RESUMEN
A series of nano-BiOBr were prepared by an effective hydrothermal method in the presence of cetyltrimethyl ammonium bromide (CTAB) and ethanol at different calcination temperatures. The as-prepared nano-BiOBr samples were characterized by measuring the specific area (S BET), UV-Vis diffuse reflectance spectrum, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The results show that the calcination temperature has an important impact on the morphology and microstructure of BiOBr. The nano-BiOBr calcined at 120 °C showed excellent photocatalytic degradation properties for benzene, with photocatalytic degradation rate of 75 % for benzene under UV irradiation for 90 min, and removal efficiency of benzene was significantly enhanced by using nano-BiOBr catalyst compared to UV irradiation alone. BiOBr catalyst possessed good photocatalytic activity even after three consecutive photocatalytic reaction cycles, illustrating its excellent stability. The photocatalytic degradation of benzene followed the first-order kinetics, and the good catalytic capability of nano-BiOBr catalyst can be attributed to its crystalline, hierarchical nanostructure and nanosheet thickness.
Asunto(s)
Benceno/química , Bismuto/química , Nanoestructuras/química , Procesos Fotoquímicos , Catálisis , Gases/química , Microscopía Electrónica de Rastreo , Microscopía Electrónica de Transmisión , Difracción de Rayos XRESUMEN
The extended Derjaguin-Laudau-Verwey-Overbeek (XDLVO) theory was utilized to quantitatively evaluate short-range interfacial interactions involved in microfiltration (MF) membrane fouling by sodium alginate (SA) at various ionic compositions. Results showed that for hydrophilic membrane surfaces, van der Waals interactions facilitated fouling, whereas acid-base interactions alleviated fouling; for hydrophobic membrane surfaces, however, van der Waals interactions mitigated fouling and acid-base interactions turned out to be favorable for fouling. Electrostatic double layer interactions contributed minimally to fouling when SA molecules came into contact with MF membrane surface. Ionic strength and Ca2+ affected SA fouling of MF membranes mainly through alteration of acid-base interactions between membrane and SA or among SA themselves. Higher ionic strength could make acid-base interaction less repulsive or more attractive, thus aggravating SA fouling of MF membrane. Although Ca2+ accelerated flux decline significantly, Ca2+ could enhance physical cleaning efficiencies. Under all tested ionic compositions, fouling potentials (K) of initial and subsequent stages correlated well with membrane-SA interfacial free energy of adhesion and SA-SA interfacial free energy of cohesion, respectively. This implies that the XDLVO theory is applicable for description of MF membrane fouling by SA at various ionic compositions.
Asunto(s)
Alginatos/química , Filtración/métodos , Membranas Artificiales , Ácido Glucurónico/química , Ácidos Hexurónicos/química , Interacciones Hidrofóbicas e Hidrofílicas , Iones , Concentración Osmolar , Electricidad EstáticaRESUMEN
To investigate pollution characteristics of dioxin-like polychlorinated biphenyls (DL-PCBs) in Gudao Region, Dongying City, twenty surface soil samples were collected in April, 2011. The DL-PCBs in soil samples were determined by Soxhelt extraction-Florisil purification-Gas Chromatography(GC)-Electron Capture Detector (ECD). The concentration of DL-PCBs in surface soils ranged from 1.4 microg x kg(-1) to 7.4 microg x kg(-1), with the mean concentration of (3.5 +/- 1.7) microg x kg(-1). The total TEQ level was between 1.2 ng x kg(-1) and 31.8 ng x kg(-1), and the mean TEQ was 5.4 ng x kg(-1), which exceeded the Canadian soil environment quality guidelines (4.0 ng x kg(-1)). The congener profiles of DL-PCBs were similar among sites. Tetra-CB and penta-CB were the major homologues in all soil samples, together accounting for more than 80% of the total DL-PCBs. The level of DL-PCBs exhibited a decreasing trend with the increasing distance from the Gudao town to the suburb, which could be attributed to the chemical plants around the town. The correlation analysis showed that the concentration of DL-PCBs was positively correlated with the organic matter content and clay particle content (R2 were 0.732 and 0.687, separately, P < 0.01), but negatively correlated with the sand particle content (R2 = -0.438, P < 0.05).
Asunto(s)
Monitoreo del Ambiente , Bifenilos Policlorados/análisis , Contaminantes del Suelo/análisis , China , Dioxinas/químicaRESUMEN
The Ag/TiO(2) nanobelt heterostructures were prepared by the acid-assisted hydrothermal method followed by an in situ photo-reduction process. The photocatalytic activity of TiO(2) nanobelts was evidently enhanced by the heterostructures between Ag nanoparticles and TiO(2) nanobelts. The nanopapers based on Ag/TiO(2) nanobelt heterostructures were fabricated via a modified paper-making process. A novel continuous photocatalytic reactor was designed, and MO removal rate of Ag/C-TiO(2) nanopaper was achieved to 100% in 40 min for single layer and only in 6 min for three layers. The self-supported TiO(2) nanopapers with porous structures also showed an excellent continuous photocatalytic performance for toluene gas under UV light irradiation, and the corresponding degradation rate was 69.5% in 184 min. Moreover, the Ag/TiO(2) nanobelts nanopaper showed a good antibacterial effect. The multifunctional TiO(2) nanopapers modified by the heterostuctures could have potential applications in the environmental and biomaterial fields.
Asunto(s)
Contaminantes Ambientales/aislamiento & purificación , Nanoestructuras , Plata/química , Titanio/química , Catálisis , Escherichia coli/efectos de los fármacos , Gases , Pruebas de Sensibilidad Microbiana , Microscopía Electrónica de Rastreo , Microscopía Electrónica de Transmisión , Fotoquímica , Difracción de Polvo , Plata/farmacología , Titanio/farmacologíaRESUMEN
The concentrations of organochlorine pesticides (OCPs) in atmospheric particulate matter in Jinan, China, over the period from July 2009 to June 2010, were determined to study their pollution levels, compositions, size distribution and seasonal variations. All target compounds except endosulfan sulfate were detected. The annual average concentration of ∑18 OCPs was 92 ± 82 pg m(-3). Total HCH, total endrin, aldrin, endosulfan compounds and total DDT compounds were the primary components, accounting for approximately 27%, 20%, 16%, 14% and 10% of total OCPs, respectively. The annual mean ng g(-1) concentrations of ∑18 OCPs in PM(2.5), PM(5), PM(10) and TSP were 481 ± 190, 433 ± 161, 414 ± 158 and 264 ± 193, respectively, indicating that most OCPs tend to be strongly absorbed by fine air particles which were strongly related to a potential health risk. Distinct seasonal trends were found in OCPs concentrations with high concentrations appearing in November and March whereas low concentrations appeared in the summer, which were significantly positively correlated with particulate mass concentrations and Air Pollution Index (API). The high OCPs levels could be attributed to the seasonal usage, long-range atmospheric transport as well as adverse meteorological conditions.
Asunto(s)
Contaminantes Atmosféricos/análisis , Hidrocarburos Clorados/análisis , Plaguicidas/análisis , Contaminantes Atmosféricos/química , Contaminación del Aire/estadística & datos numéricos , Atmósfera/química , China , Ciudades/estadística & datos numéricos , Monitoreo del Ambiente , Hidrocarburos Clorados/química , Tamaño de la Partícula , Plaguicidas/química , Estaciones del AñoRESUMEN
The levels and temporal variations of surface ozone at a coastal site in East China during summer and autumn were analyzed and the influences of meteorological parameters on ozone were investigated. An inland city was chosen as a comparison site. The main results and conclusions of this study are: (1) ozone pollution, with a maximum 1 h concentration of 150.98 ppbv, was severe during summer and autumn at the coastal site; (2) the ozone level was obviously higher at the coastal site than that at the inland site in September; (3) besides temperature and solar radiation, sea-land breeze circulation is an important factor influencing the ozone level at the coastal site, and sea breeze often induce high ozone levels (the average ozone concentration for sea breeze was about 13 ppbv higher than that for land breeze).
Asunto(s)
Contaminantes Atmosféricos/análisis , Monitoreo del Ambiente , Ozono/análisis , Estaciones del Año , Contaminantes Atmosféricos/química , China , Ciudades , Geografía , Conceptos Meteorológicos , Océanos y Mares , Factores de TiempoRESUMEN
Using a trajectory model (HYSPLIT) analyzed the ozone episodes observed at urban Jinan in 2005. There were 84 h (in 24 days) of ozone episodes (>100 ppbv) observed during the study. June was the most polluted month in the year. The earliest episode observed in May 4 was mainly caused by the favorable meteorological condition for ozone production and accumulation. A multi-day episode from 6 to 8 June was related to the passage of typhoon Nesat. 39 h (in 11 days) of ozone episodes were observed from June 10 to 24. Large scale stagnation, recirculation of air mass, intense solar radiation, high temperature and long-rang transport of pollutants were the main reason for the ozone episodes during this period.
Asunto(s)
Contaminantes Atmosféricos/análisis , Ozono/análisis , China , Ciudades , Monitoreo del Ambiente , Factores de TiempoRESUMEN
Surface ozone and some meteorological parameters were continuously measured from June 2003 to May 2004 at urban Jinan, China. The levels and variations of surface ozone were studied and the influences of meteorological parameters on ozone were analyzed. Annual and diurnal ozone variation patterns in Jinan both show a typical pattern for polluted urban areas. Daytime ozone concentrations in summer were the highest in the four seasons. However, during nighttime from 2100 to 0600 hours ozone concentrations in spring was higher than that in summer. Daily averaged ozone showed negative correlation with pressure and relative humidity and positive correlation with temperature, total solar radiation, sunshine duration and wind speed during the study period. Further studies show that, solar radiation is a primary influence factor for the daytime variations of ozone concentrations at this site; transport of pollutants by wind could enhance the pollution at this site; precipitation has a significant influence on decreasing surface ozone. A multi-day ozone episode from 16 to 21 June 2003 was observed at this site. Surface meteorological data analysis and backward trajectory computation show that the episode is associated with the influence of typhoon Soudelor, attributing to both local photochemical processes and transport of air pollutants from southeastern coastal region, especially Yangtze River Delta region.
Asunto(s)
Contaminantes Atmosféricos/análisis , Ciudades , Conceptos Meteorológicos , Ozono/análisis , China , Humanos , Periodicidad , Factores de TiempoRESUMEN
Photo-catalytic degradation of gas-phase benzene and toluene were studied in the condition of no catalyst, pure anatase catalyst, pure rutile catalyst and multi-composite catalyst. The influences of initial concentration of reactants and the catalysts of different composite on photo-catalytic degradation rate of gas-phase benzene and toluene were investigated. The results show that the degradation efficiency of benzene and toluene is improved a lot on anatase catalyst, but improved a little on rutile catalyst in relation to the crystal-structure of anatase and rutile catalyst. In the condition of no catalyst and pure rutile catalyst, toluene is easier to be degradated than benzene, and on anatase catalyst benzene is easier to be done than toluene. The initial concentration of reactant has an effect on the photo-catalytic degradation process. The degradation rates of benzene and toluene are faster in low concentration than in high concentration. A certain amount of rutile doped in anatase catalyst could improve the photo-catalytic activity. The catalyst with 80% anatase and 20% rutile shows the best photo-catalytic activity to benzene, and the catalyst with 90% anatase and 10% rutile gives the best photo-catalytic activity to toluene.
Asunto(s)
Contaminación del Aire/prevención & control , Benceno/química , Titanio/química , Tolueno/química , Contaminación del Aire/análisis , Catálisis/efectos de la radiación , Oxidación-Reducción/efectos de la radiación , Fotoquímica , VolatilizaciónRESUMEN
Based on the observational data of near surface O3, NO, NO2, CO and meteorological factors in the urban area of Ji'nan during summer 2003, the 03 concentrations and their temporal variation characteristics were studied. The correlation between O3 and its precursors (NO, NO2, CO) and related meteorological factors (solar radiation, temperature) was analyzed. The results show that O3 pollution during summer was very serious in Ji'nan, and the levels of O3, NO, NO2, NOx and CO were quite high during the observational period. O3 concentrations were well negatively correlated with NO, NO2, NO, and CO during day time. As to the meteorological factors, O3 concentrations correlated well with solar radiations, but showed no obvious correlation with the temperatures. Consequently, based on the above data and results, a regression equation that relates ozone concentrations observed in the day time to its precursors and solar radiation was constructed. The results show that the calculated values were in good agreement with the observed values.
Asunto(s)
Contaminantes Atmosféricos/análisis , Ciudades , Ozono/análisis , Estaciones del Año , China , Conceptos Meteorológicos , Modelos TeóricosRESUMEN
The concentrations of ozone (O3) and carbon monoxide (CO) on the top of Taishan Mountain were monitored, and the variations and correlation were studied. The results show that the frequency of O3 hourly concentrations more than the first-degree of National Ambient Air Quality Standard(GB-3095-1996, NAAQS) was 15.81%, and the frequency of CO concentrations more than the first-degree of NAAQS was zero. The variation of O3 concentrations appears in a narrow scope, which indicates that there is scarcely influenced by the pollution of industry around. The diurnal variation of the concentrations of O3 and that of CO both present two peaks with the peaks of O3 in the behind of CO, which indicates that the concentration variations of O3 and its precursor CO are primarily controlled by local photochemical reaction process. The daily concentrations of O3 correlated well with CO.
Asunto(s)
Contaminantes Atmosféricos/análisis , Aire/análisis , Monóxido de Carbono/análisis , Ozono/análisis , Movimientos del Aire , ChinaRESUMEN
Based on the observational data of near surface O3 in the urban area of Ji'nan during the latest two years, the O3 concentrations and their temporal variation characteristics were analyzed. The results showed that O3 concentrations fluctuated periodically,and the photochemical pollution in Ji'nan was serious. Diurnal variations of ozone concentrations exhibited with the characteristic of a single peak, and showed the maximum in the afternoon and minimum in the early morning before sunrise. Ozone concentrations in spring and summer were higher than autumn and winter, while the varying scopes of ozone concentrations in summer and autumn were broader than spring and winter. Variations of ozone concentrations in weekend days were different from weekdays, which caused by the temporal regulation of human activities.
Asunto(s)
Contaminantes Atmosféricos/análisis , Monitoreo del Ambiente/métodos , Oxidantes Fotoquímicos/análisis , Ozono/análisis , China , Ciudades , Monitoreo del Ambiente/estadística & datos numéricos , Fotoquímica , Estaciones del AñoRESUMEN
The increase of ozone concentration in urban is one of the most important research topics on environmental science. With the increase of nitrogen oxides and hydrogen-carbon compounds which are exhausted from cars, the ozone concentration in urban is obviously increased on sunlight, and threat of photochemistry smog will be possible. Therefore, it is very important to monitor and study the ozone concentration distribution in urban. The frequency-distribution, diurnal variation and monthly variation of ozone concentration were studied on the campus of Shandong University during six months monitoring. The influence of solar radiation and weather conditions on ozone concentration were discussed. The frequency of ozone concentration less than 200 microg/m3 is 96.88%. The ozone concentration has an obvious diurnal variation. The ozone concentration in the afternoon is higher than in the morning and in the evening. The maximum appears in June, when it is the strong solar radiation and high air-temperature. The weather conditions also influence the ozone concentration. The ozone concentration in clear day is higher than in rainy and cloudy day.