Organic chemicals in the aquatic ecosystem may inhibit algae growth and subsequently lead to the decline of primary productivity. Growth inhibition tests are required for ecotoxicological assessments for regulatory purposes. In silico study is playing an important role in replacing or reducing animal tests and decreasing experimental expense due to its efficiency. In this work, a series of theoretical models was developed for predicting algal growth inhibition (log EC50) after 72 h exposure to diverse chemicals. In total 348 organic compounds were classified into five modes of toxic action using the Verhaar Scheme. Each model was established by using molecular descriptors that characterize electronic and structural properties. The external validation and leave-one-out cross validation proved the statistical robustness of the derived models. Thus they can be used to predict log EC50 values of chemicals that lack authorized algal growth inhibition values (72 h). This work systematically studied algal growth inhibition according to toxic modes and the developed model suite covers all five toxic modes. The outcome of this research will promote toxic mechanism analysis and be made applicable to structural diversity. (C) 2017 Elsevier Ltd. All rights reserved.
Simultaneous removal process of SO2 and NO from flue gas using vacuum ultraviolet light (VUV)/heat/peroxymonosulfate (PMS) in a VUV spraying reactor was proposed. The key influencing factors, active species, reaction products and mechanism of SO2 and NO simultaneous removal were investigated. The results show that vacuum ultraviolet light (185 nm) achieves the highest NO removal efficiency and yield of SO4-center dot and center dot OH under the same test conditions. NO removal is, enhanced at higher PMS concentration, light intensity and oxygen concentration, and is inhibited at higher NO concentration, SO2 concentration and solution pH. Solution temperature has a double impact on NO removal. CO2 concentration has no obvious effect on NO removal. SO4-center dot and center dot OH produced from VUV-activation of PMS play a leading role in NO removal. O-3 and center dot O produced from VUV-activation of O-2 also play an important role in NO removal. SO2 achieves complete removal under all experimental conditions due to its very high solubility in water and good reactivity. The highest simultaneous removal efficiency of SO2 and NO reaches 100% and 91.3%, respectively. (C) 2017 Elsevier Ltd. All rights reserved.
This study aimed at investigating the removal efficiencies of perfluorooctanoate (PFOA), perfluorooctane sulfonate (PFOS) and bisphenol A (BPA) of two major sewage treatment works in Hong Kong: Stonecutters Island STW (SCISTW) which adopts chemically enhanced primary treatment (CEPT) process and Sha Tin STW (STSTW) which employs biological treatment. Liquid portion (LP) and particulate matter (PM) of liquid sewage samples and sludge samples were collected and followed by liquid chromatograph system. It was found that BPA (44.6 +/- 35.1%) generally achieved higher THE than the two other chemicals (PFOS (-18.8 +/- 34.8%) and PFOA (-104 +/- 86.8%)) in STSTW (p < 0.05). Most of the PFOA, PFOS and BPA was discharged through final effluent (PFOA: 95.6 +/- 1.00% and 94.5 +/- 3.13%; PFOS: 77.7 +/- 1.48% and 72.6 +/- 6.07%; BPA: 99.2 +/- 0.950% and 92.8 +/- 7.25%, respectively) rather than stored in the sludge/cake (PFOA: 4.45 +/- 1.00% and 5.47 +/- 3.13%, PFOS: 22.3 +/- 1.48% and 27.4 +/- 6.07%, BPA: 0.844 +/- 0.950% and 7.20 +/- 7.25%, respectively). After the sewage purification process, the two STW released considerable amounts of PFOA, PFOS and BPA in the final effluent (PFOA: 0.638 +/- 0.227 kg/year; PFOS: 0.409 +/- 0.126 kg/year; BPA: 10.4 +/- 3.83 kg/year in STSTW; PFOA: 3.08 +/- 1.415 kg/year; PFOS: 2.13 +/- 0.452 kg/year; BPA: 714 +/- 768 kg/year in SCISTW) and in the sludge (PFOA: 0.0360 +/- 0.0250 kg/year; PFOS: 0.149 +/- 0.00100 kg/year; BPA: 1.09 +/- 1.47 kg/year in STSTW; PFOA: 0.139 +/- 0.0670 kg/year; PFOS: 0.606 +/- 0.0780 kg/year; BPA: 3.05 +/- 3.95 kg/year in SCISTW). This study may help to provide crucial information for further development of municipal sewage system in treating synthetic emerging chemicals. (C) 2017 Elsevier Ltd. All rights reserved.
Soil aging will influence the chemical speciation of pesticides, thus affecting the uptake route to be bioavailable to the organism. So far, studies on the possible effects of the uptake route on the distribution and elimination of pesticides in the organism that also considers effects of aging are limited. In our study, Eisenia fetida was exposed to 4.5 mg kg(-1) lindane aging for 0, 30 and 180 d, and the accumulation, distribution and elimination of lindane in the earthworms were analyzed. The results showed that the 6 h Tenax-extracted fraction exhibited a good linear correlation with the lindane accumulated in the earthworms. With aging time increasing, the bioaccumulation of lindane decreased and the accumulative balance was more easily reached in the earthworms. Lindane distributions were found in the whole earthworm and the proportions of lindane content at sub-organism level and the mass distribution of each fraction were similar for 0 d and 180 d aged groups. The foregut accumulated the highest content of lindane (20%) relative to its low mass distribution proportion (10%). The elimination rate of lindane in the earthworms decreased with aging time extending. Our conclusion was that the 6 h Tenax extraction could be used to assess the bioavailability of aging lindane. Although soil aging decreased the bioavailability of lindane, the soil-bound lindane entered the earthworm through dietary route would take longer to depurate from the organisms than free lindane, which implied the potential ecological risk of bound pesticide residues. (C) 2017 Elsevier Ltd. All rights reserved.
The present study investigated the impacts of water matrix constituents (CO32-, HCO3-, Cl-, Br-, PO43-, HPO42-, H2PO4-, NO3-, SO42- and natural organic matters (NOM) on the oxidation of a mixture of benzene, toluene, ethylbenzene, and xylenes (BTEX) by thermally activated persulfate (PS). In the absence of matrix constituents, the BTEX oxidation rates decreased in the following order: xylenes > toluene approximate to ethylbenzene > benzene. HCO3-/CO32- and NOM inhibited the BTEX oxidation and the inhibiting effects became more pronounced as the HCO3-/CO32-/NOM concentration increased. SO42-, NO3-, PO43- and H2PO4- did not affect the BTEX oxidation while HPO42- slightly inhibited the reaction. The impacts of Cl- and Br- were complex. Cl- inhibited the benzene oxidation while 100 mM and 500 mM of Cl- promoted the oxidation of m-xylene and p-xylene. Br- completely suppressed the benzene oxidation while 500 mM of Br- strongly promoted the oxidation of xylenes. Detailed explanations on the influence of each matrix constituent were discussed. In addition, various halogenated degradation byproducts were detected in the treatments containing Cl- and Br-. Overall, this study indicates that some matrix constituents such as NOM, HCO3-, CO32-, H2PO4-, Cl- and Br- may reduce the BTEX removal efficiency of sulfate radical-based advanced oxidation process (SR-AOP) and the presence of Cl- and Br- may even lead to the formation of toxic halogenated byproducts. (C) 2017 Elsevier Ltd. All rights reserved.
To ascertain whether zearalenone (ZEA) could induce intestinal inflammation and investigate its possible mechanism, we investigated inflammatory cytokine release and the activation of the NLRP3 inflammasome after ZEA treatment both in vitro or in vivo. First, intestinal porcine enterocyte cell line (IPEC-J2) cells and mouse peritoneal macrophages were treated with ZEA to detect NLRP3 inflammasome activation, and the role of reactive oxygen species (ROS) in ZEA-induced inflammation was investigated. Then, Balb/c mice were fed a gavage of ZEA, and the disease activity indices (DAIs) and histological analysis were used to assess intestinal inflammation. Our study showed that the mRNA expression of NLRP3 inflammasome, pro-interleukin-1 beta (pro-IL-1 beta), and pro-interleukin-18 (pro-IL-18) was up- regulated 0.5- to 1-fold and that the release of IL-1 beta and IL-18 increased from 48 pg mL(-1) to 55 pg mL(-1) and 110 pg mL(-1) to 145 pg mL(-1), respectively. However, ROS inhibitor N-acetyl-l-cysteine (NAC) reduced IL-1 beta and IL-18 release to 45 pg mL(-1) and 108 pg mL(-1). Moreover, the same phenomenon was observed in intestinal tissues of ZEA-treated mice. In addition, clinical parameters of treated mice showed stools became loose and contained mucous. In addition, the presence of gross blood stool was found in the last 2 d. Histological analysis showed obvious inflammatory cell infiltration and tissue damage in the colon. These findings uncovered a possible mechanism of intestinal mucosal innate immunity in response to mycotoxin ZEA that ZEA could activate the ROS-mediated NLRP3 inflammasome and, in turn, contribute to the caspase-1-dependent activation of the inflammatory cytokines IL-1 beta and IL-18. (C) 2017 Elsevier Ltd. All rights reserved.
Bioapatite (BAp) is regarded as an effective material to immobilize lead (Pb2+) via the formation of stable pyromorphite. However, when applied in contaminated soil, due to its low surface area and low adsorption capacity, BAp might not sufficiently contact and react with Pb2+. Biochar, a carbon storage material, typically has high surface area and high adsorption capacity. This study investigated the feasibility of using biochar as a reaction platform to enhance BAp immobilization of Pb2+. An alkaline biochar produced from wheat straw pellets (WSP) and a slightly acidic biochar produced from hardwood (SB) were selected. The results of aqueous adsorption showed the combination of biochar (WSP or SB) and BAp effectively removed Pb2+ from the aqueous solution containing 1000 ppm Pb2+. XRD, ATR-IR, and SEM/EDX results revealed the formation of hydroxypyromorphite on both biochars surfaces. This study demonstrates that biochars could act as an efficient reaction platform for BAp and Pb2+ in aqueous solution due to their high surface area, porous structure, and high adsorption capacity. Therefore, it is mechanistically feasible to apply biochar to enhance BAp immobilization of Pb2+ in contaminated soil. (C) 2017 Elsevier Ltd. All rights reserved.
In silico and in vivo approaches were combined in an aggregate exposure pathway (AEP) to assess accumulation and effects of waterborne exposures of early life stages of zebrafish (Danio rerio) to tetrabromobisphenol A (TBBPA). Three metabolites, two of which were isomers, were detected in fish. Two additional metabolites were detected in the exposure solution. Based on kinetics modeling, proportions of TBBPA that were bioaccumulated and metabolized were 19.33% and 8.88%, respectively. Effects of TBBPA and its metabolites were predicted by use of in silico, surflex-Dock simulations that they were capable of interacting with ThR alpha and activating associated signaling pathways. TBBPA had a greater toxic contribution than its metabolites did when we evaluated the toxicity of these substances based on the toxicity unit method. The half of the internal lethal dose (ILD50) was 18.33 mu g TBBPA/g at 74 hpf. This finding was further confirmed by changes in expressions of ThR alpha and other NRs as well as associated genes in their signal pathways. Specifically, exposure to 1.6 x 10(2), 3.3 x 10(2) or 6.5 x 10(2) mu g TBBPA/L significantly down-regulated expression of ThR alpha and associated genes, ncor, c1d, ncoa2, ncoa3, and ncoa4, in the AR pathway and of er2a and er2b genes in the ER pathway. (C) 2017 Elsevier Ltd. All rights reserved.
Organophosphorus esters (OPEs) are emerging contaminants widely applied as annexing agents in a variety of industrial products, and they are robust against conventional wastewater treatments. Ultraviolet-driven (UV) radical-based advanced oxidation processes have a potential to become cost-effective treatment technologies for the removal of OPEs in water matrix, but residual and newly generated toxicities of degradation products are a concern. This study is a comprehensive attempt to evaluate UV/H2O2 for the degradation of a water dissolved OPE, tris(2-chloroethyl) phosphate (TCEP). In ultrapure water, a pseudo-first order reaction was observed, and the degradation rate constant reached 0.155 min(-1) for 3.5 mu M TCEP using 7.0 mW cm(-2) UV irradiation with 44.0 mu M H2O2. Hydroxyl radicals were involved in the oxidative degradation of TCEP, as demonstrated by the quenching of the degradation reaction in the presences of tertiary butanol or ethanol. High resolution mass spectroscopy data showed a partial transformation of TCEP to a series of hydroxylated and dechlorinated products e.g., C4H9Cl2O4P, C6H13Cl2O5P and C2H6ClO4P. Based on proteomics data at molecular and metabolic network levels, the toxicity of TCEP products was reduced obviously as the reaction proceeded, which was confirmed by the up-regulated tricarboxylic acid cycle, fatty acid metabolism and amino acid metabolism in Escherichia coli cells exposed to degradation products mixture. In conclusion, incomplete hydroxylation and dechlorination of TCEP likewise are effective for its detoxification, indicating that UV/H2O2 can be a promising treatment method for OPEs removal. (C) 2017 Elsevier Ltd. All rights reserved.
The interaction between bacteria and graphene-family materials like pristine graphene, graphene oxide (GO) and reduced graphene oxide (rGO) is such an elusive issue that its implication in environmental biotechnology is unclear. Herein, two kinds of self-assembled bio-rGO-hydrogels (BGHs) were prepared by cultivating specific Shewanella sp. strains with GO solution for the first time. The microscopic examination by SEM, TEM and CLSM indicated a porous 3D structure of BGHs, in which live bacteria firmly anchored and extracellular polymeric substances (EPS) abundantly distributed. Spectra of XRD, FTIR, XPS and Raman further proved that GO was reduced to rGO by bacteria along with the gelation process, which suggests a potential green technique to produce graphene. Based on the characterization results, four mechanisms for the BGH formation were proposed, i.e., stacking, bridging, rolling and cross-linking of rGO sheets, through the synergistic effect of activities and EPS from special bacteria. More importantly, the BGHs obtained in this study were found able to achieve unique cleanup performance that the counterpart free bacteria could not fulfill, as exemplified in Congo red decolorization and Cr(VI) bio-reduction. These findings therefore enlighten a prospective application of graphene materials for the biological treatment of wastewaters in the future. (C) 2017 Elsevier Ltd. All rights reserved.
Per- and polyfluoroalkyl substances (PFASs) are ubiquitous and high persistent in human blood, thus potentially inducing a myriad of deleterious consequences. Plasma kallikrein-kinin system (MS), which physiologically regulates vascular permeability, is vulnerable to exogenous stimulators, like PFASs with long-chain alkyl backbone substituted by electronegative fluorine. The study on the interactions of PFASs with the KKS and the subsequent effects on vascular permeability would be helpful to illustrate how the chemicals penetrate the biological vascular barriers to reach different tissues. In present study, three representative PFASs, including perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA) and perfluorohexadecanoic acid (PFHxDA), were investigated for their effects on the activation of the KKS, paracellular permeability in human retina endothelial cells (HRECs) and integrity of the adherens junctions. In contrast to either PFOS or PFOA, PFHxDA efficiently triggered KKS activation in a concentration-dependent manner based on protease activity assays. The plasma activated by PFHxDA significantly increased paracellular permeability of HRECs through the degradation of adherens junctions. As evidenced by the antagonistic effect of aprotinin, PFHxDA-involved effects on vascular permeability were mediated by KKS activation. The results herein firstly revealed the mechanistic pathway for PFHxDA induced effects on vascular endothelial cells. Regarding the possible structure related activities of the chemicals, this finding would be of great help in the risk assessment of PFASs. (C) 2017 Elsevier Ltd. All rights reserved.
With the development of psychiatric disorder in the current society, abuse of antidepressant drug fluoxetine (FLX) has made such compound an emerging contaminant in natural waters, and causes endocrine systems disturbance on some aquatic species. Herein, an efficient advanced oxidation process (AOP), electron beam irradiation was carried out to investigate the decomposition characteristics of such novel environmental pollutant, including the effects of initial concentration, pH, radical scavengers and anions. The results showed that FLX degradation followed pseudo-first-order kinetics. The degradation rate and dose constant decreased with increasing initial FLX concentration; and G-values elevated with the increase of initial concentration but reduced with increase of absorbed dose. Acidic condition was more conducive to FLX destruction than neutral and alkaline. The radical scavenger experiments indicated center dot OH was the main reactive species for the decomposition of FLX, while the reductive species e(aq)(-) and center dot H played an adjuvant role. The presence of anions slightly decreased or even no impact on FLX degradation rate. Various water matrices influenced degradation processes of FLX. Experimental results suggested radiolytic degradation showed the best performance in pure water rather than natural water no matter with filtration or not. Moreover, with the occurrence of defluorination and dealkylation during degradation process, some organic and inorganic intermediates were detected, and the possible degradation mechanisms and pathways of FLX were proposed. (C) 2017 Elsevier Ltd. All rights reserved.
Metal-free carbon materials have been presented to be potential alternatives to metal-based catalysts for heterogeneous catalytic ozonation, yet the catalytic performance still needs to be enhanced. Doping carbon with non-metallic heteroatoms (e.g., N, B, and F) could alter the electronic structure and electrochemical properties of original carbon materials, has been considered to be an effective method for improving the catalytic activity of carbon materials. Herein, fluorine-doped carbon nanotubes (F-CNTs) were synthesized via a facile method and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. The as-synthesized F-CNTs exhibited notably enhanced catalytic activity towards catalytic ozonation for the degradation of organic pollutants. The oxalic acid removal efficiency of optimized F-CNTs was approximately two times as much as that of pristine CNTs, and even exceeded those of four conventional metal-based catalysts (ZnO, Al2O3, Fe2O3, and MnO2). The XPS and Raman studies confirmed that the covalent C-F bonds were formed at the sp(3) C sites instead of sp(2) C sites on CNTs, not only resulting in high positive charge density of C atoms adjacent to F atoms, but remaining the delocalized pi-system with intact carbon structure of F-CNTs, which then favored the conversion of ozone molecules (O-3) into reactive oxygen species (ROS) and contributed to the high oxalic acid removal efficiency. Furthermore, electron spin resonance (ESR) studies revealed that superoxide radicals (O-2 center dot(-)) and singlet oxygen (O-1(2)) might be the dominant ROS that responsible for the degradation of oxalic acid in these catalytic systems. (C) 2017 Elsevier Ltd. All rights reserved.
Long-term exposure to fine particulate matter (PM2.5) has been reported to be closely associated with the neuroinflammation and synaptic dysfunction, but the mechanisms underlying the process remain unclear. Cyclooxygenase-2 (COX-2) is a key player in neuroinflammation, and has been also implicated in the glutamatergic excitotoxicity and synaptic plasticity. Thus, we hypothesized that COX-2 was involved in PM2.5-promoted neuroinflammation and synaptic dysfunction. Our results revealed that PM2.5 elevated COX-2 expression in primary cultured hippocampal neurons and increased the amplitude of field excitatory postsynaptic potentials (fEPSPs) in hippocampal brain slices. And the administration of NS398 (a COX-2 inhibitor) prevented the increased fEPSPs. PM2.5 also induced intracellular reactive oxygen species (ROS) generation accompanied with glutathione (GSH) depletion and the loss of mitochondrial membrane potential (MMP), and the ROS inhibitor, N-acetyl-L-cystein (NAC) suppressed the COX-2 overexpression and the increased fEPSPs. Furthermore, the nuclear factor kappa B (NF-kappa B) was involved in ROS-induced COX-2 and fEPSP in response to PM2.5 exposure. These findings indicated that PM2.5 activated COX-2 expression and enhanced the synaptic transmission through ROS-NF-kappa B pathway, and provided possible biomarkers and specific interventions for PM2.5-induced neurological damage. (C) 2017 Elsevier Ltd. All rights reserved.
Despite soil being the major terrestrial environmental reservoir and one of the significant sinks for many hydrophobic organic compounds including organophosphate ester flame retardants (OPFRs), limited information is available about concentration and fate of OPFRs contamination in urban soil in general and especially in case of Nepal. This study investigates the environmental concentration, spatial distribution and source apportionment of eight OPFRs in surface soil (n = 28) from four major cities of Nepal with special interest on air-soil exchange. Overall, significantly high concentrations of Sigma 8OPFR were measured in soil ranging from 25-27,900 ng/g dw (median 248 ng/g dw). In terms of compositional pattern, tris(methyl phenyl) phosphate (TMPP) was the most abundant phosphorus chemical in soil, followed by tris(2-chloroisopropyl) phosphate (TCIPP), and accounted for 35-49% and 8-25% of Sigma(8)OPFRs, respectively. The high level of these OPFRs was attributed to local sources as opposed to transboundary influence from remote areas. A Spearman's rank correlation analysis exhibited weak correlation of Sigma(8)OPFRs with TOC (Rho = 0.117, p < 0.05) and BC (Rho = 0.007, p < 0.05), suggesting little or no influence of TOC and BC on the concentration of Sigma(8)OPFRs. The fugacity fraction (ff) results indicated a strong influence of soil contamination on atmospheric level of OPFRs via volatilization. (C) 2017 Elsevier Ltd. All rights reserved.