Atmospheric Environment (v.36, #19)

Modeling the impacts of the Finnish Climate Strategy on air pollution by S Syri; N Karvosenoja; A Lehtilä; T Laurila; V Lindfors; J.-P Tuovinen (3059-3069).
This paper presents an example of how air pollution models can be used together with energy system models to study the impacts of climate change mitigation strategies on air pollution. As many mitigation measures of greenhouse gases (GHGs) affect the use of fossil fuels in energy production, they can have important side-effects on other air pollution problems. This paper studies on a national scale the impacts of the planned GHG reduction measures on multiple air pollution problems in Finland, concentrating on acidification of forest soils and lakes, tropospheric ozone levels harmful to humans and vegetation and on emissions of fine particles. The air pollutant emission scenarios with the alternative energy choices are calculated for about 200 large point sources, assuming the present emission limit legislation. Disperse emissions are treated at municipality level. The analysis extends to the year 2020. The implementation of the Kyoto protocol in Finland would induce notable reductions of multiple air pollutant emissions and related environmental impacts. A 6–11% reduction in ecosystems threatened by acidification in Southern and Central Finland would be achieved with the Finnish Climate Strategy alone. Substantial improvement in ozone levels would be reached in all scenarios compared to the current situation. The measures of the Climate Strategy could reduce the harmful ozone levels by a further 3%. The measures of the Climate Strategy would not significantly affect the primary particulate emissions in the future because the emissions from large power plants are already effectively controlled. Contrary to the fuel choices of the large units, expanded use of small-scale wood combustion can result in considerable increases of both fine particulate and VOC emissions.
Keywords: Carbon dioxide; Energy strategy; Sulfur; Nitrogen oxides; Fine particles;

Source origin and parameters influencing levels of heavy metals in TSP, in an industrial background area of Southern Italy by Maria Ragosta; Rosa Caggiano; Mariagrazia D’Emilio; Maria Macchiato (3071-3087).
In this paper, we investigate the relationships among atmospheric concentration of trace elements and some meteorological parameters. In particular, the effects of different meteorological conditions on heavy metal levels are interpreted by means of a multivariate statistical approach. The analysed variables were measured during a monitoring survey that started in 1997, and this survey was carried out in order to evaluate the atmospheric concentrations of heavy metals in the industrial area of Tito Scalo (Basilicata Region, Southern Italy). Here we present and analyse the data set collected from 1997 to 1999. The data set includes daily concentrations of total suspended particulates (TSP), daily concentrations of eight metals (Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn) in TSP and daily meteoclimatic data (temperature, rainfall, speed and wind directions). Both the concentration level and the occurrence of peak concentration events are consistent with the characteristics of the study area: abundant small and medium industrial plants in a mountainous and unpolluted zone. Regarding the origin of sources of heavy metals in TSP, the statistical procedure allows us to identify three profiles: SP1 and SP2 related to industrial sources and SP3 related to other sources (natural and/or anthropogenic). In particular, taking into account the effect of different meteorological conditions, we are able to distinguish the contribution of different fractions of the same metal in the detected source profiles.
Keywords: TSP; Heavy metals; Rainfall; Wind; Multivariate tools;

Major anions and cations were analyzed in a wet-only precipitation study for 16 months. The pH exhibited large variation, from 4.07 to 8.51 pH units. Twenty-eight percent of the observed rain volume had pH <5, whereas 42% of the rains had pH >6, as is usually observed in the Mediterranean. Comparison with our work of 15 years ago indicates a free acidity reduction by ∼18%, non-sea-salt sulfate ions reduction of ∼40% and nitrate ions reduction of 66%. Chloride and all cation concentrations were similar in the present work and that carried out in 1985–86 indicating similar sources, namely aerosol and crustal material as in MS. Calcium ions were the dominating neutralization ions. The annual wet-only deposition rates were calculated for the major species and were found to be comparable to those reported in past studies. Deposition of calcium ions dominates all deposited species, except sea salt, and indicates its significance in the neutralizing mechanisms of soils of the region, if neutralization is needed. Air mass back trajectories calculated for all analyzed samples, revealed four sectors of origin of air masses: NW to NE Europe, northern Africa, local and western Mediterranean, each with a specific chemistry. Cluster analysis and factor analysis also discriminated the samples by their sources. The main sources derived from the statistical analysis were: marine aerosols, alkalinity–acidity as inferred by the calcium ion concentrations from crustal sources and hydronium ions mainly from anthropogenic activities and ammonium salts of sulfate and nitrate also mainly from anthropogenic activities. These sources were closely correlated with the geographic sectors obtained from the air mass back trajectories.
Keywords: Saharan dust; Major anions; Major cations; pH variation; Air mass back trajectories; Cluster and factor analysis; Wet-only annual deposition rates;

Origin of high summer PM10 and TSP concentrations at rural sites in Eastern Spain by Sergio Rodrı́guez; Xavier Querol; Andrés Alastuey; Enrique Mantilla (3101-3112).
Concentrations of airborne particulates undergo a seasonal evolution characterised by a summer maximum in rural areas in Eastern Spain. In the summer months the daily mean concentrations of PM10 and TSP (PM) experience wide variations. In 3-day periods, increases in the PM concentrations from 15 to 30–40 μg/m3 are frequently reported, and increases from 15 to 40–60 μg/m3 occur several times throughout the summer. These variations are simultaneously reported at rural stations throughout the flat Ebro basin (600 m a.s.l.) and at mountain sites located at high altitude (>1000 m a.s.l.). The origin of high and low PM episodes was investigated by correlating PM levels with the concentrations of gaseous pollutants, and making use of meteorological analysis and satellite observations. The highest PM events (daily concentrations in the range 40–60 μg/m3) were documented during outbreaks of African dust. The second highest PM events (daily concentrations in the range 20–45 μg/m3) were recorded during regional episodes associated with ozone events. These summer regional PM episodes were induced by the abrupt orography surrounding the Western Mediterranean and by the regional meteorology, which favour the ageing of polluted air masses into the basin. These regional events occur in a synoptic meteorological context characterised by a weak pressure horizontal gradient over the Western Mediterranean often associated with the development of the Iberian thermal low, when advection of air masses is not significant. In this meteorological context, the transport of particulate pollutants from urban/industrial to rural sites is brought about by the breeze circulation at the coastal (sea breeze) and mountain (mountain breeze) sites. The persistence of this breeze circulation for several days (periods of up to 2 weeks were reported) results in a low renovation of air masses leading to an accumulation of airborne particulates in the regional atmosphere. The lowest PM events (daily concentrations <20 μg/m3) were reported during abrupt entries of Atlantic air into the Mediterranean.
Keywords: Aerosols; PM10; Saharan dust; Ozone; Regional pollution; Mediterranean; Spain;

Source apportionment analysis of atmospheric particulates in an industrialised urban site in southwestern Spain by Xavier Querol; Andrés Alastuey; Jesús de la Rosa; Ana Sánchez-de-la-Campa; Felicià Plana; Carmen R Ruiz (3113-3125).
A detailed physical and chemical characterisation of total suspended particles (TSP) in the highly industrialised city of Huelva (southwestern Spain) was carried out. The results evidenced a coarse grain-size prevalence (PM10 accounting for only 40% of TSP mass, 37 and 91 μg/m3, respectively). PM10 levels are in the usual range for urban background sites in Spain. The crustal, anthropogenic and marine components accounted for a mean of a 40%, 24% and 5% of bulk TSP, respectively. As expected from the industrial activities, relatively high PO4 3− and As levels for an urban site were detected. In addition to the crustal and marine components, source apportionment analysis revealed three additional emission sources influencing the levels and composition of TSP: (a) a petrochemical source, (b) a mixed metallurgical-phosphate source, (c) and an unknown source (Sb and NO3 ).Due to the high local emissions, the mean TSP anthropogenic contribution (mostly PM10) obtained for all possible air mass transport scenarios reached 18–29 μg/m3. The 2010 annual EU PM10 limit value (20 μg/m3) would be exceeded by the anthropogenic load recorded for all the air mass transport scenarios, with the exception of the North Atlantic transport (only 15% of the sampling days). Under African air mass transport scenarios (20% of sampling days), the TSP crustal contribution reached near three times the local crustal contribution. It must be pointed out that this crustal input should diminish when sampling PM10 due to the dominant coarse size distribution of this type of particles.
Keywords: Total suspended particles (TSP); Source apportionment analysis; Natural contributions; Heavy metals;

Factors controlling the diurnal variation of CO above a forested area in southeast Europe by Valérie Gros; Kostas Tsigaridis; Bernard Bonsang; Maria Kanakidou; Casimiro Pio (3127-3135).
Carbon monoxide (CO) measurements have been performed in a forested site in central Greece in the framework of the AEROBIC (AEROsol formation from Biogenic Carbon) campaign in summer 1997. The mean CO observed during the whole campaign ranged between 114 and 250 ppbv (mean of 170±27 ppbv), reflecting continental influence. The observed mean diurnal cycle of CO presented a minimum in the early morning due to the efficient deposition of CO in a shallow nocturnal layer sealed from the free tropospheric air during the night (loss rates of about 2 ppbv h−1). In the early morning and in the late afternoon, a sharp and fluctuating increase of CO was observed as the consequence of CO primary sources, likely by local traffic as suggested by the concomitant enhancements of black carbon (BC) and other combustion tracers. The morning pollution peak (6:30–8:30 local time) preceded slightly the opening of the nocturnal layer to the free troposphere, which resulted in CO reduction down to background levels at about 10:00. During the day (10:00–17:00), a slight but regular increase was observed on CO levels. For lack of simultaneous increase of other anthropogenic tracers, this CO enhancement has been attributed to its photochemical formation initiated by the oxidation of reactive biogenic hydrocarbons. This observed net production of CO averaging 1.2 ppbv h−1 is quite well reproduced by a box model containing an explicit chemical scheme of isoprene and α- and β-pinene and taking into account the measured mixing ratios and the reactivity of all biogenic organic reactive compounds when uncertainties in measurements and modelling are considered.
Keywords: Carbon monoxide; Photochemical source; Biogenic hydrocarbons; AEROBIC; Forest site;

The impact of biogenic volatile organic compound (BVOC) on the chemical composition of the boundary layer in a valley-forested site of central Greece is investigated by using a chemical box model able to simulate α - and β -pinene and isoprene photochemistry in the troposphere. The model assimilates the meteorological conditions and mixing ratios of long-lived species observed during the AEROBIC field campaign in July–August 1997. Only 23–61% of the observed ozone (O3) mixing ratios can be attributed to the local photochemistry during the first part of the experiment, whereas this contribution increases to 80–96% during the second part of the campaign. The remaining part of O3 is reaching the boundary layer mainly from the free troposphere during the morning opening of the valley. The local net photochemical production of O3 is calculated to be up to 10 ppbv h−1, up to 60% of which is attributed to BVOC chemistry. BVOC oxidation is also shown to be an important source of carbon monoxide (CO) producing 1.5–2.5 ppbv CO h−1, carbonyl compounds and organic acids in particular contributing by about 1.5–4.3, 0.2–1.1 and 0.1–1 ppbv to the daytime ambient levels of formaldehyde, acetone and formic acid, respectively. BVOC oxidation is also able to produce about 1.3 μg m−3 (0.3–2.5 μg m−3) of secondary organic aerosol (SOA) that is 9–38% of the observed total organic aerosol levels.
Keywords: Forest; AEROBIC; Ozone; Carboxylic acids; Aerosols;

Light dependency of VOC emissions from selected Mediterranean plant species by S.M Owen; P Harley; A Guenther; C.N Hewitt (3147-3159).
The light, temperature and stomatal conductance dependencies of volatile organic compound (VOC) emissions from ten plant species commonly found in the Mediterranean region were studied using a fully controlled leaf cuvette in the laboratory. At standard conditions of temperature and light (30°C and 1000 μmol m−2  s−1 PAR), low emitting species (Arbutus unedo, Pinus halepensis, Cistus incanus, Cistus salvifolius, Rosmarinus officinalis and Thymus vulgaris) emitted between 0.1 and 5.0 μg (C) (total VOCs) g−1 dw h−1, a medium emitter (Pinus pinea) emitted between 5 and 10 μg (C) g−1 dw h−1 and high emitters (Cistus monspeliensis, Lavendula stoechas and Quercus sp.) emitted more than 10 μg (C) g−1 dw h−1. VOC emissions from all of the plant species investigated showed some degree of light dependency, which was distinguishable from temperature dependency. Emissions of all compounds from Quercus sp. were light dependent. Ocimene was one of several monoterpene compounds emitted by P. pinea and was strongly correlated to light. Only a fraction of monoterpene emissions from C. incanus exhibited apparent weak light dependency but emissions from this plant species were strongly correlated to temperature. Data presented here are consistent with past studies, which show that emissions are independent of stomatal conductance. These results may allow more accurate predictions of monoterpene emission fluxes from the Mediterranean region to be made.
Keywords: Biogenic VOC emissions; Mediterranean vegetation; Leaf cuvette; Environmental control of emissions;

Visibility trends in the UK 1950–1997 by Martin Doyle; Stephen Dorling (3161-3172).
Visibility data have been examined for eight UK Meteorological Office surface network sites. Trends from 1950 to 1997 have been constructed using four different statistical methods; ridit analysis, cumulative percentiles, frequency of “very good” visibility and annual and seasonal means. Improvements in visibility have been experienced at the majority of the sites studied. Major improvements can be observed at many of the sites after 1973 and this is attributed to changes in personal behaviour, fuel use and vehicle fleet efficiency during the 1970s and especially after the 1973 oil crisis. Improvements in visibility at the Scottish sites studied are much less than at the other sites due to their locations in less populated and less polluted areas. Aldergrove, near Belfast in Northern Ireland, has also experienced less improvement in the visibility distance than the other sites.
Keywords: Visibility; Aerosols; Air pollution; Trend analysis; Visual air quality;

Interrelations of UV-global/global/diffuse solar irradiance components and UV-global attenuation on air pollution episode days in Athens, Greece by P.S. Koronakis; G.K. Sfantos; A.G. Paliatsos; J.K. Kaldellis; J.E. Garofalakis; I.P. Koronaki (3173-3181).
An investigation of global ultraviolet (G UV), global (G) and diffuse (G d) solar intensities, continuously recorded over a period of five years at a station in Athens, Greece, and stored on the basis of hourly time intervals since 1996, has revealed the following: (a) UV-global irradiation, associated with the 290–395 nm wavelength region, constitutes 4.1% of global solar. (b) UV-global irradiance ranges from an average minimum of 2.4 W m−2 and 3.1% of global solar in January to an average maximum of 45 W m−2 and 7.8%, respectively, in June, both considered at 13:00, solar time. (c) There exists a good correlation among the two dimensionless irradiance ratios G UV/G d and G d/G in the form of an exponential relationship. (d) UV-global monthly irradiation data show evidence of temporal variability in Athens, from 1996 to 2000. (e) Anthropogenic and photochemical atmospheric pollutant agents (O3, CO, SO2, NO x , smoke) causing air pollution episodes seem to affect differently solar irradiance components. The main results of analysis (measurements within ±2 h from solar noon) indicate that a buildup of O3 and NO x inside the urban Athens plume during cloudless and windless warm days could cause: (i) UV-global irradiance depletion between 5.4% and 14.4%. (ii) Diffuse solar irradiance enhancement up to 38.1%. (iii) Global solar irradiance attenuation ranging up to 6.3%.
Keywords: UV-global irradiance; Depletion; Global and diffuse solar irradiance; Air pollution; Correlation;

Organic and black carbon in PM2.5 and PM10: 1 year of data from an urban site in Helsinki, Finland by Jyrki Viidanoja; Markus Sillanpää; Jaakko Laakia; Veli-Matti Kerminen; Risto Hillamo; Päivi Aarnio; Tarja Koskentalo (3183-3193).
The results from a 1-year measurement period concerning the diurnal PM2.5 and PM10 organic carbon (OC) and black carbon (BC) concentrations are presented for a traffic-influenced site in the Helsinki metropolitan area. The measurements were based on aerosol sampling using a virtual impactor and the subsequent thermal–optical analysis to distinguish between OC and BC. Backup filters were used to estimate and correct for the positive sampling artefact. Daily-average concentrations in PM2.5 varied between 1.0 and 8.5 μg C m−3 for OC, and between 0.3 and 5.7 μg C m−3 for BC. Annual-average concentrations of OC and BC were 3.0 and 1.2 μg C m−3, respectively, in PM2.5, and 4.2 and 1.3 μg C m−3 in PM10. On an annual level, particulate organic matter (POM=1.6×OC) accounted for 50±14% and 36±8% (average±1σ) of the total PM2.5 and PM10, respectively, whereas BC stayed lower at 14±8% and 7±4%. Typically more than 90% of BC resided in the PM2.5 size fraction. The contribution of coarse particles (>2.5 μm) to the overall OC varied between the 0% and 67% (median 27%). The effect of meteorological conditions on the variability of OC and BC concentrations was examined, and the contribution of secondary organic aerosol to the total fine organic aerosol was estimated.
Keywords: Particulate matter; Organic carbon; Black carbon; Secondary organic aerosol; Urban atmosphere;

Sources and photodecomposition of formaldehyde and acetaldehyde in Rome ambient air by Massimiliano Possanzini; Vincenzo Di Palo; Angelo Cecinato (3195-3201).
Atmospheric levels of formaldehyde and acetaldehyde as well as their diurnal and seasonal variations were investigated from 1994 to 1997 in downtown Rome during sunny and wind calm days. Hourly concentrations of formaldehyde ranged from 8 to 28 ppbV in summer and 7 to 17 ppbv in winter; acetaldehyde concentrations varied correspondingly within the 3–18 and 2–7 ppbv intervals. Percentages of both aldehydes photochemically produced were estimated through a simple relationship based upon the comparison of individual ratios of formaldehyde and acetaldehyde to toluene in ambient air and automobile emission. Photochemical production was found to weigh upon atmospheric levels for 80–90% in summer days. It dropped below 35% in the winter period, when direct emission from traffic largely predominated. Photochemical summer source was more efficient for acetaldehyde than for formaldehyde, especially in the early morning. The importance of formaldehyde as the major source of hydroxyl radicals in Rome was also assessed.
Keywords: Formaldehyde; Acetaldehyde; Urban concentrations; Photochemical production; Vehicle emission; Photochemical reactivity;

The Met Office's long-range dispersion model, the Nuclear Accident Model (NAME), has been used to assess the impact of routine atmospheric radioactive discharges from the Sellafield nuclear installation on the Cumbrian coast of England (54° 25.0′ 3° 30.2′ W). The model has produced values of scaling factors for concentrations and depositions over northwest Europe. Whilst the dispersion model was designed and has been used extensively in the past for examining specific incidents of a nuclear nature, this is the first time the NAME model has been used to provide a detailed climatological impact assessment for a nuclear installation.
Keywords: Dispersion model; Radioactive discharges; Deposition; Emissions; Boundary layer depth; Stability;