10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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ROS-Generating Capacity of Particulate Matter over two Cities in Eastern Mediterranean
DESPINA PARASKEVOPOULOU, Irini Tsiodra, Aikaterini Bougiatioti, Athanasios Nenes, Nikolaos Mihalopoulos, National Observatory of Athens
Abstract Number: 1535 Working Group: Aerosol Chemistry
Abstract The capacity of particulate matter to generate reactive oxygen species (ROS) has been reported as a more important factor of health impairment than the concentration of particulate matter (PM). Although PM-induced oxidative stress has been characterized as a primary mechanism in the initiation of human cell damage, there is no well-established association between composition, sources and the exact mechanism of aerosol oxidative potential (OP) worldwide. Especially in Europe, there are limited studies that involve a relatively short number of data sets. The aforementioned necessity to correlate PM toxicity with aerosol composition and emission sources has led us to the conduction of the present study, in order to assess the adverse health impacts. Two different types of sites were used so that the obtained results are investigated on both temporal and spatial basis. Furthermore, correlations between OP and other aerosol chemical components took place using various measuring techniques, to identify the sources of aerosol OP in each studied site.
Aerosol sampling was conducted, from July 2017 to January 2018, simultaneously at an urban site in the city of Athens (Continental Greece) and at a suburban background site in the city of Heraklion (Island part of Southern Greece). A dichotomous aerosol sampler (PM2.5) was used in Athens, while in Heraklion total suspended particulate (TSP) matter was collected through a high volume air sampler. For the determination of PM oxidative potential the acellular method of dithiothreitol (DTT) assay was applied, using an innovative semi-automated system, for conducting the measurement on numerous samples, overcoming the obstacle of time consuming and intense laboring analytical processes. Concurrent estimation of inorganic and organic aerosol components’ concentrations was accomplished through Ion chromatography, Aerosol Chemical Speciation Monitor (ACSM), Aethalometer and OC/EC analyzer.
The OP presented higher values in the urban site, where the DTT activity of fine particulate matter gave an average of 0.23 ± 0.11 nmol min-1 m-3 and seems to be 10 times higher than that of the suburban background site, where the average value of DTT activity for TSP was 0.021 ± 0.013 nmol min-1 m-3. The measured OP at the urban and suburban background site ranged between 0.40 ± 0.02 nmol min-1 m-3 and 0.064 ± 0.005 nmol min-1 m-3, respectively, presenting higher values mostly during the days that there was intense biomass burning. These differences in the OP between the two sites were expected since the urban site is located in a densely populated city, where both regional and intense local aerosol sources play an important role in the composition of particulate matter. Furthermore, the investigation of correlation between OP and other PM chemical species indicated that both primary (biomass burning, fossil fuel) and secondary (aged oxidized species, photochemical reactions) aerosol sources can affect to a different extent the capacity of particulate matter to generate ROS, depending on the season of the year and the location of the site.