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Atmospheric Environment (v.44, #12)

Editorial board (pp. i).

Biochemical and cellular effects of electrophiles present in ambient air samples by Noriko Iwamoto; Akira Nishiyama; Arantzazu Eiguren-Fernandez; William Hinds; Yoshito Kumagai; John R. Froines; Arthur K. Cho; Masaru Shinyashiki (pp. 1483-1489).

Ambient vapor-phase samples collected in Riverside, California had shown that both redox and electrophilic activity were present, with the vapor phase containing higher levels of electrophiles than the particle phase. In this study, the biochemical effects of the vapor-phase electrophiles were examined using the purified thiol proteins, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), protein tyrosine phosphatase 1B (PTP1B) and KELCH-1 like ECH-associated protein 1 (Keap1). The results demonstrated that the thiol proteins were inactivated by the vapor-phase samples through covalent modifications. Next, two cellular responses, epidermal growth factor receptor (EGFR)/mitogen-activated protein (MAP) kinase and NF-E2-related factor 2 (Nrf2), to the ambient vapor-phase samples were assessed in A549 and RAW 264.7 cell lines, respectively. The vapor-phase samples, at non-oxidative concentrations, increased phosphorylation of EGFR, which is negatively regulated by PTP1B, and its downstream MAP kinase, extracellular signal-regulated kinase (ERK)1/2. Activation of Nrf2, which requires Keap1 alkylation, and expression of its downstream proteins were also observed. The electrophilic compounds present in ambient vapor-phase were shown to modify cellular proteins through covalent modification and to activate diverse cellular responses that can lead to inflammatory and adaptive responses.

Keywords: Ambient vapor-phase; Electrophiles; Particulate matters; Thiol proteins; Cell responses

Evaluation of a diode laser based photoacoustic instrument combined with preconcentration sampling for measuring surface–atmosphere exchange of ammonia with the aerodynamic gradient method by Andrea Pogány; Árpád Mohácsi; Stephanie K. Jones; Eiko Nemitz; Attila Varga; Zoltán Bozóki; Zoltán Galbács; Tamás Weidinger; László Horváth; Gábor Szabó (pp. 1490-1496).

We present here a novel instrument for measuring surface–atmosphere exchange fluxes of ammonia. The instrument is the upgraded version of a recently developed near-infrared diode laser based photoacoustic ammonia concentration monitoring instrument, i.e. the original instrument is supplemented with two additional sampling lines, an appropriate gas handling system and an advanced software controlling gradient measurements. As a result of these developments, ammonia concentration can be measured simultaneously at three different heights above the ground and ammonia fluxes can be calculated from these data using the aerodynamic gradient method. The instrument operates fully automatically, requires minimal maintenance and has a temperature controlled, waterproof housing which makes it suitable for measurements even under harsh field conditions. Preliminary tests on stability and accuracy were carried out during two two-week field measurement campaigns, with the three sampling inlets being placed at the same height together with the inlet of a reference instrument. The readings of the three channels agreed well (with correlation coefficients above 0.96). Comparison to reference instruments showed good stability of the photoacoustic instrument, there was no measurable zero-drift or change in sensitivity during the tests. Flux measurements were carried out during a three-week field campaign in southern Scotland over fertilized grassland with reference to a wet-chemical AMANDA instrument in gradient configuration. Ammonia fluxes calculated from the data of the two instruments agreed well. Fluxes up to 2500 ng m⁻² s⁻¹ were observed after fertilization. The minimum detectable ammonia flux was calculated on the basis of “virtual ammonia fluxes”, from measurements carried out with all inlets at the same height and was found to be ±60 ng m⁻² s⁻¹ which ensures reliable measurements above intensively managed grasslands or agricultural fields.

Keywords: Photoacoustic spectroscopy; Ammonia; Flux; Aerodynamic gradient method

Speciation and diurnal variation of thoracic, fine thoracic and sub-micrometer airborne particulate matter at naturally ventilated office environments by Benjamin Horemans; René Van Grieken (pp. 1497-1505).

Thoracic (PM₁₀), fine thoracic (PM_2.5) and sub-micrometer (PM₁) airborne particulate matter was sampled during day and night. In total, about 100 indoor and outdoor samples were collected for each fraction at ten different office environments. Energy-dispersive X-ray fluorescence spectrometry and ion chromatography were applied for the quantification of some major and minor elements and ions in the collected aerosols. During daytime, mass concentrations were in the ranges: 11–29, 8.1–24, and 6.6–18 μg m⁻³, with averages of 20 ± 1, 15.0 ± 0.9, and 11.0 ± 0.8 μg m⁻³, respectively. At night, mass concentrations were found to be significantly lower for all fractions. Indoor PM₁ concentrations exceeded the corresponding outdoor levels during office hours and were thought to be elevated by office printers. Particles with diameters between 1 and 2.5 μm and 2.5 and 10 μm were mainly associated with soil dust elements and were clearly subjected to distinct periods of settling/resuspension. Indoor NO₃⁻ levels were found to follow specific microclimatic conditions at the office environments, while daytime levels of sub-micrometer Cl⁻ were possibly elevated by the use of Cl-containing cleaning products. Indoor carbon black concentrations were sometimes as high as 22 μg m⁻³ and were strongly correlated with outdoor traffic conditions.

Keywords: Airborne particulate matter; Office environment; Diurnal; Inorganic composition; PM; ₁₀; PM; _2.5; PM; ₁

Gaseous and particulate water-soluble organic and inorganic nitrogen in rural air in southern Scotland by Juan M. González Benítez; J. Neil Cape; Mathew R. Heal (pp. 1506-1514).

Simultaneous daily measurements of water-soluble organic nitrogen (WSON), ammonium and nitrate were made between July and November 2008 at a rural location in south-east Scotland, using a ‘Cofer’ nebulizing sampler for the gas phase and collection on an open-face PTFE membrane for the particle phase. Average concentrations of NH₃ were 82 ± 17 nmol N m⁻³ (error is s.d. of triplicate samples), while oxidised N concentrations in the gas phase (from trapping NO₂ and HNO₃) were smaller, at 2.6 ± 2.2 nmol N m⁻³, and gas-phase WSON concentrations were 18 ± 11 nmol N m⁻³. The estimated collection efficiency of the nebulizing samplers for the gas phase was 88 (±8) % for NH₃, 37 (±16) % for NO₂ and 57 (±7) % for WSON; reported average concentrations have not been corrected for sampling efficiency. Concentrations in the particle phase were smaller, except for nitrate, at 21 ± 9, 10 ± 6 and 8 ± 9 nmol N m⁻³, respectively. The absence of correlation in either phase between WSON and either (NH₃ + NH₄⁺) or NO₃⁻ concentrations suggests atmospheric WSON has diverse sources. During wet days, concentrations of gas and particle-phase inorganic N were lower than on dry days, whereas the converse was true for WSON. These data represent the first reports of simultaneous measurements of gas and particle phase water-soluble nitrogen compounds in rural air on a daily basis, and show that WSON occurs in both phases, contributing 20–25% of the total water-soluble nitrogen in air, in good agreement with earlier data on the contribution of WSON to total dissolved N in rainfall in the UK.

Keywords: Cofer sampler; Water-soluble organic nitrogen; DON; Reactive nitrogen

Establishment of a database of emission factors for atmospheric pollutants from Chinese coal-fired power plants by Yu Zhao; Shuxiao Wang; Chris P. Nielsen; Xinghua Li; Jiming Hao (pp. 1515-1523).

Field measurements and data investigations were conducted for developing an emission factor database for inventories of atmospheric pollutants from Chinese coal-fired power plants. Gaseous pollutants and particulate matter (PM) of different size fractions were measured using a gas analyzer and an electric low-pressure impactor (ELPI), respectively, for ten units in eight coal-fired power plants across the country. Combining results of field tests and literature surveys, emission factors with 95% confidence intervals (CIs) were calculated by boiler type, fuel quality, and emission control devices using bootstrap and Monte Carlo simulations. The emission factor of uncontrolled SO₂ from pulverized combustion (PC) boilers burning bituminous or anthracite coal was estimated to be 18.0Skgt⁻¹ (i.e., 18.0×the percentage sulfur content of coal, S) with a 95% CI of 17.2S–18.5S. NO_X emission factors for pulverized-coal boilers ranged from 4.0 to 11.2kgt⁻¹, with uncertainties of 14–45% for different unit types. The emission factors of uncontrolled PM_2.5, PM₁₀, and total PM emitted by PC boilers were estimated to be 0.4A (where A is the percentage ash content of coal), 1.5A and 6.9Akgt⁻¹, respectively, with 95% CIs of 0.3A–0.5A, 1.1A–1.9A and 5.8A–7.9A. The analogous PM values for emissions with electrostatic precipitator (ESP) controls were 0.032A (95% CI: 0.021A–0.046A), 0.065A (0.039A–0.092A) and 0.094A (0.0656A–0.132A)kgt⁻¹, and 0.0147A (0.0092–0.0225A), 0.0210A (0.0129A–0.0317A), and 0.0231A (0.0142A–0.0348A) for those with both ESP and wet flue-gas desulfurization (wet-FGD). SO₂ and NO_X emission factors for Chinese power plants were smaller than those of U.S. EPA AP-42 database, due mainly to lower heating values of coals in China. PM emission factors for units with ESP, however, were generally larger than AP-42 values, because of poorer removal efficiencies of Chinese dust collectors. For units with advanced emission control technologies, more field measurements are needed to reduce emission factor uncertainties.

Keywords: Coal-fired power plant; Emission factor; Uncertainty; Monte Carlo simulation; China

Aerosol trace metals, particle morphology and total gaseous mercury in the atmosphere of Oxford, UK by M.L.I. Witt; N. Meheran; T.A. Mather; J.C.M. de Hoog; D.M. Pyle (pp. 1524-1538).

An investigation of atmospheric trace metals was conducted in Oxford, UK, a small city ∼60 miles northwest of London, in 2007 and 2008. Concentrations of Sr, Mo, Cd, Pb, V, Cr, Mn, Fe, Co, Ni, Cu and Zn in aerosol were measured in bulk and size segregated samples. In addition, total gaseous mercury (TGM) concentrations were monitored semi-continuously by cold vapour-atomic fluorescence spectroscopy. Metal concentrations in Oxford were intermediate between previously reported levels of UK rural and urban areas for most metals studied and levels of Cd, Ni and Pb were within European guidelines. Metal concentrations appeared to be influenced by higher traffic volume on a timescale of hours. The influence of traffic on the aerosols was also suggested by the observation of carbonaceous particles via scanning electron microscopy (SEM). Air mass back trajectories suggest air masses arriving in Oxford from London and mainland Europe contained the highest metal concentrations. Aerosol samples collected over Bonfire Weekend, a period of intense firework use and lighting of bonfires in the UK, showed metal concentrations 6–46 times higher than at other times. Strontium, a tracer of firework release, was present at higher concentrations and showed a change in its size distribution from the coarse to fine mode over Bonfire Weekend. The presence of an abundance of spherical Sr particles was also confirmed in SEM images. The average TGM concentration in Oxford was 3.17 ng m⁻³ (st. dev. 1.59) with values recorded between 1.32 and 23.2 ng m⁻³. This is a higher average value than reported from nearby rural locations, although during periods when air was arriving from the west, similar concentrations to these rural areas were seen in Oxford. Comparison to meteorological data suggests that TGM in Oxford's air is highest when wind is arriving from the east/southeast. This may be due to emissions from London/mainland Europe with a possible contribution from emissions from a local crematorium situated 4 miles east of the sampling site. A diurnal pattern was also observed in the TGM data with a minimum concentration during the day when mercury may have been diluted by thermal mixing of the atmospheric boundary layer. Additionally, this diurnal pattern may reflect variations in a local source of TGM.

Keywords: Hg; Fireworks; Lead; Cadmium; Iron; Pollutant; Anthropogenic

Characterization of particulate matter concentrations during controlled indoor activities by T. Glytsos; J. Ondráček; L. Džumbová; I. Kopanakis; M. Lazaridis (pp. 1539-1549).

Indoor sources have been identified as a major contributor to the increase of particle concentration in indoor environments. The work presented here is a study of the characteristics of particulate matter number size distribution and mass concentration under controlled indoor activities in a laboratory room. The objective is to characterize particulate matter concentrations indoors resulted under the influence of specific sources. Measurements were performed in an empty laboratory (period September–October 2006) using a GRIMM SMPS+C system (particle size range between 11.1 and 1083.3 nm), a DustTrak Aerosol Monitor (TSI) and a P-Trak Ultrafine Particle Counter (TSI). The studied indoor activities included candle burning, hot plate heating, water boiling, onion frying, vacuuming, hair drying, hair spraying, smoking and burning of incense stick. The AMANpsd computer algorithm was used to evaluate the modal structure of measured particle number size distribution data. Furthermore, the change of the particle number size distribution shape under the influence of different emission sources was studied versus time. Finally the particle emission rates were computed. High particle number concentrations were observed during smoking, onion frying, candle burning and incense stick burning. The highest particle mass concentrations were measured during smoking and hair spraying. The shift of the particle size distribution to larger diameters suggests the presence of strong coagulation effect during candle burning, incense stick burning, smoking and onion frying. The size distribution was mainly bimodal during onion frying and candle burning, whereas the size distribution remained unimodal during incense stick burning and smoking experiments.

Keywords: Indoor sources; Particle mass and number concentration; Number size distribution; Emission rates

Atmospheric PCB congeners across Chicago by Dingfei Hu; Hans-Joachim Lehmler; Andres Martinez; Kai Wang; Keri C. Hornbuckle (pp. 1550-1557).

We have measured PCBs in 184 air samples collected at 37 sites in the city of Chicago using an innovative system of high-volume air samplers mounted on two health clinic vans. Here we describe results of sampling conducted from November 2006 to November 2007. The samples were analyzed for all 209 PCB congeners using a gas chromatograph with tandem mass spectrometry (GC–MS/MS). The ΣPCBs (sum of 169 peaks) in Chicago ranged from 75 pg m⁻³ to 5500 pg m⁻³ and primarily varied as a function of temperature. The congener patterns are surprisingly similar throughout the city even though the temperature-corrected concentrations vary by more than an order of magnitude. The average profile resembles a mixture of Aroclor 1242 and Aroclor 1254, and includes many congeners that have been identified as being aryl hydrocarbon receptor (AhR) agonists (dioxin-like) and/or neurotoxins. The toxic equivalence (TEQ) and neurotoxic equivalence (NEQ) in air were calculated and investigated for their spatial distribution throughout the urban-industrial complex of Chicago. The NEQ concentrations are linearly correlated with ΣPCBs while the TEQ concentrations are not predictable. The findings of this study suggest that airborne PCBs in Chicago are widely present and elevated in residential communities; there are multiple sources rather than one or a few locations of very high emissions; the emission includes congeners associated with dioxin-like or neurotoxic effects and congeners associated with unidentified sources.

Keywords: Spatial distribution of PCBs; Co-planar PCBs; NEQ; TEQ; Urban air toxics

Assessing sensitivity of source term estimation by Kerrie J. Long; Sue Ellen Haupt; George S. Young (pp. 1558-1567).

Source term estimation algorithms compute unknown atmospheric transport and dispersion modeling variables from concentration observations made by sensors in the field. Insufficient spatial and temporal resolution in the meteorological data as well as inherent uncertainty in the wind field data make source term estimation and the prediction of subsequent transport and dispersion extremely difficult. This work addresses the question: how many sensors are necessary in order to successfully estimate the source term and meteorological variables required for atmospheric transport and dispersion modeling?The source term estimation system presented here uses a robust optimization technique – a genetic algorithm (GA) – to find the combination of source location, source height, source strength, surface wind direction, surface wind speed, and time of release that produces a concentration field that best matches the sensor observations. The approach is validated using the Gaussian puff as the dispersion model in identical twin numerical experiments. The limits of the system are tested by incorporating additive and multiplicative noise into the synthetic data. The minimum requirements for data quantity and quality are determined by an extensive grid sensitivity analysis. Finally, a metric is developed for quantifying the minimum number of sensors necessary to accurately estimate the source term and to obtain the relevant wind information.

Keywords: Source term estimation; Gaussian puff model; Genetic algorithm; Dispersion modeling

An investigation into long-distance health impacts of the 1996 eruption of Mt Ruapehu, New Zealand by Rewi M. Newnham; Kim N. Dirks; Dan Samaranayake (pp. 1568-1578).

During the June 1996 eruption of Mt Ruapehu, New Zealand, traces of fine particulate volcanic ash were observed in or near the cities of Hamilton and Auckland, 166–282 km from the volcano. Although no health impacts in these cities were attributed to the eruption, hospital records at both cities for the following month show the highest rates of respiratory mortality for the 1990s. Alternative explanations for this increase in respiratory mortality were investigated, including urban air pollution, adverse weather conditions and influenza. Comparable records from Wellington city, assumed to be outside the zone of ash dispersal, were used as a ‘control’. Our results suggest that at Hamilton, where non-volcanic factors can largely be eliminated as making a significant contribution, diffuse volcanic ashfall may have been an important factor in respiratory mortality during the weeks following the eruption. At Auckland, further away from the volcano but with a much larger population than Hamilton, a case for a weaker volcanic contribution can be made, but is more equivocal because of coincidentally high urban air pollution and cold, stable weather.These findings support the concept that diffuse fine volcanic ash poses a risk to respiratory health at greater distances from an eruption than is currently perceived. This is because the finest ‘respirable’ fraction of erupted material with potentially hazardous physico-chemical properties is likely to be ejected highest into the atmosphere and dispersed the greatest distance. If significant amounts reach large cities, then large numbers of individuals may be at risk, especially those already suffering poor respiratory health. This work has important implications for environmental health and hazard management in New Zealand and in other regions that may be susceptible to a similar volcanic threat.

Keywords: Volcanic ash; Respiratory mortality; Mt Ruapehu; Volcanic hazards

Evaluation of adsorbent sampling tube materials and Tenax-TA for analysis of volatile biogenic organic compounds by Robert R. Arnts (pp. 1579-1584).

Adsorbent tube materials, bed retainers and Tenax-TA were evaluated for their respective roles in adsorbing biogenic volatile organic compounds from air and their tendencies to cause chemical transformation of analytes upon thermal desorption. Stainless steel, Silcosteel^® and Sulfinert^® treated stainless steel tubes exhibited varying degrees of adsorption and reactivity towards some analytes. However, the typical short exposure of the sample stream to wall material before entering an adsorbent bed, minimizes the effect of these properties. Three forms of silica wool (untreated glass wool and siloxane-treated glass and fused silica wool), often used as adsorbent bed retainers, were evaluated and found to function as an adsorbent bed especially for oxygenated monoterpenes and sesquiterpenes. Tenax-TA was evaluated in stainless steel tubes (untreated and treated) with a 2 μm mesh woven wire disk (also untreated and treated) to circumvent the effects of using a silica wool bed retainer. Tenax-TA adsorbent in stainless steel, Silcosteel and Sulfinert tubes yielded equivalent results when compared with direct (cryogenic) pre-concentration analysis of a multi-component mixture of n-alkanes and selected biogenic VOC. Tenax-TA tubes that had been used for 15–20 bake out–sample–desorption cycles (field and laboratory sampling) were compared with freshly packed tubes and found to give equivalent results.

Keywords: Biogenic VOC; Tenax-TA; Terpenes; Sesquiterpenes

Corrigendum to “Examining intra-urban variation in fine particle mass constituents using GIS and constrained factor analysis” [Atmos. Environ. 43 (2009) 5545–5555] by Jane E. Clougherty; E. Andres Houseman; Jonathan I. Levy (pp. 1585-1586).

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Atmospheric Environment (v.44, #12)