P. Zarmpas

Mass and chemical composition of size-segregated aerosols (PM 1 , PM 2.5 , PM 10 ) over Athens, Greece: local versus regional sources

To identify the relative contribution of local versus regional sources of particulate matter (PM) in the Greater Athens Area (GAA), simultaneous 24-h mass and chemical composition measurements of size segregated particulate matter (PM1, PM2.5 and PM10) were carried out from September 2005 to August 2006 at three locations: one urban (Goudi, Central Athens, “GOU”), one suburban (Lykovrissi, Athens, “LYK”) in the GAA and one at a regional background site (Finokalia, Crete, “FKL”). The two stations in the GAA exceeded the EU-legislated PM10 limit values, both in terms of annual average (59.0 and 53.6 μg m−3 for Lykovrissi and Goudi, respectively) and of 24-h value. High levels of PM2.5 and PM1 were also found at both locations (23.5 and 18.6 for Lykovrissi, while 29.4 and 20.2 μg m−3 for Goudi, respectively). Significant correlations were observed between the same PM fractions at both GAA sites indicating important spatial homogeneity within GAA. During the warm season (April to September), the PM 1 ratio between GAA and FKL ranged from 1.1 to 1.3. On the other hand this ratio was significantly higher (1.6–1.7) during the cold season (October to March) highlighting the role of long-range transport and local sources during the warm and cold seasons respectively. Regarding the coarse fraction no seasonal trend was observed for both GAA sites with their ratio (GAA site/FKL) being higher than 2 indicating significant contribution from local sources such as soil and/or road dust. Chemical speciation data showed that on a yearly basis, ionic and crustal mass represent up to 67–70 % of the gravimetrically determined mass for PM 10 samples in the GAA Correspondence to: N. Mihalopoulos (mihalo@chemistry.uoc.gr) and 67 % for PM1 samples in LYK. The unidentified mass might be attributed to organic matter (OM) and elemental carbon (EC), in agreement with the results reported by earlier studies in central Athens. At all sites, similar seasonal patterns were observed for nss-SO 2− 4 , a secondary compound, indicating significant contribution from regional sources in agreement with PM1 observations. The contribution of local sources at both GAA sites was also estimated by considering mass and chemical composition measurements at Finokalia as representative of the regional background. Particulate Organic Matter (POM) and EC, seemed to be the main contributor of the local PM mass within the GAA (up to 62 % in PM1). Dust from local sources contributed also significantly to the local PM 10 mass (up to 33 %).

Aerosol chemical composition over Istanbul

This study examines the chemical composition of aerosols over the Greater Istanbul Area. To achieve this 325 (PM(10)) aerosol samples were collected over Bosphorus from November 2007 to June 2009 and were analysed for the main ions, trace metals, water-soluble organic carbon (WSOC), organic (OC) and elemental carbon (EC). PM(10) levels were found to be in good agreement with those measured by the Istanbul Municipality air quality network, indicating that the sampling site is representative of the Greater Istanbul Area. The main ions measured in the PM(10) samples were Na(+), Ca(2+) and non-sea-salt sulphates (nss-SO(4)(2-)). On average, 31% of Ca(2+) was found to be associated with carbonates. Trace elements related to human activities (as Pb, V, Cd and Ni) obtained peak values during winter due to domestic heating, whereas natural origin elements like Al, Fe and Mn peaked during the spring period due to dust transport from Northern Africa. Organic carbon was found to be mostly primary and elemental carbon was strongly linked to fuel oil combustion and traffic. Both OC and EC concentrations increased during winter due to domestic heating, while the higher WSOC to OC ratio during summer can be mostly attributed to the presence of secondary, oxidised and more soluble organics. Factor analysis identified six components/sources for aerosol species in PM(10), namely traffic/industrial, crustal, sea-salt, fuel-oil combustion, secondary and ammonium sulfate.

Atmospheric Deposition of Macronutrients (Dissolved Inorganic Nitrogen and Phosphorous) onto the Black Sea and Implications on Marine Productivity

AbstractTwo-sized aerosol samples were obtained from a rural site located close to Sinop on the south coastline of the Black Sea. In addition, bulk deposition samples were collected at Varna, located on the west coastline of the Black Sea. Both aerosol and deposition samples were analyzed for the main macronutrients, NO3−, NH4+, and PO43−. The mean aerosol nitrate and ammonium concentrations were 7.1 ± 5.5 and 22.8 ± 17.8 nmol m−3, respectively. The mean aerosol phosphate concentration was 0.69 ± 0.31 nmol m−3, ranging from 0.21 to 2.36 nmol m−3. Interestingly, phosphate concentration over Sinop was substantially higher than those of most Mediterranean sites. Comparison of the atmospheric and riverine inputs for the Black Sea revealed that atmospheric dissolved inorganic nitrogen (DIN) only ranged between 4% and 13%, while the atmospheric dissolved inorganic phosphorus (DIP) fluxes had significantly higher contributions with values ranging from 12% to 37%. The molar N:P ratios in atmospheric deposition fo...

Optical Properties of Aerosols Over Athens, Greece, and Their Relation with Chemical Composition

To investigate the relation between aerosol optical properties and their chemical composition, scattering and absorption of aerosols have been recorded on a routine basis during the last 4 years (2008–2011) at the Aerosol Monitoring Station of the National Observatory of Athens, at Penteli’s premises, Athens, Greece. In parallel, monitoring of PM2.5, PM2.5–10, and PM10 fractions of particulate matter was performed. Samples were analysed for complete chemical characterization of aerosols, by means of ionic chromatography and the thermal–optical transmission method for EC/OC.

Carbonaceous Aerosols Over the Mediterranean and Black Sea

The role of carbonaceous material (organic and elemental carbon) in the Mediterranean and Black sea atmosphere is yet to be unraveled. To fill this gap the present work is focused on the study of carbonaceous aerosols over the Mediterranean and Black Sea. Thus, aerosol samples were simultaneously collected at a remote site in Greece (Finokalia, Crete), a highly populated urban (Istanbul), a remote (Imbros) and two rural sites in Turkey (Sinop, Erdemli). Approximately 1,200 aerosol samples were collected and analyzed for Organic and elemental carbon (OC and EC), as well as water-soluble organic carbon (WSOC). Their seasonal variation, the factors controlling their variation and their relative contribution to aerosol mass is presented and thoroughly discussed. More specifically, organic matter constitutes a significant part of the total PM10 mass (21–33% of Particulate Organic Matter and 2–11% EC). The percentage of WSOC ranges from 37% to 40% of the OC for the four remote and rural regions, while in Istanbul constitutes 27% of OC and 10% of the total PM10 mass. Correlations with potassium and sulfate showed that the sources of organic matter in Istanbul are mainly due to the anthropogenic activities, while in rural and suburban areas to long range transport and biomass burning.

Calcium sequestration by fungal melanin inhibits calcium–calmodulin signalling to prevent LC3-associated phagocytosis

LC3-associated phagocytosis (LAP) is a non-canonical autophagy pathway regulated by Rubicon, with an emerging role in immune homeostasis and antifungal host defence. Aspergillus cell wall melanin protects conidia (spores) from killing by phagocytes and promotes pathogenicity through blocking nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-dependent activation of LAP. However, the signalling regulating LAP upstream of Rubicon and the mechanism of melanin-induced inhibition of this pathway remain incompletely understood. Herein, we identify a Ca2+ signalling pathway that depends on intracellular Ca2+ sources from endoplasmic reticulum, endoplasmic reticulum–phagosome communication, Ca2+ release from phagosome lumen and calmodulin (CaM) recruitment, as a master regulator of Rubicon, the phagocyte NADPH oxidase NOX2 and other molecular components of LAP. Furthermore, we provide genetic evidence for the physiological importance of Ca2+–CaM signalling in aspergillosis. Finally, we demonstrate that Ca2+ sequestration by Aspergillus melanin inside the phagosome abrogates activation of Ca2+–CaM signalling to inhibit LAP. These findings reveal the important role of Ca2+–CaM signalling in antifungal immunity and identify an immunological function of Ca2+ binding by melanin pigments with broad physiological implications beyond fungal disease pathogenesis.A calcium–calmodulin signalling pathway is identified as a master regulator of light chain 3 (LC3)-associated phagocytosis. Aspergillus melanin sequesters Ca2+ inside the phagosome, inhibiting this pathway, which is important in human aspergillosis.

Aerosol Chemical Mass Closure in Athens, Greece: Towards a Better Understanding of the Seasonal Variation of Aerosol Sources in the Area

This study examines the chemical composition of aerosols over Athens. To achieve this, particulate matter sampling has been conducted on a 6–24 h basis from January 2013 until now. More than 700 aerosol samples were collected at downtown Athens, in Thissio and after mass quantification, were analyzed for major ions (Cl−, Br−, \( {\text{NO}}_{3}^{ - } \), \( {\text{SO}}_{4}^{2 - } \), \( {\text{PO}}_{4}^{ - 3 } \), \( {\text{C}}_{2} {\text{O}}_{4}^{ - 2 } \), \( {\text{NH}}_{4}^{ + } \), K+, Na+, Mg2+, Ca2+), trace elements (Al, As, Ca, Cd, Co, Cr, Cu, Fe, V, Zn, Mn, Ni, Pb, P, S, Sb), organic carbon (OC) and elemental carbon (EC). Aerosol chemical mass closure calculations indicated that carbonaceous aerosol constitutes a major component, along with nitrate and sulfate anions, dust, cations and EC. Principal component analysis (PCA) was also applied to better constrain the aerosol sources over Athens with specific emphasis during the winter time, period characterized by intense biomass burning.

Short-Term Variability of Fine Inorganic Particulate Matter Over Athens, Greece

On-line, measurements of inorganic ions were performed at Thissio station (December 2014–October 2015), in order to comprehend the sources and the factors that affect variability of fine inorganic aerosol in Athens, Greece. Atmospheric air is sampled through a 1 μm cut-size impactor, to a particle-into-liquid sampler, coupled with ion chromatography. Simultaneously, fine aerosol (PM2.5) is collected daily on quartz filters, and further analysed by ion chromatography. The concentrations of Cl−, \({\text{NO}}_{3}^{ - }\) and \({\text{SO}}_{4}^{2 - }\) measured by PILS average 0.29 ± 0.20, 0.69 ± 0.35 and 1.86 ± 1.6 μg m−3, respectively, and are in accordance with the corresponding concentrations obtained by filter analysis. The seasonal variability of nss-\({\text{SO}}_{4}^{2 - }\) presents maxima during summer, while minimum appears in winter, due to the enhanced summer photochemistry combined with limited precipitation and intensive regional transport. During both seasons, sulfate presents no distinct diurnal variability according to its regional character. On the contrary, nitrate presents an opposite seasonality with winter maxima and summer minima, since high temperatures tend to dissociate fine mode ammonium nitrate into nitric acid and ammonia. Additionally, a clear diurnal variation is observed for both seasons with maximum values during nighttime due again to lower temperatures occurred during nighttime compared to daytime.