Changes in chemical composition and oxidative potential of urban PM(2.5) between 2010 and 2013 in Hungary

A comprehensive chemical characterization and oxidative potential (OP) assessment of PM2.5 was carried out at an urban site of Budapest between June 2010 and May 2013 to investigate the seasonal variability of particulate phase air pollutants and their oxidative activity. Chemical analyses included the determination of the concentration of trace elements, major water-soluble inorganic ions and carbonaceous fractions (total carbon, water-soluble organic carbon, organic carbon, elemental carbon). The OP of PM2.5 was assessed by antioxidant depletion using a synthetic respiratory tract lining fluid containing ascorbate, reduced glutathione and urate. The mean PM2.5 mass concentration (21.0 microg m(-3)) was just below the 25 microg m(-3) annual mean PM2.5 limit value set by the European Commission and showed a seasonal pattern with higher levels during winter. On average, 84% of the gravimetric mass could be reconstructed by the chemical measurements. Organic matter and secondary inorganic ions were the most dominant PM2.5 constituents contributing 40 and 29% of its mass, respectively. Changes in the yearly concentrations were not identified for the investigated compounds between 2010 and 2013. Temporal differences in both ascorbate and glutathione oxidation could be observed during the 3-year long sampling period; however, no clear seasonal trend was apparent. OP metrics were associated mainly with traffic-related trace elements; however, other PM sources (i.e., long-range transport, secondary aerosol formation) could also contribute to particulate OP in Budapest. The weak correlation between OP metrics and PM2.5 mass concentration suggests the possibility of using OP as an additional metric in epidemiology.