Tropospheric air pollution: ozone, airborne toxics, polycyclic aromatic hydrocarbons, and particles

Distributions of Polycyclic Aromatic Hydrocarbons, Aromatic Ketones, Carboxylic Acids, and Trace Metals in Arctic Aerosols: Long-Range Atmospheric Transport, Photochemical Degradation/Production at Polar Sunrise

The distributions, correlations, and source apportionment of aromatic acids, aromatic ketones, polycyclic aromatic hydrocarbons (PAHs), and trace metals were studied in Canadian high Arctic aerosols. Nineteen PAHs including minor sulfur-containing heterocyclic PAH (dibenzothiophene) and major 6 carcinogenic PAHs were detected with a high proportion of fluoranthene followed by benzo[k]fluoranthene, pyrene, and chrysene. However, in the sunlit period of spring, their concentrations significantly declined likely due to photochemical decomposition. During the polar sunrise from mid-March to mid-April, benzo[a]pyrene to benzo[e]pyrene ratios significantly dropped, and the ratios diminished further from late April to May onward. These results suggest that PAHs transported over the Arctic are subjected to strong photochemical degradation at polar sunrise. Although aromatic ketones decreased in spring, concentrations of some aromatic acids such as benzoic and phthalic acids increased during the course of polar sunrise, suggesting that aromatic hydrocarbons are oxidized to result in aromatic acids. However, PAHs do not act as the major source for low molecular weight (LMW) diacids such as oxalic acid that are largely formed at polar sunrise in the arctic atmosphere because PAHs are 1 to 2 orders of magnitude less abundant than LMW diacids. Correlations of trace metals with organics, their sources, and the possible role of trace transition metals are explained.

Intracavity Faraday modulation spectroscopy (INFAMOS): A tool for radical detection

We present the intra-cavity Faraday modulation spectroscopy technique, whereby optical feedback cavity-enhanced spectroscopy is coupled with Faraday modulation spectroscopy to greatly enhance the interaction path length of a laser beam with a paramagnetic sample in a magnetic field. We describe a first prototype based upon a cw quantum cascade laser targeting a selection of fundamental rovibrational R-branch transitions of nitric oxide (1890 cm^-1), consisting of a linear cavity (finesse F=6300) and a water-cooled solenoid. We demonstrate a minimum detectable Verdet constant of V_min=4.7×10^-14 rad cm^-1 G^-1 Hz^-1/2 (at SNR = 1), corresponding to a single-pass rotation angle of 1.6×10^-10 rad Hz^-1/2 and a limit of detection of 0.21 ppbv Hz^-1/2 NO.

Land Use Regression Models for Alkylbenzenes in a Middle Eastern Megacity: Tehran Study of Exposure Prediction for Environmental Health Research (Tehran SEPEHR)

Land use regression (LUR) has not been applied thus far to ambient alkylbenzenes in highly polluted megacities. We advanced LUR models for benzene, toluene, ethylbenzene, p-xylene, m-xylene, o-xylene (BTEX), and total BTEX using measurement based estimates of annual means at 179 sites in Tehran megacity, Iran. Overall, 520 predictors were evaluated, such as The Weather Research and Forecasting Model meteorology predictions, emission inventory, and several new others. The final models with R² values ranging from 0.64 for p-xylene to 0.70 for benzene were mainly driven by traffic-related variables but the proximity to sewage treatment plants was present in all models indicating a major local source of alkylbenzenes not used in any previous study. We further found that large buffers are needed to explain annual mean concentrations of alkylbenzenes in complex situations of a megacity. About 83% of Tehran's surface had benzene concentrations above air quality standard of 5 μg/m³ set by European Union and Iranian Government. Toluene was the predominant alkylbenzene, and the most polluted area was the city center. Our analyses on differences between wealthier and poorer areas also showed somewhat higher concentrations for the latter. This is the largest LUR study to predict all BTEX species in a megacity.

Photoionization Efficiencies of Five Polycyclic Aromatic Hydrocarbons

We have measured photoionization-efficiency curves for pyrene, fluoranthene, chrysene, perylene, and coronene in the photon energy range of 7.5-10.2 eV and derived their photoionization cross-section curves in this energy range. All measurements were performed using tunable vacuum ultraviolet (VUV) radiation generated at the Advanced Light Source synchrotron at Lawrence Berkeley National Laboratory. The VUV radiation was used for photoionization, and detection was performed using a time-of-flight mass spectrometer. We measured the photoionization efficiency of 2,5-dimethylfuran simultaneously with those of pyrene, fluoranthene, chrysene, perylene, and coronene to obtain references of the photon flux during each measurement from the known photoionization cross-section curve of 2,5-dimethylfuran.

Species characteristics and intraspecific variation in growth and photosynthesis of Cryptomeria japonica under elevated O3 and CO2

In order to predict the effects of future atmospheric conditions on forest productivity, it is necessary to clarify the physiological responses of major forest tree species to high concentrations of ozone (O3) and carbon dioxide (CO2). Furthermore, intraspecific variation of these responses should also be examined in order to predict productivity gains through tree improvements in the future. We investigated intraspecific variation in growth and photosynthesis of Cryptomeria japonica D. Don, a major silviculture species in Japan, in response to elevated concentrations of O3 (eO3) and CO2 (eCO2), separately and in combination. Cuttings of C. japonica were grown and exposed to two levels of O3 (ambient and twice-ambient levels) in combination with two levels of CO2 (ambient and 550 µmol mol-1 in the daytime) for two growing seasons in a free-air CO2 enrichment experiment. There was no obvious negative effect of eO3 on growth or photosynthetic traits of the C. japonica clones, but a positive effect was observed for annual height increments in the first growing season. Dry mass production and the photosynthetic rate increased under eCO2 conditions, while the maximum carboxylation rate decreased. Significant interaction effects of eO3 and eCO2 on growth and photosynthetic traits were not observed. Clonal effects on growth and photosynthetic traits were significant, but the interactions between clones and O3 and/or CO2 treatments were not. Spearman's rank correlation coefficients between growth traits under ambient conditions and for each treatment were significantly positive, implying that clonal ranking in growth abilities might not be affected by either eO3 or eCO2. The knowledge obtained from this study will be helpful for species selection in afforestation programs, to continue and to improve current programs involving this species, and to accurately predict the CO2 fixation capacity of Japanese forests.

Effect of biodiesel fuel on "real-world", nonroad heavy duty diesel engine particulate matter emissions, composition and cytotoxicity

Biodiesel is regarded by many as a "greener" alternative fuel to petroleum diesel with potentially lower health risk. However, recent studies examining biodiesel particulate matter (PM) characteristics and health effects are contradictive, and typically utilize PM generated by passenger car engines in laboratory settings. There is a critical need to analyze diesel and biodiesel PM generated in a "real-world" setting where heavy duty-diesel (HDD) engines and commercially purchased fuel are utilized. This study compares the mass concentrations, chemical composition and cytotoxicity of real-world PM from combustion of both petroleum diesel and a waste grease 20% biodiesel blend (B20) at a community recycling center operating HDD nonroad equipment. PM was analyzed for metals, elemental/organic carbon (EC/OC), polycyclic aromatic hydrocarbons (PAHs), and nitro-polycyclic aromatic hydrocarbons (N-PAHs). Cytotoxicity in a human lung epithelial cell line (BEAS-2B) following 24h exposure to the real-world particles was also evaluated. On average, higher concentrations for both EC and OC were measured in diesel PM. B20 PM contained significantly higher levels of Cu and Mo whereas diesel PM contained significantly higher concentrations of Pb. Principal component analysis determined Mo, Cu, and Ni were the metals with the greatest loading factor, suggesting a unique pattern related to the B20 fuel source. Total PAH concentration during diesel fuel use was 1.9 times higher than during B20 operations; however, total N-PAH concentration was 3.3 times higher during B20 use. Diesel PM cytotoxicity was 8.5 times higher than B20 PM (p<0.05) in a BEAS-2B cell line. This study contributes novel data on real-world, nonroad engine sources of metals, PAH and N-PAH species, comparing tailpipe PM vs. PM collected inside the equipment cabin. Results suggest PM generated from burning petroleum diesel in nonroad engines may be more harmful to human health, but the links between exposure, composition and toxicity are not straightforward.

Long-Lived Species Enhance Summertime Attribution of North American Ozone to Upwind Sources

Ground-level ozone (O₃), harmful to most living things, is produced from both domestic and foreign emissions of anthropogenic precursors. Previous estimates of the linkage from distant sources rely on the sensitivity approach (i.e., modeling the change of ozone concentrations that result from modifying precursor emissions) as well as the tagging approach (i.e., tracking ozone produced from specific O₃ precursors emitted from one region). Here, for the first time, we tag all O₃ precursors (i.e., nitrogen oxides (NO_x), carbon monoxide (CO), and volatile organic compounds (VOCs)) from East Asia and explicitly track their physicochemical evolution without perturbing the nonlinear O₃ chemistry. We show that, even in summer, when intercontinental influence on ozone has typically been found to be weakest, nearly 3 parts per billion by volume (ppbv) seasonal average surface O₃ over North America can be attributed to East Asian anthropogenic emissions, compared with 0.7 ppbv using the sensitivity approach and 0.5 ppbv by tagging reactive nitrogen oxides. Considering the acute effects of O₃ exposure, approximately 670 cardiovascular and 300 respiratory premature mortalities within North America could be attributed to East Asia. CO and longer-lived VOCs, largely overlooked in previous studies, extend the influence of regional ozone precursors emissions and, thus, greatly enhance O₃ attribution to source region.

Standoff monitoring of aqueous aerosols using nanosecond laser-induced breakdown spectroscopy: droplet size and matrix effects

Nanosecond laser-induced breakdown spectroscopy has been examined for the analysis of suspended matter in a free stream of air. The real-time monitoring of this scenario poses major challenges for an accurate categorization due to its changing characteristics such as composition, size, and density of particles. The effects of particle size and matrix in the optical emission responses registered from such scenarios have been evaluated. Distant (10 m) plasmas of saline solutions, containing either NaCl or Na₂SO₄ at different concentrations, have been induced by nanosecond laser pulses at a wavelength of 1064 nm. The effects of the droplet size and its concentration on differences in the laser-induced breakdown probability, the intensity of the characteristic lines, and the plasma emission continuum have been discussed. The quantification of sodium in distant water droplets has been proved. However, an initial knowledge on the average droplet size is required. The average droplet size could be determined from the slope of H I and O I lines versus the continuum plasma emission, which is only weakly influenced by the salt content in the droplets.

Ambient ozone and incident diabetes: A prospective analysis in a large cohort of African American women

BACKGROUND

Ozone is a ubiquitous air pollutant with increasing concentrations in many populous regions. Toxicological studies show that ozone can cause oxidative stress and increase insulin resistance. These pathways may contribute to metabolic changes and diabetes formation. In this paper, we investigate the association between ozone and incident type 2 diabetes in a large cohort of African American women.

METHODS

We used Cox proportional hazards models to calculate hazard ratios (HRs) for incident type 2 diabetes associated with exposure to ozone in a cohort of 45,231 African American women living in 56 metropolitan areas across the United States. Ozone levels were estimated using the U.S. EPA Models-3/Community Multiscale Air Quality (CMAQ) predictions fused with ground measurements at a resolution of 12km for the years 2007-2008.

RESULTS

The HR per interquartile range increment of 6.7ppb of ozone was 1.18 (95% CI 1.04-1.34) for incident diabetes in adjusted models. This association was unaltered in models that controlled for fine particulate matter with diameter <2.5μm (PM2.5). Associations were modified by nitrogen dioxide (NO2) levels, such that HRs for ozone levels were larger in areas of lower NO2.

CONCLUSIONS

Our results provide initial evidence of a positive association between O3 and incident diabetes in African American women. Given the ubiquity of ozone exposure and the importance of diabetes on quality of life and survival, these results may have important implications for the protection of public health.

Biodegradation of the benzo[a]pyrene-contaminated sediment of the Jiaozhou Bay wetland using Pseudomonas sp. immobilization

To remove benzo[a]pyrene (BaP) that has accumulated in the Jiaozhou Bay wetland sediment, two strains (JB1 and JB2) were selected from the BaP-contaminated the wetland sediment and immobilized in coal cinder and chitosan beads using entrapping and surface adsorption methods. Biodegradation of BaP in sediment was carried out in pots. The results showed that, supported by the coal cinder and chitosan beads, 71.9, 65.5, 58.9 and 66.1% of the BaP in the immobilized cells was degraded after 40d. These percentages were clearly higher than the 47.7% that degraded from free cells. Kinetic analysis indicated that the immobilized gel-beads might remove BaP by multiple control steps. Compared to the chitosan, coal cinder-entrapping beads exhibited a higher removal rate for BaP; however, the degradation rates from coal cinder- and chitosan-surface adsorption beads were almost the same. This result indicates that in addition to the BaP-degrading bacteria, carrier materials and immobilizing methods play an important role in determining the success of a biodegradation strategy.

Bulky DNA Adducts, Tobacco Smoking, Genetic Susceptibility, and Lung Cancer Risk

The generation of bulky DNA adducts consists of conjugates formed between large reactive electrophiles and DNA-binding sites. The term "bulky DNA adducts" comes from early experiments that employed a ³²P-DNA postlabeling approach. This technique has long been used to elucidate the association between adducts and carcinogen exposure in tobacco smoke studies and assess the predictive value of adducts in cancer risk. Molecular data showed increased DNA adducts in respiratory tracts of smokers vs nonsmokers. Experimental studies and meta-analysis demonstrated that the relationship between adducts and carcinogens was linear at low doses, but reached steady state at high exposure, possibly due to metabolic and DNA repair pathway saturation and increased apoptosis. Polymorphisms of metabolic and DNA repair genes can increase the effects of environmental factors and confer greater likelihood of adduct formation. Nevertheless, the central question remains as to whether bulky adducts cause human cancer. If so, lowering them would reduce cancer incidence. Pooled and meta-analysis has shown that smokers with increased adducts have increased risk of lung cancer. Adduct excess in smokers, especially in prospective longitudinal studies, supports their use as biomarkers predictive of lung cancer.

Single Silver Adatoms on Nanostructured Manganese Oxide Surfaces: Boosting Oxygen Activation for Benzene Abatement

The involvement of a great amount of active oxygen species is a crucial requirement for catalytic oxidation of benzene, because complete mineralization of one benzene molecule needs 15 oxygen atoms. Here, we disperse single silver adatoms on nanostructured hollandite manganese oxide (HMO) surfaces by using a thermal diffusion method. The single-atom silver catalyst (Ag₁/HMO) shows high catalytic activity in benzene oxidation, and 100% conversion is achieved at 220 °C at a high space velocity of 23 000 h^-1. The Mars-van Krevelen mechanism is valid in our case as the reaction orders for both benzene and O₂ approach one, according to reaction kinetics data. Data from H₂ temperature-programmed reduction and O core-level X-ray photoelectron spectra (XPS) reveal that Ag₁/HMO possesses a great amount of active surface lattice oxygen available for benzene oxidation. Valence-band XPS and density functional theoretical calculations demonstrate that the single Ag adatoms have the upshifted 4d orbitals, thus facilitating the activation of gaseous oxygen. Therefore, the excellent activation abilities of Ag₁/HMO toward both surface lattice oxygen and gaseous oxygen account for its high catalytic activity in benzene oxidation. This work may assist with the rational design of efficient metal-oxide catalysts for the abatement of volatile organic compounds such as benzene.

Estimating population exposure to ambient polycyclic aromatic hydrocarbon in the United States - Part I: Model development and evaluation

PAHs (polycyclic aromatic hydrocarbons) in the environment are of significant concern due to their negative impact on human health. PAH measurements at the air toxics monitoring network stations alone are not sufficient to provide a complete picture of ambient PAH levels or to allow accurate assessment of public exposure in the United States. In this study, speciation profiles for PAHs were prepared using data assembled from existing emission profile data bases, and the Sparse Matrix Operator Kernel Emissions (SMOKE) model was used to generate the gridded national emissions of 16 priority PAHs in the US. The estimated emissions were applied to simulate ambient concentration of PAHs for January, April, July and October 2011, using a modified Community Multiscale Air Quality (CMAQ) model (v5.0.1) that treats the gas and particle phase partitioning of PAHs and their reactions in the gas phase and on particle surface. Predicted daily PAH concentrations at 61 air toxics monitoring sites generally agreed with observations, and averaging the predictions over a month reduced the overall error. The best model performance was obtained at rural sites, with an average mean fractional bias (MFB) of -0.03 and mean fractional error (MFE) of 0.70. Concentrations at suburban and urban sites were underestimated with overall MFB=-0.57 and MFE=0.89. Predicted PAH concentrations were highest in January with better model performance (MFB=0.12, MFE=0.69; including all sites), and lowest in July with worse model performance (MFB=-0.90, MFE=1.08). Including heterogeneous reactions of several PAHs with O3 on particle surface reduced the over-prediction bias in winter, although significant uncertainties were expected due to relative simple treatment of the heterogeneous reactions in the current model.

A review of biomass burning: Emissions and impacts on air quality, health and climate in China

Biomass burning (BB) is a significant air pollution source, with global, regional and local impacts on air quality, public health and climate. Worldwide an extensive range of studies has been conducted on almost all the aspects of BB, including its specific types, on quantification of emissions and on assessing its various impacts. China is one of the countries where the significance of BB has been recognized, and a lot of research efforts devoted to investigate it, however, so far no systematic reviews were conducted to synthesize the information which has been emerging. Therefore the aim of this work was to comprehensively review most of the studies published on this topic in China, including literature concerning field measurements, laboratory studies and the impacts of BB indoors and outdoors in China. In addition, this review provides insights into the role of wildfire and anthropogenic BB on air quality and health globally. Further, we attempted to provide a basis for formulation of policies and regulations by policy makers in China.

Layered Double Hydroxides-Based Materials as Oxidation Catalysts

This chapter is focused on the transition-metal-containing LDHs-based materials having potential applications in both catalytic selective oxidation for obtaining chemicals and intermediates, and complete oxidation as a promising valuable technology for the destruction of Volatile Organic Compounds (VOCs).

Ethylperoxy radical: approaching spectroscopic accuracy via coupled-cluster theory

Highly reliable ground and excited state properties of the conformers of ethylperoxy radical are predicted using coupled-cluster theory. This research has implications for future characterization of intermediates in tropospheric and low-temperature combustion processes.

Real-time monitoring of respiratory absorption factors of volatile organic compounds in ambient air by proton transfer reaction time-of-flight mass spectrometry

Respiratory absorption factors (AFs) are essential parameters in the evaluation of human health risks from toxic volatile organic compounds (VOCs) in ambient air. A method for the real time monitoring of VOCs in inhaled and exhaled air by proton transfer reaction time-of-flight mass spectrometry (PTR-TOF-MS) has been developed to permit the calculation of respiratory AFs of VOCs. Isoprene was found to be a better breath tracer than O₂, CO₂, humidity, or acetone for distinguishing between the expiratory and inspiratory phases, and a homemade online breath sampling device with a buffer tube was used to optimize signal peak shapes. Preliminary tests with seven subjects exposed to aromatic hydrocarbons in an indoor environment revealed mean respiratory AFs of 55.0%, 55.9%, and 66.9% for benzene, toluene, and C8-aromatics (ethylbenzene and xylenes), respectively. These AFs were lower than the values of 90% or 100% used in previous studies when assessing the health risks of inhalation exposure to hazardous VOCs. The mean respiratory AFs of benzene, toluene and C8-aromatics were 66.5%, 70.2% and 82.3% for the three female subjects; they were noticeably much higher than that of 46.4%, 45.2% and 55.3%, respectively, for the four male subjects.

DFT study of the formation mechanism of anthraquinone from the reaction of NO2 and anthracene on NaCl clusters: the role of NaNO3

Polycyclic aromatic hydrocarbons (PAHs) and oxygenated-PAHs are globally worrisome air pollutants because of their highly direct-acting mutagenicity and carcinogenicity. The formation of oxygenated-PAHs is of crucial importance for the prevention of their atmospheric pollution successfully. In this paper, the formation mechanism of oxygenated-PAHs from the heterogeneous reaction of NO₂ with anthracene on the surface of NaCl was studied by density functional theory (DFT) calculations. At first, the various adsorption configurations of NO₂ and N₂O₄ on NaCl were investigated. The chemical conversion mechanisms among these configurations were also investigated. It is found that these structures can easily interconvert due to their low energy barriers. NaNO₃ was found to be the main product of the reaction of NO₂/N₂O₄ on NaCl. Then the oxidation mechanism of anthracene by NO₂ on the NaCl surface showed that NaNO₃ is able to oxidize anthracene and plays a catalytic role in the reaction process. This means that the formation of NaNO₃ is very important to promote the formation of 9,10-anthraquinone from the heterogeneous reaction of NO₂ with anthracene. Our calculations also showed that the introduction of water can greatly accelerate this reaction process.

Mechanism for the growth of polycyclic aromatic hydrocarbons from the reactions of naphthalene with cyclopentadienyl and indenyl

Polycyclic aromatic hydrocarbons (PAHs) are globally concerned atmospheric particle-bound pollutants due to their toxicities. A mechanistic understanding of their formation from other environmental sources is of crucial importance for successful prevention of PAH. In the present work, the formation and growth mechanism of PAHs from the reactions of naphthalene with the cyclopentadienyl and indenyl radicals was investigated by using the hybrid density functional theory (DFT) at the MPWB1K/6-311+G(3df,2p)//MPWB1K/6-31+G(d,p) level. The rate constants for the crucial elementary steps were deduced with the aid of the canonical variational transition-state (CVT) theory with the small curvature tunneling (SCT) contribution. The formation of PAHs was involved in six elementary processes including: the addition reaction, ring closure, intramolecular H-shift, C-C cleavage, intramolecular H-shift and unimolecular elimination of CH3 or H. The C-C cleavage steps were revealed as the rate determining steps due to the extremely high barrier. At high temperature conditions like the combustion and pyrolysis of many hydrocarbons, the main products are phenanthrene, 4-methyl-phenanthrene and 1-methyl-phenanthrene from the reactions of naphthalene and cyclopentadienyl, and benzo(a)anthracene, 12-methyl-phenanthrene and 7-methyl-phenanthrene from the reactions of naphthalene and indenyl radicals. The reaction of naphthalene with indenyl radical is slightly more difficult than the reaction of naphthalene with cyclopentadienyl radical because of the bigger HOMO-LUMO orbital energy difference of naphthalene with indenyl relative to that of naphthalene with cyclopentadienyl.

Role of environmental factors and microorganisms in determining the fate of polycyclic aromatic hydrocarbons in the marine environment

Polycyclic aromatic hydrocarbons (PAHs) are widespread in marine ecosystems and originate from natural sources and anthropogenic activities. PAHs enter the marine environment in two main ways, corresponding to chronic pollution or acute pollution by oil spills. The global PAH fluxes in marine environments are controlled by the microbial degradation and the biological pump, which plays a role in particle settling and in sequestration through bioaccumulation. Due to their low water solubility and hydrophobic nature, PAHs tightly adhere to sediments leading to accumulation in coastal and deep sediments. Microbial assemblages play an important role in determining the fate of PAHs in water and sediments, supporting the functioning of biogeochemical cycles and the microbial loop. This review summarises the knowledge recently acquired in terms of both chronic and acute PAH pollution. The importance of the microbial ecology in PAH-polluted marine ecosystems is highlighted as well as the importance of gaining further in-depth knowledge of the environmental services provided by microorganisms.

Ozone levels in the Spanish Sierra de Guadarrama mountain range are above the thresholds for plant protection: analysis at 2262, 1850, and 995 m a.s.l

The Sierra de Guadarrama mountain range, located at 60 km from Madrid City (Spain), includes high valuable ecosystems following an altitude gradient, some of them protected under the Sierra de Guadarrama National Park. The characteristic Mediterranean climatic conditions and the precursors emitted from Madrid favor a high photochemical production of ozone (O₃) in the region. However, very little information is available about the patterns and levels of O₃ and other air pollutants in the high elevation areas and their potential effects on vegetation. Ozone levels were monitored at three altitudes (2262, 1850, and 995 m a.s.l.) for at least 3 years within the 2005-2011 period. NO _x and SO₂ were also recorded at the highest and lowest altitude sites. Despite the inter-annual and seasonal variations detected in the O₃ concentrations, the study revealed that SG is exposed to a chronic O₃ pollution. The two high elevation sites showed high O₃ levels even in winter and at nighttime, having low correlation with local meteorological variables. At the lower elevation site, O₃ levels were more related with local meteorological and pollution conditions. Ozone concentrations at the three sites exceeded the thresholds for the protection of human health and vegetation according to the European Air Quality Directive (EU/50/2008) and the thresholds for vegetation protection of the CLRTAP. Ozone should be considered as a stress factor for the health of the Sierra de Guadarrama mountain ecosystems. Furthermore, since O₃ levels at foothills differ from concentration in high elevation, monitoring stations in mountain ranges should be incorporated in regional air quality monitoring networks.

Plasminogen activator inhibitor-1 does not contribute to the pulmonary pathology induced by acute exposure to ozone

Expression of plasminogen activator inhibitor (PAI)-1, the major physiological inhibitor of fibrinolysis, is increased in the lung following inhalation of ozone (O₃), a gaseous air pollutant. PAI-1 regulates expression of interleukin (IL)-6, keratinocyte chemoattractant (KC), and macrophage inflammatory protein (MIP)-2, which are cytokines that promote lung injury, pulmonary inflammation, and/or airway hyperresponsiveness following acute exposure to O₃ Given these observations, we hypothesized that PAI-1 contributes to the severity of the aforementioned sequelae by regulating expression of IL-6, KC, and MIP-2 following acute exposure to O₃ To test our hypothesis, wild-type mice and mice genetically deficient in PAI-1 (PAI-1-deficient mice) were acutely exposed to either filtered room air or O₃ (2 ppm) for 3 h. Four and/or twenty-four hours following cessation of exposure, indices of lung injury [bronchoalveolar lavage fluid (BALF) protein and epithelial cells], pulmonary inflammation (BALF IL-6, KC, MIP-2, macrophages, and neutrophils), and airway responsiveness to aerosolized acetyl-β-methylcholine chloride (respiratory system resistance) were measured in wild-type and PAI-1-deficient mice. O₃ significantly increased indices of lung injury, pulmonary inflammation, and airway responsiveness in wild-type and PAI-1-deficient mice. With the exception of MIP-2, which was significantly lower in PAI-1-deficient as compared to wild-type mice 24 h following cessation of exposure to O₃, no other genotype-related differences occurred subsequent to O₃ exposure. Thus, following acute exposure to O₃, PAI-1 neither regulates pulmonary expression of IL-6 and KC nor functionally contributes to any of the pulmonary pathological sequelae that arise from the noxious effects of inhaled O₃.

Air-water partition coefficients for a suite of polycyclic aromatic and other C10 through C20 unsaturated hydrocarbons

The air-water partition coefficients (Kaw) for 86 large polycyclic aromatic hydrocarbons and their unsaturated relatives were estimated using high-level G4(MP2) gas and aqueous phase calculations with the SMD, IEFPCM-UFF, and CPCM solvation models. An extensive method validation effort was undertaken which involved confirming that, via comparisons to experimental enthalpies of formation, gas-phase energies at the G4(MP2) level for the compounds of interest were at or near thermochemical accuracy. Investigations of the three solvation models using a range of neutral and ionic compounds suggested that while no clear preferential solvation model could be chosen in advance for accurate Kaw estimates of the target compounds, the employment of increasingly higher levels of theory would result in lower Kaw errors. Subsequent calculations on the polycyclic aromatic and unsaturated hydrocarbons at the G4(MP2) level revealed excellent agreement for the IEFPCM-UFF and CPCM models against limited available experimental data. The IEFPCM-UFF-G4(MP2) and CPCM-G4(MP2) solvation energy calculation approaches are anticipated to give Kaw estimates within typical experimental ranges, each having general Kaw errors of less than 0.5 log10 units. When applied to other large organic compounds, the method should allow development of a broad and reliable Kaw database for multimedia environmental modeling efforts on various contaminants.

Health Outcomes of Exposure to Biological and Chemical Components of Inhalable and Respirable Particulate Matter

Particulate matter (PM) is a key indicator of air pollution and a significant risk factor for adverse health outcomes in humans. PM is not a self-contained pollutant but a mixture of different compounds including chemical and biological fractions. While several reviews have focused on the chemical components of PM and associated health effects, there is a dearth of review studies that holistically examine the role of biological and chemical components of inhalable and respirable PM in disease causation. A literature search using various search engines and (or) keywords was done. Articles selected for review were chosen following predefined criteria, to extract and analyze data. The results show that the biological and chemical components of inhalable and respirable PM play a significant role in the burden of health effects attributed to PM. These health outcomes include low birth weight, emergency room visit, hospital admission, respiratory and pulmonary diseases, cardiovascular disease, cancer, non-communicable diseases, and premature death, among others. This review justifies the importance of each or synergistic effects of the biological and chemical constituents of PM on health. It also provides information that informs policy on the establishment of exposure limits for PM composition metrics rather than the existing exposure limits of the total mass of PM. This will allow for more effective management strategies for improving outdoor air quality.

Expanding the applicability of electrostatic potentials to the realm of transition states

Central to any reaction mechanism study, and sometimes a challenging job, is tracing a transition state in a reaction path. For the first time, electrostatic potentials (ESP) of the reactants were used as guiding tactics to predict whether there is a possibility of any transition state in a reaction surface. The main motive behind this strategy is to see whether the directionality nature of the transition state has something to do with the anisotropic natures of the ESP with their embedded directionalities. Strategically, some atmospherically important, but simple, reactions have been chosen for this study, which heretofore were believed to be barrierless. By carefully analysing the ESP maps of the reactants, regions of possible interactions were located. Using the bilinear interpolation of the 2D grids of the ESP surfaces, search co-ordinates were fine-tuned for a local gradient based approach for the search of a transition state. Out of the three reactions studied in this work, we were able to successfully locate transition states, for the first time, in two cases and the third one still proved to be barrierless. This gives a clear indication that though ESP maps can qualitatively predict the possibility of a transition state; it is not always true that there should definitely be a transition state, as some of the reaction surfaces may genuinely be barrierless. But, nevertheless this strategy definitely has credential to be tested for many more reactions, either new or already established, and may be applied to create the initial search co-ordinates for any well-established transition state search method. Moreover, we have observed that the analysis of the ESP maps of the reactants were very much useful in explaining the nature of interactions existing in those observed transition states and we hope the same can also be extended to any transition state in an electrostatically driven reaction potential energy surface.

Mechanistic and kinetic study on the reaction of ozone and trans-2-chlorovinyldichloroarsine

Singlet and triplet potential energy surfaces for the atmospheric ozonation of trans-2-chlorovnyldichloroarsine (lewisite) are investigated theoretically. Optimizations of the reactants, products, intermediates and transition states are carried out at the BHandHLYP/6-311+G(d,p) level. Single point energy calculations are performed at the CCSD(T)/6-311+G(d,p) level based on the optimized structures. The detailed mechanism is presented and discussed. Various possible H (or Cl)-abstraction and C (or As)-addition/elimination pathways are considered. The results show that the As-addition/elimination is more energetically favorable than the other mechanisms. Rice-Ramsperger-Kassel-Marcus (RRKM) theory is used to compute the rate constants over the possible atmospheric temperature range of 200-3000 K and the pressure range of 10(-8)-10(9) Torr. The calculated rate constant is in good agreement with the available experimental data. The total rate coefficient shows positive temperature dependence and pressure independence. The modified three-parameter Arrhenius expressions for the total rate coefficient and individual rate coefficients are represented. Calculation results show that major product is CHClCHAs(OOO)Cl2 (s-IM3) at the temperature below 600 K and O2 + CHClCHAsOCl2 (s-P9) play an important role at the temperature between 600 and 3000 K. Time-dependent DFT (TD-DFT) calculations indicate that CHCl(OOO)CHAsCl2 (s-IM3) and CHOAsCl2 (s-P5) can take photolysis easily in the sunlight. Due to the absence of spectral information for arsenide, computational vibrational spectra of the important intermediates and products are also analyzed to provide valuable evidence for subsequent experimental identification.

The effect of anthropogenic activity on BTEX, NO2, SO2, and CO concentrations in urban air of the spa city of Sopot and medium-industrialized city of Tczew located in North Poland

The major goal of the present study is to compare the air quality of two urban locations situated in Northern Poland - the spa City of Sopot and the medium-industrialized city of Tczew using chemometric methods. As a criterion for the assessment of atmospheric air quality, measurements of benzene, toluene, ethylbenzene and total xylenes were used (collected from atmospheric air using diffusion-type passive samplers) as well as measurements of inorganic compounds - CO, NO2 and SO2, which were subject to routine control and determined by means of automatic analysers. Studies related to determination of defined chemical compounds in the urban air in the monitored area were performed from January 2013 to December 2014. By interpreting the results obtained and using basic multivariate statistical tools (cluster analysis and principal components analysis), major sources of emissions of determined pollutants in the air in urbanized areas were defined. The study also shows the potential influence of the sea breeze on concentrations of chemical compounds in the atmospheric air in the spa city of Sopot.

Role of carbonyls and aromatics in the formation of tropospheric ozone in Rio de Janeiro, Brazil

The ozone in Rio de Janeiro has been in violation of national air quality standards. Among all of the monitoring stations, the Bangu neighbourhood has the most violations of the national standard of 160 μg m(-3) for the years 2012 and 2013. This study evaluated the reactivity of the carbonyls and aromatics in the tropospheric ozone formation processes. The samples were collected between July and October of 2013. Carbonyls were sampled using SiO2 cartridges coated with C18 and impregnated with 2,4-dinitrophenylhydrazine and were analysed by HPLC. Activated carbon cartridges and GC/MS were used to measure the concentration of monoaromatic hydrocarbons. An air quality monitoring station provided the concentrations of the criteria pollutants and the meteorological parameters. Cluster analysis and a Pearson correlation matrix were used to determine the formation of groups and the correlation of the variables. The evaluation of the volatile organic compounds (VOC) reaction with OH radicals and the MIR scale was used to extrapolate the reactivity of VOCs to the ozone formation. The average concentrations obtained were 19.7 and 51.9 μg m(-3) for formaldehyde and acetaldehyde, respectively. The mean concentrations obtained for aromatics were 1.5, 6.7, 1.5, 2.6 and 1.6 μg m(-3) for benzene, toluene, ethyl benzene, m+p-xylene and o-xylene, respectively. The cluster analysis indicated the presence of three similar groups, with one formed by gaseous criteria pollutants, another formed by the meteorological parameters, ozone and fine particles, and the last group formed by the aromatics. For the two reactivity scales evaluated, acetaldehyde and toluene were the main ozone precursors.

Photochlorination of Polycyclic Aromatic Hydrocarbons in Acidic Brine Solution

The potential for the formation of chlorinated polycyclic aromatic hydrocarbons via photochlorination of PAHs has been investigated in milli-Q water/synthetic water containing NaCl and PAHs with either UV or visible light. The photochlorination of pyrene occurred under acidic conditions in the presence of both UV and visible light, resulting in 1-chloropyrene as the main product. Benzo[a]pyrene yielded 6-chlorobenzo[a]pyrene following visible light irradiation; however the reaction was dependent upon solution pH. The photochlorination of PAHs was proposed to proceed via a consecutive reaction model. The rate constants associated with the photochlorination and photodecay processes were determined with the observed and theoretical values displaying similar trends, whereas the observed values were approximately 50-1000 times lower than the theoretical values. The lower observed values could be due to undergo photodecay rather than photochlorination of PAHs. Therefore, as photochlorination of PAHs appears to be significantly affected by solution pH, this information may allow for minimizing the impact on the environment.

Shape dependence of nanoceria on complete catalytic oxidation of o-xylene

CeO₂ nanorods exhibit the highest concentration of oxygen vacancy clusters for O₂ activation, guaranteeing the highest activity for o-xylene oxidation.

Effects of Different Water Seasons on the Residual Characteristics and Ecological Risk of Polycyclic Aromatic Hydrocarbons in Sediments from Changdang Lake, China

The sediments’ samples were collected from Changdang Lake for the concentration of fourteen polycyclic aromatic hydrocarbons in March (dry season), June (wet season), and September (temperate season) 2013. The highest average value of∑PAHswas detected as 295.28 ng/g dw in March, followed by 240.91 ng/g dw in June and 165.81 ng/g dw in September. Source characterization studies based on the analysis of diagnostic ratio (triangular plot method) suggested that the PAHs in sediments from Changdang Lake were mainly from the mixed combustion source of biomass and petroleum, and the origins of PAHs in different sampling sites have a great deal of temporal and spatial variability during different water seasons. Redundancy analysis was applied to identify the impact factors and the possible relationship between PAHs and environmental parameters. The predicted results showed that the main factors impacting PAHs temporal distribution were temperature, dissolved oxygen, pH, and oxidation-reduction potential, while conductivity showed secondary impacts on the PAHs distribution. Risk assessment of PAHs in sediments was carried out based on the US Sediments Quality Guidelines (SQGs). By comparing the present study results with SQGs standard values results showed that the adverse effects are not expected at the present levels of PAHs contamination observed in the sediments from Changdang Lake.

Modification of MnCo2Ox catalysts by NbOx for low temperature selective catalytic reduction of NO with NH3

Among the NbOx modified MnCo₂Ox catalysts by co-precipitation, MnCo₂Nb_0.5Ox presented high activity, N₂ selectivity and H₂O resistance for NH₃-SCR reaction at low temperatures.

Exploring mechanisms of a tropospheric archetype: CH3O2 + NO

Methylperoxy radical (CH3O2) and nitric oxide (NO) contribute to the propagation of photochemical smog in the troposphere via the production of methoxy radical (CH3O) and nitrogen dioxide (NO2). This reaction system also furnishes trace quantities of methyl nitrate (CH3ONO2), a sink for reactive NOx species. Here, the CH3O2 + NO reaction is examined with highly reliable coupled-cluster methods. Specifically, equilibrium geometries for the reactants, products, intermediates, and transition states of the ground-state potential energy surface are characterized. Relative reaction enthalpies at 0 K (ΔH0K) are reported; these values are comprised of electronic energies extrapolated to the complete basis set limit of CCSDT(Q) and zero-point vibrational energies computed at CCSD(T)/cc-pVTZ. A two-part mechanism involving CH3O and NO2 production followed by radical recombination to CH3ONO2 is determined to be the primary channel for formation of CH3ONO2 under tropospheric conditions. Constrained optimizations of the reaction paths at CCSD(T)/cc-pVTZ suggest that the homolytic bond dissociations involved in this reaction path are barrierless.

Relative Influence of Trans-Pacific and Regional Atmospheric Transport of PAHs in the Pacific Northwest, U.S

The relative influences of trans-Pacific and regional atmospheric transport on measured concentrations of polycyclic aromatic hydrocarbons (PAHs), PAH derivatives (nitro- (NPAH) and oxy-(OPAH)), organic carbon (OC), and particulate matter (PM) less than 2.5 μm in diameter (PM2.5) were investigated in the Pacific Northwest, U.S. in 2010-2011. Ambient high volume PM2.5 air samples were collected at two sites in the Pacific Northwest: (1.) Mount Bachelor Observatory (MBO) in the Oregon Cascade Range (2763 m above sea level (asl)) and 2.) Confederated Tribes of the Umatilla Indian Reservation (CTUIR) in the Columbia River Gorge (CRG) (954 m asl). At MBO, the 1,8-dinitropyrene concentration was significantly positively correlated with the time a sampled air mass spent over Asia, suggesting that this NPAH may be a good marker for trans-Pacific atmospheric transport. At CTUIR, NOx, CO2, and SO2 emissions from a 585 MW coal fired power plant, in Boardman OR, were found to be significantly positively correlated with PAH, OPAH, NPAH, OC, and PM2.5 concentrations. By comparing the Boardman Plant operational time frames when the plant was operating to when it was shut down, the plant was found to contribute a large percentage of the measured PAH (67%), NPAH (91%), OPAH (54%), PM2.5 (39%), and OC (38%) concentrations at CTUIR and the CRG prior to Spring 2011 and likely masked trans-Pacific atmospheric transport events to the CRG. Upgrades installed to the Boardman Plant in the spring of 2011 dramatically reduced the plant's contribution to PAH and OPAH concentrations (by ∼72% and ∼40%, respectively) at CTUIR and the CRG, but not NPAH, PM2.5 or OC concentrations.

Analysis of ambient formaldehyde in the eastern region of India along Indo-Gangetic Plain

Ambient levels of formaldehyde (HCHO) were measured in the tropical urban mega city of Kolkata from July 2012 to April 2014, based on USEPA Compendium Method TO-11A using 2,4-dinitrophenylhydrazine (2,4-DNPH). The samples were analyzed by isocratic reverse-phase high-performance liquid chromatography (HPLC) with an ultraviolet detector at a wavelength of 360 nm. High values of HCHO were recorded at our site. The highest and average HCHO mixing ratio measured for the entire study period was 803 and 217 ppbv respectively. Seasonal wind regimes have been found to influence the seasonal pattern of HCHO mixing ratio at this site resulting in relatively higher mixing ratio of HCHO during the pre-monsoon periods as compared to the others. Apart from these, sampling-based measurements of CH4 and continuous measurements of ozone (O3) and CO were also performed with the objective to study the interrelationship of HCHO with these species. The results suggest the presence of highly complex chemistry among them.

Theoretical study on the atmospheric transformation mechanism of pirimiphos-methyl initiated by O3

Pirimiphos-methyl (PMM) is a widely used organophosphorus pesticide that can be released into the atmosphere in gas and condensed phases. It possesses a PS bond and an N,N-dialkyl group adjacent to pyrimidine, which are common functional groups for pesticides. Currently, the reaction mechanisms of O3 with these functional groups are poorly understood. In this study, the mechanisms and possible degradation products for O3-initiated atmospheric oxidation of PMM were investigated using the Density Functional Theory (DFT) method. The results show that H abstraction from the alpha carbon of the N,N-diethyl group and its subsequent reactions (hydroxylation, N-dealkylation, and carbonylation reactions), as well as the transformation of the PS bond to the PO oxone form, are the most favorable reaction pathways for PMM and O3. The Gibbs free energy (ΔG) indicates that the subsequent reactions tend to take place more spontaneously once the initial reaction occurs. In addition, theoretical calculations indicate that water can serve as an effective catalyst in the N-dealkylation reaction process. Water-assisted reactions lead to the activation energy decreasing by 20.2 kcal mol(-1) compared with direct reactions, and thus may represent a dominant reaction pathway for the N-dealkylation process in the atmosphere. These theoretical results provide new insights into O3-initiated degradation of PMM and its analogues.