RESUMEN
The emission of pollutants from building decoration and furbishing materials associated with unpleasant odors is the main reason for complaints relating to poor quality indoor air. Currently, few studies have focused on the identification of odorants and the quantification of emissions from these building materials. Here, we summarize the analytical methods available for the study of indoor odorants and evaluate existing understanding of odorants from nine kinds of building materials, namely plaster board, wood-based materials, linoleum, carpets, plastics, rubber, artificial leather, paints, and adhesives. The possible odor-causing compounds emitted by these different materials and their odor threshold values are identified. Finally, suggestions are proposed for future research and control measures to minimize indoor odor pollution. Overall, olfactometry is the most important tool for odor analysis desite the non-standardized application of the technique when used in the assessment of odor emissions from building materials. In addition, there are large differences in the reported patterns of odorant emissions from building materials, although oxidized substances such as aldehydes, ketones, and acids are frequently identified in association with the aging of the materials via processes such as oxidation and ozone degradation over time.
Asunto(s)
Contaminación del Aire Interior , Ozono , Contaminación del Aire Interior/análisis , Materiales de Construcción , Odorantes/análisis , OlfatometríaRESUMEN
It is widely accepted that antibiotics provide a critical selective pressure for the horizontal transfer of antibiotic resistance between bacterial species. This study demonstrated that a combination of low doses of kanamycin and streptomycin, which inhibited the growth of recipient and donor cells, respectively, had positive effects on the transmission of the conjugation plasmids pRK2013, pSU2007, and RP4 from Escherichia coli DH5α to HB101 at their minimum inhibitory concentrations (MICs). Administration of either antibiotic alone as well as other antibiotics in combination or alone did not have this effect. Two-dimensional electrophoresis revealed that 60 proteins were downregulated and 14 proteins were upregulated in the conjugation of E. coli DH5α (pRK2013) and HB101 in the presence of kanamycin and streptomycin. Of these proteins, 64 were subsequently identified by mass spectrometry. Two antibiotic-induced genes encoding oligopeptide-binding protein (OppA) and ribose-binding protein (RbsB) were further confirmed by quantitative real-time PCR. When these genes were deleted, the number of transconjugants decreased in the same fashion as when the cells were treated with kanamycin and streptomycin. These results indicate that the process of E. coli conjugation may be promoted by combination treatment with kanamycin and streptomycin and that two proteins potentially participated in this process.
Asunto(s)
Antibacterianos/farmacología , Conjugación Genética/efectos de los fármacos , Escherichia coli/efectos de los fármacos , Kanamicina/farmacología , Estreptomicina/farmacología , Proteínas Bacterianas/análisis , Proteínas Bacterianas/genética , Proteínas Bacterianas/metabolismo , Escherichia coli/metabolismo , Regulación Bacteriana de la Expresión Génica/efectos de los fármacos , Plásmidos/genéticaRESUMEN
Concentrations of BTX (benzene, toluene and xylene), total volatile organic compounds (TVOC), formaldehyde and other carbonyl compounds were measured in different sections of a furniture mall in Beijing. The overall indoor concentrations (mean +/- standard deviation) of formaldehyde, benzene, toluene, xylene, and TVOC were (0.37 +/- 0.08), (0.04 +/- 0.03), (0.19 +/- 0.16), (0.47 +/- 0.57), and (2.76 +/- 2.18) mg/m3, respectively. Indoor concentrations of formaldehyde, xylene and TVOC were 22, 46 and 34 times higher than the corresponding outdoor concentrations respectively. Concentrations of formaldehyde, xylene and TVOC were much higher than the standard limits regulated in the national "indoor air quality standard" (GB/T 18883-2002), and the highest concentrations of formaldehyde and TVOC exceeded the standard limit 5.1 and 14.8 times respectively. Total concentration of carbonyl compounds was (689.3 +/- 94.8) microg/m3, which was 5 times higher than that outdoors. Of the carbonyls, formaldehyde and acetaldehyde were found to be the most abundant, together accounting for over 75% of the total carbonyl concentrations. Acetone, C4 carbonyls (methacrolein, methyl ethyl ketone, butanal), and hexanal also occurred at relatively high concentrations. In conclusion, indoor air pollution is serious in the furniture mall.
Asunto(s)
Contaminación del Aire Interior/análisis , Formaldehído/análisis , Diseño Interior y Mobiliario , Compuestos Orgánicos Volátiles/análisis , Acetaldehído/análisis , ChinaRESUMEN
The practical ammonia stripping effectiveness of coke-plant wastewater treatment may vary widely, and high NH4+-N shock loading will lead to the fluctuation of residual NH4+-N concentration of biological effluent. A zeolite media packed multistage-biofilm system (ZMBS) was used for coke-plant wastewater treatment for enhancing the NH4+-N treatment ability of the bio-system to shock loading, as well as achieving high COD removal efficiency. Treatment performance during steady-state and shock loading and transformation of organic pollutants in the system were investigated systematically. The experiment results indicated that when the system was operated at NH4+-N loading 0.21 kg/(m3 x d) and COD loading < or = 1.35 kg/(m3 x d), the average effluent NH4+-N and COD concentrations were (2.2 +/- 1.2) mg/L, (228 +/- 60) mg/L with average removal efficiencies of (99.1 +/- 0.5)% and (86.0 +/- 2.6)%. During the twice NH4+-N shock loadings [0.03 kg/(m3 x d) and 0.06 kg/(m3 x d)], ZMBS showed a strong resisting ability with average removal efficiencies of 99.0% and 92.9% higher than those of a compared system's 96.8% and 89.3%. By monitoring the change of water quality along the length of the ZMBS's cells, two function zones for different pollutant removal were found to exist, named as decarbonization/nitrification (C/N) zone and nitrification (N) zone, and the NH4+-N removal rate in N zone was 2-8 times as that in C/N zone. TOC concentrations of organic matters with relative molecular weight < 1 x 10(3), 1 x 10(3) to 1 x 10(4), and > 1 x 10(4), were 227.6, 104.8 and 35.0 mg/L in raw wastewater, and 31.2, 22.9 and 31.5 mg/L in the effluent, respectively. Organic matters with relative molecular weight < 1 x 10(3) and 1 x 10(3) to 1 x 10(4) in raw wastewater were removed effectively by ZMBS, but those with relative molecular weight > 1x 10(3) were the main remained substances in the effluent.
Asunto(s)
Reactores Biológicos , Nitrógeno/metabolismo , Compuestos de Amonio Cuaternario/metabolismo , Eliminación de Residuos Líquidos/métodos , Zeolitas/química , Biodegradación Ambiental , Biopelículas , Reactores Biológicos/microbiología , Coque , Nitrógeno/aislamiento & purificación , Compuestos de Amonio Cuaternario/aislamiento & purificación , Contaminantes Químicos del Agua/aislamiento & purificación , Contaminantes Químicos del Agua/metabolismoRESUMEN
The removal of trace nitrobenzene in water by the ozone-enhanced VUV photocatalysis process (VUV/TiO2/O3) was investigated, in which low-pressure mercury lamp emitting 185 nm vacuum ultraviolet and titanium dioxide film coated on the titanium plate were used as light source and photocatalyst respectively. The results show that, VUV/TiO2/O3 is an effective method to remove trace nitrobenzene in water, and the pseudo-first-order rate constant of nitrobenzene in the VUV/TiO2/O3 process is 102.8% and 30.8% higher than that in the UV/TiO2/O3 and VUV/O3 respectively. And 50 microg/L nitrobenzene in deionized water is totally removed within 60 s by the VUV/TiO2/O3 process. Higher ozone dosage is beneficial to accelerate nitrobenzene degradation, and the apparent rate constant at ozone dosage of 1.52 mg/L is 134.4% higher than that without ozone addition. Though the rate constant is slightly decreased with increase of nitrobenzene concentration, 170 microg/L nitrobenzene is removed to below the detection limit within 2 min. Common species such bicarbonate and humic acid in water significantly inhibit the removal of nitrobenzene, and the apparent rate constant is reduced 82.9% and 71.6% respectively when 2 mmol/L bicarbonate and 3.2 mg/L humic acid are added into the water. The inverse of the apparent rate constant is linear with the bicarbonate concentration. Trace nitrobenzene in surface water containing bicarbonate and natural organic matter can be removed fast and effectively by the VUV/TiO2/O3 process, and 96% nitrobenzene with initial concentration of 90 microg/L is removed within 4 min and the UV absorbance at 254 nm is also reduced 80%.
Asunto(s)
Nitrobencenos/aislamiento & purificación , Ozono/química , Titanio/química , Rayos Ultravioleta , Purificación del Agua/métodos , Catálisis , Sustancias Húmicas , Nitrobencenos/análisis , Fotoquímica , Contaminantes Químicos del Agua/análisis , Contaminantes Químicos del Agua/aislamiento & purificación , Abastecimiento de AguaRESUMEN
The conjugation protocols in myxobacterium Sorangium cellulosum are often inapplicable due to the strain-specific sensitivity to the presence of Escherichia coli cells or the resistances to many antibiotics. Here we report that the conjugative transfer of the mobilizable plasmid pCVD442 from E. coli DH5alpha (lambda pir) to Sorangium strains could be greatly increased by the presence of low doses of dual selection antibiotics in the mating medium. The improvement was efficient in either E. coli-tolerant or sensitive Sorangium strains. For those phleomycin and hygromycin tolerant Sorangium strains, chloramphenicol-resistance gene was developed as a new selectable marker by driving the resistance gene with the aphII promoter. Using the improved protocol, the epothilone biosynthetic pathway was inactivated by an insertion mutation in the biosynthetic genes of the producing Sorangium strains.
Asunto(s)
Antibacterianos/farmacología , Conjugación Genética/efectos de los fármacos , Técnicas Genéticas , Myxococcales/genética , Escherichia coli/efectos de los fármacos , Escherichia coli/genética , Myxococcales/efectos de los fármacos , Plásmidos/genéticaRESUMEN
The photodegradation of persistent and bioaccumulative perfluorooctanoic acid (PFOA) in water by 185 nm vacuum ultraviolet (VUV) light was examined to develop an effective technology to deal with PFOA pollution. PFOA degraded very slowly under irradiation of 254 nm UV light. However, 61.7% of initial PFOA was degraded by 185 nm VUV light within 2 h, and defluorination ratio reached 17.1%. Pseudo first-order-kinetics well simulated its degradation and defluorination. Besides, fluoride ion formed in water, 4 shorter-chain perfluorinated carboxylic acids (PFCAs), that is, perfluoroheptanoic acid, perfluorohexanoic acid, perfluoropentanoic acid, and perfluorobutanoic acid. These were identified as intermediates by LC-MS measurement. These PFCAs consecutively formed and further degraded with irradiation time. According to the mass balance calculation, no other byproducts were formed. It was proposed that PFCAs initially are decarboxylated by 185 nm light, and the radical thus formed reacts with water to form shorter-chain PFCA with one less CF2 unit.
Asunto(s)
Caprilatos/efectos de la radiación , Fluorocarburos/efectos de la radiación , Rayos Ultravioleta , Contaminantes Químicos del Agua/efectos de la radiación , Flúor/química , Nitrógeno , VacioRESUMEN
Perfluorinated carboxylic acids (PFCAs) especially perfluorooctanoic acid (PFOA) are a new type of persistent and bioaccumulative organic pollutants, and they have been widely detected in various environmental media. Photodegradation of five types of PFCAs i.e. PFOA, perfluoroheptanoic acid (PFHpA), perfluorohexanoic acid (PFHxA), perfluoropentanoic acid (PFPeA) and perfluorobutanoic acid (PFBA) by 185 nm vacuum ultraviolet (VUV) were examined to develop an effective method to deal with PFCAs pollution. All five PFCAs degrade significantly under the irradiation of 185 nm light and fluoride ion correspondingly forms, though PFCAs hardly degrade under irradiation of 254 nm UV light. After 6h irradiation by 185 nm light, more than 60% of PFBA degrades, while other four PFCAs degrade more than 90%, and defluorination ratio range from 71% to 21% decreasing with increasing carbon atoms contained by PFCAs. Three reaction atmosphere i.e. nitrogen, air and oxygen have no significant effect on degradation and defluorination of PFCAs. LC/MS measurement shows, PFOA degrades to PFHpA, PFHxA, PFPeA and PFBA step by step. Under irradiation of 185 nm light, PFCA firstly is decarboxylated, and the radical thus formed reacts with water to form shorter-chain PFCA and fluoride ion.
Asunto(s)
Caprilatos/metabolismo , Ácidos Carboxílicos/metabolismo , Fluorocarburos/metabolismo , Rayos Ultravioleta , Caprilatos/química , Ácidos Carboxílicos/química , Fluorocarburos/química , Fotólisis/efectos de la radiación , Contaminantes Químicos del Agua/análisis , Contaminantes Químicos del Agua/metabolismoRESUMEN
The method of Fenton oxidation cooperated with coagulation for biologically treated coking wastewater was conducted. Based on both of the removal performance and the operating costs, optimal reaction condition was proposed. Operating at H2O2 concentration 220 mg/L, Fe2+ concentration 180 mg/L, PAM concentration 4.5 mg/L, reaction time 0.5h and pH = 7, about 44.5% of COD was removed and chroma reached 35. In addition, through analyzing of the changes of molecular weight distribution and constitute of organic compounds in effluent, the pollutant transformation rule was put forward. The result shows that the effluent treated by Fenton oxidation cooperated with coagulation can reach the wastewater secondary discharge standard, and the operation costs are acceptable. This implies that the technique of Fenton oxidation cooperated with coagulation has promising in practice.
Asunto(s)
Residuos Industriales/análisis , Eliminación de Residuos Líquidos/métodos , Purificación del Agua/métodos , Coque/análisis , Restauración y Remediación Ambiental/métodos , Peróxido de Hidrógeno/química , Hierro/química , Oxidación-Reducción , Eliminación de Residuos , Contaminantes Químicos del Agua/químicaRESUMEN
Photocatalysis technology was used to investigate its removal capability of disinfection by products (DBPs). The photocatalytic degradation rates of different compounds were obviously larger than those in photolytic degradation. They were 3-7 times for halogenated alkyls and 2-3 times for alkenes and aromatic compounds. Investigation of photocatalytic degradation orderliness show that cinnamene > o-cresol > alkenes > alkyls.
Asunto(s)
Desinfectantes/análisis , Fotoquímica , Contaminantes Químicos del Agua/análisis , Purificación del Agua/métodos , Abastecimiento de Agua/análisis , Catálisis , Contaminantes Químicos del Agua/químicaRESUMEN
This study reports the photoelectrocatalytic oxidation of benzoic acid in a three-electrode photoelectroreactor. The effects of the anode bias potential, the atmosphere of reaction and the basis material for photocatalyst preparation on the removal efficiency of benzoic acid were researched. The photoelectrocatalysis was compared with photolysis, photocatalysis and electrolysis. The results of the experiments indicated the removal efficiency of benzoic acid after the photoelectrocatalytic oxidation process for 1 h could be more than 85%, much higher than the efficiency of photolysis (48%), photocatalysis (30%) and electrolysis (nearly having no effect). The synergetic effect of the photoelectricity was obvious. The working electrode and the counter electrode were arranged as two concentric columns whose diameters were different. The results showed that this kind of arrangement mode was very effective. In nitrogen atmosphere the removal efficiency of benzoic acid could be 98% when TiO2/Ti acted as the anode of the photoelectrocatalytic oxidation process for 1 h, much better than the TiO2/Al did (85%). While in oxygen atmosphere the two kinds of electrodes were both effective and the removal efficiency of benzoic acid could approach 100%.
Asunto(s)
Ácido Benzoico/química , Catálisis , Luz , Purificación del Agua/métodos , Electroquímica , Electrodos , Oxidación-Reducción , Fotoquímica , Contaminantes Químicos del Agua/aislamiento & purificación , Contaminantes Químicos del Agua/metabolismoRESUMEN
The degradations of trace hexane under high flow rate (5 L/min-17 L/min) in the gas phase by TiO2/UV, O3/UV and O3/TiO2/UV were studied. The kinetic effects of the inlet concentration of hexane, flow rate, water concentration and ozone dosage on the conversion of hexane in the three processes were examined respectively. The experimental results showed that the addition of ozone to the photocatalysis process increased the conversion of hexane significantly. The O3/TiO2/UV process was more efficient than the TiO2/UV in decomposing hexane. The degradation rate increased with increasing the initial concentration of hexane in the processes of TiO2/UV and O3/TiO2/UV. They matched well with the Langmuir-Hinshelwood (L-H) kinetic model. In the range of flow rate studied, the degradation rate increased with an increasing flow rate in both processes of TiO2/UV and O3/TiO2/UV, while was not affected in the process of O3/UV. The degradation rate in the three processes was affected by water concentration. The degradation rate of the two processes O3/UV and O3/TiO2/UV increased almost linearly with the increase of ozone dosage.
Asunto(s)
Contaminación del Aire Interior/prevención & control , Hexanos/química , Luz , Ozono , Contaminantes Atmosféricos/aislamiento & purificación , Contaminantes Atmosféricos/metabolismo , Catálisis , Electroquímica , Electrodos , Cinética , Oxidación-Reducción , Ozono/química , Fotoquímica , Rayos UltravioletaRESUMEN
Endocrine disrupting chemicals (EDCs) existed in the water treatment units of Beijing based Sewage Treatment Plant were analyzed by SPE-GC/MSD and GC/ECD. Totally 30 EDCs were detected from the influent, effluent and sludge. The results show that about 70%-99% EDCs in the influent were removed after treatment. Sludge adsorption played an important role in the reduction of EDCs. The range of phenols in sludge was 17-35 mg/kg, the range of PAEs was 25-77 mg/kg and the range of PAHs was 1.33-1.74 mg/kg. Compared with the results in other countries in literature, the existence of EDCs in the Sewage Treatment Plant was not serious.