Atmospheric Environment (v.37, #22)

A sensitivity analysis study for radm2 mechanism using automatic differentiation by Rafik Djouad; Nicole Audiffren; Bruno Sportisse (3029-3038).
A sensitivity analysis of an atmospheric multiphase mechanism is performed using an automatic differentiation tool. The sensitivity of some key concentrations is computed with respect to some input parameters (kinetic rates, microphysical parameters). The package odyssee is used in order to obtain the so-called linear tangent model giving the derivatives of outputs with respect to inputs. The direct model takes into account gas-phase reactions, aqueous-phase reactions and interfacial mass transfer and is based on the radm2 mechanism. Local sensitivity coefficients are computed for two different scenarii, rural and sub-urban. We focus in this study on the sensitivity of the gas-phase O3–NO x –HO x system with respect to some aqueous phase reactions and we investigate the influence of the reduction in the photolysis rates in the area below the cloud region. This preliminary work illustrates how powerful automatic differentiation tools may be for the study of large chemical mechanisms. We show for instance that the oxidation of trace metals (FeII, FeIII, Cu+ and Cu2+) in the case of low S(IV) polluted area is not always in disfavor of HO x gaseous concentrations, as it is usually claimed.
Keywords: Sensitivity analysis; Multiphase chemical mechanism; radm2; Automatic differentiation; Box model;

Simulated impacts of SO2 emissions from the Miyake volcano on concentration and deposition of sulfur oxides in September and October of 2000 by Junling An; Hiromasa Ueda; Kazuhide Matsuda; Hisashi Hasome; Motokazu Iwata (3039-3046).
A regional air quality Eulerian model was run for 2 months (September and October of 2000) with and without SO2 emissions from the Miyake volcano to investigate effects of the changes in the volcanic emissions on SO2 and sulfate concentrations and total sulfur deposition around the surrounding areas. Volcanic emissions were injected into different model layers in different proportions within the planetary boundary layer whereas the other emissions were released in the first model layer above the ground. Meteorological fields four times per day were taken from National Centers for Environmental Prediction (NCEP). Eight Japanese monitoring sites of EANET (Acid Deposition Monitoring Network in East Asia) were used for the model evaluation. Simulations indicate that emissions from the Miyake volcano lead to increases in SO2 and sulfate concentrations in the surrounding areas downwind in the PBL by up to 300% and 150%, respectively, and those in SO2 levels in the area found ∼390  km north away from the Miyake site in the free troposphere (FTR) by up to 120%. Total sulfur deposition amounts per month are also increased by up to 300%. Daily SO2 concentrations in different model layers display strong variability (10–450%) at sites significantly influenced by the volcano. Comparison shows that the RAQM model predicts daily SO2 variations at relatively clean sites better than those at inland sites closer to volcanoes and the model well captures the timing of SO2 peaks caused by great changes in SO2 emissions from the Miyake volcano at most chosen sites and that monthly simulated sulfate concentrations in rainwater agree quite well with observations with the difference within a factor of 2. Improvement in spatial and temporal resolutions of meteorological data and removal of the uncertainty of other volcanic emissions may better simulations.
Keywords: Regional air quality Eulerian model (RAQM); EANET; Miyake volcano; Percentage concentration change (PCC);

Composition and size distribution of submicrometer aerosol particles observed on Mt. Fuji in the volcanic plumes from Miyakejima by Hiroaki Naoe; Jost Heintzenberg; Kikuo Okada; Yuji Zaizen; Kazuhiko Hayashi; Takahiro Tateishi; Yasuhito Igarashi; Yukiko Dokiya; Kisei Kinoshita (3047-3055).
An aerosol observation campaign was conducted at the summit of Mt. Fuji (at an altitude of 3776 m), which is located 170 km northwest of Miyakejima. Individual aerosol particles were collected with an electrostatic aerosol sampler and the number–size distribution and composition were examined by electron microscopy. Number–size distributions were measured with the combination of a diffusion battery (DB) and a condensation particle counter. Sulfate and sulfur dioxide concentrations were also determined.During the first half of the campaign (13–15 September 2000), high number fractions of sulfuric-acid containing particles with a mode radius around 0.06 μm were observed in the radius range of 0.02–0.2 μm coincident with a humid maritime air mass originated from the south. Sulfate and sulfur dioxide also showed high concentrations in this period. These results suggested that the volcanic plumes of Miyakejima were transported up to the summit of Mt. Fuji. Number–size distributions determined by electron microscope were consistent with those derived using the DB. During the later half of the experiment (18–20 September), low fractions of sulfuric-acid containing particles represented only a small fraction of the total particle number, coincident with a dry continental air mass originating from the west.
Keywords: Volcanic plumes; Miyakejima; Tropospheric chemistry; Aerosol;

Estimation of SO4 contribution by dry deposition of SO2 onto the dust particles in India by Monika J Kulshrestha; Umesh C Kulshrestha; D.C Parashar; M Vairamani (3057-3063).
Dustfall deposition fluxes of major water-soluble components Cl, NO3, SO4, NH4, Na, K, Ca and Mg were estimated at five different sites of Delhi. The pH of water extracts of samples has been observed minimum at NPL ranging from 5.8 to 7.1 and maximum at Iqbalpur ranging from 7.9 to 8.7. The high values of pH of dustfall deposition suggest the dominance of crustal components that add higher alkalinity due to presence of components like Ca, Mg, etc. Dustfall fluxes were observed highest for Ca. considering the importance of alkaline nature of dust particles; the fraction of SO4 contributed by dry deposition of SO2 on the dust particles was estimated. Using these estimates, further the ambient concentrations of SO2 were calculated which were in a very good positive agreement with experimental concentration of SO2.
Keywords: Dustfall; Deposition flux; Sulphur dioxide; Sulphate aerosols;

We applied a simple size-dependent indoor air quality model associated with a compartmental lung model to characterize PM10 indoor–outdoor–personal exposure relationships for wind-induced naturally ventilated residences in Taiwan region. The natural ventilation rate was quantified by the opening effectiveness for sidewall opening (SP) and covered ridge with sidewall opening (CRSP) type homes. The predicted PM10 mass indoor/outdoor (I/O) ratios were 0.15–0.24 and 0.20–0.32, respectively, for SP and CRSP type homes. Results demonstrate that PM10 I/O ratios for a wind-induced naturally ventilated airspace depend strongly on the ambient PM size distributions, building openings design (e.g. height to length ratio of openings and roof slope), wind speed and wind angle of incidence. The predictions from our lung model agreed favorable with the experimental deposition profiles in extrathoracic (ET), bronchial–bronchiolar (BB), and alveolar–interstitial (AI) regions. Our results demonstrate that ET region has higher PM10 mass lung/indoor ratios (for north Taiwan region: 0.67–0.78; for central: 0.66–0.74) than that of BB (for north: 0.36–0.57; for central: 0.33–0.47) and AI regions (for north: 0.05–0.35; for central: 0.02–0.22). The present approach can be used in the future to appraise the significance of inter-subject lung morphology and breathing physiology variability for PM deposition and dose calculations.
Keywords: Particulate matter; Deposition; Natural ventilation; Opening effectiveness; Indoor–outdoor–personal exposure; Lung; Modeling;

Prediction of ground level lead concentration was made at five traffic intersections in Delhi, India, by the two highway models, viz., CALINE3, CAL3QHC and one particulate emission factor model PART5, where lead was actually monitored. The predicted values were compared with the monitored data at all the five monitoring sites. The CAL3QHC was found to be most suitable for the predictions at the signalized intersections.
Keywords: Vehicle; PM10; Tetraethyl lead; Figure of merit; Highway dispersion model;

This paper describes an assessment of environmental exposure to fluorine in the surroundings of an aluminium smelter, carried out by measuring fluorine concentrations in the tissues of mosses growing in the area. Forty-two samples were collected from within a 3300 m of radius of the smelter on two different occasions. Samples of either Hypnum cupressiforme Hedw. or Scleropodium purum (Hedw.) Limpr. were collected at each point, depending on which was the most abundant. The fluorine contents in the samples varied from <10 μg g−1 F (the limit of quantification of the analytical technique used) to 154 μg g−1  F. To analyse the spatial pattern of fluorine accumulation in the mosses, response surfaces were adjusted to the data using the geographic coordinates of the sampling points as independent variables. Details are given of the process used to select the best surface from among the many candidates available. The graphical and mathematical analyses of the surfaces allowed description of the effect of the distance from the smelter on fluorine concentration and of the spatial anisotropy, i.e. the existence of directions along which fluorine deposition is enhanced. Fluorine concentration decreased exponentially over all the study area, therefore the impact of the smelter decreased greatly within a short distance. The surfaces also allowed detection of differences between sampling times, in terms of the prevailing direction of pollutant movement, as well as differences in the rates of decrease in concentration with distance from the plant. Finally, it is discussed how the particular characteristics of the source of the pollutant affect its dispersal, and how some sampling difficulties encountered affected the results obtained.
Keywords: Biomonitoring; Spatial analysis; Response surface; Hypnum cupressiforme; Scleropodium purum;

A dynamic gas saturation technique was used to measure the solid-phase vapor pressures (p S o) of six polychlorinated dibenzodioxins (PCDDs) and seven polychlorinated dibenzofurans (PCDFs) at 25°C. Three polycyclic aromatic hydrocarbons (phenanthrene, anthracene, and chrysene) were also examined to validate the method. The p S o values of the three PAHs at 25°C were all within a factor of 2 of values previously obtained by a similar technique. The measured p S o values were converted to sub-cooled liquid vapor pressure (p L o) values using entropy of fusion information. For eight of the PCDD/F congeners, which included four toxicologically significant 2,3,7,8-substituted PCDD/F congeners, the p L o values obtained here at 25°C are significantly different than the values that can be extrapolated from higher temperatures using previously available p S o values. The log  p L o values at 25°C obtained in this study were regressed vs.: (1) corresponding values of gas chromatography retention index (GC-RI); (2) number of chlorines; (3) molecular weight; and (4) melting point. The best correlation was obtained using GC-RI, and was used together with information on the temperature-dependent molar enthalpy of vaporization to develop equations for predicting temperature-dependent p L o values for all 210 PCDD/Fs.

The rate constant for the nighttime degradation of 114 heterogeneous organic compounds, through reaction with nitrate radicals in the troposphere, is predicted here by quantitative structure–activity relationships modelling. The multiple linear regression approach is based on a variety of theoretical molecular descriptors, selected by the genetic algorithms-variable subset selection procedure. The proposed model, calculated on a limited subset of compounds selected by a D-optimal experimental design and checked for reliability and robustness, has good predictivity, verified by internal (Q LMO 2=89.6%) and “external” validation (Q EXT 2=95.7%). The model applicability domain was always verified by the leverage approach in order to propose reliable predicted data. The average root-mean square error for the prediction of log  k NO3 was 0.57, similar to (and even smaller than) the typical experimental error range.
Keywords: QSAR; Theoretical molecular descriptors; External validation; Prediction; Nitrate radical degradation;

Particulate organic compounds in the atmosphere surrounding an industrialised area of Prato (Italy) by Alessandra Cincinelli; Stefano Mandorlo; Rebecca M. Dickhut; Luciano Lepri (3125-3133).
Atmospheric aerosols were collected during the period from May 2000 through January 2001 at 13 different sites in and around the Baciacavallo sewage treatment plant in Prato (Italy). The urban area surrounding the plant contains significant textile industrial activity and a main arterial road. Aerosol-associated n-alkane, polycyclic aromatic hydrocarbon (PAH), nonylphenol (NP) and nonylphenolethoxylate (NPnEO) (n=1–3) concentrations were measured in order to evaluate contributions from the sewage treatment plant, naturally produced aerosols, transportation and industrial activities to the air quality in the vicinity of the sewage treatment plant. Aerosol-associated n-alkane concentrations ranged from 36.7 to 205 ng/m3 and their possible origin was determined by the presence of typical petroleum characteristics such as the unresolved complex mixture and an odd/even carbon ratio (Carbon Preference Index). PAH concentrations ranged from 0.855 to 24.2 ng/m3, in accordance with those generally found for urban aerosols in Europe. NP and NPnEO (n=1–3), as well as fine aerosol particulate matter (PM10) were significantly correlated with relative wind direction with increased levels observed in the ambient atmosphere when the relative wind direction was from the Baciacavallo sewage treatment plant. This study confirms the use of NP and NPnEO (n=1–3) as markers of sewage treatment emissions and the importance of the contribution of aerosols produced by sewage treatment plant aeration tanks to the local atmospheric composition.
Keywords: n-Alkanes; Polycyclic aromatic hydrocarbons (PAHs); Nonylphenols (NP); Nonylphenolethoxylates (NPnEO) (n=1–3); Particulate organic matter; Sewage plant;

Bulk deposition (wet+dry) of 14 polycyclic aromatic hydrocarbons (PAHs) was measured every week from 5 March 2001 to 4 March 2002 on a suburban site at Evreux located 100 km West of Paris (France). Measured concentrations in bulk depositions ranged from 1.1 to 222 ng l−1 with an average of 71.5 ng l−1. The most prevalent PAHs are phenanthrene, fluoranthene and pyrene, which represent 60% of the total concentration on average. The potentially carcinogenic PAHs represent 22% of the PAH concentrations. Statistical analysis, in particular principal component analysis (PCA), allowed us to analyse this data set, highlighting the influence of meteorological parameters (temperature, precipitation amount) on PAH concentration, both quantitatively and qualitatively. The temperature played an important role for PAH concentration in bulk deposition and influenced the efficiency of washout, while rainfall amounts seemed to have a minor influence. Thus, we found seasonal trends in PAH concentration. High rainfall correlated with high proportions of light PAHs. Finally, the study of wind directions allowed us to localize sources of PAHs and to estimate their respective contribution. The influence of the urban area of Rouen on PAH concentrations measured at Evreux is emphasized.
Keywords: PAHs; Bulk deposition; PCA; Meteorological parameters;

This study demonstrates for the first time that faecal coliform bacteria can survive airborne transfer in Antarctica, but are unlikely to survive for prolonged periods following deposition due to environmental stresses. The dispersal and survival of airborne faecal coliform bacteria from the sewage outfall at Rothera Research Station (Adelaide Island, Antarctic Peninsula) was examined. Northerly winds created the potential for sewage aerosols to be blown the 150 m from the outfall to the research station. During moderate wind velocities (∼15 m s−1), faecal coliform bacteria were detected up to 175 m downwind of the outfall amongst the station buildings. However, moderate doses of solar UV radiation (∼20 W m−2) were capable of reduced the number of viable wind-deposited bacteria by up to 99.9%, compared with periods of low solar UV radiation (∼1 W m−2). Further experiments showed that, within 1 h of deposition, desiccation stress and solar radiation independently reduced coliform viability by up to 99.8% and 99.98%, respectively. These results imply that airborne faecal coliforms are unlikely to survive for prolonged periods following deposition or cause infection of local wildlife or human populations, though this may not be the case for more stress-resistant microorganisms.
Keywords: Antarctica; Sewage; Relative humidity; Solar radiation; Pollution;

Measurements of sulfur dioxide and ozone dry deposition over short vegetation in northern China—a preliminary study by Atsuyuki Sorimachi; Kazuhiko Sakamoto; Hidekazu Ishihara; Tsutomu Fukuyama; Masahiro Utiyama; Hongjie Liu; Wei Wang; Dagang Tang; Xuhui Dong; Hao Quan (3157-3166).
We measured dry deposition fluxes of SO2 and O3 over a field covered mostly with short grass in a suburb of Beijing during late summer and early winter as an initiatory attempt to obtain information on dry deposition in northern China. The measurement was based on a micrometeorological gradient method, and only the data conforming to neutral atmospheric stability were analyzed because the data we collected were not adequate to extend the analysis to other stability cases. The data were further screened out according to a few selection criteria to ensure their credibility. For the selected periods V d (deposition velocity) of SO2 showed a maximum in the morning and a minimum in the afternoon, with little seasonal dependence in this behavior. The mean (±standard deviation) V d was 0.2 (±0.1) cm s−1 in late summer and 0.4 (±0.2) cm s−1 in early winter. The diurnal variation of V d seemed to be more or less governed by that of R a (aerodynamic resistance) +R b (quasi-laminar boundary layer resistance), which was considerably larger than R c (canopy resistance). The mean (±standard deviation) V d of O3 was 0.2 (±0.2) cm s−1 in late summer and 0.4 (±0.3) cm s−1 in early winter, thus much the same as those for SO2. The variation of O3 V d was qualitatively similar to that of SO2, but in this case R c was comparable to or larger than R a+R b. Little distinct seasonal dependence was evident for O3 deposition, either. A tendency was discernible for R c to increase in the afternoon, which was probably caused by a decline in stomatal conductance due to an increase in vapor pressure deficit and/or a rise in temperature.
Keywords: Deposition velocity; Sulfur dioxide; Ozone; Gradient; Short vegetation;