Teresa Nunes

Carbonaceous aerosols in industrial and coastal atmospheres

Abstract Total suspended and size-segregated aerosol samples were collected at one industrial and one coastal location. Measurements of inorganic ions, trace elements and organic/elemental carbon (OC/EC) permitted us to conclude that at the marine site most carbonaceous mass is associated with vehicle emissions and long-range transport, being well correlated with lead. At the industrial location the picture is not so clear because lead is also emitted by local industries. A good correlation, however, exists for EC between both sites, indicating that elemental carbon is well mixed in the lower troposphere and has a regional character. EC and OC frequently have a bimodal size distribution, each mode being approximately log-normal. At both sites ≈ 78% of EC and 68–76% of OC are in the fine-particle mode fraction. High levels of elemental carbon are present in aged polluted air masses transported from industrialized regions in Europe. These air masses contain relatively much less particulate organic carbon. During long-range transport the organic constituents of the aerosol are depleted while elemental carbon is transported efficiently.

Outdoor/indoor air quality in primary schools in Lisbon: a preliminary study

Simultaneous measurements of outdoor and indoor pollution were performed at three schools in Lisbon. Volatile organic compounds (VOCs), formaldehyde and NO2 were passively monitored over a two-week period. Bacterial and fungal colony-forming units and comfort parameters were also monitored at classrooms and playgrounds. The highest indoor levels of CO2 (2666 μg/m3), NO2 (40.3 μg/m3), VOCs (10.3 μg/m3), formaldehyde (1.03 μg/m3) and bioaerosols (1634 CFU/m3), and some indoor/outdoor ratios greater than unity, suggest that indoor sources and building conditions might have negative effects on air indoors. Increasing ventilation rates and use of low-emission materials would contribute towards improving indoor air quality.

Seasonal and air-mass trajectory effects on rainwater quality at the south-western european border

Abstract Rainwater was collected daily, at the Portuguese west coast, between April 1985 and October 1989 and analysed for pH, conductivity, Cl − , NO 3 − , SO 2 2− and NH 4 + concentrations. A seasonal variation was observed for sulphates and nitrates, with minimum concentrations during autumn and maximum during winter and spring. No seasonal pattern could be detected for acidity. The level of acidity in rainwater is highly dependent on the history of the air mass. Levels of acidity 10 × higher than average were found in rain events associated with air masses proceeding from industrialized countries in Europe and transported over the ocean. However, as these rain events constitute only a small fraction of total wet deposition, and approximately 80% of total precipitation is associated with transport from the Atlantic Ocean, the average pH is 5.3.

Volatile organic compounds in rural atmospheres of central Portugal

Atmospheric concentrations of volatile organic compounds were measured at two rural sites in central Portugal. The sites were chosen to be in line with the summer northwesterly sea breezes in order to study the evolution of the chemical composition of air masses during transport to inland areas. The most abundant non-oxygenated hydrocarbon in the ambient air was isoprene and the monoterpenes alpha-pinene, beta-pinene and 1,8 cineol. The maximum isoprene levels (6-7 ppb) were recorded at the most inland site, suggesting an enrichment of coastal air masses with biogenic emissions during transport over eucalyptus forests. Formaldehyde was the most prominent carbonyl compound in the atmosphere but acetaldehyde and acrolein were also abundant. Concentrations of carbonyl compounds had a tendency to be higher inland, particularly for glyoxal, methyl glyoxal, methyl vinyl ketone, metacrolein and pentanal. The observed increases indicate that carbonyls were produced by photochemical oxidation of biogenic hydrocarbons in aged air masses with coastal origin. Isoprene, monoterpenes and various carbonyls exhibited pronounced diurnal variations, which are explained on the basis of emissions from vegetation, oxidation pathways of biogenic hydrocarbons and meteorological conditions.

Emission of volatile organic compounds from Portuguese eucalyptus forests

Abstract Emission to the atmosphere of volatile organic compounds (VOCs) by Eucalyptus globulus was studied in the laboratory with young specimen, and in the field with adult trees. Eucalyptus emits both monoterpenes and isoprene. The leaves of young trees emit at higher rates than the leaves of adult trees. The emission of isoprene is highly predominant during the day. The emission of isoprene is dependent on temperature and solar radiation. The emission rate follows the Guenther algorithm if a based emission factor of 32 μg g dw −1 h −1 is used, increasing with temperature, to a maximum at 40°C. At higher temperatures there is a decrease in the emission rate. The main C10 emitted compound is 1,8-cineol. Cineol emissions increase exponentially with temperature, and are also seasonally dependent. Application of the emission algorithm to the Portuguese eucalyptus forests shows that during summer isoprene and monoterpene emissions by eucalyptus are of the same order of anthropogenic VOC production. Furthermore, in certain regions, in the center-north of Portugal, where eucalyptus forests are predominant, isoprene emissions can reach an order of magnitude higher than anthropogenic production of VOCs during daytime periods in July and August.

Kinetic and thermodynamic behaviour of volatile ammonium compounds in industrial and marine atmospheres

Abstract Measurements of volatile ammonium aerosol compounds and respective acidic and basic gaseous precursors were taken at an industrial site emitting HCl, HNO 3 and NH 3 and at a marine suburban location. Because of fresh industrial emissions the gaseous acid and base concentration products show values orders of magnitude higher than thermodynamic equilibrium previsions, at the industrial site. To our knowledge these are the first published field measurements that strongly confirm that gas-particle equilibrium conditions are not attained instantaneously in the atmosphere and that kinetic constraints play an important role on gas-particle conversion for ammonium chloride and ammonium nitrate compounds. The results permit to conclude that, for temperature conditions lower than 15°C, transformation rates are not high, several minutes being necessary, at least, for the equilibrium between gaseous precursors and ammonium particulate products to be reached. At the marine suburban location a diurnal variation was observed for gaseous and particulate compounds in agreement with known emission and transformation mechanisms. The behaviour of nitric and hydrochloric acids in the marine atmosphere can be better explained if kinetic limitations are considered for the reaction of HNO 3 with NaCl aerosol particles and for the transference of acids and ammonia to the particulate phase.

Particulate and gaseous air pollutant levels at the Portuguese west coast

Abstract A field study was conducted at a coastal site near Aveiro, Portugal, where inorganic compounds and trace elements were measured on the atmospheric suspended aerosol, and nitric acid, hydrochloric acid and ammonia detected in the gaseous phase. The levels of hydrochloric and nitric acids were of the same order of other values detected on non-urban sites in industrialized Europe. The concentrations of aerosol constituets were higher than would be expected for a region located on the western corner of the European continent. The existence of high pressure conditions over Western Europe and the Iberian Peninsula during most of the sampling period, with persistence of stagnant air masses and slow transport from the continent can be an explanation for the observed values. Principal Component and Cluster Analysis permitted the detection of six aerosol source groups, five regional (namely soil emission, transport, oil combustion, secondary pollutants and sea spray), and one, possibly local, that could not be identified with precision.

Polycyclic aromatic hydrocarbons and their derivatives (nitro-PAHs, oxygenated PAHs, and azaarenes) in PM2.5 from Southern European cities

Atmospheric particulate matter (PM2.5) samples were collected over two one month periods during winter and summer in three Southern European cities (Oporto - traffic site, Florence - urban background, Athens - suburban). Concentrations of 27 polycyclic aromatic hydrocarbons (PAHs), 15 nitro-PAHs (NPAHs), 15 oxygenated-PAHs (OPAHs) and 4 azaarenes (AZAs) were determined. On average, the winter-summer concentrations of ΣPAHs were 16.3-5.60, 7.75-3.02 and 3.44-0.658ngm-3 in Oporto, Florence and Athens, respectively. The corresponding concentrations of ΣNPAHs were 15.8-9.15, 10.9-3.36 and 15.9-2.73ngm-3, whilst ΣOPAHs varied in the ranges 41.8-19.0, 11.3-3.10 and 12.6-0.704ngm-3. Concentrations of ΣAZAs were always below 0.5ngm-3. Irrespective of the city, the dominant PAHs were benzo[b+j+k]fluoranthene, retene, benzo[ghi]perylene and indeno[1,2,3-cd]pyrene. The most abundant OPAH in all cities was 1,8-naphthalic anhydride, whereas 5-nitroacenaphthene was the prevailing NPAH. The ΣOPAHs/ΣPAHs and ΣNPAHs/ΣPAHs were higher in summer than in winter, suggesting increasing formation of derivatives by photochemical degradation of PAHs. Molecular diagnostic ratios suggested that, after traffic, biomass burning was the dominant emission source. Apart from being influenced by seasonal sources, the marked differences between winter and summer may indicate that these diagnostic ratios are particularly sensitive to photodegradation, and thus should be applied and interpreted cautiously. The lifetime excess cancer risk from inhalation was, in part, attributable to PAH derivatives, acclaiming the need to include these compounds in regular monitoring programmes. On average, 206, 88 and 26 cancer cases per million people were estimated, by the World Health Organisation method, for the traffic-impacted, urban background and suburban atmospheres of Oporto, Florence and Athens, respectively.

Impact of Sahara Dust Transport on Cape Verde Atmospheric Element Particles

The objectives of this study were to (1) conduct an elemental characterization of airborne particles sampled in Cape Verde and (2) assess the influence of Sahara desert on local suspended particles. Particulate matter (PM10) was collected in Praia city (14°94’N; 23°49’W) with a low-volume sampler in order to characterize its chemical composition by k0-INAA. The filter samples were first weighed and subsequently irradiated at the Portuguese Research Reactor. Results showed that PM10 concentrations in Cape Verde markedly exceeded the health-based air quality standards defined by the European Union (EU), World Health Organization (WHO), and U.S. Environmental Protection Agency (EPA), in part due to the influence of Sahara dust transport. The PM10 composition was characterized essentially by high concentrations of elements originating from the soil (K, Sm, Co, Fe, Sc, Rb, Cr, Ce, and Ba) and sea (Na), and low concentrations of anthropogenic elements (As, Zn, and Sb). In addition, the high concentrations of PM measured in Cape Verde suggest that health of the population may be less affected compared with other sites where PM10 concentrations are lower but more enriched with toxic elements.

Assessment of air pollution sources in an industrial atmosphere using principal component and multilinear regression analysis

Aerosol samples collected in the industrial area of Estarreja, Portugal, were used to assess the source classes responsible for the particulate levels observed in the local atmosphere. Principal Component Analysis was applied separately to the concentrations of aerosol constituents and meteorological variables to obtain the number of Principal Components and to verify the influence of weather conditions on ambient air quality. The technique led to the conclusion that soil and transport emissions represent important aerosol sources even in this industrial environment. The quantitative contribution of each source class was calculated using Multilinear Regression Analysis; 37% of the aerosol mass had a soil origin, 8% was from sea spray, 18% resulted from transport emissions and 24% contained ammonium salts. Twelve percent of total suspended particle (TSP) mass could not be explained by any of the six Principal Components retained. Ammonium salts and two other minor Principal Components seem to result mainly from industrial emissions. More specific information about the contribution of each particular source was not possible with this technique.