In total, more than 800.000 single particle mass spectra have been acquired during the whole campaign (January/February 2005). To process such a high amount of data, an algorithm able to detect the presence or absence of previously selected masses/compounds has been developed. The presence or absence of specific mass peaks in every single particle mass spectrum is determined, and related to the simultaneous presence or absence of other peaks in the same particle. These kind of results can then be correlated with the wind speed and direction, and provide information about the origin of the aerosol. In this study, six key compounds have been selected: carbon, sulfate, nitrate, chlorine, ammonium and sodium. Carbon particles have their origin in combustion sources. Sulfate and nitrate give information about secondary chemistry. Chlorine is present in the coal used for heating in the Krakow area. Ammonium and sodium were frequently observed species in the aerosols from Krakow. For every single spectrum, the presence or absence of the above mentioned compounds, and all their possible combinations within a particle, has been established. The result is 64 groups, corresponding to 64 hypothetical different types of particles. Using the algorithm, key species of relevant interest may be selected, and its occurrence tracked within the samples. Some of the relevant results are:
i) Indoor/outdoor: Characteristic peak (at m/z +42), which is believed to come from organic nitrogen containing particles, is observed more often inside for all apartments than outside (Figure 1). This kind of particles could be an indicator of human activity. Generally no striking difference between indoor and outdoor for coal and non-coal heated apartments is found. The sources of indoor aerosols come from the outdoor air.
ii) Site sampling: Carbon-containing particles highly dominate the aerosol. Most abundant groups contain internal mixtures of carbon, sulfate and sodium, with nitrate and chlorine in less amount (Figure 2). The four sites under examination show strong similarities in the single particle composition, and the day-by-day variations of the species follow a similar trend. This fact suggests that aerosol composition is uniform throughout the city. Furthermore, the relatively high amounts of chlorine detected in the particles, together with very high carbon content, suggest coal burning as a major source of pollution.
iii) Direct measurements: From the 17th to 19th January 2005, a smog episode occurred in Krakow. The SPASS measurements started at 20:00 o’clock on the 17th. At that time, the aerosols in Nowa Huta presented high amounts of single particles containing carbon, about 90%. Less than 20% of single particles contained sulfate. Throughout the night and into the morning of the 18th of January, the relative carbon content remained almost constant, whereas the sulfate content, together with chlorine, ammonium and nitrate raised steadily. The relatively high percentages of chlorine (over 30% in some periods) suggest that coal burning is a major source of aerosols. Regarding the mixing state, only a few of the 64 possible groups mentioned above are enough to represent most of the aerosol population. At 20:00 on the 17th January, around 30% of particles are composed of pure carbon, but the percentage falls down throughout the smog episode (Figure 3). The rest of the groups, representing over 70% of the aerosol population, are internally mixed with carbon, sodium, chlorine and sulfate.
This and other results of particle speciation and state of mixing will be presented.
MIRA SALAMA Daniel;
GRUENING Carsten;
JENSEN Niels;
CAVALLI Paolo;
PUTAUD Jean-Philippe;
RAES Frank;
2007-03-05
OPOCE
JRC36779
