Atmospheric Environment (v.34, #19)

This paper describes the experimental potential of a classic ground-based passive remote sensing technique, the dispersive correlation spectroscopy (DCS), for the study of non-industrial urban plumes. The text presents this technique as an alternative tool to study some aspects of air pollution in cities, in contrast to the information supplied by air pollution monitoring networks. The results obtained with DCS in the study of Madrid plume in winter, one of the most important cases of urban pollution taking place in southern Europe, are presented here as an example of the DCS application. This highly inhabited zone, where pollutant emissions have essentially an urban origin, stays frequently under the influence of high-pressure systems, which strongly condition the efficient ventilation of the area and produce air pollution episodes of certain importance. The study presented here has been based on the previous technical improvement of the commercial COSPEC V instrument and on its use as a passive remote sensor from a mobile laboratory measuring NO2 total column. The formation process of the Madrid plume, its horizontal limits and the dynamics of transport are some of the aspects documented with this technique.
Keywords: Dispersive correlation spectroscopy; COSPEC remote sensor; Nitrogen dioxide; Urban air pollution; Transport of air pollutants;

Determination of the terpene flux from orange species and Norway spruce by relaxed eddy accumulation by C.S Christensen; P Hummelshøj; N.O Jensen; B Larsen; C Lohse; K Pilegaard; H Skov (3057-3067).
Terpene fluxes from a Norway spruce (Picea abies) forest and an orange orchard (Citrus clementii and Citrus sinensis) were measured by relaxed eddy accumulation (REA) during summer 1997. α-pinene and β-pinene were the most abundant terpenes emitted from Norway spruce and constituted approximately 70% of the flux. A much lower flux was observed for myrcene, limonene and γ-terpinene and both α-terpinene and camphor were only occasionally detected. The average terpene flux was 107.6 ng m−2  s−1 which corresponds to 0.73 μg g(dw)−1  h−1 (30°C) when calculated relatively the weight of the dry biomass. The five terpenes which were detected in all samples at the orange orchard were limonene, sabinene, α-pinene, trans-ocimene and β-pinene with an average flux of 126.3 ng m−2  s−1. Cis-ocimene, linalool and myrcene were occasionally detected but no systematic upward or downward flux was observed. The results from a laboratory intercomparison made in Spain deviated by maximum 7%. The flux measured at the two sites exhibited a strong diurnal variation with maximum in the afternoon and minimum in the morning hours and evenings. The applied REA system is new in its design and the major advantage is that the air is sampled at a constant flow rate on the adsorbent tubes. This is realised by having two primary Teflon lines with a relatively large flow rate (6 l min−1). The air is then sampled from these two Teflon lines on two identical adsorbent tubes at a constant and much lower rate by using two precision pumps operated at approximately 60 ml min−1. The terpenes collected on the adsorbent tubes were significantly decomposed by ozone during sampling unless ozone scrubbers were applied.
Keywords: Biogenic hydrocarbons; Emissions; Terpenes; Norway spruce; Orange trees; Relaxed eddy accumulation;

The city of Barcelona and its surrounding area, located in the western Mediterranean basin, can reach high levels of O3 in spring and summertime. To study the origin of this photochemical pollution, a numerical modeling approach was adopted and the episode that took place between 3 and 5 August 1990 was chosen. The main meteorological mesoscale flows were reproduced with the meteorological non-hydrostatic mesoscale model MEMO for 5 August 1990, when weak pressure synoptic conditions took place. The emissions inventory was calculated with the EIM-LEM model, giving highly disaggregated anthropogenic and biogenic emissions in the zone studied, an 80×80 km2 area around the city of Barcelona. Major sources of VOC were road traffic (51%) and vegetation (34%), while NO x were mostly emitted by road traffic (88%). However, emissions from some industrial stacks can be locally important and higher than those from road traffic. Photochemical simulation with the MARS model revealed that the combination of mesoscale wind flows and the above-mentioned local emissions is crucial in the production and transport of O3 in the area. On the other hand, the geostrophic wind also played an important role in advecting the air masses away from the places O3 had been generated. The model simulations were also evaluated by comparing meteorological measurements from nine surface stations and concentration measurements from five surface stations, and the results proved to be fairly satisfactory.
Keywords: Photochemical modeling; Tropospheric ozone; Barcelona area; Complex topography; Emissions;

Occurrence of C10–C13 polychlorinated n-alkanes in the atmosphere of the United Kingdom by Andrew J. Peters; Gregg T. Tomy; Kevin C Jones; Peter Coleman; Gary A Stern (3085-3090).
Short-chain (C10–C13) polychlorinated n-alkanes (PCAs) have been measured in the air in the United Kingdom at 2 week intervals over a period of 12 months. The mean concentration of PCAs over the sampling period was 320±320 pg m−3 (arithmetic mean±1 S.D.) with a geometric mean of 160 pg m−3. Hexa- and hepta-chlorinated dodecane congeners are the predominant PCA components in the UK atmosphere. Analyses of gas phase and particulate phase PCAs indicate that 95% of the PCA content of the atmosphere is in the gas phase. No seasonal trend or dependence on temperature was observed. The data can be divided into 2 significantly different (P<0.01) populations: one group of incidences of lower concentrations of 150±110 pg m−3 and one of higher concentrations of 800±170 pg m−3. The incidences of elevated concentrations could not be related to increased air temperature or other meteorological factors on the time-scale employed and suggest that atmospheric PCA concentrations in the UK may be dominated by episodic incidences of advective transport of contaminated air masses and/or releases to the environment from regional primary point sources rather than by temperature-dependent transport processes. Levels of PCAs in the UK atmosphere are similar to values obtained at a semi-rural location in Canada and at least an order of magnitude higher than in the Canadian Arctic atmosphere. These data represent the first detailed study on the occurrence of PCAs in the atmosphere and show that PCAs can be a major component of the persistent organic pollutant burden of the atmosphere which has the potential of undergoing long-range atmospheric transport processes.
Keywords: Polychlorinated alkanes; Chlorinated paraffins; Atmosphere; Air; Monitoring;

PM10 levels in communities close to and away from opencast coal mining sites in Northeast England by Tanja Pless-Mulloli; Andrew King; Denise Howel; Ian Stone; John Merefield (3091-3101).
Concerns about levels of particulate matter of less than 10 μm (PM10) and their potential health effects have been raised by residents living near opencast coal mining sites in the UK. PM10 levels were measured by TEOM in 5 matched pairs of communities in northeast England, 5 near active opencast sites and 5 further away, to characterise the PM10 exposure of residents. 14 609 paired 30-min TEOM readings, and weather data were collected during 1996–97, over 6 weeks each in four pairs and for 24 weeks in one pair. Co-located samplers collected PM10 on an approximately weekly basis and samples were analysed using scanning electron microscopy with energy dispersive analysis (SEM-EDS). The patterns of PM10 levels over time were similar in Opencast and Control Communities and were mostly similar to readings from nearby automated urban network stations. This suggested regional influences on PM10 levels. The geometric mean PM10 was 17.0 μg m−3 in Opencast and 14.9 μg m−3 in Control Communities (arithmetic mean 22.1 μg m−3 in Opencast 18.2 μg m−3 in Control Communities): Opencast Communities thus had 14% higher PM10 levels than Control Communities on average. While the size distribution and proportion of shale particles indicated the opencast site as contributor to the PM10 load in adjacent communities, elevated PM10 levels in Opencast Communities were not positively linked with permitted working hours or wind direction being from the site to the community. No consistent relationship was found between PM10 levels and wind speed or day of the week.
Keywords: Particulate matter; Non-urban; Exposure; TEOM; Shale;

Time-resolved chemical ionization mass spectrometry (CIMS) has been used to investigate the variations of the mixing ratios of benzene, toluene and the C2-benzenes (xylenes and ethyl benzene) in automotive exhaust during transient engine operation. A significant increase of the benzene/toluene ratios from 0.35 to 1.31 (median) was found upon introduction of a catalytic converter system. A preliminary emission model was developed from these test stand measurements to simulate benzene/toluene ratios of passenger car fleets with variable proportions of three-way catalyst vehicles. Although only the emissions of gasoline-driven passenger cars have been considered so far, the predicted increase of the benzene/toluene ratios during the introduction period of the three-way catalyst from 1980 to 2000 is in good agreement with the observed increase of the atmospheric benzene/toluene ratio measured at a suburban monitoring site (Dübendorf, Switzerland) which is strongly influenced by road traffic emissions. At this site, the atmospheric concentrations of benzene and alkyl benzenes have been detected at hourly intervals since 1993. A steady decrease of the yearly mean from 3.54 to 2.00 ppb for toluene and from 2.87 to 1.33 ppb for the sum of C2-benzenes was found from 1994 to 1998, respectively, when the proportion of three-way catalyst passenger cars increased from 60 to 82%. Nevertheless, the mean benzene concentration was only affected to a small degree (from 1.10 to 0.97 ppb) within the same period of time. Thus, the observed increase of the atmospheric benzene/toluene-mixing ratios from 0.32 to 0.58 (mean) is in good agreement with the predicted values from the presented emission model. Reduced catalyst conversion efficiency for benzene with respect to alkylated benzenes can explain most of the observed increase of the benzene/toluene and benzene/C2-benzenes mixing rations. In addition, benzene emissions e.g. from the class of light duty vehicles, which are operated more frequently at sub-optimal combustion conditions, may also contribute to the unexpectedly stable atmospheric benzene concentration at the investigated suburban monitoring site.
Keywords: Urban atmosphere; Vehicle emissions; Aromatic hydrocarbons; On-line CI-MS; Time-resolved exhaust gas analysis; Benzene toluene mixing ratio;

Changes in the occurrence of silver, gold, platinum, palladium and rhodium in Mont Blanc ice and snow since the 18th century by Katja Van de Velde; Carlo Barbante; Giulio Cozzi; Ivo Moret; Tania Bellomi; Christophe Ferrari; Claude Boutron (3117-3127).
Ag, Au, Pt, Pd and Rh have been measured at various depth intervals of a 140 m snow/ice core electromechanically drilled at an altitude of 4250 m in the French–Italian Alps. The measurements were made by double focusing ICP-MS with micro concentric nebulisation. It provides the first time series for these metals for the last two centuries. Observed concentrations range from 0.2 to 12 pg g−1 for Ag, 0.07–0.35 pg g−1 for Au, 0.08–0.62 pg g−1 for Pt, 0.5–10 pg g−1 for Pd and 0.01–0.39 pg g−1 for Rh. Since the 18th century, no clear increase is observed for Au and Pt. For Pd, Rh and especially Ag, however, concentrations are higher in the last decades than in ancient ice. From a qualitative review of the different possible natural and anthropogenic sources, it appears that volcanoes, mining and smelting activities, industry and waste incinerators could be significant sources of these metals in high-altitude Mont Blanc snow and ice. Pronounced seasonal variations in the concentrations of Pd, Rh and especially Ag are observed in ice dating from the 1960s. They are largely due to changes in the vertical structure of the regional troposphere during the year. For Au and Pt, on the other hand, there are no clear seasonal variations, which suggests that these two metals originate from distant sources.
Keywords: Heavy metals; Alps; Mont Blanc; Pollution history; Regional pollution;

Major component contributions to PM10 composition in the UK atmosphere by Alan B. Turnbull; Roy M. Harrison (3129-3137).
Physical and chemical characteristics of PM10, including chloride, nitrate, sulphate, and black smoke, have been measured on a seasonal basis at four coastal, rural, and urban sites across the UK. Weekly campaigns with 6 h sample resolution were conducted, and the results related to meteorological conditions and air mass back trajectories. Seasonal and location- specific mean values are reported, along with an indication of diurnal characteristics. Although the urban site reflected generally higher values for the anthropogenic pollutants, long-range transport of primary and secondary particles was significant. The data have been analysed using a four-component multi-linear regression model including black smoke as a surrogate for primary combustion particles, secondary particles (sulphate and nitrate), chloride, and a constant which describes “other”, mainly coarse mode particles. Regression coefficients have been calculated on a site and seasonal basis. “Other” particles were higher during the summer and in the urban environment with an overall mean value of 5 μg m−3. Secondary nitrate and sulphate were strongly related to meteorological conditions and less to location. Overall, the four-component model accounts quite well (r2=0.76 for all data) for PM10 mass and for some sites and seasons gives an excellent fit to the data. Addition of dummy variables representing season, urban/rural location and time of sampling gives an improvement in fit, with r2=0.84. Application of the coefficients derived from the “all data” model shows secondary particles contributing 28–35% of site-mean PM10, primary combustion particles from 20 to 57%, sodium chloride, 11–34% and “other”, mainly crustal particles, 3–21%. It is felt that this probably underestimates the crustal contribution, but the reasons are unclear.

Analysis of the fine urban aerosol (<1 μm) was made using direct sampling of urban aerosol on to porous carbon films (PCF). The efficiency of collection was low but the samples were representative and enabled transmission electron microscopy (TEM) for sub-micron particle analysis. Measurement was made of the fractal dimensions and diameter of particles. PCF were used in the simultaneous collection of urban roadside and background aerosol, on four dates between March and August 1997 in Plymouth, UK. The aerosol was classified in to agglomerate and non-agglomerate groups. At the roadside agglomerate particles accounted for 94% of the particles analysed, this fell to 89% of the particles in the background samples. The analysis of agglomerate particles by energy dispersive X-ray spectroscopy confirmed their carbonaceous nature. A variety of agglomerate particles were found having coatings and mixed morphologies. The morphology of particles was analysed using two fractal analysis techniques to derive a density fractal dimension and a perimeter fractal dimension. These measures quantitatively describe the space filling quality and the roughness of the boundary of the two dimensional projection of the particle. The average perimeter fractal dimension (PFD) of aerosol was consistently significantly greater at the roadside than the background (+0.02), in analysis both including and excluding the non-fractal particles. There is evidence of a change in the average morphology of aerosol between roadside and background aerosol which is still the case when non-fractal particles are removed. This morphology change may be due to the inclusion of particles from other non-agglomerate sources, which have a low fractal dimension or it may be indicative of a smoother, aged roadside aerosol at the background site. The consistency of the difference between the roadside and the background aerosol morphology suggests that there is some morphology change that occurs in particles between the roadside and the background site.
Keywords: Individual particle analysis; Carbonaceous particles; Urban aerosol; Particle shape; Transmission electron microscopy (TEM); Fractal dimension;

The particulate emissions near a large steel plant, located inside the town of Genoa (Italy) have been studied from May to December 1997. We have used two-stage continuous streaker samples and subsequent PIXE (particle-induced X-ray emission) analysis with hourly resolution, to follow both seasonal and daily trends. A first streaker sampler remained installed very close to the plant cokery and furnaces, while another sampler was moved to different locations in town. Samples were analysed by PIXE, deducing concentrations for elements from Na to Pb. We have always collected the PM10 fraction of the aerosol: during part of the campaign, the fine (PM2.5) and coarse (PM2.5–10) aerosol fractions have been also resolved. We have measured and analysed about 8500 PIXE spectra. The steel plant emissions have been identified and resolved from other aerosol sources using principal component analysis (PCA) and other statistical techniques. Finally, the impact of the steel smelter on its surrounding has been evaluated.
Keywords: Aerosol analysis; PIXE; Steel; Principal component analysis; Italy; Genoa;

Photochemical ozone creation potentials (POCP) and replacement of solvents in Europe by Yvonne Andersson-Sköld; Lars Holmberg (3159-3169).
Photochemical ozone creation potentials (POCP) have been calculated under 12 different emission conditions and the replacement of current solvents by oxygenates have been investigated under two European emission conditions. As expected the higher the NO x /VOC ratio, the more pronounced the deviation among POCP values for individual VOC, and the more useful the method of ranking VOC according to their ability to contribute to ozone. The replacement of current solvents by oxygenates significantly reduces the ozone levels in polluted air, such as the London plume. The replacement of current solvents in European air, plumes 1 and 2 in and has a limited effect on the ozone levels. The influence on other species such as PAN and aldehydes is, however, also, under these conditions, significant when replacing current solvents by oxygenates.
Keywords: Ozone; VOC; NO x ; Photochemical ozone creation potential; POCP; Replacement of solvents; PAN; Aldehydes; Europe; Different emission conditions;

A project aimed at assessing a variety of particulate indicators was carried out at three locations in the city of Basel within the scope of the Basel Air Quality Risk Assessment Project (BRISKA). Size specific particle number concentrations (0.018–0.421 μm), particle mass distributions (0.04–49 μm), and particle-bound polycyclic aromatic hydrocarbon (pPAH) concentrations were measured. Locations differed in housing and traffic characteristics. For particle number and pPAH concentrations, one separate continuous 27–28-h measurement was performed at each location. Simultaneously, non continuous measurements assessing the particle mass distribution were performed. Distinct day profiles corresponding to the diurnal traffic profile were observed for absolute particle numbers and pPAH concentrations. The number of ultrafine particles as well as pPAH concentrations were more closely correlated to the number of heavy duty vehicles (r=0.67–0.86 and 0.85–0.90), respectively, than to the number of light duty vehicles (r=0.43–0.59 and 0.64), respectively. The highest particle number concentrations were found in the ultrafine particle mode (<0.1 μm) averaging between 82–87% of the total particle numbers <0.421 μm while the accumulation mode (0.1–2.8 μm) made up for most of the particle mass (mean >82%). For size specific absolute mass concentrations, the highest concentrations were generally found in the early morning and evening hours. The mass distribution within the accumulation mode differed from rush hour episodes, in between rush hour episodes and a lawn mowing episode.
Keywords: PAH; Ultrafine particles; Particulate matter; Health; Traffic;

Emission factor estimates of cereal waste burning in Spain by I. Ortiz de Zárate; A. Ezcurra; J.P. Lacaux; Pham Van Dinh (3183-3193).
Every year more than 5 million ha of cereal fields are affected by fires in order to eliminate cereal waste in Spain. The characteristics of this type of fire with intense flames are similar to those of the African dry savanna heading fires. This paper surveys the atmospheric emission caused by this process by combining results of field and combustion chamber experiments. Combustion chamber experiments show that during the flaming phase 88% of the fire exposed carbon is converted into CO2 and during the smoldering phase this percentage changes to 74%. These combustion chamber experiments also show that the soluble part of the aerosols emitted during the course of fires only represent 3% of the total particulate matter (TPM) produced, being the ions K+ and CI the predominant ones. The cereal waste fire process can be represented by an arithmetic combination that takes into account the amounts of mass burned during the two phases of the fire: 0.90 flaming +0.10 smoldering. Emission factor estimates from field burning experiment are 13±7 g TPM kg−1(dm) and 2.8±0.2 g NO x  kg−1 (dm). Finally, we obtain average emissions of 80–130 Gg TPM, 17–28 Gg NO x , 210–350 Gg CO and 8–14 Tg CO2 in Spain. These emissions represent nearly 25% of the total NO x and 50% of the total CO2 emissions by other pollution sources during the burning period in Spain.
Keywords: Biomass burning; Cereal waste in Spain; Gases and particle emissions; Field burning; Combustion chamber experiment;

Polycyclic aromatic hydrocarbon deposition on the ice sheet of Greenland. Part I: superficial snow by P. Masclet; V. Hoyau; J.L. Jaffrezo; H. Cachier (3195-3207).
After a long-range transport in the air, atmospheric chemical substances of anthropic or natural origin are deposited on the Greenland surface mainly during snowfall episodes. The surface snow conserves the geochemical imprint of these compounds, especially when they are unreactive. As part of the TAGGSI program, carried out in Greenland from 1993 to 1996, the deposition and the transfer of polycyclic aromatic hydrocarbons, from atmosphere to ice sheet, was studied by determining the concentrations of these species in a 5 m depth snow pit and in a 75 m depth ice core. This first part concerns the snow samples collected in the snow pit. With a sampling step of 5 cm, the seasonal and interannual variation of the deposits was determined. The snow strata were dated on the basis of the calcium deposits, which are particularly high during Arctic haze. Correlations with carbon, ammonium, and sulphates are performed. The good quality of the correlations shows the coincidence of the deposits of chemical substances presumed to be of the same origin: total PAH and black carbon; (pyrene+fluoranthene) and sulphates; retene and ammonium.
Keywords: Arctic; Aerosols; Snow; Ice sheet; Polycyclic aromatic hydrocarbons; Particulate organic matter; Photochemistry; Wet deposition; Carbon; Ammonium; Sulphate;

New Directions: TEOMs and the volatility of UK non-urban PM10: a regulatory dilemma by Andrew M King; Tanja Pless-Mulloli; John Merefield; Ian Stone (3211-3212).

Aerosol and bulk deposition trends in the 1990's, Eastern Erzgebirge, Central Europe by Jörg Matschullat; Willy Maenhaut; Frank Zimmermann; Juliane Fiebig (3213-3221).
Atmospheric aerosols were collected in the Eastern Erzgebirge, Germany, and a multi-element survey was carried out by PIXE, INAA, and GF-AAS for samples from 1992–1994 and 1996–1997 (Al, As, Ba, Br, Ca, Cl, Cr, Cu, Fe, Ga, Ge, I, In, K, Mg, Mn, Na, Ni, P, Pb, S, Se, Si, Sr, Ti, V, Zn). For comparison, new bulk deposition data for open field and canopy throughfall stations are presented from the same area (Ag, Al, As, Ba, Be, Bi, Ca, Cd, Cl, Co, Cr, Cu, F, Fe, Ga, Ge, I, In, K, Mg, Mn, Mo, NO3 , Na, Ni, Pb, PO4 2−, Rb, SO4 2−, Sb, Se, Sn, Sr, Th, Ti, Tl, U, V, Y, Zn, Zr). The most prominent result is that emission control in Central Europe is taking effect. The concentrations of many anthropogenic constituents in both bulk deposition and in aerosols today have declined considerably. In the formerly highly polluted Eastern Erzgebirge, deposition can now be addressed as comparable to rural areas without major local or regional influences.
Keywords: Aerosol; Dry deposition; Bulk deposition; Atmospheric deposition trends; Trace elements; Multi-element study; PIXE; INAA; GF-AAS; Germany; Erzgebirge; Black triangle;

Lidar observation of the nocturnal boundary layer formation over Sofia, Bulgaria by I Kolev; P Savov; B Kaprielov; O Parvanov; V Simeonov (3223-3235).
A study of the formation of stable stratification after sunset is presented. The dynamics of atmospheric parameters (e.g., the wind velocity and temperature profiles, height of various layers, etc.) associated with the interaction processes of mountain–valley circulation and urban heat island is followed. The observations are carried out using lidars (aerosol and Raman), kytoon (tethered balloon) and pilot balloons over the city of Sofia (42°39′N, 23°23′ E, 591 m above MSL) and cover heights from 70 to 900 m. The presence of neighboring mountains and the urban heat island effect lead to the formation of three temperature inversions (ground, elevated and capping) and specific vertical profiles of the wind velocity. The formation mechanism is considered of two-layer aerosol structure in the atmosphere over the urban area and its dynamics observed by the lidar after sunset. The results obtained are compared with a model developed on the basis of common models: one describing nocturnal boundary layer development within a mountain valley and the other dealing with stable stratification formation in the case of urban area situated on plain terrain.
Keywords: Remote sensing; Lidar; Aerosol; Wind shear; Temperature inversion; Nocturnal boundary layer; Urban boundary layer; Urban area;

Chemical and mineralogical composition of solid fraction of ambient aerosol at different levels (Kopisty near Most, NW Bohemia) by David Havlı́ček; Rudolf Přibil; Ondřej Dubovský; Ludmila Dobiášová; Pavel Sedlák (3237-3244).
The dependence of the chemical and mineralogical composition of solid fraction of aerosols on the sampling height was studied using a meteorological mast located in a highly industrialized region of the Czech Republic. The aerosol was collected at an altitude of 2, 20, 40, 60 and 80 m above the earth's surface using a high-volume impactor capable of sampling all the particles with a diameter greater than 0.5 μm. The contents of seven identified minerals indicated that the concentration of soil minerals in the solid fraction of aerosol decreases sharply with altitude, whereas the proportion of fly ash emitted by coal-powered power plants in the region increases with altitude. The lowest concentration of aerosol was found at a sampling height of 40 m.
Keywords: Aerosols; Chemical composition; Mineral composition; Sampling height;

210 Pb in ground-level air in Belgrade city area by D Todorovic; D Popovic; G Djuric; M Radenkovic (3245-3248).
Concentrations of 210 Pb in ground level air in the city area (Belgrade, Central Serbia) were measured in the period from 1985 to 1996. The activity of 210 Pb in air filters was determined on a HPGe detector by standard gamma spectrometry. Total standard error of the method was estimated to be below 25%.The average monthly concentrations of 210 Pb in the ground level air in the period from 1985 to 1996 were in the range of 0.30–3.17 mBq m−3 with the maxima in fall–winter periods and minimums in springs and early summers. The seasonal indices were 1.12–1.59 for fall–winter and 0.77–0.92 for spring–summer periods. The ratios of maximum-to-minimum concentrations in each year were relatively stable over the period, with slight increase in 1985, 1989 and 1995. The investigations are part of the long-term measurements of natural and man-made radionuclides in the ground-level air in the region.
Keywords: Radionuclides; Air activity concentrations; Monitoring; Seasonal variations;