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Atmospheric Environment (v.39, #33)
Assessment of ambient air PM10 and PM2.5 and characterization of PM10 in the city of Kanpur, India by Mukesh Sharma; Shaily Maloo (pp. 6015-6026).
This research was initiated to study the air quality in the city of Kanpur, India in terms of PM10 and PM2.5 and chemical composition in terms of heavy metals and benzene-soluble organic fraction (BSOF) for PM10. Three sampling locations, Indian Institute of Technology (IIT) (control site), Vikas Nagar (VN) (commercial site) and Juhi Colony (JC) (residential site) were selected. Total forty-seven 24-h samples were collected for PM2.5 and PM10 during October 2002–February 2003 at these locations. The collected PM10 samples were subjected to chemical analysis for determination of heavy metals and toxic organic fraction by measuring BSOF. PM10 (45–589μgm−3), PM2.5 (25–200μgm−3), BSOF (1–170μgm−3) and heavy metals were highest at VN followed by JC and IIT. The study concluded that the overall air quality in the city of Kanpur was much inferior to other cities in India and abroad. Similar to PM10 and PM2.5, heavy metals were almost 5–10 times higher than levels in European cities. The study concluded that there was a need to address the issue of PM2.5 monitoring and control. Because regular PM2.5 monitoring may take some time, a linear model for predicting PM2.5 using routinely monitored parameters PM10 and BSOF was suggested for preliminary assessment. The model was checked for its adequacy and it was validated.
Keywords: PM; 10; PM; 2.5; Fine particulate; Benzene-soluble fraction; Heavy metals; India
Enhanced dissolution of volatile organic compounds into urban dew water collected in Yokohama, Japan by Hiroshi Okochi; Masanori Kataniwa; Daisuke Sugimoto; Manabu Igawa (pp. 6027-6036).
Simultaneous sampling of six chlorinated hydrocarbons (CHs) and five monocyclic aromatic hydrocarbons (MAHs) in dew water and in the ambient air was performed from 1998 to 2000 in Yokohama, Japan. Dichloromethane (volume-weighted mean concentration (VWM): 2.43nM) and trichloroethylene (VWM: 2.91nM) were abundant among CHs in dew water, while toluene (VWM: 9.69nM) and p-dichlorobenzene (VWM: 6.06nM) were abundant among MAHs. The contribution of total measured volatile organic compounds (VOCs) concentration to dissolved organic carbon (DOC) concentration in dew water was only 0.02wt% on average. The concentrations of VOCs except for dichloromethane and benzene in dew water were several hundred times higher than those in rainwater collected at the same site. In particular more hydrophobic VOCs with higher octanol–water partition coefficientKOW tended to be concentrated in dew water, indicating that urban dew water has stronger hydrophobicity than rainwater. Dew water contained higher amounts of VOCs than would have been expected from the ambient gas-phase concentrations and Henry's law constants. The enrichment factors, which were defined as the ratio of the observed concentration to the estimated, ranged from 6.98 (for dichloromethane) to 62.7 (for trichloroethylene) on average. Relatively high correlations (r>0.55) between the enrichment factors of highly hydrophobic VOCs (Kow>103) and the ratios of DOC to total inorganic ion concentration (TIC), which could be a potential surrogate of surface tension for urban dew water, indicated that the existence of any dissolved organic compounds, which could reduce the surface tension, in dew water also caused the enrichment of highly hydrophobic VOCs.
Keywords: Chlorinated hydrocarbons; Monocyclic aromatic hydrocarbons; Henry's law; Enrichment factor; Hydrophobicity
Fine organic aerosols collected in a humid, rural location (Great Smoky Mountains, Tennessee, USA): Chemical and temporal characteristics by Liya E. Yu; Michelle L. Shulman; Royal Kopperud; Lynn M. Hildemann (pp. 6037-6050).
Fine organic aerosols collected at the Great Smoky Mountain National Park, Tennessee (USA) during 15 July –25 August 1995 as part of the Southeastern Aerosol and Visibility Study (SEAVS) were chemically characterized. The water-soluble organic species (WSOS) often dominated over the solvent-soluble organic species (SSOS) at this remote, humid sampling site, contributing 76–98% of the total identified organic mass in 17 out of the 21 daytime samples analyzed. Nighttime samples tended to have slightly larger concentrations of total SSOS than the daytime, with nocturnal/diurnal organic mass ratios greater than 1.0 in 7 out of the 10 paired samples. However, for total WSOS mass, the nocturnal-to-diurnal ratios were less than 0.3 in 7 out of the 10 paired samples, reflecting much more substantial depletion and/or less production of the more polar organics during nighttime. Based on identified species, the organic-mass-to-organic-carbon (OM–OC) ratios at the SEAVS site are estimated as 2.0, 2.2, and 1.3 for the daytime total organics, WSOS, and SSOS, respectively. For the nighttime samples, the OM–OC ratio for total identified organics is estimated to be 1.8, slightly lower than the daytime ratio due to the smaller mass fraction of WSOS present at night.
Keywords: Organic aerosol; Humid rural location; Water-soluble organic species; Solvent-soluble organic species
BTX measurements in a medium-sized European city by Georgios A. Pilidis; Spyros P. Karakitsios; Pavlos A. Kassomenos (pp. 6051-6065).
The BTX levels are significantly high compared to the EU directive for benzene in European cities with population around or higher one million. Since there are hundreds of towns in Europe with smaller population, it is important to know the levels of aromatics in these areas.This work presents the results of a benzene, toluene and xylene (BTX) measurement campaign that took place in Ioannina, a medium-sized Greek city. As a result of traffic situation and the local meteorological conditions, pollution levels in Ioannina are unusually high, at least for a city of that size. BTX levels were measured using passive samplers placed at several points around the city, as well as across a selected street canyon using both passive and active samplers, combined with simultaneous measurements of traffic flow and wind speed. The measurement procedure was repeated in an exact manner for all four seasons and the results suggest that benzene levels, at all sampling points, exceed the limit set by EU Directive 2000/69. Benzene levels appear correlated to traffic density, while benzene/toluene/xylene ratios present a seasonal variation linked to meteorological conditions.
Keywords: Benzene; Toluene; Xylene; Passive samplers; Active samplers; Urban air quality
Long-range transport of aerosols and their impact on the air quality of Taiwan by C.-Y. Chuan-Yao Lin; Shaw C. Liu; C.C.-K. Charles C.-K. Chou; S.-J. Saint-Jer Huang; C.-M. Chung-Ming Liu; C.-H. Ching-Huei Kuo; C.-Y. Chea-Yuan Young (pp. 6066-6076).
The impact of long-range transport on the air quality of Taiwan was assessed by using measurements at stations of the air quality monitoring network of the Taiwan Environment Protection Administration over the winter monsoon periods of 2000 and 2001. The primary long-range transport process can be clearly identified to be the prevailing northeasterly following the cold front of winter monsoon that originates in the Asian continent. Based on pollutants concentration differences among different meteorological conditions, we estimate that the long-range transport of particulate pollutants contributes to about 30μgm−3 to the PM10 concentrations in northern and eastern Taiwan. A smaller contribution is estimated for the western plain of Taiwan. Contributions of the long-range transport to CO and SO2 are about 230 and 0.5ppb, respectively. The identified, dust events have the highest average inflow concentration (about 71±34μgm−3) of PM10. The dust impacts on PM10 have been estimated to be nearly 100% at windward background stations along the north and northeast coast. In the northern cities of Taiwan, such as Taipei and Hsinchu, the impacts decrease to around 60–80% as local emission increase. Due to geographic blocking, a smaller impact is estimated for the western plain of Taiwan. However, the identified frontal pollution cases have significant impact on CO and SO2, which is more evident than the impact of dust events. In general, impacts of long-range transport on air pollutants at coastal stations are greater than those in urban areas.
Keywords: Long-range transport; PM; 10; Dust storm; Air pollutants; Impact
On-site measurements of hydrogen sulfide and sulfur dioxide emissions from tidal flat sediments of Ariake Sea, Japan by Md. Abul Kalam Azad; S.-I. Shin-Ichi Ohira; Mitsutomo Oda; Kei Toda (pp. 6077-6087).
Emission variability of hydrogen sulfide and sulfur dioxide from tidal flat sediments to atmosphere in Ariake Sea, Japan was studied using a diffusion scrubber-based portable instrument. Ariake Sea is a typical closed sea consisting of a huge marsh area along the coast. Seasonal, spatial and diurnal variability in emission rates were examined. In addition, depth profiles of the gas emissions were examined with the profiles of anions, heavy metals, water and organic contents. Unexpectedly, SO2 emission was much higher than H2S in all measurements, while an opposite emission trend was observed in diurnal and spatial patterns of H2S and SO2 emissions. The mechanisms of these gas emissions are discussed. Total sulfur fluxes to the atmosphere as H2S and SO2 during the study averaged 7.1μgSm−2h−1 for muddy sites and 28μgSm−2h−1 for sandy sites. Sulfur fluxes from tidal flats were comparable to the artificial sulfur emission from the neighboring towns.
Keywords: Hydrogen sulfide; Sulfur dioxide; Tidal flat sediment; Ariake Sea; Sulfur emission
A model for vehicle-induced non-tailpipe emissions of particles along Swedish roads by G. Omstedt; B. Bringfelt; C. Johansson (pp. 6088-6097).
One of the most important parameters that controls the suspension of road dust particles in the air is road surface moisture. This is calculated every hour from a budget equation that takes into account precipitation, evaporation and runoff. During wet conditions a road dust layer is built up from road wear which strongly depends on the use of studded tyres and road sanding. The dust layer is reduced during dry road conditions by suspension of particles due to vehicle-induced turbulence. The dust layer is also reduced by wash-off due to precipitation. Direct non-tailpipe vehicle emissions due to the wear and tear of the road surface, brakes and tyres are accounted for in the traditional way as constant emission factors expressed as mass emitted per vehicle kilometre.The model results are compared with measurements from both a narrow street canyon in the city centre of Stockholm and from an open highway outside the city. The model is able to account for the main features in the day-to-day mean PM10 variability for the street canyon and for the highway. A peak in the PM10 concentration is typically observed in late winter and early spring in the Nordic countries where studded tyres are used. This behaviour is due to a combination of factors: frequent conditions with dry roads, high number of cars with studded tyres and an accumulated road dust layer that increases suspension of particles. The study shows that using a constant emission factor for PM10 or relating PM10 emissions to NO x cannot be used for prediction of day-to-day variations in PM10 concentrations in the traffic environments studied here. The model needs to describe variations in dust load, wetness of the road and how dust suspension interacts with these processes.
Keywords: Road dust; Road wear; Suspension; Coarse particles; PM; 10; PM; 2.5
Organic and inorganic pollutants in storage rooms of the Lower Saxony State Museum Hanover, Germany by A. Schieweck; B. Lohrengel; N. Siwinski; C. Genning; T. Salthammer (pp. 6098-6108).
Indoor pollution in cultural institutions such as museums, libraries and archives is of particular importance. On the one hand, it is essential to provide a healthy indoor climate for museum staff and visitors; on the other hand, cultural assets have to be protected against deterioration. Building materials, preservatives and other products are possible sources of a number of hazardous compounds. In many cases, conservators handle cultural artifacts where the type of preservation is unknown. Therefore, systematic measurements of indoor pollutants in storage rooms of the Lower Saxony State Museum Hanover have been accomplished. Concentrations of volatile organic compounds (VOCs), formaldehyde and organic acids in the ambient air were determined by active sampling and chemical analysis. Semi-volatile organic compounds (SVOCs) and selected elements were examined by sampling and analyzing settled dust. The climatic conditions (temperature and relative humidity) were recorded as well. Most of the VOCs detected in the ambient air are associated with packaging and building products used for furnishing magazines and building exhibition cases. Furthermore, they are associated with products used for preservation and restoration. Wooden shelves and drawers were identified as sources of terpenes and other VOCs. Compounds such as lindane and 1,4-dichlorobenzene are still used as preservatives against insects and fungi. In settled dust, increased concentrations of lead, arsenic and chlorine were found. This result also indicates the application of certain preservatives. The spectrum of detected air pollutants reflects the different application of chemicals and building products in the individual departments. The results have been evaluated with regard to possible adverse effects both on human health and on works of art.
Keywords: Museums; Storage rooms; Air pollutants; Nuclear radiation; Dust analysis; Biocides
Exotic dust incursions into central Spain: Implications for legislative controls on atmospheric particulates by Teresa Moreno; Xavier Querol; Andrés Alastuey; Mar Viana; Wes Gibbons (pp. 6109-6120).
The area of Castilla-La Mancha in central Spain is repeatedly visited by mineral dust incursions from the deserts of NW Africa. Such exotic atmospheric intrusions raise background PM10 levels, making urban areas much more likely to exceed daily limits of 50μgm−3 and become subject to fines under European environmental law. Data from a 3-year (2001–2003) study of hourly PM10 values demonstrate that average background dust levels in remote sites rise from 6–8μgm−3 when Atlantic-derived W/SW winds are blowing, to 24–7μgm−3 when African events take place. In four Castilla-La Mancha towns, numbers of exceedence days (ED: when PM10>50μgm−3) per year averaged 31 in Guadalajara (suburban site with annual daily PM10 average ADPM10=27μgm−3), 68 in Toledo (ADPM10=38μgm−3) and 139 in Albacete (ADPM10=47μgm−3; both urban sites), and 151 in Puertollano (industrial urban site with ADPM10=51μgm−3). Thirty-four percent of ED occurred during African dust incursions, and current law allows exclusion of such days from annual data (which also reduces the ADPM10 by 2–4μgm−3). Rather than simply excluding such days, a more scientifically satisfactory approach would be to allow subtraction of the estimated component of exotic background dust present daily at every urban monitoring station, and thus identify towns subject to high levels of locally derived anthropogenic PM10. Such an approach reduces ADPM10 values by the same amount as above (2–4μgm−3) if only African-derived PM10 values (as measured at remote background stations) are subtracted, although ΣED shows a relative increase. If, however, an attempt is made to estimate and subtract the total amount of exotic PM10 (i.e. not just African non-locally derived) at the four sites, this reduces the ADPM10 by 8–12μgm−3, and ΣED also drops significantly. Whichever approach is adopted, however, our data confirm that the legally allowable number of ED is far more strict than the annual limit value. This inconsistency will make it especially difficult for many southern European towns, with their abundant dry dust resuspension and regular incursions of African dust, to achieve PM exceedence targets in 2005. We argue that further refinement of aerosol pollution law is necessary to ensure that penalties for exceeding legally acceptable levels of atmospheric particulates are scientifically well founded and fair.
Keywords: European environmental law; African dust; PM; 10; Central Spain
A new air quality regime classification scheme for O3, NO2, SO2 and PM10 observations sites by J. Flemming; R. Stern; R.J. Yamartino (pp. 6121-6129).
The paper presents an objective air quality classification scheme for observed ozone (O3), nitrogen dioxide (NO2), sulphur dioxide (SO2) and particulate matter (PM10) time series in Germany. The classification is based on the medians of daily average concentration and relative daily variation. Six (O3 and NO2) and five (SO2 and PM10) different regimes were identified by means of hierarchical clustering. The stability of the clusters in relation to variable scaling and transformation was ensured by a cross-validation test based on re-sampling. Quick classification rules were developed, which permit a rapid and easy classification of any further observed or modelled annual time series. The climatological properties of the defined regimes were examined in terms of the mean and maximum values, as well as inter-annual, yearly, weekly and daily variability. The polluted regimes are characterised by a pronounced weekly cycle. O3 and NO2 classifications agree reasonably well for most stations, but the range of SO2 and PM10 concentrations is large within specific O3 regimes.
Keywords: Air pollution regime; Hierarchical clustering; Air pollution climatology
Modelling of air pollution on a military airfield by Krzysztof Brzozowski; Wojciech Kotlarz (pp. 6130-6139).
The paper presents a numerical study of exhaust emission and pollutant dispersion of carbon monoxide on a military airfield. Investigations have been carried out for typical conditions of aircraft usage in the Polish Air Force Academy in Dęblin. Two different types of aircraft have been taken into account. One of them is an MI-2 helicopter, the second is a TS-11 plane. Both are used in military pilot education in Poland. Exhaust emission of CO from those aircrafts has been obtained in an experiment carried out on an engine test stand. CO concentrations have been calculated for different meteorological conditions (averaged from 5 years observations) and selected conditions of aircraft use. The finite volume method has been used to discretise the equation describing the process of pollutant dispersion. In addition, the two-cycle decomposition method has been employed to solve the set of ordinary differential equations of the first order obtained after discretisation of the advection–diffusion equation. A meteorological pre-processor, based on relationships resulting from the Monin–Obukhov theory, is used to define eddy diffusivity and the profile of air speed in the lower layer of the atmosphere. In the paper, the computer model and calculated average concentration of CO in the Dęblin airfield during typical flights are presented. The goal of the computational analysis is to predict CO pollution level in the workplace of aircraft service personnel.
Keywords: Aircraft emission; Carbon monoxide; Air quality; Modelling
Surface ozone enhancements in the south of Brazil owing to large-scale air mass transport by C. Boian; V.W.J.H. Kirchhoff (pp. 6140-6146).
Surface ozone mixing ratios were monitored in the north-west region of the state of Parana (at a site near the city of Maringa, 23.1°S, 53.1°W), from August 2001 to November 2002, in a specific experiment to determine the impact of large-scale transport, over a region of small biomass burning activity (non-source regions). Surface ozone measurements, backward trajectories and meteorological conditions were used to determine the influence of large-scale transport. Surface ozone enhancements were observed when the anticyclonic circulation was well defined and the air masses came from significant source regions of biomass burning (states of Tocantins, Para, Mato Grosso and Mato Grosso do Sul). An example of such enhancement is obtained between 25 and 31 August 2001, when the measured average ozone mixing ratio was 89 parts per billion by volume (ppbv) ± 7.4, with maximum values between 93 and 173ppbv. Comparison of this and the background concentration during the wet season (January, for example) shows a significant enhancement of 76ppbv. During the same month, but under the influence of a different transport regime, 8–24 August 2001, considerably lower values were measured (47.2±7.2ppbv).
Keywords: Biomass burning; Ozone; Transport; Backward trajectories; Air masses
Numerical and experimental studies of wind environment in an urban morphology by Martin Skote; Mats Sandberg; Ulla Westerberg; Leif Claesson; Arne V. Johansson (pp. 6147-6158).
The purpose of the paper is to examine the relation between urban morphology (three-dimensional structure) and windiness. We regard a city as a porous obstacle, which is open at the top. We consider the interaction between the atmospheric boundary layer and a city to be both a function of the overall shape (silhouette or skyline) and the internal resistance to the flow caused by the friction when the wind flows over the urban surfaces. We regard the street pattern as an interconnected flow network with the crossings as nodes. Flow along the streets is generated by pressure differences.We here use a highly idealized city model consisting of a circular block divided into two or four equally large sectors. Two types of cases are studied, the first with only one street through the city model with different angles between the street and the oncoming wind. The second case also contains a perpendicularly crossing street (through the center). Both wind tunnel experiments and numerical flow computations (computational fluid dynamics, CFD) are used and compared. The general agreement between the two is good and the CFD method offers new possibilities for quantifying the urban wind environment.
Keywords: City model; Street canyon; Boundary layer; Wind tunnel; Computer simulation
Origin of particulate matter pollution episodes in wintertime over the Paris Basin by B. Bessagnet; A. Hodzic; O. Blanchard; M. Lattuati; O. Le Bihan; H. Marfaing; Rouil L. Rouïl (pp. 6159-6174).
Several wintertime pollution events due to particulate matter on the Paris Basin in 2003 are investigated in this paper. High-pressure systems close to Scandinavia or the North Sea involve highly stable conditions with slight Northeasterly flux on France leading to high airborne pollutant concentrations. An evaluation of the CHIMERE model results against observations over the Paris area is proposed. While PM10, nitrate and ammonium seem fairly well reproduced, sulfate concentrations remain difficult to predict. A specific study, by removing Ile-de-France emissions, displays on 21 February and 21 March episodes an important ammonium nitrate contribution, mainly originating from outside the Paris area. According to the model results, the Paris Basin has also a large influence up to the Southwest of France. In a similar way, an investigation of the possible sources outside the Paris basin, displays a strong influence of emissions from Germany, the Netherlands and Belgium during these episodes. To a lesser extent, Italy has an influence on the Paris area at the end of the episodes. It is also demonstrated that in some situations, the contribution of locally produced or emitted particles is prevalent at the ground level. The influence of French emissions is also studied from 20 to 25 March displaying an influence on Spain and a strong impact at the end of the episode successively on Great Britain, Belgium, the Netherlands when winds veer Southeast and West. This influence is also significant up to Eastern Europe.
Keywords: Modeling study; Aerosols; Episodes; Model evaluation; Emission inventory; Ammonium nitrate
Study of chemical composition in wet atmospheric precipitation in Eshidiya area, Jordan by Omar Ali Al-Khashman (pp. 6175-6183).
The present study investigated the chemical composition of wet atmospheric precipitation samples in the Eshidiya area in south Jordan. The samples were analyzed from October 2003 to May 2004. All samples were analyzed for major ions (Cl−,NO3-,HCO3-,SO42-, Na+, K+, Ca2+, Mg2+ andNH4+) and trace metals (Cd, Cu, Pb, Zn, Fe and Ni). The highest concentration of elements is observed at the beginning of the rainfall season when large amounts of dust accumulate in the atmosphere scavenged by rain. The daily sample pH values ranged from 5.33 to 7.90 with a median value of 6.65±0.68. Rain water quality is characterized by low salinity and neutralized pH. High values of pH were attributed to the neutralization by natural alkaline local dusts which contain a large fraction of calcite and dolomite. The major ions in rainwater samples showed high Ca2+,HCO3-,SO42-, Cl− and Mg2+ concentrations. For trace metals, the study identified that the origin of these metals from local anthropogenic activities (from soil and phosphate mine, heating activities during the cold period of year (January to April) and the anthropogenic activities.In general, the results of this study suggest that the rainwater chemistry is strongly influenced by natural sources rather than anthropogenic and marine sources.
Keywords: Precipitation chemistry; Acidity; Chemical elements; Jordan
Comments on the parameterization of lightning-produced NO in global chemistry-transport models by B.A. Ridley; K.E. Pickering; J.E. Dye (pp. 6184-6187).
Many current global chemistry-transport models limit the annual global source strength of reactive nitrogen from lightning activity to ∼5TgNyr−1. However, there is strong evidence from aircraft and cloud-resolving model studies and theory that production of NO by an intracloud flash is not an order of magnitude smaller than from a cloud-to-ground flash, an assumption commonly used in the global models. We suggest that modification of the global models to accept comparable production of NO by both types of discharge and the necessarily larger input of NO to higher altitudes will require a reduction in their global annual source strength from lightning activity in order to match existing observations.
Keywords: Convection; Lightning; Nitric oxide; Nitrogen oxides; Thunderstorms
Physicochemical characteristics of atmospheric aerosol during winter in the São Paulo Metropolitan area in Brazil by Regina M. Miranda; Maria F. Andrade (pp. 6188-6193).
In order to characterize atmospheric aerosol in the São Paulo Metropolitan Area, aerosols were sampled during the winter months of August 1999 and August 2000. A micro-orifice uniform deposit impactor (MOUDI) was used. Samples were submitted to gravimetry, as well as to proton-induced X-ray emission (PIXE), carbon (black and organic) and ion-chromatography analysis. These analyses supplied information about mass concentrations and physicochemical properties of the particles. Due to the higher humidity, which can increase soluble particles diameters, and reduced atmospheric stagnation seen in 2000, average PM10 concentrations were higher (105μgm−3) in the winter of 1999 than in the winter of 2000 (60μgm−3). The PIXE analysis revealed metals and metal compounds, soil-derived elements, Si-rich particles, sulfates, carbonates, chlorides and other anthropogenic air-borne particles, supposing molecules in their usual composition. Mass balance for PM2.5 revealed significant participation of organic and black carbon, probably resulting from diesel burning by the heavy-duty fleet.
Keywords: Aerosol; Particulate material; PIXE; Sao paulo; Meteorological conditions
The Washington aerial spray drift study: Modeling pesticide spray drift deposition from an aerial application by Ming-Yi Tsai; Kai Elgethun; Jaya Ramaprasad; Michael G. Yost; Allan S. Felsot; Vincent R. Hebert; Richard A. Fenske (pp. 6194-6203).
A routinely scheduled aerial organophosphorus pesticide application of methamidophos in central Washington State was monitored in the summer of 2002. The sprayed potato crop surrounded a rural agricultural community where residences were within 200 meters of the sprayed fields. Modeling pesticide spray drift is critical for exposure assessment of the residential population. Herein the objective is to model spray drift deposition with regard to model selection, calibration, and prediction for a particular application event. The US Environmental Protection Agency's Fugitive Dust Model (FDM) was chosen for its flexibility in terms of both inputs and outputs. Model calibration was accomplished by varying the aerosol size distribution in comparison with collected deposition samples and locating the minimum relative bias measure. From the calibrated model, a map of total pesticide deposition within the community indicated spray drift occurring despite adherence to general precautionary pesticide application guidelines. The calibrated model also provided 15-min time-resolved deposition images over the 5-h application period. These time-resolved maps revealed that actual community deposition occurred in only 2 of the 20 time periods when the source, due to the changing wind, was oriented towards the community. Despite the limitations of FDM in modeling a liquid aerosol, the calibration of the model to samplers located in the areas of interest allows it to serve as a potential tool for conducting exposure assessment within the community.
Keywords: FDM; Gaussian dispersion; Deposition sampling; Pesticide aerosol
Identification of local sources of lead in atmospheric deposits in an urban area in Southern Brazil using stable lead isotope ratios by Nicolai Mirlean; Daniel Robinson; Koji Kawashita; Maria Lidia Vignol; Conceicao Rommulo Conceição; Farid Chemale (pp. 6204-6212).
Lead concentrations of several thousand mgkg−1 were found in the atmospheric deposit samples and tens of thousand mgkg−1 in the soil samples in the city of Rio Grande in southern Brazil. Stable lead isotopes ratios were used to identify local sources of lead contamination. A significant source of lead in samples taken in a nearby fishing village was the production of lead weights by local fishermen. In suburban areas of the city lead used in roof construction, appears to be a major source of lead in atmospheric samples. Atmospheric samples obtained in the oldest part of the city, show anomalous lead results possibly due to lead paint from abandoned buildings. Sources of lead were differentiated on the basis of their206Pb/207Pb and208Pb/207Pb ratio.
Keywords: Atmospheric deposition; Contamination; Lead isotope ratios; Lead weights; Paint
Nucleation and scattering properties of ice cloud due to seeding of sodium chloride as aqueous solution and dust by Sahana Paul; L.N. Biswas; U.K De; K. Goswami (pp. 6213-6222).
Sodium chloride in three forms, as aqueous solution and as dust of two size ranges are seeded in a cold room for heterogeneous ice nucleation in the temperature range between −24°C and 0°C. Maximum nucleation for all the three seeding agents occurs at −21.2°C, which is the eutectic temperature of sodium chloride and water mixture. However, the number density of ice nucleation at the eutectic temperature is highest for the finer variety of dust and lowest for the solution. On the other hand, largest size crystals are produced by the solution and smallest size crystals are produced by the finer variety of dust, at the same temperature.It is observed that the optical properties of ice cloud depends more on the crystal size. The variation of scattering co-efficient, extinction co-efficient and optical depth with temperature are noted for the scattering angles of 30°, 36°, 144° and 150°. The duration of growth of crystals and the same for the subsequent falling down of crystals can be estimated from the time variation of scattering intensity. It is observed that ice crystals due to the solution take maximum time to grow and minimum time to fall down.
Keywords: Heterogeneous nucleation; Eutectic point; Scattering co-efficient; Extinction co-efficient; Optical depth
A critical assessment of shrinkage-based regression approaches for estimating the adverse health effects of multiple air pollutants by Steven Roberts; Michael Martin (pp. 6223-6230).
Most investigations of the adverse health effects of multiple air pollutants analyse the time series involved by simultaneously entering the multiple pollutants into a Poisson log-linear model. Concerns have been raised about this type of analysis, and it has been stated that new methodology or models should be developed for investigating the adverse health effects of multiple air pollutants. In this paper, we introduce the use of the lasso for this purpose and compare its statistical properties to those of ridge regression and the Poisson log-linear model. Ridge regression has been used in time series analyses on the adverse health effects of multiple air pollutants but its properties for this purpose have not been investigated. A series of simulation studies was used to compare the performance of the lasso, ridge regression, and the Poisson log-linear model. In these simulations, realistic mortality time series were generated with known air pollution mortality effects permitting the performance of the three models to be compared. Both the lasso and ridge regression produced more accurate estimates of the adverse health effects of the multiple air pollutants than those produced using the Poisson log-linear model. This increase in accuracy came at the expense of increased bias. Ridge regression produced more accurate estimates than the lasso, but the lasso produced more interpretable models. The lasso and ridge regression offer a flexible way of obtaining more accurate estimation of pollutant effects than that provided by the standard Poisson log-linear model.
Keywords: Time series; Air pollution; Mortality; Lasso; Ridge regression
The air quality impact of cordon and distance based road user charging: An empirical study of Leeds, UK by Gordon Mitchell; Anil Namdeo; David Milne (pp. 6231-6242).
Traffic assignment, pollutant emission and dispersion models were applied to a major UK city so as to assess the air quality impacts of five road pricing schemes. Schemes were evaluated with reference to: exceedence of air quality standards for six pollutants; greenhouse gas emission; redistribution of pollution, an environmental justice concern; and road network performance as traffic speed and trip distance. Results were compared to alternatives of do nothing, network development and clean fuel promotion. The air quality benefits of a modest distance-based charge are highlighted. However, whilst road pricing shows potential as an air quality management tool, its value and suitability are strongly sensitive to prior air quality and emission source apportionment in the application city.
Keywords: Air quality management; Urban; Road pricing; Traffic emission; Dispersion modelling
Modeling wind-blown desert dust in the southwestern United States for public health warning: A case study by Dazhong Yin; Slobodan Nickovic; Brian Barbaris; Beena Chandy; William A. Sprigg (pp. 6243-6254).
A model for simulating desert dust cycle was adapted and applied for a dust storm case in the southwest United States (US). This is an initial test of the model's capability as part of a future public health early warning system. The modeled meteorological fields, which drive a dust storm, were evaluated against surface and upper-air measurement data. The modeled dust fields were compared with satellite images, in situ surface PM2.5 and PM10 data, and visibility data in the areas affected by the dust event. The model predicted meteorological fields reasonably well. The modeled surface and upper-air field patterns were in agreement with the measured ones. The vertical profiles of wind, temperature, and humidity followed closely with the observed profiles. Statistical analyses of modeled and observed meteorological variables at surface sites showed fairly good model performance. The modeled dust spatial distributions were comparable with the satellite-observed dust clouds and the reduced visibility patterns. Most encouragingly, the model-predicted and observed PM2.5 peak hours matched reasonably well. The model produced better PM2.5 peak hours than PM10 peak hours. The temporal varying trends of daily and hourly PM2.5 and PM10 concentrations at most of the measurement sites were similar to those observed. Discrepancies between the values of the modeled and the measured surface PM2.5 and PM10 concentrations differed with time and location. Sometimes the modeled and measured concentrations can have one order of magnitude differences. These revealed there were possible deficiencies in the simulation of the dust production strength and location, and the representation of dust particle size in the modeling. Better land surface data and size representation of the dust production are expected to further improve model performance.
Keywords: Public health warning system; Dust particulate matter pollution; Desert dust cycle modeling; PM2.5 and PM10 concentrations; Model evaluation
An approach to monitor the fraction of elemental carbon in the ultrafine aerosol by Harry ten Brink; Gerard Hoek; Andrey Khlystov (pp. 6255-6259).
Attempts were made to measure the fraction of elemental carbon (EC) in ultrafine aerosol by modifying an Ambient Carbonaceous Particulate Monitor (ACPM, R&P 5400). The main modification consisted in placing a quartz filter in one of the sampling lines of this dual-channel instrument. With the filter all aerosol and EC contained in it is collected, while in the other line of the instrument the standard impactor samples only particles larger than 0.14μm. The fraction of EC in particles smaller than 0.14μm is derived from the difference in concentration as measured via the two sampling lines.Measurements with the modified instrument were made at a suburban site in Amsterdam, The Netherlands. An apparent adsorption artefact, which could not be eliminated by the use of denuders, precluded meaningful evaluation of the data for total carbon. Blanks in the measurements of EC were negligible and the EC data were hence further evaluated. We found that the concentration of EC obtained via the channel with the impactor was systematically lower than that in the filter-line. The average ratio of the concentrations was close to 0.6, which indicates that approximately 40% of the EC was in particles smaller than 0.14μm. Alternative explanations for the difference in the concentration in the two sampling lines could be excluded, such as a difference in the extent of oxidation. This should be a function of loading, which is not the case. Another reason for the difference could be that less material is collected by the impactor due to rebound, but such bounce of aerosol is very unlikely in The Netherlands due to co-deposition of abundant deliquesced and thus viscous ammonium compounds. The conclusion is that a further modification to assess the true fraction of ultrafine EC, by installing an impactor with cut-off diameter at 0.1μm, would be worth pursuing.
Keywords: Soot; Elemental carbon; Ultrafines; Organic carbon