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Atmospheric Environment (v.41, #22)
Nonlinearity in human health response to ozone: Experimental laboratory considerations by Milan J. Hazucha; Allen S. Lefohn (pp. 4559-4570).
Results from controlled laboratory exposures of human volunteers indicate that higher ozone (O3) hourly average concentrations elicit a greater effect on hour-by-hour physiologic response (i.e., forced expiratory volume in 1s [FEV1]) than lower hourly average values, which implies a nonlinear dose–response relationship. The current 8-h average human-health O3 standard is not adequate for describing this nonlinear FEV1 hour-by-hour pattern of response. Consequently, it is recommended that physiologically consistent sigmoidally shaped dose–response models based on controlled human laboratory data be integrated into the air quality standard-setting process. The sigmoidally shaped model is continuous, does not require the identification of a population threshold concentration, and deals with plateau considerations at the high end of the distribution of exposures. For developing a consistent standard to protect human health, it is important to identify those ambient-type concentration patterns that elicit adverse human health effects. Such a standard should be ultimately based not only on spirometric response but other potentially important health impairment endpoints. Because of the paucity of experimental results that utilize ambient-type concentration regimes, additional studies are needed to create a database that uses realistic ambient-type exposures (i.e., variable concentration regimes) for human laboratory studies. The ambient-type concentration patterns that elicit an adverse health effect can be subsequently integrated into a form and level of a protective standard.
Keywords: Confounders and other influences; Diurnal variability; Human health response; Nonlinear dose–response; Threshold; Sigmoidal model; FEV; 1; Ozone standard
Determination of direct photolysis rate constants and OH radical reactivity of representative odour compounds in brewery broth using a continuous flow-stirred photoreactor by Jurgens Marion Jürgens; Fritz Jacob; Perihan Ekici; Albrecht Friess; Harun Parlar (pp. 4571-4584).
A method based on photolysis was developed for the appropriate treatment of organic pollutants in air exhausting from breweries upon wort decoction, and thereby causing smell nuisance. A continuous flow stirred photoreactor was built-up exclusively, allowing OH radicals to react with selected odorous compounds contained in exhaust vapours, such as: 2-methylpropanal, 3-methylbutanal, 2-methylbutanal, 3-methyl-1-butanol, n-hexanal, 2-methylbutyl isobutyrate, 2-undecanone, phenyl acetaldehyde, myrcene, limonene, linalool, humulene, dimethylsulphide, and dimethyltrisulphide. These substances were quantified in brewery broth before and after UV irradiation using high-resolution gas chromatography–mass spectrometry (HRGC–MS). For odour analysis, high-resolution gas chromatography-flame ionisation detection (HRGC-FID) coupled with sensory methods was used. Determined quantum yields of about 10−3 for phenyl acetaldehyde, myrcene, and humulene pointed out that direct photolysis contributed to their decay. Quantum yields of below 10−4 for the other substances indicated that UV irradiation did not contribute significantly to their degradation processes. Hydroxyl radical reaction rate constants and Henry constants of organic compounds were also measured. Substances accompanied with low Henry constants converted rapidly, whereas those with higher ones, relatively slowly. Determined aroma values concluded that after UV–H2O2 treatment, only dimethylsulphide and myrcene remained as important odorous compounds, but in significantly reduced concentrations. The UV–H2O2 treatment of brewery broth has been proved effective to reduce smell-irritating substances formed upon wort decoction.
Keywords: Exhaust vapour; Emission; Organic odour compounds; OH radicals; Direct photolysis
A functional group characterization of organic PM2.5 exposure: Results from the RIOPA study by Adam Reff; Barbara J. Turpin; John H. Offenberg; Clifford P. Weisel; Jim Zhang; Maria Morandi; Thomas Stock; Steven Colome; Arthur Winer (pp. 4585-4598).
The functional group (FG) composition of urban residential outdoor, indoor, and personal fine particle (PM2.5) samples is presented and used to provide insights relevant to organic PM2.5 exposure. PM2.5 samples (48h) were collected during the Relationship of Indoor, Outdoor, and Personal Air (RIOPA) study at 219 non-smoking homes (once or twice) in Los Angeles County, CA, Elizabeth, NJ, and Houston, TX. Fourier transform infrared (FTIR) spectra of PM2.5 samples were collected, and FG absorbances were quantified by partial least squares (PLS) regression, a multivariate calibration method.There is growing evidence in the literature that a large majority of indoor-generated PM2.5 is organic. The current research suggests that indoor-generated PM2.5 is enriched in aliphatic carbon–hydrogen (CH) FGs relative to ambient outdoor PM2.5. Indoor-generated CH exceeded outdoor-generated CH in 144 of the 167 homes for which indoor or outdoor CH was measurable; estimated indoor emission rates are provided. The strong presence of aliphatic CH FGs in indoor PM2.5 makes particulate organic matter substantially less polar indoors and in personal exposures than outdoors. This is a substantial new finding. Based on the quantified FGs, the average organic molecular weight (OM) per carbon weight (OC), a measure of the degree of oxygenation of organic PM, is in the range of 1.7–2.6 for outdoor samples and 1.3–1.7 for indoor and personal samples. Polarity or degree of oxygenation effects particle deposition in exposure environments and in the respiratory system.
Keywords: Organic aerosol; OM/OC; FTIR; Indoor air; Exposure assessment
Primary and secondary carbonaceous species in PM2.5 samples in Milan (Italy) by G. Lonati; S. Ozgen; M. Giugliano (pp. 4599-4610).
Seasonal elemental carbon (EC) and organic carbon (OC) concentration levels in PM2.5 samples collected in Milan (Italy) are presented and discussed, enriching the world-wide database of carbonaceous species in fine particulate matter (PM). High-volume PM2.5 sampling campaigns were performed from August 2002 through December 2003 in downtown Milan at an urban background site. Compared to worldwide average concentrations, in Milan warm-season OC and both warm- and cold-season EC are relatively low; conversely, cold-season OC concentrations are rather high. Consequently, high values for the OC/EC ratio are observed, especially in the winter period. The relation between OC/EC ratio values and wind direction is investigated, pointing out that the highest ratios are associated to winds blowing from those nearby areas where wood consumption for domestic heating is larger. Information on the OC partitioning between its primary and secondary fraction are derived by means of the EC-tracer method and principal component analysis. In the warm-season, OC is mainly of secondary origin, secondary organic aerosol (SOA) accounting for about 84% of the particulate organic matter and 25–28% of the PM2.5 mass. For the cold season the full application of the EC-tracer method was not possible and the primary organic aerosol deriving from traffic could only be estimated. However, principal component analysis (PCA) suggest a prevailing primary origin for OC, thus raising the attention on space heating emissions, and on wood combustion in particular, for air quality control. The role of traffic emissions on PM2.5 concentration levels, as a primary source, are also assessed: EC and primary organic matter from traffic account for a warm-season 30% and a cold-season 7% of the total carbon in PM2.5, that is for about 10% and 6% of PM2.5 mass, respectively. This latter small primary contribution estimated for the cold-season points out that stationary sources, which were not thought to play a significant role on PM concentration levels, may conversely be as much responsible for ambient particulate pollution.
Keywords: Particulate matter; Carbonaceous species; SOA; OC/EC ratio; EC-tracer method
Single particle Raman spectroscopy for investigating atmospheric heterogeneous reactions of organic aerosols by Alex K.Y. Lee; Chak K. Chan (pp. 4611-4621).
Heterogeneous reactions of organic aerosols with atmospheric oxidants are important processes that affect the hygroscopicity and cloud condensation nuclei (CCN) activities of atmospheric aerosols. An electrodynamic balance (EDB) coupled with Raman spectroscopy is a particularly attractive platform for studying atmospheric reactions since it allows long-duration (days) particle levitation and reactions at atmospherically relevant low-oxidant concentrations can be investigated. In this study, we demonstrated the use of an EDB/Raman system to investigate the heterogeneous reactions of oleic acid particles with ozone (240–280ppb) under ambient temperatures (22–24°C) and dry conditions (relative humidity <5%) over a period of 20h. The Raman signatures of the ozone-processed oleic acid particles indicate the formation of oxidation products predominately consisting of peroxidic compounds (OO groups of peroxides and/or ozonides), carbonyl (CO) and hydroxyl (OH) functional characteristics, which are consistent with the predictions of the Criegee mechanism as well as the results reported in the literature. We also confirmed that the Raman signatures of the reacted particles at atmospheric and much higher (>10ppm) ozone concentrations are practically the same, which provides assurance to the use of elevated ozone concentrations in reaction studies of the oleic acid–ozone system in the literature. The ratio of the percentage of mass loss (due to evaporation of volatile organic products) to the percentage of oleic acid conversion was estimated to be 0.05. Furthermore, the oxidation products that remained in the particle phase were more hygroscopic than were their hydrophobic parent molecules.
Keywords: Organic aerosols; Oleic acid; Heterogeneous reactions; Hygroscopic properties; Electrodynamic balance (EDB); Raman spectroscopy
Operational air pollution modelling in the UK—Street canyon applications and challenges by Sotiris Vardoulakis; Marios Valiantis; James Milner; Helen ApSimon (pp. 4622-4637).
Local air quality management requires the use of screening and advanced modelling tools that are able to predict roadside pollution levels under a variety of meteorological and traffic conditions. So far, more than 200 air pollution hotspots have been identified by local authorities in the UK, many of them associated with NO2 and/or PM10 exceedences in heavily trafficked urban streets that may be classified as street canyons or canyon intersections. This is due to the increased traffic-related emissions and reduced natural ventilation in such streets. Specialised dispersion models and empirical adjustment factors have been commonly used to account for the entrapment of pollutants in street canyons. However, most of the available operational tools have been validated using experimental datasets from relatively deep canyons ( H/ W⩾1) from continental Europe. The particular characteristics of low-rise street canyons ( H/ W<1), which are a typical feature of urban/sub-urban areas in the UK, have been rarely taken into account.The main objective of this study is to review current practice and evaluate three widely used regulatory dispersion models, WinOSPM, ADMS-Urban 2.0 and AEOLIUS Full. The model evaluation relied on two comprehensive datasets, which included CO, PM10 and NO x measurements, traffic information and relevant meteorological data from two busy street canyons in Birmingham and London for a 1-year period. The performance of the selected models was tested for different times of the day/days of the week and varying wind conditions. Furthermore, the ability of the models to reproduce roadside NO2/NO x concentration ratios using simplified chemistry schemes was evaluated for one of the sites. Finally, advantages and limitations of the current regulatory street canyon modelling practice in the UK, as well as needs for future research, have been identified and discussed.
Keywords: Street canyon; Road-traffic emissions; Dispersion modelling; Model verification; Air quality management
Optical and chemical properties of marine boundary-layer aerosol around Japan determined from shipboard measurements in 2002 by Masataka Shiobara; Keiichiro Hara; Masanori Yabuki; Hiroshi Kobayashi (pp. 4638-4652).
Shipboard measurements of the optical and chemical properties of marine boundary-layer aerosol were made around Japan over the period from 28 August to 25 September 2002. Measurements were conducted aboard the Research Vessel (R/V) Shirase along cruise tracks beginning from Yokosuka, and proceeding on to Hakodate, Sakata, Sasebo, Naha, Kure, and Yokkaichi. This paper describes the results of optical measurements using an Optical Particle Counter (OPC), an Integrating Nephelometer (IN), and a Particle Soot/Absorption Photometer (PSAP), as well as chemical analyses of water-soluble aerosol particles collected by impactor and filter systems. Coulter Multisizer measurements were used for water-insoluble aerosol particles. The complex refractive index (CRI), scattering and absorption coefficients, and size distribution of aerosols were estimated from combined measurements made using OPC, IN, and PSAP. Contrasting aerosol characteristics were observed during different stages of the cruise. Discussion on these differences focuses mainly on two legs: Leg-1 from Yokosuka to Hakodate and Leg-4 from Sasebo to Naha. Backward trajectory analyses indicate that the air sampled during Leg-1 originated from the Pacific Ocean, whereas the air sampled during Leg-4 originated from the Chinese Continent via the Korean Peninsula. For the first half of Leg-1, the number concentration was low and larger particles were relatively predominant. The real and imaginary parts of the CRI were estimated to be 1.38–1.40 and close to zero, respectively. This estimation is consistent with the results of chemical analyses, which show that the sea salt is rich in aerosols sourced from remote ocean areas. In contrast, small particles were predominant during Leg-4, and the real and imaginary parts of the CRI were estimated to be 1.52–1.59 and approximately −0.002, respectively. These findings are also consistent with chemical analyses that reveal a mixture of mineral dust and sulfate aerosol likely transported from China and Korea. The Coulter Multisizer measurements conducted during Leg-4 reveal abundant water-insoluble particles with a mode radius of 1.35μm.
Keywords: Aerosol; Optical and chemical properties; Japan; Shipboard measurement
Roadside measurements of size-segregated particulate organic compounds near gasoline and diesel-dominated freeways in Los Angeles, CA by Harish C. Phuleria; Rebecca J. Sheesley; James J. Schauer; Philip M. Fine; Constantinos Sioutas (pp. 4653-4671).
Individual organic compounds such as hopanes and steranes (originating in lube oil) and selected polycyclic aromatic compounds (PAHs) (generated via combustion) found in particulate emissions from vehicles have proven useful in source apportionment of ambient particulate matter (PM). Detailed information on the size-segregated (ultrafine and accumulation mode) chemical characteristics of organic PM during the winter season originating from a pure gasoline traffic freeway (CA-110), and a mixed-fleet freeway with the highest fraction of heavy-duty diesel vehicles in the state of California (I-710) is reported in this study. Hopanes and steranes as well as high molecular weight PAHs such as benzo(ghi)perylene (BgP) and coronene levels are found comparable near these freeways, while elemental carbon (EC) and lighter molecular weight PAHs are found much elevated near I-710 compared to CA-110. The roadway organic speciation data presented here are compared with the emission factors (EFs) measured in the Caldecott tunnel, Berkeley, CA [Phuleria, H.C., Geller, M.D., Fine, P.M., Sioutas, C., 2006. Size-resolved emissions of organic tracers from light- and heavy-duty vehicles measured in a California roadway tunnel. Environmental Science and Technology 40, 4109–4118] for light-duty vehicles (LDVs) and heavy-duty vehicles. Very good agreement is observed between CA-110 measurements and LDV EFs as well as I-710 measurements and corresponding reconstructed EFs from Caldecott tunnel for hopanes and steranes as well as heavier PAHs such as BgP and coronene. Our results, therefore, suggest that the EFs for hopanes and steranes obtained in tunnel environments, where emissions are averaged over a large vehicle-fleet, enable reliable source apportionment of ambient PM, given the overall agreement between the roadway vs tunnel concentrations of these species.
Keywords: PAH; Hopane and sterane; Roadside measurement; Particulate matter
Evidence of impact of aerosols on surface ozone concentration in Tianjin, China by Hai Bian; Suqin Han; Xuexi Tie; Meiling Sun; Aixia Liu (pp. 4672-4681).
In this study, we will present evidence that aerosol particles have strong effects on the surface ozone concentration in a highly polluted city in China. The measured aerosol (PM10), UV flux, and O3 concentrations were analyzed from 1 November (1 Nov) to 7 November (7 Nov) 2005 in Tianjin, China. During this period, the aerosol concentration had a strong day-by-day variation, ranging from 0.2 to 0.6mgm−3. The ozone concentration also shows a strong variability in correlation with the aerosol concentration. During 1 Nov, 2 Nov, 6 Nov, and 7 Nov, the ozone concentration was relatively high (about 30–35ppbv; defined as a high-ozone period), and during 3 Nov to 5 Nov, the ozone concentration was relatively low (about 5–20ppbv; defined as a low-ozone period). The analysis of the measurement shows that the ozone concentration is strongly correlated to the measured UV flux. Because there were near cloud-free conditions between 1 Nov and 7 Nov, the variation of the UV flux mainly resulted from the variation of aerosol concentration. The result shows that higher aerosol concentrations produce a lower UV flux and lower ozone concentrations. By contrast, the lower aerosol concentration leads to a higher UV flux and higher ozone concentrations. A chemical mechanism model (NCAR MM) is applied to interpret the measurement. The model result shows that the extremely high aerosol concentration in this polluted city has a very strong impact on photochemical activities and ozone formation. The correlation between aerosol and ozone concentrations appears in a non-linear feature. The O3 concentration is very sensitive to aerosol loading when aerosol loading is high, and this sensitivity is reduced when aerosol loading is low. For example, the ratio of Δ[O3]/Δ[AOD] is about −16ppbvAOD−1 when AOD is less than 2, and is only −4ppbvAOD−1 when AOD is between 2 and 5. This result implies that a future decrease in aerosol loading could lead to a rapid increase in the O3 concentration in this region.
Keywords: Aerosols impact on ozone; China
Secondary organic aerosol importance in the future atmosphere by Kostas Tsigaridis; Maria Kanakidou (pp. 4682-4692).
In order to investigate the secondary organic aerosol (SOA) response to changes in biogenic volatile organic compounds (VOC) emissions in the future atmosphere and how important will SOA be relative to the major anthropogenic aerosol component (sulfate), the global three-dimensional chemistry/transport model TM3 has been used. Emission estimates of biogenic VOC (BVOC) and anthropogenic gases and particles from the literature for the year 2100 have been adopted.According to our present-day model simulations, isoprene oxidation produces 4.6TgSOAyr−1, that is less than half of the 12.2TgSOAyr−1 formed by the oxidation of other BVOC. In the future, nitrate radicals and ozone become more important than nowadays, but remain minor oxidants for both isoprene and aromatics. SOA produced by isoprene is estimated to almost triple, whereas the production from other BVOC more than triples. The calculated future SOA burden change, from 0.8Tg at present to 2.0Tg in the future, is driven by changes in emissions, oxidant levels and pre-existing particles. The non-linearity in SOA formation and the involved chemical and physical feedbacks prohibit the quantitative attribution of the computed changes to the above-mentioned individual factors. In 2100, SOA burden is calculated to exceed that of sulfate, indicating that SOA might become more important than nowadays. These results critically depend on the biogenic emissions and thus are subject to the high uncertainty associated with these emissions estimated due to the insufficient knowledge on plant response to carbon dioxide changes. Nevertheless, they clearly indicate that the change in oxidants and primary aerosol caused by human activities can contribute as much as the change in BVOC emissions to the increase of the biogenic SOA production in the future atmosphere.
Keywords: Secondary organic aerosol; Biogenic emissions; Global modeling; Future; Anthropogenic impact
Relative rate measurements of reactions of unsaturated alcohols with atomic chlorine as a function of temperature by Rodriguez Ana Rodríguez; Rodriguez Diana Rodríguez; Amparo Soto; Alberto Notario; Alfonso Aranda; Diaz-de-Mera Yolanda Díaz-de-Mera; I. Iván Bravo (pp. 4693-4702).
The kinetics of two structurally similar unsaturated alcohols, 3-butene-2-ol and 2-methyl-3-butene-2-ol (MBO232), with Cl atoms have been investigated for the first time, as a function of temperature using a relative method. As far as we know, the present work also provides the first value for 3-buten-2-ol. The coefficient at room temperature was also obtained for 2-propene-1-ol (allyl alcohol). The reactions were investigated using a 400L Teflon reaction chamber coupled with gas chromatograph-coupled with flame-ionization detection (GC-FID) detection. The experiments were performed at atmospheric pressure and at temperatures between 256 and 298K in air or nitrogen as the bath gas. The obtained kinetic data were used to derive the Arrhenius expressions, kMBO232=(2.83±2.50)×10−14exp(2670±249)/ T, k3-buten-2-ol=(0.65±1.60)×10−15exp(3656±695)/ T (in units of cm3molecule−1s−1). Finally, results and atmospheric implications are discussed and compared with the reactivity with OH and NO3 radicals.
Keywords: Atmospheric chemistry; Chlorine atoms; Gas-phase reaction; Relative method; Alcohols
Functional group analysis of high-molecular weight compounds in the water-soluble fraction of organic aerosols by Vera Samburova; Tatiana Didenko; Erast Kunenkov; Christian Emmenegger; Renato Zenobi; Markus Kalberer (pp. 4703-4710).
In this study, we present the analysis of functional groups of humic-like substances (HULIS) isolated from atmospheric aerosols (<1μm). Aerosol samples were collected in an urban area (Dübendorf, Switzerland) both in summer and winter. Quantification of carboxylic, arylic, phenolic and aliphatic functional groups of HULIS was performed by a specially adapted and optimized H-NMR method. The concentrations of carboxylic, arylic, phenolic and aliphatic functional groups were between 9×10−11 and 6×10−8mol/m3 for all samples, corresponding up to 14% of the total HULIS mass. A good correlation between the H-NMR results and the potentiometric titration of carboxylic groups was observed for all winter and summer samples. The p K distributions of carboxylic groups of HULIS were calculated from potentiometric titration data. p K spectra showed that p K values of most carboxylic groups is between 3 and 5. The H-NMR data show that the content of aromatic groups is higher in winter than in summer. This may either be due to emission of aromatic compounds by wood burning or to slower degradation reaction of aromatics in winter.
Keywords: Organic aerosol; HULIS; Functional group analysis; H-NMR; Titration
Methane emissions from two tundra wetlands in eastern Antarctica by Renbin Zhu; Yashu Liu; Liguang Sun; Hua Xu (pp. 4711-4722).
During the summertime of 2005/2006 net methane(CH4) fluxes and environmental variables were investigated in two tundra wetlands Wolong Marsh and Tuanjie Marsh of eastern Antarctica, using the closed chamber technique. At Wolong Marsh, the measurements were made at four wet tundra sites, four mesic tundra sites, and two dry sites.CH4 flux for wet tundra sites averaged163.4μgm-2h-1 and for the mesic sites132.4μgm-2h-1. For the dry sites, all theCH4 fluxes showed the negative values with an average of-99.9μgm-2h-1. At Tuanjie Marsh, flux measurements were made at two open ponds, two shallow fens and two dry sites. The averageCH4 flux for the pond sites was170.4μgm-2h-1 and for the fen sites134.7μgm-2h-1. For the dry sitesCH4 fluxes were approximately one order of magnitude lower than those for pond and fen sites and averaged18.4μgm-2h-1. Spatial variations inCH4 flux were primarily driven by the water table position at two tundra wetlands, whereas temporal variations inCH4 flux from wet and mesic sites were related with the thermal regime of tundra soil layers. The fluxes from six observation sites showed a consistent diurnal cycle with the peak at 14:00 and the lowest at 2:00 (local time), which was correlated with ground temperature at the depth of 0–10cm. TheCH4 emissions from coastal wetlands could constitute an important part of the annualCH4 budget for Antarctic tundra ecosystems.
Keywords: Methane flux; Natural wetlands; Antarctica; Temporal variation; Spatial variation; Water table
Detecting and characterising small changes in urban nitrogen dioxide concentrations by David C. Carslaw; Nicola Carslaw (pp. 4723-4733).
Detecting and quantifying abnormal changes in the concentration of urban air pollutants can be difficult due to the influence of meteorology and atmospheric chemistry. This study presents methods to detect and characterise small changes in the concentration of nitrogen dioxide (NO2) that deviate from expected behaviour. Generalized additive models (GAMs) are used to describe daily mean NO2 concentrations at roadside monitoring sites to determine how concentrations deviate from measured concentrations. Structural change methods are applied to time series describing this difference to identify change-points, where concentrations of NO2 deviate significantly from expected behaviour. Methods are also used which quantify the timing and uncertainty associated in the timing of these change-points. For most time series data considered in London, concentrations of NO2 underwent relatively abrupt changes rather than smoothly varying increases; changes which remain largely undetected in raw time series data. Most change-points occurred in late 2002 or early 2003, and the factors, which may have contributed to them, are discussed. These methods can also identify technical problems with monitoring equipment and are applicable to other instances where detecting sudden atmospheric composition change is important.
Keywords: Change-point; Structural change; Trend; Primary nitrogen dioxide; Meteorological normalisation
Organochlorine pesticides, polybrominated biphenyl ethers and lead isotopes during the spring time at the Waliguan Baseline Observatory, northwest China: Implication for long-range atmospheric transport by Hairong Cheng; Gan Zhang; Jerry Xunyi Jiang; Xiangdong Li; Xiang Liu; Jun Li; Yucheng Zhao (pp. 4734-4747).
Located in the center of the Asian continent, the Waliguan Baseline Observatory (WBO) is the highest and the most inland Global Atmospheric Watch (GAW) station in the world. In the present study, organochlorine pesticides (OCPs) and polybrominated biphenyl (PBDEs) were analyzed in the daily collected samples at the WBO from 2 April to 23 May 2005, in an attempt to investigate the long-range atmospheric transport (LRAT) of persistent organic pollutants (POPs) in northwest China. The mean concentrations of OCPs at WBO were slightly higher than the Arctic regions, and the concentrations of total PBDEs (8.3±4.0pgm−3) was comparable with other remote areas. The low temperature dependence of the POP concentrations in the air, and the absence of local use of these compounds implied LRAT to WBO. As suggested by backward air trajectory analysis, the high concentrations of γ-HCH, DDTs and PBDEs, during the sampled spring period, were mainly related to air mass passing over the neighboring countries (e.g., Russia, Kazakhstan). Additional evidence was also obtained by the lead isotopic composition analysis, which showed similar206Pb/207Pb and208Pb/207Pb ratios as those of ores in these countries. The present results indicate that the WBO may serve as an excellent GAW station for monitoring the LRAT of POPs in the Asian continent.
Keywords: OCPs; PBDEs; POPs; Pb isotopes: Waliguan Observatory; Asian continent; Long-range atmospheric transport
Simultaneous measurement of light-scattering properties and particle size distribution for aerosols: Application to ammonium sulfate and quartz aerosol particles by Daniel B. Curtis; Murat Aycibin; Mark A. Young; Vicki H. Grassian; Paul D. Kleiber (pp. 4748-4758).
An apparatus for measuring the scattering phase function and linear polarization of aerosol particles has been developed. The apparatus uses an elliptical mirror and CCD camera to image the full angular scattering range simultaneously. An in-line aerodynamic particle sizer (APS) in the particle flow stream provides for the simultaneous measurement of the aerosol particle size distribution. This apparatus allows for a comparison of measured optical properties with theoretical model calculations based on the measured aerosol size distribution. The system was calibrated and tested using monodisperse polystyrene latex (PSL) spheres and with ammonium sulfate (AS) aerosol. We have also used the apparatus for measuring the scattering phase function and linear polarization for light scattering from irregular quartz aerosol particles. Our results show that Mie theory substantially overestimates the backscattering cross-section for quartz particles in the size parameter range X∼2–4, in agreement with previous experimental work and theoretical modeling studies. We also present a normalized synthetic phase function for quartz dust aerosol in the accumulation mode size range (0.1–2.0μm).
Keywords: Aerosol; Mie scattering; Mineral dust; Quartz; Ammonium sulfate
Enumerating actinomycetes in compost bioaerosols at source—Use of soil compost agar to address plate ‘masking’ by M.P.M. Taha; G.H. Drew; A. Tamer Vestlund; D. Aldred; P.J. Longhurst; S.J.T Pollard (pp. 4759-4765).
Actinomycetes are the dominant bacteria isolated from bioaerosols sampled at composting facilities. Here, a novel method for the isolation of actinomycetes is reported, overcoming masking of conventional agar plates, as well as reducing analysis time and costs. Repeatable and reliable actinomycetes growth was best achieved using a soil compost media at an incubation temperature of 44°C and 7 days’ incubation. The results are of particular value to waste management operators and their advisors undertaking regulatory risk assessments that support environmental approvals for compost facilities.
Keywords: Actinomycetes; Bioaerosols; Compost; Enumeration; Risk assessment
NO X fluxes from three kinds of agricultural lands in the Yangtze Delta, China by Shuangxi Fang; Yujing Mu (pp. 4766-4772).
Static chamber method was adopted to measure the surface exchanges of NO and NO2 between three kinds of agricultural lands and the atmosphere during spring–summer period in the Yangtze Delta, China. The average NO fluxes were 20.9, 27.4 and 21.4ngNm−2s−1, respectively, for cabbage (CA, cultivation of celery occurred along with cabbage), potato (PO) and soybean (SY) fields. The average NO2 fluxes were −1.12, 0.93 and −0.68ngNm−2s−1, respectively, for the cabbage, potato and soybean fields. Apparently, negative linear correlation was found between the NO2 fluxes from the CK plot (tilled conventionally but did not cultivate any seeds) and its ambient concentrations, and the compensation point was calculated to be 0.92ppbv. The total NO emission from the vegetable lands and SY land in this region during spring–summer period was roughly estimated to be 15.9GgN, which accounted for about 11.2% of the estimated value of total NO emissions in the July of 1999 from Chinese agricultural fields.
Keywords: NO; NO; 2; Fluxes; Agricultural lands