Active Intra-Abdominal Drainage Following Abdominal Digestive System Surgery: A Meta-Analysis and Systematic Review

Our objective is to compare the early outcomes associated with passive (gravity) drainage (PG) and active drainage (AD) after surgery. Studies published until April 28, 2022 were retrieved from the PubMed, Cochrane Central Register of Controlled Trials (CENTRAL), EMBASE, Web of Science databases. Nine studies with 14,169 patients were identified. Two groups had the same intra-abdominal infection rate (RR: 0.55; P = 0.13); In subgroup analysis of pancreaticoduodenectomy, active drainage had no significant effect on postoperative pancreatic fistula (POPF) rate (RR: 1.21; P = 0.26) and clinically relevant POPF (CR-POPF) (RR: 1.05; P = 0.72); Active drainage was not associated with lower percutaneous drainage rate (RR: 1.00; P = 0.96), incidence of sepsis (RR: 1.00; P = 0.99) and overall morbidity (RR: 1.02; P = 0.73). Both groups had the same POPF rate (RR: 1.20; P = 0.18) and CR-POPF rate (RR: 1.20; P = 0.18) after distal pancreatectomy. There was no difference between two groups on the day of drain removal after pancreaticoduodenectomy (Mean difference: −0.16; P = 0.81) and liver surgery (Mean difference: 0.03; P = 0.99). Active drainage is not superior to passive drainage and both drainage methods can be considered.</p

Identifying Iron Foundries as a New Source of Unintentional Polychlorinated Naphthalenes and Characterizing Their Emission Profiles

Iron foundries have been identified as dioxin sources in previous field investigations. Similar formation mechanisms between dioxins and unintentional polychlorinated naphthalenes (PCNs) have led us to speculate that iron foundries are also potential PCN sources. In this study, PCNs in stack gas and fly ash samples representing atmospheric and residue emissions from 13 typical iron foundry plants were analyzed. The average emission factor of ∑_2–8PCNs to residue was calculated to be 61 μg t^–1, with a range of 10–107 μg t^–1. The emission factors of ∑_2–8PCNs to air in two case plants were 267 and 1472 μg t^–1. The derived emission factors might be useful for estimating annual emissions and understanding the contribution of PCNs from iron foundries. The possible formation mechanisms of PCNs, based on the PCN profiles, are discussed. Successive reductions in the abundance of homologues were observed to occur with the increase in chlorine substituted numbers. Abundances of congeners containing more β-position chlorines in the naphthalene skeleton were much higher than those of congeners containing more α-position chlorines for penta-, hexa-, and hepta- homologues, which suggests that the β-positions are favored for chlorination. Potential chlorination pathways from tetra- to octa- homologues are proposed

A Novel Method for Profiling and Quantifying Short- and Medium-Chain Chlorinated Paraffins in Environmental Samples Using Comprehensive Two-Dimensional Gas Chromatography–Electron Capture Negative Ionization High-Resolution Time-of-Flight Mass Spectrometry

Chlorinated paraffins (CPs) are complex technical mixtures containing thousands of isomers. Analyzing CPs in environmental matrices is extremely challenging. CPs have broad, unresolved profiles when analyzed by one-dimensional gas chromatography (GC). Comprehensive two-dimensional GC (GC×GC) can separate CPs with a high degree of orthogonality. A novel method for simultaneously profiling and quantifying short- and medium-chain CPs, using GC×GC coupled with electron capture negative ionization high-resolution time-of-flight mass spectrometry, was developed. The method allowed 48 CP formula congener groups to be analyzed highly selectively in one injection through accurate mass measurements of the [M – Cl]⁻ ions in full scan mode. The correlation coefficients (<i>R</i>²) for the linear calibration curves for different chlorine contents were 0.982 for short-chain CPs and 0.945 for medium-chain CPs. The method was successfully used to determine CPs in sediment and fish samples. By using this method, with enhanced chromatographic separation and high mass resolution, interferences between CP congeners and other organohalogen compounds, such as toxaphene, are minimized. New compounds, with the formulas C₉H₁₄Cl₆ and C₉H₁₃Cl₇, were found in sediment and biological samples for the first time. The method was shown to be a powerful tool for the analysis of CPs in environmental samples

Molecular Mechanism of Dioxin Formation from Chlorophenol based on Electron Paramagnetic Resonance Spectroscopy

Few studies have investigated the free radical intermediates involved in the formation of polychlorinated dibenzo-<i>p</i>-dioxins and dibenzofurans (PCDD/Fs) from chlorophenol. This study clarified the reaction pathways during thermochemical formation of PCDDs from 2,3,6-trichlorophenol (TCP) over a Cu­(II)­O/silica matrix, which was used to simulate fly ash, at 298–523 K. The reaction was studied using electron paramagnetic resonance (EPR) spectroscopy and theoretical calculations. In situ EPR indicated the TCP radical (TCPR) formed by hydrogen abstraction of TCP. Five elementary processes including dimerization of TCPR, <i>ortho</i>-chloride abstraction, Smiles rearrangement, ring closure, and intra-annular elimination of Cl were proposed to occur during formation of PCDDs. The proposed mechanism was further confirmed by the detection of PCDD products from thermochemical experiments in a tube furnace. Several dominant congeners, including 1,2,6,9-tetrachlorodibenzo-<i>p</i>-dioxin (TeCDD), 1,2,6,7-TeCDD, 1,2,8,9-TeCDD, and 1,4,6,9-TeCDD were detected by gas chromatography/quadrupole time-of-flight mass spectrometry, and further confirmed by gas chromatography/high resolution mass spectrometry. The detected PCDD products agree with the proposed PCDD formation mechanism. Relatively high temperatures were found to lead to dechlorination of TCPR to form phenoxy radicals in addition to PCDD/Fs. These radicals will be attached to particles, which will increase their lifetimes. These reactions were further verified by molecular orbital theory calculations. The discovery of persistent phenoxy radicals is of environmental significance because of their potential toxicity. The details of this mechanism could be used for controlling PCDD/F formation during industrial thermal processes

Long-Term Temporal Trends of Polychlorinated Biphenyls and Their Controlling Sources in China

Polychlorinated biphenyls (PCBs) are industrial organic contaminants identified as persistent, bioaccumulative, toxic (PBT), and subject to long-range transport (LRT) with global scale significance. This study focuses on a reconstruction and prediction for China of long-term emission trends of intentionally and unintentionally produced (UP) ∑₇PCBs (UP-PCBs, from the manufacture of steel, cement and sinter iron) and their re-emissions from secondary sources (e.g., soils and vegetation) using a dynamic fate model (BETR-Global). Contemporary emission estimates combined with predictions from the multimedia fate model suggest that primary sources still dominate, although unintentional sources are predicted to become a main contributor from 2035 for PCB-28. Imported e-waste is predicted to play an increasing role until 2020–2030 on a national scale due to the decline of intentionally produced (IP) emissions. Hypothetical emission scenarios suggest that China could become a potential source to neighboring regions with a net output of ∼0.4 t year^–1 by around 2050. However, future emission scenarios and hence model results will be dictated by the efficiency of control measures

Metal-Catalyzed Formation of Organic Pollutants Intermediated by Organic Free Radicals

Metal compounds play important roles in the formation of organic pollutants during thermal-related processes. However, the metal-catalyzed predominant organic pollutants have not previously been characterized nor have any detailed catalytic mechanisms been clarified. Here, we preciously distinguished the multiple organic free radical intermediates on metal catalyst surfaces during the organic pollutant formation through laboratory and theoretical studies. Differences between the organic free radical intermediate species, concentrations, and formation mechanisms under the catalysis of different metal compounds were investigated. The results were verified mutually with the differed characteristics of organic pollutant products. CuO predominantly catalyzed the formation of highly chlorinated phenoxy radical intermediates and dioxins. High proportions of semiquinone radicals and oxygen-containing derivatives were found on ZnO surfaces. Differently, methyl-substituted phenoxy radicals and long-chain products formed on Al2O3 surfaces. The results will be instructive for the target emission control of priority organic pollutants during thermal-related processes rich in different metal compounds

Secondary Copper Smelters as Sources of Chlorinated and Brominated Polycyclic Aromatic Hydrocarbons

The generation of and extent to which chlorinated and brominated polycyclic aromatic hydrocarbons (Cl/Br-PAHs) are formed and released from secondary copper smelters remain unknown. This field study, to our knowledge, is the first to identify secondary copper smelters as new sources of Cl/Br-PAHs. Mass concentrations of ∑₁₉Cl-PAHs and ∑₁₉Br-PAHs ranged from 5.8 to 271 ng Nm^–3 and 0.59 to 52.4 ng Nm^–3, respectively. A comparison of Cl/Br-PAH concentrations in stack gas and fly ash from secondary copper smelters indicated that the use of scrap copper as raw material or the addition of coal or heavy oil as reductant may contribute to the elevated formation and emission of Cl/Br-PAHs. Congener profiles of Cl/Br-PAHs in stack gas and fly ash from secondary copper smelters were different with those of Cl/Br-PAHs from waste incinerations and other previously reported sources, thus could be used as possible fingerprints and source apportionments of environmental Cl/Br-PAHs. Atmospheric levels of Cl/Br-PAHs in the workplace or smelter surroundings were determined and potential exposures were assessed. Although chlorination of PAHs was previously recognized as an important formation pathway of Cl/Br-PAHs, it was not verified to be the major formation pathway for Cl/Br-PAHs from secondary copper smelters in this study

Pivotal Roles of Metal Oxides in the Formation of Environmentally Persistent Free Radicals

Environmentally persistent free radicals (EPFRs) are emerging pollutants that can adversely affect human health. Although the pivotal roles of metal oxides in EPFR formation have been identified, few studies have investigated the influence of the metal oxide species, size, or concentration on the formation of EPFRs. In this study, EPFR formation from a polyaromatic hydrocarbon with chlorine and hydroxyl substituents (2,4-dichloro-1-naphthol) was investigated using electron paramagnetic resonance spectroscopy. The effect of the metal oxide on the EPFR species and its lifetime and yield were evaluated. The spectra obtained with catalysis by CuO, Al₂O₃, ZnO, and NiO were obviously different, indicating that different EPFRs formed. The abilities of the metal oxides to promote EPFR formation were in the order Al₂O₃ > ZnO > CuO > NiO, which were in accordance with the oxidizing strengths of the metal cations. A decay study showed that the generated radicals were persistent, with a maximum 1/<i>e</i> lifetime of 108 days on the surface of Al₂O₃. The radical yields were dependent on the concentration and particle size of the metal oxide. Metal oxide nanoparticles increased the EPFR concentrations more than micrometer-sized particles

Thermochemical Formation of Polybrominated Dibenzo‑<i>p</i>‑Dioxins and Dibenzofurans Mediated by Secondary Copper Smelter Fly Ash, and Implications for Emission Reduction

Heterogeneous reactions mediated by fly ash are important to polychlorinated dibenzo-<i>p</i>-dioxin and dibenzofuran (PCDD/Fs) formation. However, the formation of polybrominated dibenzo-<i>p</i>-dioxins and dibenzofurans (PBDD/Fs) through heterogeneous reactions is not yet well understood. Experiments were performed to investigate the thermochemical formation of PBDD/Fs at 150–450 °C through heterogeneous reactions on fly ash from a secondary copper smelter. The maximum PBDD/F concentration was 325 times higher than the initial PBDD/F concentration in the fly ash. The PBDD/F concentration after the experiment at 150 °C was five times higher than the initial concentration. PBDD/Fs have not previously been found to form at such a low temperature. Secondary-copper-smelter fly ash clearly promoted PBDD/F formation, and this conclusion was supported by the low activation energies that were found in Arrhenius’s law calculations. Thermochemical formation of PBDD/Fs mediated by fly ash deposited in industrial facilities could explain “memory effects” that have been found for PCDD/Fs and similar compounds released from industrial facilities. Abundant polybrominated diphenyl ethers (PBDEs) that were formed through fly ash-mediated reactions could be important precursors for PBDD/Fs also formed through fly ash-mediated reactions. The amounts of PBDEs that formed through fly ash-mediated reactions suggested that secondary copper smelters could be important sources of reformed PBDEs

Thermal Oxidation Degradation of 2,2′,4,4′-Tetrabromodiphenyl Ether over Li_αTiO_<i>x</i> Micro/Nanostructures with Dozens of Oxidative Product Analyses and Reaction Mechanisms

Flowerlike Li_αTiO_<i>x</i> micro/nanostructures were successfully synthesized to degrade 2,2′,4,4′-tetrabromodiphenyl ether (BDE-47) at 250–350 °C. The pseudo-first-order kinetics rate constant of the reaction at 300 °C was in the range of 0.034–0.055 min^–1. The activation energy was as low as 39.9–48.1 kJ/mol. The excellent performance attained over Li_αTiO_<i>x</i> was attributed to Li dopant having the electron-donating effect, which enhanced the oxygen species mobility. The oxidative reaction was believed to be the dominant degradation pathway following the Mars–van Krevelen mechanism, being accompanied by the weak hydrodebromination occurrence generating the trace mono- to tri-BDEs. More than 70 types of oxidation products containing diphenyl ether backbone, single-benzene rings, and ring-opened products were detected by GC-MS with derivatization, ESI-FT-ICR-MS, and ion chromatography. An increase in the number of ring-cracked oxidative products under prolonged reaction was observed by ESI-FT-ICR-MS analysis according to the van Krevelen diagram. In the oxidative reaction, a series of oxidative products, such as OH-tri-BDEs and OH-tetra-BDEs, first formed via the nucleophilic O^2– attack and subsequently transformed into dibromophenol, tribromophenol, and benzenedicarboxylic and benzoic acids, etc. They could be further attacked by electrophilic O₂^– and O^– and completely cracked to small molecules such as formic, acetic, propionic, and butyric acids