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During nervous system development, spinal commissural axons project toward and across the ventral midline. They are guided in part by netrin-1, made by midline cells, which attracts the axons by activating the netrin receptor DCC. However, previous studies suggest that additional receptor components are required. Here, we report that the Down's syndrome Cell Adhesion Molecule (DSCAM), a candidate gene implicated in the mental retardation phenotype of Down's syndrome, is expressed on spinal commissural axons, binds netrin-1, and is necessary for commissural axons to grow toward and across the midline. DSCAM and DCC can each mediate a turning response of these neurons to netrin-1. Similarly, Xenopus spinal neurons exogenously expressing DSCAM can be attracted by netrin-1 independently of DCC. These results show that DSCAM is a receptor that can mediate turning responses to netrin-1 and support a key role for netrin/DSCAM signaling in commissural axon guidance in vertebrates.
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Proteínas de Membrana/metabolismo , Fatores de Crescimento Neural/metabolismo , Receptores de Superfície Celular/metabolismo , Medula Espinal/embriologia , Proteínas Supressoras de Tumor/metabolismo , Animais , Axônios/metabolismo , Células COS , Chlorocebus aethiops , Embrião de Mamíferos/metabolismo , Técnicas In Vitro , Proteínas de Membrana/química , Receptores de Netrina , Netrina-1 , Estrutura Terciária de Proteína , Ratos , Medula Espinal/citologia , Medula Espinal/metabolismo , XenopusRESUMO
Indoor semivolatile organic compounds (SVOCs), present in the air, airborne particles, settled dust, and other indoor surfaces, can enter the human body through several pathways. Knowing the partitioning between gaseous and particulate phases is important in identifying specific pathway contributions and thereby accurately assessing human exposure. Numerous studies have developed equilibrium equations to predict airborne particle/gas (P/G) partitioning in air (KP) and dust/gas (D/G) partitioning in settled dust (KD). The assumption that P/G and D/G equilibria are instantaneous for airborne and settled dust phases, commonly adopted by current indoor fate models, is not likely valid for compounds with high octanol-air partition coefficients (KOA). Here, we develop steady-state based equations to predict KP and KD in the indoor environment. Results show that these equations perform well and are verified by worldwide monitoring data. It is suggested that instantaneous steady state could work for P/G and D/G partitioning of SVOCs in indoor environments, and the equilibrium is just a special case of the steady state when log KOA < 11.38 for P/G partitioning and log KOA < 10.38 for D/G partitioning. These newly developed equations and methods provide a tool for more accurate assessment for human exposure to SVOCs in the indoor environment.
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Poluentes Atmosféricos , Poluição do Ar em Ambientes Fechados , Ácidos Ftálicos , Compostos Orgânicos Voláteis , Poluentes Atmosféricos/análise , Poluição do Ar em Ambientes Fechados/análise , Poeira/análise , Gases , HumanosRESUMO
The risk of human exposure to particulate novel brominated flame retardants (NBFRs) in the atmosphere has received increasing attention from scientists and the public, but currently, there is no reliable approach to predict the intake of these compounds on the basis of their size distribution. Here, we develop a reliable approach to predict the size-dependent inhalation intake of particulate NBFRs, based on the gas/particle (G/P) partitioning behavior of the NBFRs. We analyzed the concentrations of eight NBFRs in 363 size-segregated particulate samples and 99 paired samples of gaseous and bulk particles. Using these data, we developed an equation to predict the G/P partitioning quotients of NBFRs in particles in different size ranges (KPi) based on particle size. This equation was then successfully applied to predict the size-dependent inhalation intake of particulate NBFRs in combination with an inhalation exposure model. This new approach provides the first demonstration of the effects of the temperature-dependent octanol-air partitioning coefficient (KOA) and total suspended particle concentration (TSP) on the intake of particulate NBFRs by inhalation. In an illustrative case where TSP = 100 µg m-3, inhalation intake of particulate NBFRs exceeded the intake of gaseous NBFRs when log KOA > 11.4.
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Retardadores de Chama , Atmosfera , Poeira/análise , Monitoramento Ambiental , Retardadores de Chama/análise , Éteres Difenil Halogenados/análise , HumanosRESUMO
Substituted diphenylamine antioxidants (SDPAs) are additives used in various commodities and are commonly found in environmental samples. However, limited information was available on their fate and removal in wastewater treatment plants (WWTPs). This paper reports the results on the occurrence and removal efficiency of ten selected SDPAs in six WWTPs equipped with different treatment processes in Northeast China. Quite similar distributions of different SDPA congeners were shown in the studied WWTPs, with ditertoctyl-diphenylamine (C8/C8-DPA), tertbutyl-tertoctyl-diphenylamine (C4/C8-DPA), and tertoctyl-diphenylamine (C8-DPA) being always dominant in the influent, effluent, and sludge (total > 80%). A cyclic activated sludge system combined with a V-shape filter achieved the highest removal efficiencies of SDPAs among various treatment processes. Styrenated-diphenylamine1 (S-DPA1) (96 ± 10%), C8-DPA (95 ± 5.5%), and distyrenated-diphenylamine1 (DS-DPA1) (94 ± 9.3%) showed high and stable removal efficiencies, whereas C4/C8-DPA (85 ± 31%) and C8/C8-DPA (84 ± 62%) showed considerably varied removal efficiencies. Per-day discharges of SDPAs to the receiving environment through effluent and sludge were estimated as 828 ± 350 and 5578 ± 5196 mg, respectively. A median of 85% of the initial mass loadings of SDPAs was found in the sludge samples, suggesting that the observed removal of SDPAs in the WWTPs was caused by their sorption to the sludge, rather than biodegradation/transformation. This work provides an overall description of the occurrence, fate, and mass balance of SDPAs in WWTPs in Northeast China and highlights a new emission route to the environment via WWTPs.
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Poluentes Químicos da Água , Purificação da Água , Antioxidantes/análise , China , Difenilamina , Monitoramento Ambiental , Esgotos , Eliminação de Resíduos Líquidos , Águas Residuárias , Poluentes Químicos da Água/análiseRESUMO
This paper assesses the occurrence, distribution, source, and toxicity of polycyclic aromatic hydrocarbons (PAHs), and their methylated form (Me-PAHs) in sewage sludge from 10 WWTPs in Northeastern China was noted. The concentrations of ∑PAHs, ∑Me-PAHs ranged from 567 to 5040 and 48.1 to 479 ng.g-1dw, which is greater than the safety limit for sludge in agriculture in China. High and low molecular weight 4 and 2-ring PAHs and Me-PAHs in sludge were prevalent. The flux of sludge PAHs and Me-PAHs released from ten WWTPs, in Heilongjiang province, was calculated to be over 100 kg/year. Principal component analysis (PCA), diagnostic ratios and positive matrix factorization (PMF) determined a similar mixed pyrogenic and petrogenic source of sewage sludge. The average values of Benzo[a]pyrene was below the safe value of 600 ng.g-1 dependent on an incremental lifetime cancer risk ILCR of 10-6. Sludge is an important source for the transfer of pollutants into the environment, such as PAHs and Me-PAHs. Consequently, greater consideration should be given to its widespread occurrence.
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Monitoramento Ambiental/métodos , Hidrocarbonetos Policíclicos Aromáticos/análise , Medição de Risco , Esgotos/análise , Poluentes do Solo/análise , Agricultura/métodos , China , Cromatografia Líquida de Alta Pressão , Metilação , Neoplasias/prevenção & controle , Controle de Qualidade , Testes de ToxicidadeRESUMO
Diffuse intrinsic pontine glioma (DIPG) is an aggressive pediatric brainstem tumor with a 5-year survival of <1%. Up to 80% of the DIPG tumors contain a specific K27M mutation in one of the two genes encoding histone H3 (H3K27M). Furthermore, p53 mutations found in >70-80% of H3K27M DIPG, and mutant p53 status is associated with a decreased response to radiation treatment and worse overall prognosis. Recent evidence indicates that H3K27M mutation disrupts tri-methylation at H3K27 leading to aberrant gene expression. Jumonji family histone demethylases collaborates with H3K27 mutation in DIPG by erasing H3K27 trimethylation and thus contributing to derepression of genes involved in tumorigenesis. Since the first line of treatment for pediatric DIPG is fractionated radiation, we investigated the effects of Jumonji demethylase inhibition with GSK-J4, and mutant p53 targeting/oxidative stress induction with APR-246, on radio-sensitization of human H3K27M DIPG cells. Both APR-246 and GSK-J4 displayed growth inhibitory effects as single agents in H3K27M DIPG cells. Furthermore, both of these agents elicited mild radiosensitizing effects in human DIPG cells (sensitizer enhancement ratios (SERs) of 1.12 and 1.35, respectively; p < 0.05). Strikingly, a combination of APR-246 and GSK-J4 displayed a significant enhancement of radiosensitization, with SER of 1.50 (p < 0.05) at sub-micro-molar concentrations of the drugs (0.5 µM). The molecular mechanism of the observed radiosensitization appears to involve DNA damage repair deficiency triggered by APR-246/GSK-J4, leading to the induction of apoptotic cell death. Thus, a therapeutic approach of combined targeting of mutant p53, oxidative stress induction, and Jumonji demethylase inhibition with radiation in DIPG warrants further investigation.
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Neoplasias do Tronco Encefálico , Fracionamento da Dose de Radiação , Glioma , Mutação de Sentido Incorreto , Quinuclidinas/farmacologia , Radiossensibilizantes/farmacologia , Proteína Supressora de Tumor p53 , Substituição de Aminoácidos , Neoplasias do Tronco Encefálico/genética , Neoplasias do Tronco Encefálico/metabolismo , Neoplasias do Tronco Encefálico/patologia , Neoplasias do Tronco Encefálico/terapia , Linhagem Celular Tumoral , Glioma/genética , Glioma/metabolismo , Glioma/patologia , Glioma/terapia , Histona Desmetilases/antagonistas & inibidores , Histona Desmetilases/genética , Histona Desmetilases/metabolismo , Humanos , Proteína Supressora de Tumor p53/antagonistas & inibidores , Proteína Supressora de Tumor p53/genética , Proteína Supressora de Tumor p53/metabolismoRESUMO
Arctic and alpine treelines worldwide differ in their reactions to climate change. A northward advance of or densification within the treeline ecotone will likely influence climate-vegetation feedback mechanisms. In our study, which was conducted in the Taimyr Depression in the North Siberian Lowlands, w present a combined field- and model-based approach helping us to better understand the population processes involved in the responses of the whole treeline ecotone, spanning from closed forest to single-tree tundra, to climate warming. Using information on stand structure, tree age, and seed quality and quantity from seven sites, we investigate effects of intra-specific competition and seed availability on the specific impact of recent climate warming on larch stands. Field data show that tree density is highest in the forest-tundra, and average tree size decreases from closed forest to single-tree tundra. Age-structure analyses indicate that the trees in the closed forest and forest-tundra have been present for at least ~240 yr. At all sites except the most southerly ones, past establishment is positively correlated with regional temperature increase. In the single-tree tundra, however, a change in growth form from krummholz to erect trees, beginning ~130 yr ago, rather than establishment date has been recorded. Seed mass decreases from south to north, while seed quantity increases. Simulations with LAVESI (Larix Vegetation Simulator) further suggest that relative density changes strongly in response to a warming signal in the forest-tundra while intra-specific competition limits densification in the closed forest and seed limitation hinders densification in the single-tree tundra. We find striking differences in strength and timing of responses to recent climate warming. While forest-tundra stands recently densified, recruitment is almost non-existent at the southern and northern end of the ecotone due to autecological processes. Palaeo-treelines may therefore be inappropriate to infer past temperature changes at a fine scale. Moreover, a lagged treeline response to past warming will, via feedback mechanisms, influence climate change in the future.
Assuntos
Mudança Climática , Larix/fisiologia , Regiões Árticas , Sibéria , Temperatura , ÁrvoresRESUMO
Granulomatous mastitis (GM) is a relatively uncommon inflammatory breast lesion with multiple suggested etiologies. Although most GM cases show association with lactation and pregnancy, a minority of cases have been linked to hyperprolactinemia caused by either dopamine antagonist medications or with intracranial lesions, such as pituitary adenoma. The goal of this study is to review the GM cases reported in the literature with a specific emphasis on those cases associated with hyperprolactinemia and prolactinomas and to identify cases of GM seen at the Cleveland Clinic Florida which demonstrate co-occurrences of GM and intracranial lesions. CoPath and Epic data bases at Cleveland Clinic Florida were searched for cases describing inflammatory breast lesions in patients with pituitary pathology. Chart reviews were conducted and pertinent medical history was extracted for case reports. H&E-stained paraffin-embedded sections retrieved from Cleveland Clinic Florida pathology storage were evaluated by light microscopy. Four cases showing a co-occurrence of GM and hyperprolactinemia were consequently identified. A prolactin-secreting pituitary adenoma was present in two of the three GM cases. The third case demonstrated a concomitant craniopharyngioma, which was also associated with a rise in serum prolactin. This phenomenon was presumably attributable to compression, resulting in compromised transport of dopamine to the adenohypophysis and subsequent disinhibition of prolactin secretion by lactotrophs. The fourth patient with GM had a similar history of elevated prolactin. Classical histopathological features of GM were found in all four cases, including noncaseating granulomas, multinucleated giant cells, epithelioid histiocytes, and chronic inflammation. Intriguingly, complete resolution of inflammatory breast lesions along with normalization of prolactin levels occurred following the surgical excision of the craniopharyngioma, suggesting that intracranial lesion-induced hyperprolactinemia might be directly causal in GM. Therefore, the authors would suggest screening for pituitary tumors and evaluate prolactin levels in the workup of GM patients without a recent history of lactation and pregnancy and no other identified etiology.
Assuntos
Mastite Granulomatosa/etiologia , Hiperprolactinemia/etiologia , Adenoma/etiologia , Adenoma/patologia , Adulto , Bromocriptina/uso terapêutico , Antagonistas de Dopamina/efeitos adversos , Feminino , Mastite Granulomatosa/tratamento farmacológico , Mastite Granulomatosa/patologia , Humanos , Hiperprolactinemia/diagnóstico por imagem , Hiperprolactinemia/tratamento farmacológico , Hiperprolactinemia/patologia , Neoplasias Hipofisárias/etiologia , Neoplasias Hipofisárias/patologia , Ultrassonografia MamáriaRESUMO
Naturally occurring axonal pruning and neuronal cell death help to sculpt neuronal connections during development, but their mechanistic basis remains poorly understood. Here we report that beta-amyloid precursor protein (APP) and death receptor 6 (DR6, also known as TNFRSF21) activate a widespread caspase-dependent self-destruction program. DR6 is broadly expressed by developing neurons, and is required for normal cell body death and axonal pruning both in vivo and after trophic-factor deprivation in vitro. Unlike neuronal cell body apoptosis, which requires caspase 3, we show that axonal degeneration requires caspase 6, which is activated in a punctate pattern that parallels the pattern of axonal fragmentation. DR6 is activated locally by an inactive surface ligand(s) that is released in an active form after trophic-factor deprivation, and we identify APP as a DR6 ligand. Trophic-factor deprivation triggers the shedding of surface APP in a beta-secretase (BACE)-dependent manner. Loss- and gain-of-function studies support a model in which a cleaved amino-terminal fragment of APP (N-APP) binds DR6 and triggers degeneration. Genetic support is provided by a common neuromuscular junction phenotype in mutant mice. Our results indicate that APP and DR6 are components of a neuronal self-destruction pathway, and suggest that an extracellular fragment of APP, acting via DR6 and caspase 6, contributes to Alzheimer's disease.
Assuntos
Precursor de Proteína beta-Amiloide/metabolismo , Axônios/metabolismo , Caspase 6/metabolismo , Caspases/metabolismo , Neurônios/citologia , Neurônios/metabolismo , Receptores do Fator de Necrose Tumoral/metabolismo , Doença de Alzheimer/metabolismo , Precursor de Proteína beta-Amiloide/química , Animais , Caspase 3/metabolismo , Morte Celular , Ligantes , Camundongos , Fragmentos de Peptídeos/química , Fragmentos de Peptídeos/metabolismo , Ligação Proteica , Transdução de Sinais , Proteína X Associada a bcl-2/genética , Proteína X Associada a bcl-2/metabolismoRESUMO
To obtain a comprehensive understanding about that occurrence, sources, and effects on human health of polycyclic aromatic hydrocarbons (PAHs) in road environmental samples from Harbin, concentrations of 32 PAHs in road dust, green belt soil, and parking lot dust samples were quantified. The total PAH concentrations ranged from 0.95 to 40.7 µg/g and 0.39 to 43.9 µg/g in road dust and green belt soil, respectively, and were dominated by high molecular weight PAHs (HMW-PAHs). Despite the content of PAHs in arterial roads being higher, the composition profile of PAHs was hardly influenced by road types. For parking lot dust, the range of total PAH concentrations was 0.81-190 µg/g, and three-ring to five-ring PAHs produced the maximum contribution. Compared with surface parking lots (mean: 6.12 µg/g), higher total PAH concentrations were detected in underground parking lots (mean: 33.1 µg/g). The diagnostic ratios of PAHs showed that petroleum, petroleum combustion, and biomass/coal combustion were major sources of PAHs in the samples. Furthermore, according to the Incremental Lifetime Cancer Risk model, the cancer risks of three kinds of samples for adults and children were above the threshold (10-6). Overall, this study demonstrated that PAHs in the road environment of Harbin have a certain health impact on local citizens.
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The historical annual loading to, removal from, and cumulative burden in the Arctic Ocean for ß-hexachlorocyclohexane (ß-HCH), an isomer comprising 5-12% of technical HCH, is investigated using a mass balance box model from 1945 to 2020. Over the 76 years, loading occurred predominantly through ocean currents and river inflow (83%) and only a small portion via atmospheric transport (16%). ß-HCH started to accumulate in the Arctic Ocean in the late 1940s, reached a peak of 810 t in 1986, and decreased to 87 t in 2020, when its concentrations in the Arctic water and air were â¼30 ng m-3 and â¼0.02 pg m-3, respectively. Even though ß-HCH and α-HCH (60-70% of technical HCH) are both the isomers of HCHs with almost identical temporal and spatial emission patterns, these two chemicals have shown different major pathways entering the Arctic. Different from α-HCH with the long-range atmospheric transport (LRAT) as its major transport pathway, ß-HCH reached the Arctic mainly through long-range oceanic transport (LROT). The much higher tendency of ß-HCH to partition into the water, mainly due to its much lower Henry's Law Constant than α-HCH, produced an exceptionally strong pathway divergence with ß-HCH favoring slow transport in water and α-HCH favoring rapid transport in air. The concentration and burden of ß-HCH in the Arctic Ocean are also predicted for the year 2050 when only 4.4-5.3 t will remain in the Arctic Ocean under the influence of climate change.
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Flexible crystal() structures, which exhibit() single-crystal()-to-single-crystal() (SCSC) transformations(), are attracting attention() in many applied aspects: magnetic() switches, catalysis, ferroelectrics and sorption. Acid treatment() for titanosilicate material() AM-4 and natural() compounds with the same structures led to SCSC transformation() by loss() Na+, Li+ and Zn2+ cations with large structural() changes (20% of the unit()-cell() volume()). The conservation() of crystallinity through complex() transformation() is possible due() to the formation() of a strong hydrogen bonding() system(). The mechanism() of transformation() has been characterized using single-crystal() X-ray() diffraction analysis(), powder() diffraction, Rietvield refinement, Raman spectroscopy and electron microscopy. The low migration() energy() of cations in the considered materials() is confirmed using bond()-valence and density() functional() theory() calculations, and the ion conductivity of the AM-4 family's materials() has been experimentally verified.
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Polycyclic aromatic hydrocarbons (PAHs) are a class of toxic organic pollutants. Until now, they have been detected in many regions and various environmental matrix. However, not all PAHs are usually detected by researchers, and no methods is established to analyze systematically hundreds of PAHs. In this study, 123 PAHs were identified and quantified using gas chromatography-tandem triple-quadrupole mass spectrometry (GC-MS/MS), which were divided into 3 groups: 32 regular PAHs (R-PAHs), 50 methyl-PAHs (Me-PAHs), 30 Nitro-PAHs (N-PAHs) and 11 hydroxyl-PAHs (OH-PAHs). The developed method was applied to detect the target PAHs in 6 marine gaseous samples and 6 particulate samples collected on board the research vessel Snow Dragon. Limits of detection (LOD) and limits of quantification (LOQ) were determined from 0.009 to 2.50 and 0.03-8.33 pg/m3, respectively. Recoveries of the internal standards in atmosphere were from 88% to 112%, 70%-104%, and 72%-102% for R-PAHsãMe-PAHsãN-PAHs and OH-PAHs, respectively, which showed the reliability of the experimental method. The total concentrations of 123 PAHs in marine air and particle samples were from 1532 to 7877 and 206-1022 pg/m3, respectively.
Assuntos
Hidrocarbonetos Policíclicos Aromáticos , Atmosfera/análise , Cromatografia Gasosa-Espectrometria de Massas/métodos , Hidrocarbonetos Policíclicos Aromáticos/análise , Reprodutibilidade dos Testes , Espectrometria de Massas em Tandem/métodosRESUMO
The high levels of parabens (including methyl-, ethyl- and propyl congeners), triclocarban (TCC) and triclosan (TCS) used every year in China might be a problem to the typical wastewater treatment plant (WWTP). This study addresses measurements of parabens, TCC and TCS Northern China WWTP and a modelling assessment on the occurrence, fate and removal pathways in WWTP. Per-capita emissions of the three parabens, TCC and TCS to the WWTP were estimated as 0.41, 0.11 and 0.07 mg/d. After the wastewater treatment processes, 94, 92 and 87% of parabens, TCC and TCS were removed. The major removal pathway of parabens was biodegradation while that of TCC and TCS were sorption to sludge. Computer simulations on the fate processes of parabens, TCC and TCS in the WWTP using the SimpleTreat 4.0 model suggested the model could generally reproduce the measurements with root mean squared errors (RMSEs) of less than 10 ng/L. However, the model underestimated the removal of TCC and TCS from water to sludge in the primary tank. These discrepancies were attributed to the uncertainty of the predicted organic carbon-water partition coefficients (Koc) to which the modelling results are highly sensitive. The model predictions using updated Koc became more accurate and RMSEs of TCC and TCS were reduced by 40 and 80%, respectively. The modelling assessment suggests that the SimpleTreat, as a generic model to simulate chemical fate processes in WWTPs, has the potential to be applied to other similar WWTPs in China for estimating environmental releases of parabens, TCC and TCS at a larger spatial scale.
Assuntos
Carbanilidas , Triclosan , Poluentes Químicos da Água , Carbanilidas/análise , Parabenos/análise , Triclosan/análise , Águas Residuárias , Poluentes Químicos da Água/análiseRESUMO
Serpentine heat treatment at temperatures of 650-750 °C yields magnesium-silicate reagent with high chemical activity. Precise and express control of roasting conditions in laboratory kilns and industrial aggregates is needed to derive thermally activated serpentines on a large scale. Color change in serpentines with a high iron content during roasting might be used to indicate the changes in chemical activity in the technological process. This study gives a scientific basis for the express control of roasting of such serpentines by comparing the colors of the obtained material and the reference sample. Serpentines with different chemical activity were studied by X-ray diffraction, Mössbauer spectroscopy, and optical spectroscopy. The color parameters were determined using RGB (red, green, blue), CIELAB (International Commission on Illumination 1976 L*a*b), and HSB (hue, brightness, saturation) color models. The color of heat-treated samples was found to be affected by changes in the crystallochemical characteristics of iron included in the structure of the serpentine minerals. The color characteristics given by the CIELAB model were in good coherence with the acid-neutralizing ability and optical spectra of heat-treated serpentines. Thus, in contrast to the long-term analysis by these methods, the control by color palette provides an express assessment of the quality of the resulting product.
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Polycyclic aromatic hydrocarbons (PAHs), 33 methylated PAHs (Me-PAHs), and 14 nitrated PAHs (NPAHs) were measured in wastewater treatment plants (WWTPs) to study the removal efficiency of these compounds through the WWTPs, as well as their source appointment and potential risk in the effluent. The concentrations of ∑PAHs, ∑Me-PAHs, and ∑NPAHs were 2.01-8.91, 23.0-102, and 6.21-171 µg/L in the influent, and 0.17-1.37, 0.06-0.41 and 0.01-2.41 µg/L in the effluent, respectively. Simple Treat 4.0 and meta-regression methods were applied to calculate the removal efficiencies (REs) for the 63 PAHs and their derivatives in 10 WWTPs and the results were compared with the monitoring data. Overall, the ranges of REs were 55.3-95.4% predicated by the Simple Treat and 47.5-97.7% by the meta-regression. The results by diagnostic ratios and principal component analysis PCA showed that "mixed source" biomass, coal composition, and petroleum could be recognized to either petrogenic or pyrogenic sources. The risk assessment of the effluent was also evaluated, indicating that seven carcinogenic PAHs, Benzo[a]pyrene, Dibenz[a,h]anthracene, and Benzo(a)anthracene were major contributors to the toxics equivalency concentrations (TEQs) in the effluent of WWTPs, to which attention should be paid.
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In this paper, two level III fugacity models are developed and applied using an environmental system containing six compartments, including air, aerosols, soil, water, suspended particulate matters (SPMs), and sediments, as a "unit world". The first model, assumes equilibrium between air and aerosols and between water and SPMs. These assumptions lead to a four-fugacity model. The second model removes these two assumptions leading to a six-fugacity model. The two models, compared using four PBDE congeners, BDE-28, -99, -153, and -209, with a steady flux of gaseous congeners entering the air, lead to the following conclusions. 1. When the octanol-air partition coefficient (KOA) is less than 1011.4, the two models produce similar results; when KOA > 1011.4, and especially when KOA > 1012.5, the model results diverge significantly. 2. Chemicals are in an imposed equilibrium in the four-fugacity model, but in a steady state and not necessary an equilibrium in the six-fugacity model, between air and aerosols. 3. The results from the six-fugacity model indicate an internally consistent system with chemicals in steady state in all six compartments, whereas the four-fugacity model presents an internally inconsistent system where chemicals are in equilibrium but not a steady state between air and aerosols. 4. Chemicals are mass balanced in air and aerosols predicted by the six-fugacity model but not by the four-fugacity model. If the mass balance in air and aerosols is achieved in the four-fugacity model, the condition of equilibrium between air and aerosols will be no longer valid.
Assuntos
Poluentes Atmosféricos , Aerossóis , Poluentes Atmosféricos/análise , Gases , SoloRESUMO
The logarithm of gas/particle (G/P) partition quotient (logKP) has been found to have a linear relationship with logKOA (octanol-air partition coefficient) with slope mo and intercept bo and logPL (subcooled liquid vapor pressure) with slope mp and intercept bp. In the sister paper of the present work, analytical equations to predict the slope mo and intercept bo based on logKOA and predict the slope mp and intercept bp based on logPL are developed using steady state theory. In this work, the equations are evaluated using world-wide monitoring data (262 pairs for mo and bo values and 292 pairs for mp and bp values produced from more than 10,000 monitiring data worldwide) for selected seven groups of semi-volatile organic compounds (SVOCs), including polybrominated diphenyl ethers (PBDEs), polychlorinated dibenzo-p-dioxins and polychorinated dibenzofurans (PCDD/Fs), polyclorinated biphenyl (PCBs), polycyclic aromatic hydrocarbons (PAHs), polychlorinated naphthalenes (PCNs), organochlorinated pesticides (OCPs), novel brominated flame retardants (NBFRs), and other selected halogenated flame retardants. The slopes and intercepts predicted by the steady state equations reproduce the trends observed in monitoring regression results for the seven SVOC groups, with 44.4% of the variation of monitoring mo values accounted for by logKOA and 48.2% of the variation of monitoring mp values accounted for by logPL. Theoretically, the values of mo can be any value between 0 and 1 dependent on the values of KOA, and are not constrained to 1 as in equilibrium theory. Likewise, the values of mp can be any value between 0 and -1 dependent on the values of PL, and not constrained to -1 predicted by the equilibrium theory. The influence of sampling artifacts on the G/P partitioning of SVOCs has most likely been overemphasized by the equilibrium theory. Thus, the equilibrium approach should be abandoned in favor of the steady state approach for calculating the G/P partition quotients for SVOCs with high KOA values (>1011.38) or low PL values (<10-4.92).
Assuntos
Poluentes Atmosféricos , Dibenzodioxinas Policloradas , Compostos Orgânicos Voláteis , Poluentes Atmosféricos/análise , Dibenzofuranos , Monitoramento Ambiental , Éteres Difenil Halogenados/análise , Octanóis , Pressão de Vapor , Compostos Orgânicos Voláteis/análiseRESUMO
The waste of apatite-nepheline ore processing was chosen as the material of study for the present investigation. The chemical and phase compositions have been analyzed and the route of the new technology has been developed. Treatment of the waste with diluted hydrochloric acid enables to separate apatite, nepheline, titano-magnetite minerals from titanite (CaSiTiO5). The obtained titanite concentrate contains 30-32% of titanium dioxide. Interaction of titanite with hydrochloric acid under heating and stirring conditions results in calcium leaching. The titanite decomposition is accompanied by titanium and silica oxides precipitation. The resulting solid has been used as a precursor for the synthesis of functional materials. Mechanochemical activation of the precursor provides the structural and morphological disorder of the initial particles. Thermodynamic stability of activated particles is achieved by chemisorption or roasting.