N. Mihalopoulos

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.

Properties of Aged Aerosols in the Eastern Mediterranean

Three month-long campaigns (FAME-07, -08, -09, -11) have been conducted at Finokalia in order to assess the water uptake, volatility and oxidation state of aged organic particulate matter (PM) along with aerosol nucleation. Finokalia is a remote coastal station located in the southeast of the Mediterranean Sea on the island of Crete, Greece. The site lacks local sources as there is no notable human activity at a range of approximately 15 km. The PM that reaches the site is heavily influenced by the surrounding source regions and the organic content highly oxidized. During the summer aerosols always contained water even under very low relative humidity (RH < 20%) possibly due to their acidity. Organic aerosol was highly and almost uniformly oxidized and the resulting mass spectra did not change throughout the summer campaign, even after it was thermally treated, indicating a high oxidation state. An organic aerosol evaporation model was used to simulate the behaviour of the thermally treated aerosol and showed that aged organic PM was two or more orders of magnitude less volatile than laboratory-generated secondary organic PM. Nucleation is controlled by the gas phase ammonia levels and the resulting PM acidity, at least during the summer, resulting in low number of particle formation events per year.

Aerosol Size over the Broader Greek Area Based on Satellite and Ground Measurements

A first estimate of aerosol size over the broader Greek area (33.5°N-42.5°N and 18.5°E-29.5°E) is attempted by using satellite- and ground-based measurements for the 10-year period 2000–2010. A complete spatial coverage is ensured by daily gridded data derived from measurements taken from the MODerate resolution Imaging Spectroradiometer (MODIS) instrument onboard the NASA’s Terra and Aqua satellites. More specifically, MODIS Collection 5.1 Angstrom Exponent (α), Fine Fraction (FF) and aerosol Mean Effective Radius (reff) 1° × 1° latitude-longitude data are used, over both land and sea. The obtained results reveal a geographical variability of aerosol size over the Greek area. Values of FF and α, are greater over the northern than southern part of the region, exhibiting a north-to-south gradient, as well as over land than sea. The smallest FF and α values (≈0.1 and 0.5, respectively) appear over the southern Aegean and Ionian Sea, and south of Crete, indicating the influence of transported coarse dust particles from the Sahara desert. These patterns of aerosol size are also confirmed by the distribution of reff values (0.25–0.58 μm) over the region. The satellite-based results are evaluated against daily surface AERONET with the MODIS sea products providing a better agreement than the land ones.