Institutional Repository of Research Center for Eco-Environmental Sciences, CAS
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Molecular Mechanism of Dioxin Formation from Chlorophenol based on Electron Paramagnetic Resonance Spectroscopy
No full textFew studies have investigated the free radical intermediates involved in the formation of polychlorinated dibenzo-p-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, ortho-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-p-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
Oral Exposure to Silver Nanoparticles or Silver Ions May Aggravate Fatty Liver Disease in Overweight Mice
No full textAs the applications and environmental release of silver ions and nanoparticles are increasing, increasing human exposure to these pollutants has become an emerging health concern. The impeding effects of such pollutants on susceptible populations are severely under-studied. Here, we demonstrate that silver nanoparticles (Ag NPs), at a dose that causes no general toxicity in normal mice, promotes the progression of fatty liver disease from steatosis to steatohepatitis only in overweight mice. Exposure to Ag+ ions induces the same effects in overweight mice. Ag NPs rather than Ag ions cause this disease progression based on our findings that Ag+ ions are partly reduced to Ag NPs in fatty livers, and the toxic effect is correlated with the liver dose of Ag NPs, not Ag+ ions. Furthermore, the Ag NP-induced pro-inflammatory activation of Kupffer cells in the liver, enhancement of hepatic inflammation, and suppression of fatty acid oxidation are identified as key factors in the underlying mechanisms
Preparation and Structural Analysis of Nano-Silver Loaded Poly(styrene-co-acrylic acid) Core-Shell Nanospheres with Defined Shape and Composition
No full textA systematic study for the preparation and structural analysis of poly(styrene-co-acrylic acid) composite nanospheres (PSA) and silver nanoparticles loaded poly(styrene-co-acrylic acid) composite nanospheres (nAg@PSA) is reported. Poly(styrene-co-acrylic acid) nanospheres were synthesized by soap-free emulsion polymerization of styrene (St) and acrylic acid (AA) in water. Ag nanoparticles (Ag-NPs) were well-dispersed on the surfaces of poly(styrene-co-acrylic acid) composite nanospheres by in situ chemical reduction of AgNO3 using NaBH4 as a reducing agent in water. The particle size of PSA nanospheres was uniform. The surfaces of PSA nanospheres were distributed by highly uniform half-sphere arrays. Those half-sphere protruded more with the increase of the feeding amount of AA or the feed ratios of AA and St. The carboxyl groups content of nanospheres was directly proportional to the nanosphere surface area. This relationship and X-ray photoelectron spectroscopy and transmission electron microscopy images of the PSA nanospheres indicate that the acrylic acid was mainly distributed on the surface of the polystyrene spheres with unnegligible thickness. The number of Ag-NPs depends on immobilized carboxyl groups on the surface of PSA, according to thermogravimetry, ultraviolet-visible, X-ray diffraction and transmission electron microscopy results
Profiles, sources and potential exposures of parent, chlorinated and brominated polycyclic aromatic hydrocarbons in haze associated atmosphere
No full textProfiles, sources and potential exposures of chlorinated and brominated polycyclic aromatic hydrocarbons (CIPAHs and BrPAHs) in haze associated atmosphere remain unclear. Haze events happened frequently during heating period in Beijing provided a typical urban context to investigate the concentrations, profiles, sources and potential exposures of CIPAHs, BrPAHs and their non-halogenated parent compounds (PAHs) in air samples. Average concentrations of PAHs, CIPAHs and BrPAHs during heating periods (with more frequent haze events) were about 3-9 times higher than during non-heating periods. Concentrations of particulate matter (PM)-associated CIPAHs and BrPAHs were higher in heating period than in non-heating period, while for gas -associated CIPAHs and BrPAHs, this distinction was not significant. Congener patterns and congener profiles indicated that with increasing coal combustion during the heating period, concentrations of PAHs and CIPAHs in air were elevated in comparison to the non-heating period. Inhalation of PM-associated PAHs, CIPAHs and BrPAHs accounted for higher exposure than inhalation of gas phase and dermal contact of both gas phase and particulate phase. In this study we found that the particulate phase is the dominant exposure pathway of atmospheric PAHs, CIPAHs and BrPAHs during haze days, which is different from previous studies. (C) 2017 Elsevier B.V. All rights reserved
The receptor genes PfBMPR1B and PfBAMBI are involved in regulating shell biomineralization in the pearl oyster Pinctada fucata
No full textMounting evidence suggests that TGF beta/BMP signaling pathway is most likely involved in shell biomineralization in molluscs, but the function of pathway receptors is poorly studied. Here, we cloned and identified two homologous BMP receptor genes, PfBMPR1B and PfBAMBI, from the pearl oyster Pinctada fucata. Real-time quantitative PCR and in situ hybridization revealed that these genes were expressed in mantle edge and pallial, specifically located at the outer epithelia. Knockdown of PfBMPR1B by RNA interference ( RNAi) significantly decreased the expression levels of matrix protein ( MP) genes and induced the abnormal ultrastructure of prismatic and nacreous layers. Conversely, knockdown of PfBAMBI significantly increased the expression levels of a portion of MP genes and induced the overgrowth of nacreous layer crystals. In the RNAi and shell notching experiments, MP gene expressions were competitively regulated by PfBMPR1B and PfBAMBI. In addition, the receptor inhibitor LDN193189 reduced the expression levels of MP genes in mantle primary cells and larvae, and induced abnormal D-shaped shell formation during larval development. Collectively, these results clearly show that PfBMPR1B and PfBAMBI are involved in regulating shell biomineralization in P. fucata. Our study therefore provides the direct evidence that BMP receptors participate in mollusc biomineralization
Thermochemical emission and transformation of chlorinated paraffins in inert and oxidizing atmospheres
No full textChlorinated paraffins (CPs) generally function as flame retardants and plasticizers in various materials. They are most likely to be processed by thermal processes during the entire life cycle. However, data on the formation and emission of CPs during thermal processes are still not fully understood. In this study, we simulated industrial thermal processes to investigate the emission of medium-chain chlorinated paraffins (MCCPs) and short-chain chlorinated paraffins (SCCPs) using commercial CP52 as the feedstock. We found that CP52 decomposed very easily at 210-320 degrees C. The decomposition of CPs generated large quantities of MCCPs and SCCPs. These remained in the residue at low temperature (similar to 200 degrees C) and were gradually released into the gas phase at higher temperatures. MCCPs and SCCPs were not detected in either the residue or the gas phase when the temperature exceeded 400 degrees C. However, considerable concentrations of aromatic and chlorinated aromatic hydrocarbons (Cl-PAHs) were identified in the gas phase, and they were formed as the amount of SCCPs and MCCPs decreased. Cl-PAHs were dominated by low-chlorinated chlorobenzenes, polychlorinated biphenyls, and polychlorinated naphthalenes. Oxygen promoted the release and decomposition of SCCPs in the gas phase. The results of the present study revealed the release of MCCPs and SCCPs and their synergistic emission with CI-PAHs when CPs were subjected to heat. This work may also provide data for developing multiple techniques to control the emission of CPs and Cl-PAHs. (C) 2017 Elsevier Ltd. All rights reserved
TiO2 particles in seafood and surimi products: Attention should be paid to their exposure and uptake through foods
No full textThe sustainable development of nanotechnology requires a thorough understanding of the life cycle of synthesized nanomaterials, including environmental release, deposition, exposure, and potential health risks. Titanium dioxide (TiO2) materials containing nanosized TiO2 (nTiO(2)) are commonly used as food additives. Thus, dietary intake through foods is the most important route for the exposure of TiO2 materials. Given the toxic effects of nTiO(2) on the gastrointestinal tract and other tissues, it is imperative to investigate their sources and concentrations in popular foods. Therefore, we conducted a survey on TiO2 particles in white-colored seafood and surimi products in Beijing. Our data indicated that the total Ti levels reached 6-12 mu g/g (dry weight) in some white-colored seafood products, such as squid and cuttlefish, whereas relatively low concentrations were observed in jellyfish at approximately 1-3 mu g/g (dry weight). For the locally favorite surimi-based food products in the market, the Ti concentrations ranged from 2 to 81 mu g/g (dry weight). The exposure assessment showed that the average daily intake of TiO2 particles through foods varied from 0.02 to 3.09 mu g TiO2/Kg(bw)/day, reflected by the Ti concentrations in this study, and that young people of age 20-30 showed the highest exposure level. Together, these results show relatively high concentrations of TiO2 particles in some seafood and surimi products available in the market, and our findings therefore call for attention on TiO2 particle exposure and uptake through daily foods. (C) 2017 Elsevier Ltd. All rights reserved
From harmful Microcystis blooms to multi-functional core-double-shell microsphere bio-hydrochar materials
No full textHarmful algal blooms (HABs) induced by eutrophication is becoming a serious global environmental problem affecting public health and aquatic ecological sustainability. A novel strategy for the utilization of biomass from HABs was developed by converting the algae cells into hollow mesoporous bio-hydrochar microspheres via hydrothermal carbonization method. The hollow microspheres were used as microreactors and carriers for constructing CaO2 core-mesoporous shell-CaO2 shell microspheres (OCRMs). The CaO2 shells could quickly increase dissolved oxygen to extremely anaerobic water in the initial 40 min until the CaO2 shells were consumed. The mesoporous shells continued to act as regulators restricting the release of oxygen from CaO2 cores. The oxygen-release time using OCRMs was 7 times longer than when directly using CaO2. More interestingly, OCRMs presented a high phosphate removal efficiency (95.6%) and prevented the pH of the solution from rising to high levels in comparison with directly adding CaO2 due to the OH- controlled-release effect of OCRMs. The distinct core-double-shell micro/nanostructure endowed the OCRMs with triple functions for oxygen controlled-release, phosphorus removal and less impact on water pH. The study is to explore the possibility to prepare smarter bio-hydrochar materials by utilizing algal blooms
Adsorption Mechanisms of Dodecylbenzene Sulfonic Acid by Corn Straw and Poplar Leaf Biochars
No full textBiochar is an eco-friendly, renewable, and cost-effective material that can be used as an adsorbent for the remediation of contaminated environments. In this paper, two types of biochar were prepared through corn straw and poplar leaf pyrolysis at 300 degrees C and 700 degrees C (C300, C700, P300, P700). Brunaer-Emmett-Teller N-2 surface area, scanning electron microscope, elemental analysis, and infrared spectra were used to characterize their structures. These biochars were then used as adsorbents for the adsorption of dodecylbenzene sulfonic acid (DBSA). The microscopic adsorption mechanisms were studied by using infrared spectra, C-13-nuclear magnetic resonance spectra, and electron spin resonance spectra. The surface area and pore volume of C700 (375.89 m(2)/g and 0.2302 cm(3)/g) were the highest among all samples. Elemental analysis results showed that corn straw biochars had a higher aromaticity and carbon to nitrogen (C/N) ratio than the poplar leaf biochars. High temperature caused the increase of carbon content and the decrease of oxygen content, which also gave the biochars a higher adsorption rate. Pseudo-second order kinetic provided a better fit with the experimental data. Adsorption isotherm experiments showed that the adsorption isotherm of C300 fit the linear model. For other biochars, the adsorption isotherms fitted Langmuir model. Biochars with high temperatures exhibited enhanced adsorption capacity compared with ones at low temperatures. The q(max) values of biochars to DBSA followed the order of P700 > C700 > P300. The adsorption mechanisms were complex, including partition, anion exchange, the formation of H bonds, covalent bonds, and charge transfer. The adsorption by covalent bonding might be the key mechanism determining the adsorption capacity of P700
Accelerated degradation of iopamidol in iron activated persulfate systems: Roles of complexing agents
No full textAs an environment-friendly activator, iron ions (Fe(II) and Fe(III)) have been extensively studied in homogeneous activation of persulfate (PS) to remove organic pollutants from water. However, the slow reduction of Fe(III) to Fe(II) and the subsequent low activation efficiency limit the wide applications of PS/Fe(II) or PS/Fe(III). In this study, the roles of four complexing agents, including gallic acid (GA), ethylene diamine tetraacetic acid, (S,S)-ethylenediamine-N,N'-disuccinic acid trisodium salt and citric acid in the activation of PS/Fe(III) were comparatively investigated with iopamidol (IPM) used as a model organic pollutant. Results indicate that GA was the most effective with an increase in the observed pseudo first-order rate constant (k(obs)) by 9.2 folds for IPM degradation by PS/Fe(III). Through radical scavenger (ethanol and tert-butanol) tests and electron paramagnetic resonance analysis, HO center dot and SO4 center dot- were identified to be responsible for the accelerated degradation of IPM, and Ha played a more important role. Intrinsically, the promoted Fe(III) reduction and PS decomposition accelerated the degradation of IPM. The transformation by-products of IPM in the PS/Fe(III)/GA system were identified and potential degradation pathways were proposed. Besides, the accelerated degradation of other three organic pollutants (methyl orange, congo red, and diclofenac) further demonstrated the applicability of the PS/Fe(III)/GA system to water treatment. (C) 2017 Elsevier B.V. All rights reserved