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Analysis of PM10 using Scanning Electron MicroscopyComparison between a Traffic Site and a Forest Site

S. Wagener1, J.K. Gietl, O. Klemm

University of Münster, Institute of Landscape Ecology, Germany1now IUTA Duisburg e.V.

IntroductionAirborne atmospheric particulate material with a diameter < 10 μm (PM10) was collected on 12 days between November 2006 and January 2007 at a traffic site in Münster, and a forest site in the “Eggegebirge” mountain range (NW Germany). The measurements were performed synchronously twice per day. About 3000 individual particles were analyzed for morphology and element contents applying SEM-EDX.

Method and AnalysisFive-stage Berner type impactors with aluminium and Tedlar® foils were used for sampling. Single particle analysis was carried out by using a scanning electron microscopy, type JEOL 840 for morphology, and energy dispersive X-ray (EDX) spectrometry for element contents. Based on the element analysis, particles were assigned to groups. The percentage of each group of the whole of all analysed particles was computed. With the morphology and the correlations between the percentages of all groups, the particle groups were identified.

sulphateiron-richsilicate-rich oxygen-rich

For this study, data access was granted by the Landesamt für Natur, Umwelt und Verbraucherschutz NRW. Equipment access was granted by the Institute for Planetology, University of Münster, especially with the help of Thorsten Grund. For further information please contact: [email protected].

Percental composition of particulate material as function of impactor stages

To investigate the different influences on particle composition, the aerosol was analysed regarding the following aspects:

Influence of the air massesA correlation between sea salt and air masses of marine origin is found at both measurement sites

Influence of the time of dayIron-rich and silicate-rich particle occurrence are higher in the afternoon

Influence of the locationSoot and oxygen-rich particles are much more abundant at the traffic site, sodium-rich particles in the Eggegebirge

Influence of the particle sizeThe most obvious difference has been found between the impactor stages; whereas the first two stages (smallest particles) are dominated by soot and sulphate, all groups are found in stages 3 and 4 (stage 5 has not been analysed)

European Aerosol Conference, 24 – 29. August 2008; Helexpo Thessalonike, Greece

Poster T10A042P; Session PMx / PM10 / PM2.5

Corresponding author: Otto Klemm2

ConclusionsThe sampling location, the time of day and the air masses essentially affect the percental allocation of the aerosol composition. The appearance of the particle groups is mainly determined by the different stages. Thus it appears, that the largest differences of particle composition is affected rather by the different size classes than by any other aspects.

A five stage Berner type impactor for the sampling ; Cutoff diameters: Stage 1:

0.053 µm; stage 2: 0.19 µm; stage 3: 0.42 µm; stage 4: 1.2 µm; stage 5: 3.5 µm

Source Identification Using the information from these results and the morphology, source identification could be performed.

Possible sources of the identified particle groups

Münster Eggegebirge

soot traffic, domestic fuel domestic fuel, (traffic)

C-residual presumably traffic, domestic fuelunknown, presumably traffic, domestic fuel

sea saltseaspray, other unknown anthropogenic sources seaspray

Na-richseaspray, combustion of biomass, other unknown anthropogenic sources

seaspray

sulphate(mainly (NH4)2SO4)

agriculture, traffic agriculture