs) in soils is challenging due to their slow desorption rates and the insufficient extraction efficiency of the available methods. Herein, magnetic poly(ß-cyclodextrin) microparticles (Fe3O4@PCD) were combined with hydroxypropyl-ß-cyclodextrin (HPCD) or methanol (MeOH) as solubilizing agents to develop a rapid and effective method for the bioaccessibility measurement of PAHs. Fe3O4@PCD was first validated for the rapid and quantitative adsorption of PAHs from MeOH and HPCD solutions. The solubilizing agents were then coupled with Fe3O4@PCD to extract PAHs from soil-water slurries, affording higher extractable fractions than the corresponding solution extraction and comparable to or higher than single Fe3O4@PCD or Tenax extraction. The desorption rates of labile PAHs could be markedly accelerated in this process, which were 1.3-12.0 times faster than those of single Fe3O4@PCD extraction. Moreover, a low HPCD concentration was sufficient to achieve a strong acceleration of the desorption rate without excessive extraction of the slow desorption fraction. Finally, a comparison with a bioaccumulation assay revealed that the combination of Fe3O4@PCD with HPCD could accurately predict the PAH concentration accumulated in earthworms in three field soil samples, indicating that the method is a time-saving and efficient procedure to measure the bioaccessibility of PAHs.

Tetrafluoroterephthalonitrile-crosslinked ß-cyclodextrin polymer as a binding agent of diffusive gradients in thin-films for sampling endocrine disrupting chemicals in water.

ß-Cyclodextrin (ß-CD) is an inexpensive and reproducible material derived from corn starch. It is possible that tetrafluoroterephthalonitrile-crosslinked ß-cyclodextrin polymer (TFN-CD), a cheap but efficient adsorbent, could be a suitable binding agent for use in the passive sampling technique, diffusive gradients in thin-films (DGT). Herein, the TFN-CD binding gel was prepared and then evaluated as the binding phase of DGT to sample six endocrine disrupting chemicals (EDCs) in water. The TFN-CD dispersed uniformly in the binding gel due to its hydrophilicity. The quantitative recoveries (99.3%-106%) of EDCs from the TFN-CD binding gel could be conveniently achieved by ultrasonic extraction using 5 mL methanol for 10 min. Compared with the excellent HLB (hydrophilic-lipophilic-balanced resin) binding gel, the TFN-CD binding gel had comparable or even faster adsorption kinetics, although the equilibrium adsorption capacity was slightly lower. The effective adsorption capacities of TFN-CD-based DGT (TFN-CD-DGT) were roughly estimated to enable a 7-days deployment in EDC solution of 25.7-30.0 µg L-1. Studies of influencing factors showed that the ionic strength (0-0.5 M), pH (3.73-9.13), dissolved organic matter (0-20 mg L-1) and long-term storage (204 days) had negligible influence on the performance of TFN-CD-DGT. Finally, the TFN-CD-DGT was successfully used to record sudden increases in bulk concentrations during simulated discharge events in pond water. These results demonstrate that TFN-CD is a suitable binding agent for sampling of EDCs, and the low cost of TFN-CD could be conducive to the application of DGT in large-scale sampling.

Assessment of commercial porous polyethylene frit for extraction of polycyclic aromatic hydrocarbons from water.

Exploring commercial and inexpensive sorbents for extraction of organic pollutants is still an active area of research. Ultrahigh molecular weight polyethylene sieve plate (UMPESP) is a commercially available, low-cost, and porous frit, which has been widely used in solid-phase extraction cartridges to fix the filling materials. In this work, UMPESP was investigated for the extraction of polycyclic aromatic hydrocarbons (PAHs) from water samples. The desorption and sorption efficiencies of UMPESP were first evaluated and compared with two previously reported sorbents, low-density polyethylene plastic pellet (LDPEP) and silicone rod (SR). The comparative results showed that quantitative desorption of analytes from UMPESP, which could be easily achieved with 2 × 1.5 mL n-hexane, was more effective than that of LDPEP (>6 × 1.5 mL n-hexane) and comparable to that of SR. Additionally, shorter equilibrium time was rendered by UMPESP (shaking for 120 min) compared with SR (>480 min), due to the porous structure and larger surface area of the former. Different parameters that affect the extraction efficiency, including organic modifier, ionic strength, and pH value, were then studied. The optimized method coupled with gas chromatography-mass spectrometry afforded good linearity in a concentration range of 10-5000 ng L-1 (except acenaphthene in the range of 25-5000 ng L-1) with coefficients of determination ranging from 0.9957 to 0.9995 and relative standard deviations below 13.8%. The limits of detection and quantification were 0.04-3.35 ng L-1 and 0.13-11.16 ng L-1, respectively. Finally, the method was successfully applied to determine PAHs in real water samples, and the results showed no statistically significant difference with the concentrations derived from liquid-liquid extraction.

Magnetic solid-phase extraction as a novel method for the prediction of the bioaccessibility of polycyclic aromatic hydrocarbons.

Chemical methods used to predict the bioaccessibility of hydrophobic organic compounds (HOCs) still need further development and improvement. In this work, magnetic solid-phase extraction (MSPE) based on poly(ß-cyclodextrin)-coated magnetic polydopamine (Fe3O4@PDA@PCD) was first introduced to assess the bioaccessibility of polycyclic aromatic hydrocarbons (PAHs) in soils. Due to its good hydrophilicity and submicrometer scale, Fe3O4@PDA@PCD displayed a higher extraction rate for PAHs in an aqueous solution (equilibrium time < 5 min) than Tenax resin, which had an equilibrium time longer than 30 min. The merits of Fe3O4@PDA@PCD are beneficial to accelerate the desorption of PAHs from soil, especially for high molecular weight PAHs, in which the amounts extracted by Fe3O4@PDA@PCD were 1.2-2.8 times higher than those extracted by Tenax resin. The desorption kinetics data were well fitted with a two- or three-fraction model. The fitting results indicated that the MSPE method can be used to predict the bioaccessible fractions of PAHs. By comparing the prediction results obtained from the MSPE method with bioassays using earthworms, a significant linear correlation (R2 = 0.98) with a slope statistically close to 1 was obtained. These results suggested that the MSPE method can act as a simple and efficient method to measure the bioaccessibility of PAHs in soil.

Facile synthesis of polydivinylbenzene coated magnetic polydopamine coupled with pressurized liquid extraction for the extraction and cleanup of polycyclic aromatic hydrocarbons in soils.

Due to the trace levels of polycyclic aromatic hydrocarbons (PAHs) in soil and the complexity of soil matrices, effective sample pretreatment methods are of great significance to obtain accurate analytical results. In this paper, polydopamine (PDA) encapsulated Fe3O4 particles were used as seeds for in situ polymerization of divinylbenzene (DVB) to derive magnetic hybrid material Fe3O4@PDA@PDVB. Coupled with pressurized liquid extraction, Fe3O4@PDA@PDVB was investigated as a selective adsorbent for the extraction and cleanup of PAHs in soil. The prepared magnetic material was characterized and demonstrated to possess strong hydrophobicity and superparamagnetism. Under optimal conditions, Fe3O4@PDA@PDVB can effectively extract 15 PAHs from a 30% methanol solution within 2 min, and it is more selective for PAHs than for n-alkane in soil extracts. The matrix effect significantly decreased after extraction by the prepared material, which showed superiority to a silica gel column method (EPA 3630C Method). The developed method was linear (5-1000 ng g-1) with coefficient of determination (R2) ranging from 0.9986-0.9998, and the limits of detection were 0.13-0.54 ng g-1. Additionally, repetitive experiments indicated that the prepared material was reproducible and reusable with relative standard deviations below 8.4% and 8.6%, respectively. Finally, the new method was successfully employed to determine the concentrations of PAHs in genuine soil and standard reference material, and the results were comparable to those of widely utilized EPA methodology.

Polydopamine-coated polyethylene sieve plate as an efficient and convenient adsorption sink for the bioaccessibility prediction of PAHs in soils.

Bioaccessibility measurements of polycyclic aromatic hydrocarbons (PAHs) in soils are significant for exposure risk assessment. The current physicochemical methods require tedious operation processes, underestimate the actual risks, or are unsuitable for high organic content soils. In this work, an efficient and convenient method based on polydopamine-coated polyethylene sieve plate (PDA@PESP) and hydroxypropyl-ß-cyclodextrin (HPCD) was developed to predict the bioaccessibility of PAHs in multi-type soils. The PDA@PESP can be prepared via in situ self-polymerization, allowing to extract PAHs from HPCD solution quantitatively and rapidly. When applied to evaluate the bioaccessibility with PDA@PESP as an adsorption sink and HPCD as a diffusive carrier, the proposed method can significantly improve the extractable fraction of PAHs compared to single HPCD extraction in particular for high organic carbon content soil and high-ring PAHs. The desorption kinetics data indicated that the method can predict the bioaccessible fraction of PAHs. In addition, the method predicted a satisfactory accumulation into earthworms (Eisenia fetida) with a slope statistically approximated to 1. A highly significant linear regression (R2 = 0.95) was also found between the proposed method and Tenax desorption in historically contaminated soils, demonstrating that the method is an efficient and convenient approach for the bioaccessibility prediction of PAHs in soils.

Study on four metal organic frameworks as cleanup adsorbents for polycyclic aromatic hydrocarbons determined by GC-MS/MS.

A new application of MOFs as adsorbents in the cleanup procedure of polycyclic aromatic hydrocarbons (PAHs) in soils was explored. Four MOFs, specifically MIL-101(Cr), MIL-125(Ti), MIL-100(Fe) and UiO-66(Zr), were synthesized and characterized. A screening study was carried out to select the best adsorbent for the purification of sixteen PAHs in complex soil extract. It is found that the nature of metal ion, pore size, surface area and surface charge affect the purification efficiencies of the various MOFs. MIL-101(Cr) was then selected because of its best purification efficiency. The effects of amount of adsorbent, cleanup solvent and cleanup time on cleanup efficiency were investigated. Under the optimum conditions, the matrix effect of the target analytes was reduced by more than 65%. The method was then combined with ultrasonic extraction and quantitation by gas chromatography with triple quadrupole mass spectrometric detection. The method allows for the determination of PAHs in soils with linear in the range of 5-5000 ng g-1 and with LODs between 50 and 420 pg g-1. The method was applied to the analysis of (spiked) soil samples, and results compared well with the established EPA method. Graphical abstract Schematic presentation of metal organic frameworks (MOF) as cleanup adsorbents for purifying polycyclic aromatic hydrocarbons in soil organic matter (SOM) and further determined by gas chromatography with triple quadrupole mass spectrometry detection (GC-MS/MS).

Preparation of phenyl-modified magnetic silica as a selective magnetic solid-phase extraction adsorbent for polycyclic aromatic hydrocarbons in soils.

Accurate analysis of polycyclic aromatic hydrocarbons (PAHs) in soils remains a challenge due to the complexity of sample matrices. In this paper, phenyl-modified magnetic mesoporous silica (Fe3O4@mSiO2-Ph-PTSA) was synthesized with p-toluenesulfonic acid (PTSA) as the catalyst and used as a selective adsorbent for the clean-up of PAHs extracted from soils. The material prepared without PTSA as the catalyst (Fe3O4@mSiO2-Ph) was synthesized for comparison. The synthesized materials were first systematically characterized and evaluated. It was found that the grafting amount of the phenyl group onto Fe3O4@mSiO2-Ph-PTSA was higher than that onto Fe3O4@mSiO2-Ph. The extraction efficiency obtained by extracting PAHs from the extracted soil matrix solution demonstrated that Fe3O4@mSiO2-Ph-PTSA possessed a much higher extraction efficiency than that of Fe3O4@mSiO2-Ph, which can be attributed to the greater amount of phenyl groups grafted on Fe3O4@mSiO2 in the presence of the PTSA catalyst. Moreover, contrast experiments showed that Fe3O4@mSiO2-Ph-PTSA displayed higher selectivity towards PAHs than towards n-alkanes and that the π-π interaction played a key role in the adsorption process. In the presence of the soil extract matrix, the parameters affecting the extraction efficiency of Fe3O4@mSiO2-Ph-PTSA for PAHs were optimized. Under the optimal conditions, coupled with pressurized liquid extraction and gas chromatograph-mass spectrometer, the proposed method for the determination of PAHs in soils was linear in the range of 5-500 ng g-1, and the correlation coefficients (R) ranged between 0.9994 and 0.9999. The limits of detection (LODs) and limits of quantification (LOQs), which were based on signal-to-noise ratios of 3 and 10, respectively, were in the range of 0.07-0.41 ng g-1 and 0.24-1.37 ng g-1. The developed method displayed a better clean-up effect than that for silica gel column method, and the matrix effect markedly decreased compared to that of the uncleaned condition. Finally, the developed method was successfully applied for the detection of PAHs in environmental soils, and the data were consistent with the results obtained by the silica gel column method. The analytical results were also consistent with those for the real environment.

[Characteristics and Source Apportionment of VOCs of a Petrochemical Industrial Park During Autumn in China].

An online continuous monitoring system was used to determine the volatile organic carbons (VOCs) in the ambient air of a typical petrochemical industrial park in autumn (Sep., Oct., Nov.) of 2014. The composition, photochemical reactivity, temporal variation, and source of VOCs were analyzed. The results indicated that the mixing ratio of VOCs in autumnal ambient air of the study area was higher than those of other cities and industrial areas. Alkanes were the most abundant group in the VOC mixing ratio, and no significant temporal difference was observed among the three months studied. However, the alkanes, alkenes, and aromatics presented obvious diurnal variation, with single peak and trough values, while the acetylene exhibited "W"-shaped variation, with two minimum and one maximum values. Source apportionment using positive matrix factorization (PMF) indicated that the sources of VOCs in the study area of natural gas transportation and solvents, such as from leakage or volatile oil refinery processing, followed by other traffic sources and asphalt have some contribution. Alkenes and alkanes were the dominant groups of the source apportionment composition, as expressed by the propylene-equivalent (Propy-Equiv) and maximum incremental reactivity (MIR) methods, respectively.

Rapid preparation of methyltrimethoxy-modified magnetic mesoporous silica as an effective solid-phase extraction adsorbent.

A time-saving method was applied to synthesize methyltrimethoxy-modified magnetic mesoporous silica with or without p-toluenesulfonic acid as the catalyst for magnetic solid-phase extraction. The synthesized materials were systematically characterized. Results demonstrated that methyltrimethoxy modified magnetic mesoporous silica with p-toluenesulfonic acid as the catalyst has a relatively smaller aperture and extreme hydrophobicity (water contact angle of 135°). To evaluate the feasibility of these prepared materials as effective adsorbents, it was combined with gas chromatography and electron capture detection to determine 26 polychlorinated biphenyls in environmental water. The result revealed that methyltrimethoxy modified magnetic mesoporous silica with p-toluenesulfonic acid as the catalyst had the best extraction efficiency and recovery. Under the optimized extracted conditions, the proposed method showed good linearity within the concentration range of 5 to 200 ng/L with correlation coefficients of 0.9969 to 0.9999. The limits of detection and quantification based on signal-to-noise ratios of 3 and 10 were in the range of 0.16 to 0.91 and 0.52 to 3.0 ng/L, respectively. The polychlorinated biphenyl concentrations in environmental water samples were successfully determined using the developed method. PCB008 and PCB110 were 4.05 and 8.52 ng/L in Red-Star lake water (Hubei Province, China), respectively.

Facile preparation of hexadecyl-functionalized magnetic core-shell microsphere for the extraction of polychlorinated biphenyls in environmental waters.

Alkyl moieties which can retain target analytes due to their lipophilicity are important in sample preparation. In this work, hexadecyl-functionalized magnetic core-shell microspheres (Fe3O4@SiO2-C16) was successfully prepared by one-pot sol-gel method and used for magnetic solid-phase extraction of polychlorinated biphenyls (PCBs) in environmental water samples. Optimized preparation method was achieved by altering the adding moment of hexadecyl-silane. The resultant materials were systematically characterized by scanning electron microscope, transmission electron microscope, Fourier transform infrared spectroscopy, energy dispersive X-ray spectrometry, tensionmeter, and vibrating sample magnetometer. The results demonstrated that the optimized adsorbent exhibited core-shell structure, superparamagnetic (66 emu/g), and extremely hydrophobic (water contact angle of 122°) properties. To evaluate the extraction performance, the prepared material coupled with gas chromatography-triple quadrupole mass spectrometry (GC-MS/MS) was applied to determinate PCBs. The extraction conditions were optimized. Under the optimal conditions, the proposed method showed a good linearity range of 1-100 ng L-1 with correlation coefficients (R) of 0.9989-0.9993. Based on a signal-to-noise ratio of 3 and 10, the limits of detection (LODs) and limits of quantification (LOQs) were in the range 0.14-0.27 and 0.39-0.91 ng L-1, respectively. The intra- and inter-day relative standard deviations (RSDs) were less than 9.06%. The absolute recoveries of PCBs in spiked real water samples were in the range of 75.17 to 101.20%. Additionally, reusability and batch-to-batch reproducibility of the resultant material were acceptable with RSDs less than 5.64 and 3.25%, respectively. Graphical Abstract The synthesis procedure of Fe3O4@SiO2-C16 and determination of PCBs in water sample 129 × 50 mm (300 × 300 DPI).