Atmospheric Environment (v.41, #23)
Editorial board (i).
Calculation of concentration of aerosol particles around a slot sampler by S.K. Zaripov; M.V. Vanyunina; A.N. Osiptsov; E.V. Skvortsov (4773-4780).
A mathematical model and numerical procedure are proposed for investigation of aspiration efficiency and the particle concentration field around a slot sampler in a moving gas. A potential-flow model for the carrier gas and a Lagrangian method for calculation of particle trajectories and concentration are employed. The particle concentration patterns around the slot and at the sampler inlet are studied. The dependence of the aspiration efficiency on the ratio of the wind and sampling velocities is analyzed. It is shown that the local aspiration efficiency calculated on the symmetry axis of the slot gives satisfactory approximation for the integral aspiration efficiency.
Keywords: Aerosol sampling; Aspiration efficiency; Particle concentration;
Fine particulate matter and carbon monoxide exposure concentrations in urban street transport microenvironments by S. Kaur; M.J. Nieuwenhuijsen; R.N. Colvile (4781-4810).
Personal exposure studies are crucial alongside microenvironment and ambient studies in order to get a better understanding of the health risks posed by fine particulate matter and carbon monoxide in the urban transport microenvironment and for making informed decisions to manage and reduce the health risks. Studies specifically assessing the PM2.5, ultrafine particle count and carbon monoxide personal exposure concentrations of adults in an urban transport microenvironment have steadily increased in number over the last decade. However, no recent collective summary is available, particularly one which also considers ultrafine particles; therefore, we present a review of the personal exposure concentration studies for the above named pollutants on different modes of surface transportation (walking, cycling, bus, car and taxi) in the urban transport microenvironment. Comparisons between personal exposure measurements and concentrations recorded at fixed monitoring sites are considered in addition to the factors influencing personal exposure in the transport microenvironment.In general, the exposure studies examined revealed pedestrians and cyclists to experience lower fine particulate matter and CO exposure concentrations in comparison to those inside vehicles—the vehicle shell provided no protection to the passengers. Proximity to the pollutant sources had a significant impact on exposure concentration levels experienced, consequently individuals should be encouraged to use back street routes. Fixed monitoring stations were found to be relatively poor predictors of CO and PM2.5 exposure concentration levels experienced by individuals in the urban transport microenvironment. Although the mode of transport, traffic and meteorology parameters were commonly identified as significant factors influencing exposure concentrations to the different pollutants under examination, a large amount of the exposure concentration variation in the exposure studies remained unexplained.
Keywords: Exposure concentrations; Urban transport microenvironment; PM2.5; Ultrafine particle count; Carbon monoxide;
Sulfuric odorous compounds emitted from pig-feeding operations by Ki Youn Kim; Han Jong Ko; Hyeon Tae Kim; Yoon Shin Kim; Young Man Roh; Cheol Min Lee; Hyun Soo Kim; Chi Nyon Kim (4811-4818).
The objective of the study was to quantify the concentration and emission levels of sulfuric odorous compounds emitted from pig-feeding operations. Five types of pig-housing rooms were studied: gestation, farrowing, nursery, growing and fattening rooms. The concentration range of sulfuric odorous compounds in these pig-housing rooms were 30–200 ppb for hydrogen sulfide (H2S), 2.5–20 ppb for methyl mercaptan (CH3SH), 1.5–12 ppb for dimethyl sulfide (DMS; CH3SCH3) and 0.5–7 ppb for dimethyl disulfide (DMDS; CH3S2CH3), respectively. The emission rates of H2S, CH3SH, DMS and DMDS were estimated by multiplying the average concentration (mg m−3) measured near the air outlet by the mean ventilation rate (m3 h−1) and expressed either per area (mg m−2 h−1) or animal unit (AU; liveweight of the pig, 500 kg) (mg pig−1 h−1). As a result, the emission rates of H2S, CH3SH, DMS and DMDS in the pig-housing rooms were 14–64, 0.8–7.3, 0.4–3.4 and 0.2–1.9 mg m−2 h−1, respectively, based on pig's activity space and 310–723, 18–80, 9–39 and 5–22 mg AU−1 h−1, respectively, based on pig's liveweight, which indicates that their emission rates were similar, whether based upon the pig's activity space or liveweight. In conclusion, the concentrations and emission rates of H2S were highest in the fattening room followed by the growing, nursery, farrowing and gestation rooms whereas those of CH3SH, DMS and DMDS concentrations were largest in the growing room followed by the nursery, gestation and farrowing rooms.
Keywords: Sulfuric odorous compound; Pig feeding operation; H2S; CH3SH; DMS; DMDS;
Forest bound estuaries are higher methane emitters than paddy fields: A case of Godavari estuary, East Coast of India by Reddithota J. Krupadam; Rashmi Ahuja; Satish R. Wate; Yerramilli Anjaneyulu (4819-4827).
In the Godavari estuary, ambient methane concentrations were monitored for a period of 5 years and the data reveals that the estuary sampling stations have shown a high average maximum value of methane 14.8 ppmv while nearby paddy field sampling stations the methane concentration were 3–4 fold lower than the estuary. The acidic nature of the estuary soils (pH 5.8–6.2) along with redox potential - 120 mV favours high methane emissions. The samples collected from the edge of the estuary have shown 0.12–0.15% of Fe 2 + wherein ambient methane concentrations were 4.8–5.6 ppmv. It was observed that the anoxic condition with high available iron in the soil improves anaerobic decomposition of organic matter to produce methane. The litter production from nearby mangrove vegetation in the estuary is approximately 22,000 tons/annum is a causative factor for higher methane emissions. Remote sensing data was used and developed thematic maps for spatial and temporal distribution of methane using geographical information system. The seasonal trend showed high ambient concentration of methane in winter season, which is mainly due to high moisture content, ( OH ⋅ ) radical and lower temperature. The results suggest that high organic matter (2.5–4.2%) along with soil conditions in the estuary are influencing for higher methane emissions, while in paddy fields the available organic matter for methanogenesis is limited.
Keywords: Methane emissions; Thematic maps; Soil chemistry; Godavari estuary;
Active biomonitoring of airborne fluoride near an HF producing factory using standardised grass cultures by J. Franzaring; A. Klumpp; A. Fangmeier (4828-4840).
In order to study the pollution gradient in the vicinity of an HF producing factory, a biomonitoring programme was performed employing VDI standardised grass cultures. Specimen plants of Lolium multiflorum cv. Lema were exposed at 11 sites over five monthly periods and the biomass produced was used for subsequent F-analyses. Meteorological data from the study region confirmed that wind direction accounted for changes in the pollution pattern over periods of time. Fluoride concentrations in the grass cultures, however, were unrelated to temperature and precipitation sums during the exposures. The biomass production of the grass cultures proved to be unrelated to these parameters as well but, with the enhanced growth of the plants, the fluoride concentrations were lower due to the dilution of the element with higher biomass accumulation. Because the contribution of particulate fluoride was unknown, both the washed grass cultures and the washing water were analysed in order to determine the amount of external fluoride. Washing reduced the fluoride concentrations by 22% on average, indicating that most of the element was internal fluoride stemming from stomatal uptake. Larger amounts of fluoride, however, could be washed off from grass cultures exposed at sites close to the factory indicating that dust emissions played a greater role at these locations. Because particulate emissions were supposed to arise from CaF2 and the waste-product anhydrite, grass cultures were also analysed for calcium and sulphur. While calcium concentrations were generally high but unrelated to fluoride, sulphur concentrations showed a slight relationship to the F-concentrations determined in the unwashed plants. Latter findings indicate the co-deposition of the two elements as surface bound, external loads, but bioindication could not clarify to what extent both elements were partitioned in the gas-to-particle phase. We therefore recommend using the grass culture method in air quality programmes to identify any exceedances of European feeding stuff standards in the vicinity of large emitters.
Keywords: Hydrogen fluoride; Chemical industry; Verein Deutscher Ingenieure (VDI); European feed standards; Particulate fluoride;
Number size distribution of atmospheric aerosols during ACE-Asia dust and precipitation events by Jiyoung Kim; Chang H. Jung; Byoung-Cheol Choi; Sung-Nam Oh; Fred J. Brechtel; Soon-Chang Yoon; Sang-Woo Kim (4841-4855).
Measurements of size-resolved particle number concentrations during the Asian Pacific Regional Aerosol Characterization Experiment (ACE-Asia) field campaign were made at the Gosan super-site, South Korea. In East Asia, dust and precipitation phenomena play a crucial role in atmospheric environment and climate studies because they are major sources and sinks of atmospheric aerosols, especially in the springtime. Total Ozone Mapping Spectrometer (TOMS) Aerosol Index and backward trajectories are analyzed to investigate the spatial and temporal evolution of dust storms. The size distributions between dust and non-dust periods and times with and without precipitation are compared. In order to understand the temporal evolution of the aerosol size distribution during dust and precipitation events, a simple aerosol dynamics model is employed. The model predicted and observed size distributions are compared with the measured data. The results show that the coarse mode particle number concentrations increase by a factor of 10–16 during dust events. During precipitation, however, particles in the coarse mode are scavenged by impaction mechanism. It is found that the larger particles are more efficiently scavenged. The degree of scavenged particle varies depending on the rainfall rate, raindrop size distribution and aerosol size distribution.
Keywords: Scavenging; Asian dust; Optical particle counter; ACE-Asia; Size distribution;
Attenuation of UV-B radiation in the atmosphere: Clouds effect, at Qena (Egypt) by M. El-Nouby Adam; Sayed M. El Shazly (4856-4864).
The effects of clouds (amount, type and height) on the surface UV-B radiation have been investigated at Qena, Egypt (26°17′, 32°10′, 96 m asl) using 2 years data (2004–2005) carried out by South Valley University (SVU)-meteorological research station. Thus, the characteristics of cloud's statistical property during the study period were employed to evaluate the general feature of the region of this study. However, ≈86% of all the observations were ⩽2 octas and the overcast conditions (8 octas) were very rarely over the study region (only 0.2% of all cases). These observations included 10% low-level clouds, 3.16% mid-level clouds and 7.59% high-level clouds. The dominated types of these clouds are stratocumulus (8.9%) and cirrus (5.8%).The hourly values of cloudless sky UV-B radiation (UV-B0) and consequently the cloud modification factor (CMF) were estimated. An empirical model was developed for CMF as a function of the amount of cloud at low- and mid-level and high-level clouds. The correlation coefficients were equal to 0.985 and 0.987, respectively. In addition, a general expression of the CMF for situations those are considered as the effect of different clouds was found. The efficiency of this model has been tested in combination with a cloudless sky empirical model using independent data set. For this purpose, the hourly values of UV-B at selected cloudless and cloudy days were estimated. A good agreement was observed between the measured and the predicted values of our model. The mean value of the correlation coefficients of these selected days was 0.98.In addition, the attenuation of UV-B radiation could be determined by considering low- and mid-level and high-level clouds. The reduction of UV-B radiation as a function of cloud amount was non-linear for the both cases. At cloud amount of 100%, UV-B radiation was reduced by 83% on average by the high-level clouds.
Keywords: Egypt; UV-B radiation attenuation; Cloudless sky UV-B; Clouds;
Variations of the increasing trend of tropospheric NO2 over central east China during the past decade by Youjiang He; Itsushi Uno; Zifa Wang; Toshimasa Ohara; Nobuo Sugimoto; Atsushi Shimizu; Andreas Richter; John P. Burrows (4865-4876).
A numerical analysis using a regional chemical transport model (CTM) is presented in comparison with Global Ozone Monitoring Experiment (GOME) and SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) satellite NO2 measurements over East Asia from 1996 to 2005 from a climatological perspective. Modeling results agree well with satellite retrievals in geographical distribution patterns, with systematic underestimation of the absolute values. The sharp increase in NO2 vertical column densities (VCDs) over central east China (CEC) after the year 2000 (14.1–20.5% yr−1 for the satellite observations and 10.8% yr−1 for model simulations) is analyzed quantitatively over different megacity clusters. The distinct emission increase patterns are responsible for the different increase trends observed over the Beijing megacity cluster (BJ), the Yangtze Delta (YD) and other CEC regions. The growth rate of satellite measured and CMAQ-modeled NO2 VCDs for the YD is much higher than that in other regions, with no clear seasonal variation. Apart from BJ and YD, NO2 emissions from other regions in CEC also expand considerably.
Keywords: Tropospheric NO2; Increasing trend; NO x emission; Satellite; Central east China;
The effects of increasing atmospheric ozone on biogenic monoterpene profiles and the formation of secondary aerosols by Delia M. Pinto; Päivi Tiiva; Pasi Miettinen; Jorma Joutsensaari; Harri Kokkola; Anne-Marja Nerg; Ari Laaksonen; Jarmo K. Holopainen (4877-4887).
Monoterpenes are biogenic volatile organic compounds (BVOCs) which play an important role in plant adaptation to stresses, atmospheric chemistry, plant–plant and plant–insect interactions. In this study, we determined whether ozonolysis can influence the monoterpenes in the headspace of cabbage. The monoterpenes were mixed with an air-flow enriched with 100, 200 or 400 ppbv of ozone (O3) in a Teflon chamber. The changes in the monoterpene and O3 concentrations, and the formation of secondary organic aerosols (SOA) were determined during ozonolysis. Furthermore, the monoterpene reactions with O3 and OH were modelled using reaction kinetics equations. The results showed that all of the monoterpenes were unequally affected: α-thujene, sabinene and d-limonene were affected to the greatest extend, whereas the 1,8-cineole concentration did not change. In addition, plant monoterpene emissions reduced the O3 concentration by 12–24%. The SOA formation was dependent on O3 concentration. At 100 ppbv of O3, virtually no new particles were formed but clear SOA formation was observed at the higher ozone concentrations. The modelled results showed rather good agreements for α-pinene and 1,8-cineole, whereas the measured concentrations were clearly lower compared to modelled values for sabinene and limonene. In summary, O3-quenching by monoterpenes occurs beyond the boundary layer of leaves and results in a decreased O3 concentration, altered monoterpene profiles and SOA formation.
Keywords: Brassica oleracea (cabbage); BVOCs; Monoterpenes; Ozone; Secondary organic aerosols (SOA);
Atmospheric corrosion effects of HNO3—Comparison of laboratory-exposed copper, zinc and carbon steel by Farid Samie; Johan Tidblad; Vladimir Kucera; Christofer Leygraf (4888-4896).
The influence of nitric acid (HNO3) on the atmospheric corrosion of copper, zinc and carbon steel was investigated in laboratory exposures at 65% relative humidity (RH), 25 °C and 0.03 cm s−1 air velocity. The deposition velocity (V d) of HNO3 on the specimens, the corrosion rates and corrosion products were determined by gravimetry, ion chromatography, X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) microspectroscopy. Comparisons were also made with literature data on the corrosion effects of sulfur dioxide (SO2), nitrogen dioxide (NO2) and ozone (O3).At 65% RH, the V d of HNO3 on all metals was at least 70% of that of an ideal absorbent, i.e., an impregnated filter with perfect absorption for HNO3. The V d of HNO3 was much higher than that of SO2, NO2 or O3, which is mainly attributed to the relatively high sticking coefficient, high solubility and high reactivity of HNO3 compared to the other gases. During identical exposures to HNO3, the corrosion rate of carbon steel was nearly three times higher than that of copper or zinc. However, when comparing the corrosion effects induced by HNO3 with those induced by SO2 alone or in combination with either NO2 or O3, HNO3 turned out to be far more aggressive than SO2. Relative to SO2, zinc is the metal most sensitive to HNO3, followed by copper and with carbon steel least sensitive to HNO3.
Keywords: Nitric acid; Materials degradation; Deposition velocity; Iron; Gerhardtite; Cuprite; Nitrate;
δ 13C and δ 15N of moss Haplocladium microphyllum (Hedw.) Broth. for indicating growing environment variation and canopy retention on atmospheric nitrogen deposition by Xue-Yan Liu; Hua-Yun Xiao; Cong-Qiang Liu; You-Yi Li (4897-4907).
Mosses have been recognized as a useful tool for biomonitoring atmospheric deposition and assessing regional environment. This study was carried on whether the same moss growing in areas with identical regional atmospheric deposition while under different growing environments would have the same indicating signals.Similar variations in mean δ 13C and δ 15N signatures were found between mosses collected from five habitats, with an increasing sequence from mosses under canopies to epilithic mosses, indicating that habitats were potentially regulating δ 13C and δ 15N values of mosses. Dryer habitats (lower water availability) and input of more aerosol N were the main reasons for higher δ 13C and δ 15N values of mosses at open sites (especially for epilithic species), while more negative values of mosses under canopies were attributed to their wetter habitats and less uptake of aerosol N. Additionally, δ 15N values not δ 13C varied linearly with canopy thickness from −7.84‰ (1 m) to −4.71±0.7‰ (4 m), suggesting δ 15N was more sensitive for indicating canopy retention.Consequently, isotopic data of mosses under different environments could not be compared for atmospheric deposition research with each other even collected at the same site. Moss δ 13C and δ 15N were affected not only by regional atmospheric N sources but also by their growing environments. δ 15N of epilithic Haplocladium microphyllum at open sites can be taken as confident bio-indicator of atmospheric N deposition, which would deepen the application of stable nitrogen isotope of bryophytes in atmosphere–plant system study.
Keywords: Atmospheric nitrogen deposition; Indicating; Canopy; Moss; Retention;
Particle size and composition distribution analysis of automotive brake abrasion dusts for the evaluation of antimony sources of airborne particulate matter by Akihiro Iijima; Keiichi Sato; Kiyoko Yano; Hiroshi Tago; Masahiko Kato; Hirokazu Kimura; Naoki Furuta (4908-4919).
Abrasion dusts from three types of commercially available non-steel brake pads were generated by a brake dynamometer at disk temperatures of 200, 300 and 400 °C. The number concentration of the abrasion dusts and their aerodynamic diameters (D p) were measured by using an aerodynamic particle sizer (APS) spectrometer with high temporal and size resolution. Simultaneously, the abrasion dusts were also collected based on their size by using an Andersen low-volume sampler, and the concentrations of metallic elements (K, Ti, Fe, Cu, Zn, Sb and Ba) in the size-classified dusts were measured by ICP-AES and ICP-MS. The number distributions of the brake abrasion dusts had a peak at D p values of 1 and 2 μm; this peak shifted to the coarse side with an increase in the disk temperature. The mass distributions calculated from the number distributions have peaks between D p values of 3 and 6 μm. The shapes of the elemental mass distributions (Ti, Fe, Cu, Zn, Sb and Ba) in size-classified dusts were very similar to the total mass distributions of the brake abrasion dusts. These experimental results indicated that the properties of brake abrasion dusts were consistent with the characteristics of Sb-enriched fine airborne particulate matter. Based on these findings and statistical data, the estimation of Sb emission as airborne particulate matter from friction brakes was also discussed.
Keywords: Airborne particulate matter; PM2.5; Particle size distribution; Brake dust; Antimony;
Influence of the surface microlayer on atmospheric deposition of aerosols and polycyclic aromatic hydrocarbons by Sabino del Vento; Jordi Dachs (4920-4930).
Atmospheric dry deposition is an important process for the introduction of aerosols and pollutants to aquatic environments. The objective of this paper is to assess, for the first time, the influence that the aquatic surface microlayer plays as a modifying factor of the magnitude of dry aerosol deposition fluxes. The occurrence of a low surface tension (ST) or a hydrophobic surface microlayer has been generated by spiking milli-Q water or pre-filtered seawater with a surfactant or octanol, respectively. The results show that fine mode (<2.7 μm) aerosol phase PAHs deposit with fluxes 2–3 fold higher when there is a low ST aquatic surface due to enhanced sequestration of colliding particles at the surface. Conversely, for PAHs bound to coarse mode aerosols (>2.7 μm), even though there is an enhanced deposition due to the surface microlayer for some sampling periods, the effect is not observed consistently. This is due to the importance of gravitational settling for large aerosols, rendering a lower influence of the aquatic surface on dry deposition fluxes. ST (mN m−1) is identified as one of the key factor driving the magnitude of PAH dry deposition fluxes (ng m−2 d−1) by its influence on PAH concentrations in deposited aerosols and deposition velocities (v d, cm s−1). Indeed, v d values are a function of ST as obtained by least square fitting and given by Ln(v d)=−1.77 Ln(ST)+5.74 (r 2=0.95) under low wind speed (average 4 m s−1) conditions.
Keywords: Atmospheric deposition; PAHs; Surfactants; Surface microlayer;
Effects of missing seasonal data on estimates of period means of dry and wet deposition by Joseph E. Sickles; Douglas S. Shadwick (4931-4939).
The current study uses resampling to investigate the impacts of cyclic seasonal behavior on 1- and 5-year period means composed from seasonal mean values in the presence of missing data. This is an empirical study using complete years of seasonal monitoring data collected in the eastern US and extracted from the clean air status and trends network (CASTNET) dry and the National Atmospheric Deposition Program/National Trends Network (NADP/NTN) wet deposition data archives. Estimators of period means with missing seasonal data are determined using means of the non-missing values as estimates of the missing data. Estimates are evaluated in terms of 95% inclusion intervals (e.g., estimates are within ±X% of the true value ⩾95% of the time). For dry deposition, missing transition seasons (i.e., spring or fall) usually yield estimates of annual means that are within ±20% of the true annual mean ⩾95% of the time. Missing summers or winters usually have larger impacts on estimates of annual means of dry deposited species than missing transition seasons. A missing summer has the largest impact on estimates of annual means of dry deposition for all constituents, except SO2, where winter is especially important. For wet deposition, a missing season yields estimates of annual means that are within ±30% of the true annual mean ⩾95% of the time. A missing summer has the largest impact on estimates of annual means of wet deposition for all constituents, except NH4 +, where spring and fall are important. A strategy requiring at least 3 years of seasonal representation for three seasons with the fourth season having at least two seasonal values, yields estimates of wet deposition that are within ±17% of the true 5-year means ⩾95% of the time for all species. Corresponding confidence statements for dry deposition results are considerably stronger, with estimates that are within ±10% of the true 5-year mean ⩾95% of the time.
Keywords: Period mean; Uncertainty; Confidence statement; Inclusion interval; Missing data; CASTNET; NADP; Deposition;
Impact of the tropical storm Delta on the gross alpha, gross beta, 90Sr, 210Pb, 7Be, 40K and 137Cs activities measured in atmospheric aerosol and water samples collected in Tenerife (Canary Islands) by F. Hernandez; L. Karlsson; J. Hernandez-Armas (4940-4948).
On 28 and 29 November 2005, the tropical storm Delta struck the Canary Islands (Spain) and the western shores of Morocco. Gravimetric and radiometric measurements carried out in atmospheric aerosol and water samples, collected after the storm, showed increased levels of total suspended particles (TSP) in the atmosphere and gross alpha, gross beta as well as 90Sr activities in both the atmosphere and drinking water. These variations were most likely produced by local re-suspension of soil material. However, 210Pb and 7Be activities, measured in atmospheric aerosols, did not increase until a week after the storm had passed. 40K and 137Cs activities, also measured in atmospheric aerosols, did not vary significantly with respect to previous weeks indicating that the slightly higher levels of TSP, measured during the week when the storm occurred, were not produced by the long-range transport of re-suspended aerosols from the African continent, as it has been observed in other occasions at this site. Gross alpha, gross beta, 40K and 90Sr levels in drinking water samples increased after the storm over their average values by approximately 245%, 245%, 130% and 440%, respectively. These results indicate how important the local re-suspension and later deposition/scavenging of aerosols may be on the water supply in Tenerife.
Keywords: Aerosols; Atmospheric radionuclides; Tropical storm; Drinking water;
Wind tunnel investigation on the retention of air pollutants in three-dimensional recirculation zones in urban areas by Marcos Sebastião de Paula Gomes; André Augusto Isnard; José Maurício do Carmo Pinto (4949-4961).
The article discusses an experimental investigation of turbulent dispersion processes in a typical three-dimensional urban geometry, in reduced scale, in neutrally stable conditions. Wind tunnel experiments were carried out for characterizing the flow and the dispersion of a pollutant around a scaled model (1:400) of a group of eight 10-floor buildings surrounding a square. The situation corresponded to the dispersion of fine inertialess particles released from a line source positioned upstream of the urban geometry. After the sudden interruption of the source generation, the particles persisted in the recirculation cavity between the buildings, with the concentration decaying exponentially with time. This is in accordance with previous works on the dispersion process around bluff bodies of different shapes [e.g., Humphries and Vincent, 1976. An experimental investigation of the detention of airborne smoke in the wake bubble behind a disk. Journal of Fluid Mechanics 73, 453–464; Vincent, 1977. Model experiments on the nature of air pollution transport near buildings. Atmospheric Environment 11, 765–774; Fackrell, 1984. Parameters characterizing dispersion in the near wake of buildings. Journal of Wind Engineering and Industrial Aerodynamics 16, 97–118]. The main parameter in the investigation was the characteristic time constant for the concentration decay. The measurements of the variation in the concentration of the fine particles were performed by means of a photo-detection technique based on the attenuation of light. The velocity fields were evaluated with the particle image velocimetry (PIV) technique. The dimensionless residence time H for the particles (H=τU/L, where τ is the time constant for the concentration decay, U the free-stream velocity, and L is a characteristic dimension for the urban geometry, as defined by Humphries and Vincent [1976. An experimental investigation of the detention of airborne smoke in the wake bubble behind a disk. Journal of Fluid Mechanics 73, 453–464] was determined for various locations in the scaled model, in the range of Reynolds numbers (Re) between 8000 and 64,000. H was found to be 6.5±1.0.
Keywords: Atmospheric pollution; Urban areas; Residence time; Bluff bodies; Wind tunnel experiments;
Effectiveness of urban shelter-in-place—I: Idealized conditions by Wanyu R. Chan; William W. Nazaroff; Phillip N. Price; Ashok J. Gadgil (4962-4976).
For a large-scale, unanticipated release of a toxic chemical into the atmosphere, it is recommended for nearby populations to shelter indoors. Two new metrics to quantify the community-scale effectiveness of shelter-in-place (SIP) are introduced. The casualty reduction factor (CRF) quantifies the expected reduction in casualties if SIP is performed. The safety-factor multiplier (SFM) quantifies the extent of toxic-load reduction for individuals in each exposed building. In this paper, idealized models are combined to explore the relationships among important input parameters and the SIP-effectiveness metrics. A Gaussian plume model predicts ambient concentrations for a hypothetical release event. A box model predicts indoor concentrations in buildings. A toxic-load model links exposure to health consequences. SIP effectiveness varies significantly with the toxic-load exponent, m, which characterizes the dose–response relationship. Another influential variable is a dimensionless time scale, ξ, equal to the release duration multiplied by the building air-exchange rate. Other factors that influence SIP effectiveness include the magnitude of the release relative to the toxicity of the pollutant, atmospheric transport and dispersion rates, and punctual termination of SIP once the toxic cloud has passed. SIP can be effective for short-duration releases (ξ<1), especially for chemicals with m of 2–3 or higher. If m=1, punctual termination at the end of the event can be important to ensure SIP effectiveness.
Keywords: Outdoor–indoor exposure; Acute health effect; Toxic chemical; Emergency response;
Examination of atmospheric ammonia levels near hog CAFOs, homes, and schools in Eastern North Carolina by Sacoby M. Wilson; Marc L. Serre (4977-4987).
Hog concentrated animal feeding operations (CAFOs) release ammonia (NH3) in Eastern North Carolina (NC) to the atmosphere which is potentially hazardous for nearby human populations at community locations particularly homes and schools. We present NH3 weekly average concentrations that were collected using passive diffusion tubes from October 2003 to May 2004 (20 sites) and from July 2004 to October 2004 (23 sites) near community locations in close proximity to hog CAFOs. The data for each phase of sampling was stratified by distance from the nearest hog CAFO. The mean Phase I levels were 16, 8, 7 and 5 ppb for distances <0.5, 0.5–1, 1–2, and 2 km or more, respectively. The mean levels for Phase II were 29, 16, and 11 ppb for distances <0.5, 0.5–1, and 1 km or more, respectively. The results of the distance stratification are the best results of this study and provide the strongest evidence that distance to one or more CAFOs is the key variable in controlling weekly NH3 atmospheric concentration at the community level in Eastern NC. Statistical analyses confirmed that source terms such as distance to a hog CAFO and live weight per operation, as well as temperature, wind speed and wind direction were important predictors of atmospheric NH3 at community locations. The results indicate potential zones of exposure for human populations who live or go to school near hog CAFOs.
Keywords: Ammonia; Hog; Passive diffusion; CAFOs; Emission; Exposure;
Sampling precautions for the measurement of nitrated polycyclic aromatic hydrocarbons in ambient air by A. Albinet; E. Leoz-Garziandia; H. Budzinski; E. ViIlenave (4988-4994).
Because of the toxicity of polycyclic aromatic hydrocarbons (PAHs) and of their oxidation products, such as nitrated and oxygenated PAHs (NPAHs and OPAHs), the determination of their concentrations is of great interest in terms of atmospheric pollution control. Then, normalisation of sampling procedures appears essential. In this context, this paper presents a comparison of particulate PAH, OPAH and NPAH concentrations determined with two different samplers (cascade impactor and conventional high volume sampler) installed in parallel during several field sampling campaigns carried out under different environmental conditions. For winter and summer periods, the PAH and OPAH concentrations determined with both sampling systems were considered as equivalent. In the summer period, NPAH concentrations quantified with both sampling devices were similar whereas in the winter period, the conventional high volume sampler underestimated their concentrations by a factor of 3–4. This underestimation was observed in the same proportion for all the 17 quantified NPAHs. Analytical error, NPAH formation during the sampling and NPAH degradation by reaction with gaseous oxidants associated to sampling methodology were unable to explain such differences between both samplers used in parallel. A probable hypothesis is that the heating of the PM 10 head of the high volume sampler in the winter period generates an increase of the internal sampler temperature that could intensify the chemical degradation of the NPAHs inducing the underestimation of their concentrations in the atmosphere. Further investigations will be necessary to confirm the importance of the temperature on the chemical degradation of these compounds and to understand the different behaviour of PAHs and OPAHs. Consequently, we suggest using oxidant scrubber to prevent chemical degradation of PAHs and derivatives during their sampling. Moreover, we advise against the heating of the sampling head which could induce an increase of these reactions of degradation especially for NPAHs.
Keywords: Polycyclic aromatic hydrocarbons; Nitrated polycyclic aromatic hydrocarbons; Oxygenated polycyclic aromatic hydrocarbons; Sampling artefacts;