Aerosol-ozone correlations during dust transport episodes

Abstract

Abstract. Its location in the Mediterranean region and its physical characteristics render Mt. Cimone (44 • 11 N, 10 • 42 E), the highest peak of the Italian northern Apennines (2165 m asl), particularly suitable to study the transport of air masses from the north African desert area to Europe. During these northward transports 12 dust events were registered in measurements of the aerosol concentration at the station during the period June-December 2000, allowing the study of the impact of mineral dust transports on free tropospheric ozone concentrations, which were also measured at Mt. Cimone. Three-dimensional backward trajectories were used to determine the air mass origin, while TOMS Aerosol Index data for the Mt. Cimone area were used to confirm the presence of absorbing aerosol over the measurement site.A trajectory statistical analysis allowed identifying the main source areas of ozone and aerosols. The analysis of these back trajectories showed that central Europe and north and central Italy are the major pollution source areas for ozone and fine aerosol, whereas the north African desert regions were the most important source areas for coarse aerosol and low ozone concentrations. During dust events, the Mt. Cimone mean volume concentration for coarse particles was 6.18 µm 3 /cm 3 compared to 0.63 µm 3 /cm 3 in dust-free conditions, while the ozone concentrations were 4% to 21% lower than the monthly mean background values. Our observations show that surface ozone concentrations were lower than the background values in air masses coming from north Africa, and when these air masses were also rich in coarse particles, the lowest ozone values were registered. Moreover, preliminary results on the possible impact of the dust events on PM 10 and ozone values measured in Italian urbanCorrespondence to: P. Bonasoni (p.bonasoni@isac.cnr.it) and rural areas showed that during the greater number of the considered dust events, significant PM 10 increases and ozone decreases have occurred in the Po valley.

Deposition of atmospheric nitrous acid on alkaline snow surfaces

“…For this work we discuss only the relevant coarse aerosol fraction (1 mm Dp 20 mm) range. Frequent increases of coarse particle concentration at MTC are attributed to transport of Saharan air masses rich in mineral dust [Bonasoni et al, 2004].…”

Iodine monoxide in the north subtropical free troposphere

“…Under these conditions, the composition of air reaching the station is dependent on the history of the airmass. O 3 presents concentrations inside the dust cloud up to 50 % lower than for dust free conditions (Bonasoni et al, 2004).…”

A case of extreme particulate matter concentrations over Central Europe caused by dust emitted over the southern Ukraine

“…Asian dust transported to areas affected by high levels of anthropogenic pollution is in particular impacting on atmospheric chemistry (Krueger et al, 2004;Wang et al, 2007) because sulfate and nitrate species efficiently react on the surface of the calcite-rich dust particles. Dust may also play an important role in ozone chemistry (Bonasoni et al, 2004). Changed meteorological conditions as consequence of climate change are expected to influence dust production and transport, with increasing atmospheric dust loads and radiative forcing in drier climates Woodward et al (2005).…”