Emissions of parent, nitro, and oxygenated polycyclic aromatic hydrocarbons from residential wood combustion in rural china

Residential wood combustion is one of the important sources of air pollution in developing countries. Among the pollutants emitted, parent polycyclic aromatic hydrocarbons (pPAHs) and their derivatives, including nitrated and oxygenated PAHs (nPAHs and oPAHs), are of concern because of their mutagenic and carcinogenic effects. In order to evaluate their impacts on regional air quality and human health, emission inventories, based on realistic emission factors (EFs), are needed. In this study, the EFs of 28 pPAHs (EF(PAH28)), 9 nPAHs (EF(PAHn9)), and 4 oPAHs (EF(PAHo4)) were measured for residential combustion of 27 wood fuels in rural China. The measured EF(PAH28), EF(PAHn9), and EF(PAHo4) for brushwood were 86.7 ± 67.6, 3.22 ± 1.95 × 10(-2), and 5.56 ± 4.32 mg/kg, which were significantly higher than 12.7 ± 7.0, 8.27 ± 5.51 × 10(-3), and 1.19 ± 1.87 mg/kg for fuel wood combustion (p < 0.05). Sixteen U.S. EPA priority pPAHs contributed approximately 95% of the total of the 28 pPAHs measured. EFs of pPAHs, nPAHs, and oPAHs were positively correlated with one another. Measured EFs varied obviously depending on fuel properties and combustion conditions. The EFs of pPAHs, nPAHs, and oPAHs were significantly correlated with modified combustion efficiency and fuel moisture. Nitro-naphthalene and 9-fluorenone were the most abundant nPAHs and oPAHs identified. Both nPAHs and oPAHs showed relatively high tendencies to be present in the particulate phase than pPAHs due to their lower vapor pressures. The gas-particle partitioning of freshly emitted pPAHs, nPAHs, and oPAHs was primarily controlled by organic carbon absorption.     

Improved separation of complex polycyclic aromatic hydrocarbon mixtures using novel column combinations in GC × GC/ToF-MS

Complex mixtures of polycyclic aromatic hydrocarbons (PAHs) are difficult to resolve because of the high degree of overlap in compound vapor pressures, boiling points, and mass spectral fragmentation patterns. The objective of this research was to improve the separation of complex PAH mixtures (including 97 different parent, alkyl-, nitro-, oxy-, thio-, chloro-, bromo-, and high molecular weight PAHs) using GC × GC/ToF-MS by maximizing the orthogonality of different GC column combinations and improving the separation of PAHs from the sample matrix interferences, including unresolved complex mixtures (UCM). Four different combinations of nonpolar, polar, liquid crystal, and nanostationary phase columns were tested. Each column combination was optimized and evaluated for orthogonality using a method based on conditional entropy that considers the quantitative peak distribution in the entire 2D space. Finally, an atmospheric particulate matter with diameter <2.5 μm (PM(2.5)) sample from Beijing, China, a soil sample from St. Maries Creosote Superfund Site, and a sediment sample from the Portland Harbor Superfund Site were analyzed for complex mixtures of PAHs. The highest chromatographic resolution, lowest synentropy, highest orthogonality, and lowest interference from UCM were achieved using a 10 m × 0.15 mm × 0.10 μm LC-50 liquid crystal column in the first dimension and a 1.2 m × 0.10 mm × 0.10 μm NSP-35 nanostationary phase column in the second dimension. In addition, the use of this column combination in GC × GC/ToF-MS resulted in significantly shorter analysis times (176 min) for complex PAH mixtures compared to 1D GC/MS (257 min), as well as potentially reduced sample preparation time.     

Increased amygdala fMRI activation after secretin administration.

It has recently been reported that secretin activates gene expression in the central nucleus of the amygdala in rats. To examine the neurophysiological effects of secretin on amygdalar activation in humans, the authors measured Blood Oxygen Level Dependent functional magnetic resonance imaging signal change during facial affect processing in a placebo-controlled double-blind study. The authors studied 12 healthy male subjects who were presented with three stimulus conditions: viewing happy, fearful, and neutral faces, before and after infusion with either secretin or placebo. To test whether treatment was associated with distinct patterns of activation, the two conditions (Pre and Post) were subjected to a subtraction analyses in SPM99 and hypotheses regarding the activation of the left and right amygdala were tested using a region-of-interest approach. Subtraction of treatment minus baseline activation during the fear condition yielded significant (p=.001) activation in the right amygdala and a nonsignificant increase in activation in the left amygdala. No significant differences were seen between the treatment conditions for the amygdala when viewing happy or neutral faces. These preliminary findings indicate that secretin may alter responsivity to affective stimuli. The presence of increased activation of the amygdala during the viewing of fearful faces is consistent with findings from animal studies and suggests a mechanism by which secretin may modulate social behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Design strategies for the molecular level synthesis of supported catalysts

Supported catalysts, metal or oxide catalytic centers constructed on an underlying solid phase, are making an increasingly important contribution to heterogeneous catalysis. For example, in industry, supported catalysts are employed in selective oxidation, selective reduction, and polymerization reactions. Supported structures increase the thermal stability, dispersion, and surface area of the catalyst relative to the neat catalytic material. However, structural and mechanistic characterization of these catalysts presents a formidable challenge because traditional preparations typically afford complex mixtures of structures whose individual components cannot be isolated. As a result, the characterization of supported catalysts requires a combination of advanced spectroscopies for their characterization, unlike homogeneous catalysts, which have relatively uniform structures and can often be characterized using standard methods. Moreover, these advanced spectroscopic techniques only provide ensemble averages and therefore do not isolate the catalytic function of individual components within the mixture. New synthetic approaches are required to more controllably tailor supported catalyst structures. In this Account, we review advances in supported catalyst synthesis and characterization developed in our laboratories at Northwestern University. We first present an overview of traditional synthetic methods with a focus on supported vanadium oxide catalysts. We next describe approaches for the design and synthesis of supported polymerization and hydrogenation catalysts, using anchoring techniques which provide molecular catalyst structures with exceptional activity and high percentages of catalytically significant sites. We then highlight similar approaches for preparing supported metal oxide catalysts using atomic layer deposition and organometallic grafting. Throughout this Account, we describe the use of incisive spectroscopic techniques, including high-resolution solid state NMR, UV-visible diffuse reflectance (DRS), UV-Raman, and X-ray absorption spectroscopies to characterize supported catalysts. We demonstrate that it is possible to tailor and isolate defined surface species using a molecularly oriented approach. We anticipate that advances in catalyst design and synthesis will lead to a better understanding of catalyst structure and function and, thus, to advances in existing catalytic processes and the development of new technologies.     

Semivolatile fluorinated organic compounds in Asian and western U.S. air masses

Semivolatile fluorinated organic compounds (FOCs) were measured in archived air sample extracts collected from Hedo Station Observatory (HSO) on Okinawa, Japan and Mount Bachelor Observatory (MBO), Oregon U.S. during the springs of 2004 (MBO and HSO) and 2006 (MBO). Fluorotelomer alcohols (FTOHs) were measured in both Asian and western U.S. air masses, though western U.S. air masses had significantly higher concentrations. Concentrations of fluorotelomer olefins in Asian air masses and 8:2 fluorotelomer acrylate in U.S. air masses were reported for the first time. N-ethyl perfluorooctane sulfonamide, N-methyl perfluorooctane sulfonamido ethanol, and N-ethyl perfluorooctane sulfonamido ethanol were also measured in Asian and western U.S. air masses but less frequently than FTOHs. The atmospheric sources and fate of FTOHs were investigated by estimating their atmospheric residence times, calculating FTOH concentration ratios, investigating FTOH correlations with nonfluorinated semivolatile organic compound concentrations, and determining air mass back trajectories. Estimated atmospheric residence times for 6:2 FTOH, 8:2 FTOH, and 10:2 FTOH were 50, 80, and 70 d, respectively, and the average concentration ratio of 6:2 FTOH to 8:2 FTOH to 10:2 FTOH at MBO in 2006 was 1.0 to 5.0 to 2.5. The relative order of these atmospheric residence times may explain the observed enhancement of 8:2 FTOH and 10:2 FTOH (relative to 6:2 FTOH) at MBO compared to North American indoor air (FTOH average ratio of 1.0 to 2.0 to 1.0). FTOH concentrations in western U.S. air masses were positively correlated (p < 0.05) with gas-phase polycyclic aromatic hydrocarbon and polychlorinated biphenyl concentrations and negatively correlated (p < 0.05) with agricultural pesticide concentrations. In comparison to western U.S. air masses, trans-Pacific air masses did not contain elevated concentrations of these compounds, whereas lower boundary layer air masses that passed over urban areas of the western U.S. did. This suggests that semivolatile FOCs are emitted from urban areas in the western U.S.     

Removal of fragrance materials during U.S. and European wastewater treatment

The concentrations and removals of 16 fragrance materials (EMs) were measured in 17 U.S. and European wastewater treatment plants between 1997 and 2000 and were compared to predicted values. The average FM profile and concentrations in U.S. and European influent were similar. The average FM profile in primary effluent was similar to the average influent profile; however, the concentration of FMs was reduced by 14.6-50.6% in primary effluent. The average FM profile in final effluent was significantly different from the primary effluent profile and was a function of the design of the wastewater treatment plant. In general, the removal of sorptive, nonbiodegradable FMs was correlated with the removal of total suspended solids in the plant, while the removal of nonsorptive, biodegradable FMs was correlated with 5-day Biological Oxidation Demand removal in the plant. The overall plant removal (primary + secondary treatment) of FMs ranged from 87.8 to 99.9% for activated sludge plants, 58.6-99.8% for carousel plants, 88.9-99.9% for oxidation ditch plants, 71.3-98.6% for trickling filter plants, 80.8-99.9% for a rotating biological contactor plant, and 96.7-99.9% for lagoons. The average concentration of FMs in final effluent ranged from the limit of quantitation (1-3 ng/L) to 8 microg/L. Measured FM removal and concentrations were compared to predicted values, which were based on industry volume, per capita water use, octanol-water partition coefficient, and biodegradability.     

Atmospheric concentrations and air-soil gas exchange of polycyclic aromatic hydrocarbons (PAHs) in remote, rural village and urban areas of Beijing-Tianjin region, North China

Forty passive air samplers were deployed to study the occurrence of gas and particulate phase PAHs in remote, rural village and urban areas of Beijing-Tianjin region, North China for four seasons (spring, summer, fall and winter) from 2007 to 2008. The influence of emissions on the spatial distribution pattern of air PAH concentrations was addressed. In addition, the air-soil gas exchange of PAHs was studied using fugacity calculations. The median gaseous and particulate phase PAH concentrations were 222 ng/m³ and 114 ng/m³, respectively, with a median total PAH concentration of 349 ng/m³. Higher PAH concentrations were measured in winter than in other seasons. Air PAH concentrations measured at the rural villages and urban sites in the northern mountain region were significantly lower than those measured at sites in the southern plain during all seasons. However, there was no significant difference in PAH concentrations between the rural villages and urban sites in the northern and southern areas. This urban-rural PAH distribution pattern was related to the location of PAH emission sources and the population distribution. The location of PAH emission sources explained 56%-77% of the spatial variation in ambient air PAH concentrations. The annual median air-soil gas exchange flux of PAHs was 42.2 ng/m²/day from soil to air. Among the 15 PAHs measured, acenaphthylene (ACY) and acenaphthene (ACE) contributed to more than half of the total exchange flux. Furthermore, the air-soil gas exchange fluxes of PAHs at the urban sites were higher than those at the remote and rural sites. In summer, more gaseous PAHs volatilized from soil to air because of higher temperatures and increased rainfall. However, in winter, more gaseous PAHs deposited from air to soil due to higher PAH emissions and lower temperatures. The soil TOC concentration had no significant influence on the air-soil gas exchange of PAHs.     

Inhalation cancer risk associated with exposure to complex polycyclic aromatic hydrocarbon mixtures in an electronic waste and urban area in South china

Atmospheric particulate matter samples were collected from May 2010 to April 2011 in a rural e-waste area and in Guangzhou, South China, to estimate the lifetime inhalation cancer risk from exposure to parent polycyclic aromatic hydrocarbons (PAHs), high molecular weight PAHs (MW 302 PAHs), and halogenated PAHs (HPAHs). Seasonal variations in the PAH concentrations and profiles within and between the e-waste and urban areas indicated different PAH sources in the two areas. Benzo[b]fluoranthene, benzo[a]pyrene, dibenz[ah]anthracene, and dibenzo[al]pyrene made the most significant contribution to the inhalation cancer risk. MW 302 PAHs accounted for 18.0% of the total cancer risk in the e-waste area and 13.6% in the urban area, while HPAHs made a minor contribution (<0.1%) in both the areas. The number of lifetime excess lung cancers due to exposure to parent PAHs, MW 302 PAHs, and HPAHs ranged from 15.1 to 1198 per million people in the e-waste area and from 9.3 to 737 per million people in Guangzhou. PAH exposure accounted for 0.02 to 1.94% of the total lung cancer cases in Guangzhou. On average, the inhalation cancer risk in the e-waste area was 1.6 times higher than in the urban area. The e-waste dismantling activities in South China led to higher inhalation cancer risk due to PAH exposure than the urban area.