Distribution, Elimination, and Rearrangement of Cyclic Volatile Methylsiloxanes in Oil-Contaminated Soil of the Shengli Oilfield, China

Cyclic methylsiloxane standards (D4, D5, and D6) and linear methylsiloxanes (L3 through L16) were detected with high total concentrations (from 5.20 × 10⁴ to 1.07 × 10⁶ ng/g dw) in 18 oil sludge samples collected from the Shengli oilfield during 2008–2013. In 306 soil samples from this oilfield, the mean concentrations (43.4–125 ng/g dw) and the detection frequencies (65–76%) of D4–D6 were 10.9–11.9 and 2.05–2.24 times higher than those in reference soil samples, respectively. The concentrations of total cyclic siloxanes (ΣCyclic) had positive correlations (<i>R</i>² = 0.79, <i>p</i> < 0.05) with the total petroleum hydrocarbons concentration (TPH) in soil, indicating that oil production could release cyclic siloxanes to the environment. During 2008–2013, an increasing tendency (mean of 13.4% per annum) of ΣCyclic was found in soil with high TPH (>5000 mg/kg) but was not found in soil with lower TPH. Elimination experiments showed that petroleum hydrocarbons could reduce the degradation and volatilization rates of D4, D5, and D6 in impacted oilfield soil. The half-lives of D4, D5, and D6 in the opened and capped soil systems with TPH = 400–40 000 mg/kg were 1.19–22.2 and 1.03–7.43 times larger than those in common soil (TPH = 80 mg/kg), respectively. Furthermore, the petroleum hydrocarbons could affect the rearrangement-reaction rates of D5 and D6 in soil

Facile Synthesis of Magnetic Covalent Organic Framework with Three-Dimensional Bouquet-Like Structure for Enhanced Extraction of Organic Targets

A facile strategy for the fabrication of novel bouquet-shaped magnetic porous nanocomposite via grafting a covalent organic framework (COF, TpPa-1) onto the surface-modified Fe₃O₄ nanoparticles (Fe₃O₄ NPs) was reported. The magnetic TpPa-1 (a COF synthesized from 1,3,5-triformylphloroglucinol (Tp) and <i>p</i>-phenylenediamine (Pa-1)) contains clusters of core–shell magnetic nanoparticles and interconnected porous TpPa-1 nanofibers. Thus, it possesses larger specific surface area, higher porosity, and supermagnetism, making it an ideal sorbent for enrichment of trace analytes. Its performance was evaluated by the magnetic solid-phase extraction (MSPE) of trace polycyclic aromatic hydrocarbons (PAHs) from environmental samples prior to high-performance liquid chromatographic analysis. The results indicated that the magnetic TpPa-1 possessed superior enrichment capacity of such organic compounds

Easy Synthesis of Surface-Tunable Carbon-Encapsulated Magnetic Nanoparticles: Adsorbents for Selective Isolation and Preconcentration of Organic Pollutants

We have prepared core/shell structured carbon-encapsulated magnetic nanoparticles (CMNPs) with a simple method by using inorganic iron salt and glucose solution as precursor substance. The synthetic procedure does not require the use of organic solvents. We have utilized X-ray photoelectron spectroscopy, infrared spectroscopy, X-ray diffraction, and Raman analysis to examine the surface properties of CMNPs prepared at different temperature. The specific surface areas, magnetization and contents of graphitized carbon on carbon shell of CMNPs increase with heat treatment temperature. The obtained CMNPs are used to adsorb or preconcentrate bisphenol A (BPA), 4-n-nonylphenol (4-NP), 4-tert-octylphenol (4-OP), diethyl phthalate (DEP), dipropyl phthalate (DPP), dibutyl phthalate (DBP) dicyclohexyl phthalate (DCHP), dioctyl phthalate (DOP), sulfonamide, tetracyclines, and quinolones antibiotics organic compounds from water samples. The adsorption of analytes is mainly based on π–π stacking interaction, hydrophobic interaction and hydrogen bonds between analytes and graphitic carbon. As a result, the adsorption or extraction behaviors of CMNPs to analytes are controlled by the content of oxygen-containing species and graphitized carbon on carbon shell of CMNPs. CMNPs prepared at 200 °C have ample oxygen-containing species (80%) on surface and favor the adsorption and extraction of quinolones antibiotics. CMNPs heated at 300–500 °C with the graphitization efficiency of carbon shell lower than 50% exhibit great preconcentration performance to BPA, 4-NP, 4-OP, DBP, DCHP, DOP, tetracyclines, and quinolones antibiotics. CMNPs prepared at 850 °C are highly graphitized (80%) and have strong adsorption affinity to all model analytes; however, they can quantitatively extract only highly polar sulfonamide antibiotics and moderately polar DEP, DPP because of hard desorption of other model analytes. We suggest that the appropriate adsorbent to certain organic contaminants can be obtained with this technique just by tuning the heat temperature without any post-treatment

Methylsiloxanes Release from One Landfill through Yearly Cycle and Their Removal Mechanisms (Especially Hydroxylation) In Leachates

In one yearly cycle (2016), D4 and D5 were detected in biogas samples (<i>n</i> = 36, 0.105–2.33 mg/m³) from a Chinese municipal landfill, while D4–D6 were detected in influents/effluents of leachate storage pond (<i>n</i> = 72, < LOQ-30.5 μg/L). Mass loads of cVMS in both biogas (591–6575 mg/d) and leachate influents (659–5760 mg/d) increased from January to July (summer), and then decreased from July to December (winter). Removal experiments indicated that 1) hydrolysis and volatilization were predominant removal mechanism for D4 and D5, respectively, in leachate storage pond, responsible for their more significant removal (94.5–100%) in August; 2) indirect phototransformation (<i>t</i>_1/2 = 25.5–87.0 days), such as hydroxylation by OH radical generated in leachates, was the predominant (50.0–75.5%) removal pathway for D6, which led to the largest removal efficiencies (65.2–73.7%) in June, the month with the largest sun light intensity and highest photosensitizer (e.g., Fe²⁺ and NO₃^–) concentrations. Monohydroxylated products of D5 and D6, D4TOH and D5TOH, were detected in leachate effluents (39.6–187 ng/L) during May-July. Compared to D5 and D6, volatilization half-lives of D4TOH (86.3 days) and D5TOH (177 days) in leachates were 2.9 and 1.4 times longer, while their hydrolysis half-lives (7.50 days for D4TOH and 21.5 days for D5TOH) were 7.1 and 10 times shorter, respectively

Methyl Siloxanes in Environmental Matrices around a Siloxane Production Facility, and Their Distribution and Elimination in Plasma of Exposed Population

In this study, we systematically investigated methyl siloxanes (D4–D6, L3–L16) exposure to workers from and residents living near a siloxanes manufacturing facility by measuring their concentrations in both environmental matrices (air, dust/soil, <i>n</i> = 62) and human plasma samples (<i>n</i> = 201). For the seventeen target compounds, the average concentrations in indoor matrixes from six workshops of the facility ranged from 0.6 μg/m³ to 2.7 mg/m³ in air samples and from 0.36 μg/g to 1.16 mg/g in dust samples, which were 3–5 orders of magnitudes higher than those levels at the reference zone. In plasma samples from the current workers in six workshops and residents living near the facility, the average concentrations of methyl siloxanes were 5.61–451 and 4.56–13.5 ng/g, respectively, which were 1–2 magnitudes higher than those in the reference group. Plasma methyl siloxanes concentrations of people from different workshops were positively correlated with their exposure levels, indicating that high occupational exposure in siloxane production process elevated human plasma concentrations. However, there was no significant correlation between human plasma concentrations with their duration of occupation. These methyl siloxanes were eliminated from human plasma with half-lives ranging from 2.34 to 9.64 days, which increased with the increasing number of Si–O bonds for most analogues

Human Exposure and Elimination Kinetics of Chlorinated Polyfluoroalkyl Ether Sulfonic Acids (Cl-PFESAs)

The incomplete mass-balance of organic fluorine in human serum indicates the existence of unknown per- and polyfluoroalkyl substances (PFASs) with persistent and bioaccumulative properties. Here we characterized human exposure and elimination kinetics of chlorinated polyfluoroalkyl ether sulfonic acids (Cl-PFESAs) in metal plating workers (<i>n</i> = 19), high fish consumers (<i>n</i> = 45), and background controls (<i>n</i> = 8). Cl-PFESAs were detected in >98% of the sampled individuals with serum concentrations ranging <0.019–5040 ng/mL. Statistically higher median serum levels were observed in high fish consumers (93.7 ng/mL) and metal plating workers (51.5 ng/mL) compared to the background control group (4.78 ng/mL) (Kruskal–Wallis rank sum test, <i>p</i> < 0.01). Cl-PFESAs could account for 0.269 to 93.3% of ∑PFASs in human serum indicating that this compound class may explain a substantial fraction of previously unidentified organic fluorine in the Chinese population. Estimated half-lives for renal clearance (median 280 years; range 7.1–4230 years) and total elimination (median 15.3 years; range 10.1–56.4 years) for the eight carbon Cl-PFESA suggest that this is the most biopersistent PFAS in humans reported to date. The apparent ubiquitous distribution and slow elimination kinetics in humans underscore the need for more research and regulatory actions on Cl-PFESAs and PFAS alternatives with similar chemical structures

Variations of the Level, Profile, and Distribution of PFAS around POSF Manufacturing Facilities in China: An Overlooked Source of PFCA

The occurrence of per- and polyfluoroalkyl substances (PFAS) was investigated inside two manufacturing facilities in China. Levels, profiles, and spatial distribution of the detected PFAS were found to be distinctly site-specific and influenced by the area’s historic function, production structure of the plant, downpour-induced accidental pollution, and variations in the adsorption and transport of compounds. Very high concentrations of PFAS [mainly C4 and C8 perfluoroalkyl sulfonic acids (PFSAs)] were found in topsoil and groundwater from both plants, with the highest values of 4.89 × 106 μg/kg dw and 1.10 × 104 μg/L, respectively. Elevated concentrations of perfluoroalkyl carboxylic acids (PFCAs) in this study were attributed to their unintentional formation during the electrochemical fluorination process, which might be an overlooked source of PFCA. PFAS generally showed decreasing trends from shallow layers to the bottom of the soil core and demonstrated some downward migrations at different soil depths with time, and C4–C8 PFAS presented a deeper seepage than their long-chain homologues. Total organic carbon appeared to be more important for PFAS sorption to the topsoil than to the soil core. Workers were at potential risk of exposure to perfluorooctanesulfonic acid via soil at production and storage related sites. This study provides a critical reference for the systematic control of PFAS pollution around manufacturing facilities and a proof for an overlooked source of PFCA

Tissue Distribution and Whole Body Burden of the Chlorinated Polyfluoroalkyl Ether Sulfonic Acid F‑53B in Crucian Carp (<i>Carassius carassius</i>): Evidence for a Highly Bioaccumulative Contaminant of Emerging Concern

Following the global actions to phase out perfluoroctanesulfonic acid (PFOS) a large number of alternative per- and polyfluoroalkyl substances, with poorly defined hazard properties, are being used in increasing quantities. Here, we report on the first detection of the chlorinated polyfluoroalkyl ether sulfonic acid F-53B in biological samples and determine the tissue distribution and whole body bioaccumulation factors (BAF_whole body) in crucian carp (<i>Carassius carassius</i>). Analysis of fish samples from Xiaoqing River (XR) and Tangxun Lake (TL) demonstrated a similar level of F-53B contamination with median concentrations in blood of 41.9 and 20.9 ng/g, respectively. Tissue/blood ratios showed that distribution of F-53B primarily occurs to the kidney (TL: 0.48, XR: 0.54), gonad (TL: 0.36, XR: 0.54), liver (TL: 0.38, XR: 0.53), and heart (TL: 0.47, XR: 0.47). Median Log BAF_whole body values for F-53B (XR: 4.124, TL: 4.322) exceeded regulatory bioaccumulation criterion and were significantly higher than those of PFOS in the same data sets (XR: 3.430, TL: 3.279). On the basis of its apparent omnipresence and strong bioaccumulation propensity, it is hypothesized that F-53B could explain a significant fraction of previously unidentified organofluorine in biological samples from China, and regulatory actions for this compound are encouraged

Genotype and allele frequencies of thirty-two SNPs in the ARHGAP18 gene of schizophrenia patients and controls.

<p>Genotype and allele frequencies of thirty-two SNPs in the ARHGAP18 gene of schizophrenia patients and controls.</p

SNP association analysis for ARHGAP18 in stage 2 and combined sample set.

<p>SNP association analysis for ARHGAP18 in stage 2 and combined sample set.</p