Euripides G. Stephanou

Formation of atmospheric particles from organic acids produced by forests

Aerosol formation in the atmosphere is an important process to understand, in that such particles may act as the cloud condensation nuclei responsible for the ‘cloud–climate’ effect, and could locally be hazardous to health. The number-concentration of total atmospheric aerosols and cloud condensation nuclei is largely contributed by organic aerosols. Much of the organic aerosol is formed from atmospheric gas-to-particle conversion, and the common and widespread non-methane hydrocarbons emitted by vegetation have been investigated as possible precursors. But strong evidence for a quantitative link between biogenic hydrocarbon emission and organic aerosol formation has so far been lacking. Here we present measurements of gaseous and particulate atmospheric species from a forested area to show that some hydrocarbons (for example, terpenes) emitted by vegetation are photo-oxidized to organic acids (for example, pinonic acids), which condense to form organic aerosols. Thus the forests, through their production of large quantities of organic aerosols, could be of considerable significance both for climate (through cloud-condensation-nuclei formation) and for heterogeneous atmospheric chemical processes.

Development of Land Use Regression Models for PM2.5, PM2.5 Absorbance, PM10 and PMcoarse in 20 European Study Areas; Results of the ESCAPE Project

Land Use Regression (LUR) models have been used increasingly for modeling small-scale spatial variation in air pollution concentrations and estimating individual exposure for participants of cohort studies. Within the ESCAPE project, concentrations of PM(2.5), PM(2.5) absorbance, PM(10), and PM(coarse) were measured in 20 European study areas at 20 sites per area. GIS-derived predictor variables (e.g., traffic intensity, population, and land-use) were evaluated to model spatial variation of annual average concentrations for each study area. The median model explained variance (R(2)) was 71% for PM(2.5) (range across study areas 35-94%). Model R(2) was higher for PM(2.5) absorbance (median 89%, range 56-97%) and lower for PM(coarse) (median 68%, range 32- 81%). Models included between two and five predictor variables, with various traffic indicators as the most common predictors. Lower R(2) was related to small concentration variability or limited availability of predictor variables, especially traffic intensity. Cross validation R(2) results were on average 8-11% lower than model R(2). Careful selection of monitoring sites, examination of influential observations and skewed variable distributions were essential for developing stable LUR models. The final LUR models are used to estimate air pollution concentrations at the home addresses of participants in the health studies involved in ESCAPE.

Abiotic Stress Generates ROS That Signal Expression of Anionic Glutamate Dehydrogenases to Form Glutamate for Proline Synthesis in Tobacco and Grapevine

Glutamate dehydrogenase (GDH) may be a stress-responsive enzyme, as GDH exhibits considerable thermal stability, and de novo synthesis of the α-GDH subunit is induced by exogenous ammonium and senescence. NaCl treatment induces reactive oxygen species (ROS), intracellular ammonia, expression of tobacco (Nicotiana tabacum cv Xanthi) gdh-NAD;A1 encoding the α-subunit of GDH, increase in immunoreactive α-polypeptide, assembly of the anionic isoenzymes, and in vitro GDH aminating activity in tissues from hypergeous plant organs. In vivo aminating GDH activity was confirmed by gas chromatorgraphy–mass spectrometry monitoring of 15N-Glu, 15N-Gln, and 15N-Pro in the presence of methionine sulfoximine and amino oxyacetic acid, inhibitors of Gln synthetase and transaminases, respectively. Along with upregulation of α-GDH by NaCl, isocitrate dehydrogenase genes, which provide 2-oxoglutarate, are also induced. Treatment with menadione also elicits a severalfold increase in ROS and immunoreactive α-polypeptide and GDH activity. This suggests that ROS participate in the signaling pathway for GDH expression and protease activation, which contribute to intracellular hyperammonia. Ammonium ions also mimic the effects of salinity in induction of gdh-NAD;A1 expression. These results, confirmed in tobacco and grape (Vitis vinifera cv Sultanina) tissues, support the hypothesis that the salinity-generated ROS signal induces α-GDH subunit expression, and the anionic iso-GDHs assimilate ammonia, acting as antistress enzymes in ammonia detoxification and production of Glu for Pro synthesis.

Organic aerosols in Eastern Mediterranean: components source reconciliation by using molecular markers and atmospheric back trajectories

Molecular markers, such as n-alkanes, hopanes, PAHs, n-alkanols, n-alkanals, n-alkan-2-ones and n-alkanoic acids, and atmospheric back trajectories have been conjointly used to reconcile Eastern Mediterranean marine organic aerosols with their emission sources. In the urban site, local inputs of polar and non polar lipids control the aerosol composition. In addition the presence of iso- and anteisoalkanes in the aliphatic fraction of all urban samples analysed, demonstrated the contribution of cigarette smoke to urban aerosols. The composition of the aliphatic and aromatic fractions demonstrated a clear petrogenic input. In the rural site the composition and concentrations of the PAH fraction were dependant on the origin of air masses, and showed a rather pyrolytic origin. They were higher for air masses from the north than for air masses originating from the south. Some molecular markers, such as 6,10,14-trimethylpentadecan-2-one and α,ω-dicarboxylic acids with Cn > C20, characterized rural aerosols corresponding to air masses with a pronounced marine origin.

Ambient air pollution and low birthweight: a European cohort study (ESCAPE)

BACKGROUND Ambient air pollution has been associated with restricted fetal growth, which is linked with adverse respiratory health in childhood. We assessed the effect of maternal exposure to low concentrations of ambient air pollution on birthweight. METHODS We pooled data from 14 population-based mother-child cohort studies in 12 European countries. Overall, the study population included 74 178 women who had singleton deliveries between Feb 11, 1994, and June 2, 2011, and for whom information about infant birthweight, gestational age, and sex was available. The primary outcome of interest was low birthweight at term (weight <2500 g at birth after 37 weeks of gestation). Mean concentrations of particulate matter with an aerodynamic diameter of less than 2·5 μm (PM2·5), less than 10 μm (PM10), and between 2·5 μm and 10 μm during pregnancy were estimated at maternal home addresses with temporally adjusted land-use regression models, as was PM2·5 absorbance and concentrations of nitrogen dioxide (NO2) and nitrogen oxides. We also investigated traffic density on the nearest road and total traffic load. We calculated pooled effect estimates with random-effects models. FINDINGS A 5 μg/m(3) increase in concentration of PM2·5 during pregnancy was associated with an increased risk of low birthweight at term (adjusted odds ratio [OR] 1·18, 95% CI 1·06-1·33). An increased risk was also recorded for pregnancy concentrations lower than the present European Union annual PM2·5 limit of 25 μg/m(3) (OR for 5 μg/m(3) increase in participants exposed to concentrations of less than 20 μg/m(3) 1·41, 95% CI 1·20-1·65). PM10 (OR for 10 μg/m(3) increase 1·16, 95% CI 1·00-1·35), NO2 (OR for 10 μg/m(3) increase 1·09, 1·00-1·19), and traffic density on nearest street (OR for increase of 5000 vehicles per day 1·06, 1·01-1·11) were also associated with increased risk of low birthweight at term. The population attributable risk estimated for a reduction in PM2·5 concentration to 10 μg/m(3) during pregnancy corresponded to a decrease of 22% (95% CI 8-33%) in cases of low birthweight at term. INTERPRETATION Exposure to ambient air pollutants and traffic during pregnancy is associated with restricted fetal growth. A substantial proportion of cases of low birthweight at term could be prevented in Europe if urban air pollution was reduced. FUNDING The European Union.

Marine organic geochemistry of the Eastern Mediterranean: 1. Aliphatic and polyaromatic hydrocarbons in Cretan Sea surficial sediments

Abstract As part of a lipid biogeochemical study, aliphatic and polyaromatic hydrocarbons were determined in surficial sediments from the Cretan Sea (South Aegean Sea) in the Eastern Mediterranean. Total concentrations of both aliphatic (AHC) and polyaromatic (PAH) hydrocarbons were low (562–5697 and 14.6–158.5 ng/g, respectively) with respect to other coastal sediments worldwide and compare with concentrations found in open sea areas. The composition of AHC was dominated by unresolved complex mixture (UCM) indicating the presence of petroleum-related hydrocarbon inputs as confirmed by the detection of specific α,β-hopanes. PAH consisted mainly of pyrolytic four- to five-ring compounds. UCM and PAH amounts revealed that Cretan Sea receives low supply of anthropogenic material compared to NW Mediterranean. The spatial distributions of AHC and PAH indicated that urban run-off and transport from the continental self are the major input pathway of anthropogenic and biogenic hydrocarbons from terrestrial sources in the near shore area, whereas atmospheric transport might be the significant source of hydrocarbons in the deep area.

Measurement of particulate aliphatic and polynuclear aromatic hydrocarbons in Santiago de Chile : source reconciliation and evaluation of sampling artifacts

Abstract Using a novel sampler, particulate organic compounds were collected in Santiago de Chile from June 9 to August 10, 1997. This sampler consists of a diffusion denuder to remove gas-phase organics prior to particle collection, a Teflon filter, and a PUF cartridge downstream of the filter. PAHs and n -alkanes were measured using gas chromatography/mass spectrometry analysis. Volatilization of particles collected on the Teflon filter varied from 15 to 85% for both n -alkanes and PAHs, with strong dependence on molecular weight. The relative distribution of n -alkanes and the values of molecular diagnostic ratios, such as Carbon preference index, indicated a mixed origin with strong anthropogenic input. Indeed, CPI values ranged from 0.66 to 1.96 (for the whole range of n -alkanes). The percent contribution of leaf “wax” n -alkanes (4.55–20.83%) indicated the low contribution of biogenic sources. In addition, the distribution pattern of PAHs was characteristic of anthropogenic emissions. The dominant contribution of combustion-related PAHs (CPAHs), 74–84%, indicated that vehicular emissions was the major source of PAHs.

Persistent organic chemicals in sewage effluents. 2. Quantitative determinations of nonylphenols and nonylphenol ethoxylates by glass capillary gas chromatography

Nonylphenols and nonylphenol ethoxylates with one and two oxyethylene groups have been quantitatively determined in the effluents of six mechanical-biological sewage treatment plants. In three plants total concentrations of nonylphenolic compounds in the effluents ranged from 36 to 202 pg/L, representing from 0.5% to 2.3% of the total residual dissolved organic carbon. In three plants operated at low loading conditions nonylphenolic compounds were not detectable (<lo pg/L). These compounds are believed to be refractory metabolites of nonionic surfactants of the nonylphenol polyethoxylate type. In particular, the nonylphenols must be considered as compounds of high toxicity to aquatic organisms.

Particle Size Distribution of Airborne Microorganisms and Pathogens during an Intense African Dust Event in the Eastern Mediterranean

Background The distribution of microorganisms, and especially pathogens, over airborne particles of different sizes has been ignored to a large extent, but it could have significant implications regarding the dispersion of these microorganisms across the planet, thus affecting human health. Objectives We examined the microbial quality of the aerosols over the eastern Mediterranean region during an African storm to determine the size distribution of microorganisms in the air. Methods We used a five-stage cascade impactor for bioaerosol collection in a coastal city on the eastern Mediterranean Sea during a north African dust storm. Bacterial communities associated with aerosol particles of six different size ranges were characterized following molecular culture–independent methods, regardless of the cell culturability (analysis of 16S rRNA genes). Results All 16S rDNA clone libraries were diverse, including sequences commonly found in soil and marine ecosystems. Spore-forming bacteria such as Firmicutes dominated large particle sizes (> 3.3 μm), whereas clones affiliated with Actinobacteria (found commonly in soil) and Bacteroidetes (widely distributed in the environment) gradually increased their abundance in aerosol particles of reduced size (< 3.3 μm). A large portion of the clones detected at respiratory particle sizes (< 3.3 μm) were phylogenetic neighbors to human pathogens that have been linked to several diseases. Conclusions The presence of aerosolized bacteria in small size particles may have significant implications to human health via intercontinental transportation of pathogens.

Determination of organic molecular markers in marine aerosols and sediments: one-step flash chromatography compound class fractionation and capillary gas chromatographic analysis

n-Alkanes, polycyclic aromatic hydrocarbons (PAHs), n-alkanals, n-alkan-2-ones, long-chain alkenones, oxy-PAHs, n-alkanols, sterols and free alkanoic acids have been reliably determined in various environmental matrices by using one-step flash chromatography compound class fractionation and subsequent gas chromatography (GC)–MS and/or GC–flame ionization detection analysis. The obtained recoveries, for the whole analytical procedure were 62–98% for n-alkanes, 60–100% for PAHs, 75% for n-alkanals, 96–100% for nitroarenes, 65–73% for oxy-PAHs, 88–98% for n-alkanols, 80–89% for steroidal alcohols and 98% for alkanoic acids. This analytical protocol has been applied, and proved suitable, for the determination of more than 170 organic compounds in samples, such as aerosols and marine sediments, collected during a 1 year period in a coastal environment of Eastern Mediterranean.