Atmospheric Environment (v.37, #4)

Air pollutant recirculation is a common feature of coastal cities as a result of the diurnal variation of the land/sea breeze circulation. On the western coast of Australia, a thermally induced synoptic scale trough interacts with this local circulation to enhance the sea breeze flow, allowing pollutant to penetrate further inland. As well a low wind speed zone formed offshore near the trough axis leads to increased ozone concentrations and the rotation of the trough axis during its onshore movement spreads these higher concentrations of air pollutant over a larger area.
Keywords: Recirculation; Coastal urban; Ozone; Vehicle emissions;

Gas-phase chemistry of atmospheric Cl atoms: a PLP-RF kinetic study with a series of ketones by J Albaladejo; A Notario; C.A Cuevas; E Jiménez; B Cabañas; E Martı́nez (455-463).
The pulsed laser photolysis-resonance fluorescence technique (PLP-RF) has been used to determine the absolute rate coefficients for the gas-phase reactions of Cl atoms with a series of ketones at room temperature (298 K). The rate coefficients obtained (in units of cm3  molecule−1  s−1) are: 2-butanone (3.30±0.20)×10−11, 2,3-butadione (4.92±0.44)×10−13, 2-pentanone (4.57±0.28)×10−11, 3-pentanone (4.50±0.32)×10−11, 2-hexanone (6.54±0.58)×10−11, 3-hexanone (6.69±0.62)×10−11 and cyclohexanone (6.75±0.52)×10−11. The measured values were independent of pressure over the range 20–200 Torr. These rate coefficients were compared with previous studies carried out by different techniques, when data were available. Results and atmospheric implications are discussed and compared with the reactivity with OH radicals.
Keywords: Atmospheric chemistry; Chlorine atoms; Gas-phase reaction; Laser photolysis; Ketones;

Determination of average emission factors for vehicles on a busy road by G. Gramotnev; R. Brown; Z. Ristovski; J. Hitchins; L. Morawska (465-474).
In this paper, the CALINE4 software package, designed for calculation of concentrations of carbon monoxide near a busy road, is adapted for the analysis of aerosols of fine and ultra-fine particles, generated by vehicles on the road. A scaling procedure of the CALINE4 package is developed and justified. A new efficient method of determination of the average emission factor for fine particle emission from the average fleet (one average vehicle) on a given road is also developed. This method is based on measurements of the average particle number concentration at just one point near the road.An example of a specific road in the Brisbane area, Australia, is considered. The average emission factor for vehicles on this road is calculated to be ∼4.5×1014 particle/vehicle/mile. The obtained scaling coefficient is shown to be correct, and the procedure is directly applicable for the analysis of an arbitrary road with different types of vehicles and their average speed.Good agreement between the experimental results and the predicted theoretical dependencies of concentration on distance from the road clearly confirms the applicability of the CALINE4 package for the analysis of propagation of fine particle aerosols from a busy road. Statistical analysis of the experimental and theoretical results demonstrates that the concentration of fine and ultra-fine particles approximately reduces as a power law in distance from the road.
Keywords: Aerosol; Fine particles; Busy road; CALINE4; Emission factor;

Ozone uptake modelling and flux-response relationships—an assessment of ozone-induced yield loss in spring wheat by Helena Danielsson; Gunilla Pihl Karlsson; Per Erik Karlsson; H. Håkan Pleijel (475-485).
Measurements of stomatal conductance on field grown spring wheat (Triticum aestivum L.) from two experiments conducted in southwest Sweden were combined to validate and adjust the Jarvis type of multiplicative stomatal conductance model presented by Emberson et al. (Environ. Pollut. 109 (2000) 403). The adjusted model (Östad model) and the Emberson model are based on the boundary line technique. The aging of the flag leaf became important for stomatal conductance at about 500 degrees days after anthesis, on average 30 days after anthesis. Elevated ozone concentrations were assumed to influence the stomatal conductance in relation to the effect on the leaf life span. During the hours after noon the stomata tended to close to an extent that could not be explained by the combined effects of leaf temperature, leaf-to-air vapour pressure difference (VPDLA) or solar radiation. For these reasons factors describing the reduction of stomatal conductance caused by ozone and time of day were introduced in the calibration of the Östad stomatal conductance model. VPDLA induced closure of stomata at ≈1.5 kPa. In elevated carbon dioxide concentration (680 μmol mol−1) the stomatal conductance was reduced by approximately 60%. Test with the data from Östad showed that the Östad multiplicative model had an r 2-value of 0.59 for the relationship between calculated and observed conductance.The Östad as well as the Emberson models were used to estimate the cumulated uptake of ozone (CUO) by the wheat flag leaves. The relationship between CUO based on the Östad model cumulated from anthesis to harvest, with a threshold for the uptake rate of 5 nmol m−2  s−1 and relative yield loss, resulted in a higher r 2-value (0.90) than any other CUO model or relationships based on the accumulated ozone exposure over 40 nmol mol−1 (AOT40). The corresponding relationships between relative yield and CUO based on the Emberson model and with AOT40 were however also statistically significant.
Keywords: AOT40; Ozone uptake; Stomatal conductance; Triticum aestivum; Yield;

Contribution of HONO sources to the NO x /HO x /O3 chemistry in the polluted boundary layer by Bernard Aumont; Frédéric Chervier; Sophie Laval (487-498).
The contribution of HONO photolysis to the primary production of OH radicals and the impact of HONO sources to the O3 and NO x budgets has been investigated using a two-layer box model. Three sources of HONO were considered: direct emissions, heterogeneous production on the ground surface and heterogeneous production on the aerosol surface. We considered two scenarios representing typical urban and polluted rural area and simulations were conducted for both summer and winter conditions. For summertime conditions, HONO sources were found to have a slight impact on the NO x /HO x /O3 concentration profiles, except for conditions favoring the formation of photochemical pollution episodes where it becomes significant. For wintertime conditions, HONO sources were found to be major contributors to the primary OH production, leading to major changes in the HO x and NO x budget all day long.
Keywords: Nitrous acid; Photochemical pollution; Pollution model;

Concentration and chemical composition of PM2.5 in Shanghai for a 1-year period by Boming Ye; Xueli Ji; Haizhen Yang; Xiaohong Yao; Chak K Chan; Steven H Cadle; Tai Chan; Patricia A Mulawa (499-510).
Weekly PM2.5 samples were collected in Shanghai, China at two sites, Tongji University and Hainan Road. Sampling started in March 1999 and was conducted for 1 year. The ambient mass concentration and chemical composition of the PM2.5 were determined. Chemical analyses included elemental composition, water-soluble ions, and organic and elemental carbon. Weekly PM2.5 mass concentrations ranged from 21 to 147 μg/m3, with annual average concentrations of 57.9 and 61.4 μg/m3 at the two sites, respectively. Seasonal variation of PM2.5 concentrations was significant, with the highest concentrations observed from mid-November through December and the lowest from June through September. Ammonium sulfate and nitrate accounted for 41.6% of the PM2.5 mass with sulfate alone accounting for 23.4% of the PM2.5 mass. Carbonaceous material accounted for 41.4% of the PM2.5 mass, with 73% of that mass being organic, as defined by the TOR analysis method. Crustal components averaged 9.6% of the PM2.5 mass. Potassium, which was 95% water soluble, accounted for 2.7% of the PM2.5 mass.
Keywords: Particulate matter; PM2.5; Composition; Shanghai; China; Sources; Seasonal variation;

The Treasure Valley secondary aerosol study I: measurements and equilibrium modeling of inorganic secondary aerosols and precursors for southwestern Idaho by Hampden Kuhns; Val Bohdan; Judy C Chow; Vicken Etyemezian; Mark C Green; Douglas Herlocker; Steven Kohl; Michael McGown; June Ramsdell; William R Stockwell; Michael Toole; John Watson (511-524).
The SCAPE2 aerosol equilibrium model was applied to measured concentrations of PM2.5 aerosol and precursor gases. Ambient measurements in the Treasure Valley, Idaho were collected during stagnation episodes between December 1999 and March 2000 when conditions were favorable for the formation of secondary inorganic aerosol. SCAPE2 results agreed well with measurements for the episodes tested; Monte Carlo simulation using the uncertainties of the model input variables indicated that discrepancies between measured and modeled results were within the range of analytical precision. Air pollution control strategies were evaluated by perturbing the model input concentrations of total sulfate, nitrate, and ammonium. The largest reductions in secondary aerosol concentrations occurred when total nitrate was reduced, indicating that the formation of ammonium nitrate was limited by the availability of nitrate.
Keywords: Particulates; Secondary aerosol formation; Nitrate; Ammonia; Nitrogen oxides; Equilibrium;

The Treasure Valley secondary aerosol study II: modeling of the formation of inorganic secondary aerosols and precursors for southwestern Idaho by William R Stockwell; Hampden Kuhns; Vicken Etyemezian; Mark C Green; Judith C Chow; John G Watson (525-534).
Many locations with very high mixing ratios of ammonia, nitrogen oxides and relatively low sulfate mixing ratios are found in urban areas of the western United States during the wintertime. These urban areas may also experience episodes with high humidity with high levels of secondary inorganic ammonium nitrate particles. Photochemical simulations of the formation of secondary sulfate and ammonium nitrate aerosol were made to investigate possible secondary particle control strategies for Treasure Valley, Idaho. The simulation conditions were based on the field study of Kuhns et al. (Atmos. Environ. 2002, this issue). It was found that under these conditions that almost all of the sulfate and approximately 95% of the nitric acid would be found in the particulate phase. Reductions in the emission rates of volatile organic compounds were found to be most effective in reducing secondary inorganic aerosol concentrations while reductions in nitrogen oxide emission rates would be expected to increase aerosol concentrations. This response of aerosol formation rates is due to the effects of the nitrogen oxide and volatile organic compound emission rates on the concentration of hydroxyl radical mixing ratios.
Keywords: Particulates; Secondary aerosol formation; Modeling; Ammonia; Nitrogen oxides; VOC;

Volcanically influenced iron and aluminum cloud water deposition to Hawaii by Claudia R. Benitez-Nelson; Sue M. Vink; Jacqueline H. Carrillo; Barry J. Huebert (535-544).
Fog or cloud water (CW) deposition plays an important role in particle scavenging and the delivery of trace constituents to the Earth's surface. In this study, CW concentrations of total dissolvable iron (Fe) and aluminum (Al) were measured in 60 samples spanning 26 individual CW events throughout 1999 in Hawaii Volcanoes National Park on the island of Hawaii. Al concentrations ranged from 8 to 10,489 nM, with a median of 344 nM while Fe concentrations ranged from < 1 to 6419 nM with a median of 32 nM. CW deposition fluxes for Fe and Al ranged from 0.15–0.52 mmol Fe m−2  yr−1 and 0.621.35 mmol Al m−2  yr−1, depending on the estimation method used. The large range in concentrations is higher than expected for a relatively pristine ecosystem. It appears that this inconsistency is due to emissions from the currently active nearby volcano, Kilauea. Categorizing CW events into volcanically versus less or non-volcanically impacted events suggests that although volcanically impacted events only accounted for 12% of fog water deposition, Kilauea Volcano was responsible at least 42% of the measured CW Al deposition and 61% of the CW Fe deposition measured for 1999.
Keywords: Iron; Alumnium; Atmospheric deposition; Volcanic emissions; Fog water; Cloud water; Air pollution;

Comparison of hybrid receptor models to locate PCB sources in Chicago by Ying-Kuang Hsu; Thomas M. Holsen; Philip K. Hopke (545-562).
Results of three hybrid receptor models, potential source contribution function (PSCF), concentration weighted trajectory (CWT), and residence time weighted concentration (RTWC), were compared for locating polychlorinated biphenyl (PCB) sources contributing to the atmospheric concentrations in Chicago. Variations of these models, including PSCF using mean and 75% criterion concentrations, joint probability PSCF (JP-PSCF), changes of point filters and grid cell sizes for RTWC, and PSCF using wind trajectories started at different altitudes, are also discussed.Modeling results were relatively consistent between models. However, no single model provided as complete information as was obtained by using all of them. CWT and 75% PSCF appears to be able to distinguish between larger sources and moderate ones. RTWC resolved high potential source areas. RTWC and JP-PSCF pooling data from all sampling sites removed the trailing effect often seen in PSCF modeling. PSCF results using average concentration criteria, appears to identify both moderate and major sources. Each model has advantages and disadvantages. However, used in combination, they provide information that is not available if only one of them is used. For short-range atmospheric transport, PSCF results were consistent when using wind trajectories starting at different heights.Based on the archived PCB data, the modeling results indicate there is a large potential source area between Joliet and Kankakee, IL, and two moderate sources to the northwest and south of Chicago. On the south side of Chicago in the neighborhood of Lake Calumet, several PCB sources were identified. Other unidentified potential source location(s) will require additional upwind/downwind field sampling to verify modeling results.
Keywords: Hybrid receptor models; PCBS; Source identification; Wind trajectory; North America; United States; Chicago;

Aerosol chemistry during the NICE dark and light campaigns by K Teinilä; R Hillamo; V.-M Kerminen; H.J Beine (563-575).
Size-segregated aerosol measurements were made in Ny Ålesund, Svalbard, as a part of an EU funded project nitrogen cycle and effects on the oxidation of atmospheric trace species at high latitudes (NICE). The measurements were made during two field campaigns: the dark campaign that took place during the Polar night and the light campaign that took place after the Polar sunrise in winter/spring 2001. Three particle types (sulfate, sea-salt, and crustal particles) could be identified and their concentrations varied independently of each other during the measurements. Non-sea-salt sulfate (nss-SO4 2–) was the most abundant ion during the campaigns, and its rather high concentrations indicates that long-range transport was an important source of the sulfate aerosol at the measurement site. The concentration of ammonium followed typically that of nss-SO4 2–, but was much lower, making the bulk aerosol quite acidic. Methanesulfonate could be detected during the light campaign only, which suggests that the contribution of biogenic sulfur to the observed SO4 2– was neglible during the dark campaign and small but notable (average <15%) during the light campaign. Nss-SO4 2–, ammonium and methanesulfonate were found predominantly in the submicron size range and their similar modal structures indicate that they were internally mixed. Sodium and chloride were the most abundant ions after sulfate, which demonstrates the important role of sea-salt particles to the overall aerosol mass during the measurements. The concentrations of crustal tracers, non-sea-salt calcium and non-sea-salt magnesium, behaved differently during the campaigns, which is probably due to the presence of two different crustal sources affecting the measurement site. The concentration of nitrate was relatively low during both campaigns, being typically less than one-tenth of the respective nss-SO4 2– concentration. The acidic nature of submicron particles explains also why little nitrate was found in the submicron size range. During the dark campaigning most of the nitrate was bound to sea-salt particles, whereas during the light campaign it was also bound to crustal particles.
Keywords: Arctic aerosol; Impactor measurements;

Knowledge-based and statistically modeled relationships between residential moisture damage and occupant reported health symptoms by Ulla Haverinen; Mikko Vahteristo; Demetrios Moschandreas; Aino Nevalainen; Tuula Husman; Juha Pekkanen (577-585).
This study continues to develop a quantitative indicator of moisture damage induced exposure in relation to occupant health in residential buildings. Earlier, we developed a knowledge-based model that links moisture damage variables with health symptoms. This paper presents a statistical model in an effort to improve the knowledge-based model, and formulates a third, simplified model that combines aspects of the both two models. The database used includes detailed information on moisture damage from 164 houses and health questionnaire data from the occupants. Models were formulated using generalized linear model formulation procedures, with 10 moisture damage variables as possible covariates and a respiratory health symptom score as the dependent variable. An 80% random sample of the residences was used for the formulation of models and the remaining 20% were used to evaluate them. Risk ratios (RR) for the respiratory health symptom score among the 80% sample were between 1.32 (1.12–1.55) and 1.48 (1.19–1.83), calculated per 10 points index increase. For the 20% sample, RRs were between 1.71 (1.13–2.58) and 2.34 (1.69–3.23), respectively. Deviance values in relation to degrees of freedom were between 2.00–2.12 (80% sample) and 1.50–1.81 (20% sample). The models developed can be simulated as continuous variables and they all associated significantly with the symptom score, the association being verified with a subset of the database not employed in the model formulation. We concluded that the performance of all models was similar. Therefore, based on the knowledge-based and statistical models, we were able to construct a simple model that can be used in estimating the severity of moisture damage.
Keywords: Indoor air; Exposure indicators; Modeling; Mold; Respiratory;

Corrigendum to “High water vapour pressure deficit influence on Quercus ilex and Pinus pinea field monoterpene emission in the central Iberian Peninsula (Spain)” by L. Núñez; J. Plaza; R. Pérez-Pastor; M. Pujadas; B.S. Gimeno; V. Bermejo; S. Garcı&#x0301;a-Alonso (587).