Source apportionment of Swiss carbonaceous aerosols using radiocarbon analyses of different fractions

References:

S. Szidat et al., 2007: Dominant impact of residential wood burning on particulate matter in Alpine valleys during winter, Geophys. Res. Lett., 34, L05820, doi:10.1029/2006GL028325.

S. Szidat et al., 2006: Contributions of fossil fuel, biomass burning, and biogenic emissions to carbonaceous aerosols in Zürich as traced by 14C. J. Geophys. Res. 111, D07206, doi:10.1029/2005JD006590

Acknowledgements:

Cantons of Lucerne, Grisons and Zürich

Swiss Federal Office for the Environment (BAFU)

N. Perron1, M. N. Wehrli2, S. Szidat1,2, J. Sandradewi1, A. S. H. Prévôt1, U. Baltensperger1

1Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, Villigen, Switzerland, 2Dept. of Chemistry and Biochemistry, University of Bern, Bern, Switzerland

Aerosols were collected on quartz fiber filters using HiVol samplers, at four different sites in Switzerland.

AEROSOL SAMPLING SITES

Radiocarbon : a powerful tracer that enables to quantify the fossil and non-fossil contributions to the

OC and EC fractions of the carbonaceous aerosol (TC).

14C SOURCE APPORTIONMENT RESULTS

Alpine valley (Roveredo, Dec 2005)

OCnon fossil is by far the most important fraction. At least two thirds of it can be attributed to biomass burning.

High contribution from heating wood stoves, which surpassed by far the traffic-related emissions, even close to the highway.

Swiss Plateau (Reiden, Sedel and Zürich, Jan-Feb 2006)

Comparable particulate carbon composition, in spite of very different environments.

Little influence of local sources: the air composition on the Swiss Plateau was controlled by a several-day accumulation of regional sources, due to persistent strong temperature inversions over a large area.

Fig. 2: Sites in Switzerland where winter 2005/2006 campaigns were conducted.

Fig. 1: Fossil and non-fossil contributions to the OC and EC fractions.

In all cases, EC is dominated by fossil sources.

OC is dominated everywhere by non-fossil sources.

The contribution of OCbiomass burning versus secondary production from biogenic emissions was estimated by the EC/OC wood burning emission ratio of 0.16 ± 0.05.

Biomass burning is always significant. In the case of Roveredo, the contribution of secondary aerosols is as high as the uncertainty of the estimation.

TC

14C-depleted

Characterised by contemporary 14C/12C ratios

OC

EC

Fossil fuel combustion

Primary and secondary production

Primary emission

Biomass burning

Secondary biogenic

production

Primary and secondary production

Primary emission

Sedel: rural environment

Roveredo: Alpine valley village, close

to a highway

Reiden: motorway site

Zürich: urban background

Fig. 3: Average percentage contributions of fossil and biomass-burning sources to EC and fossil and non-fossil sources to OC for our four sampling sites in winter 2005/2006. The values in brackets are as high as their corresponding uncertainties.

CONCLUSIONS

RoveredoSedel

14%

48% (6%)

(25%)

7%5%13%

24%

37%

21%

5%

17%

22%

39%

17%

4%17%

23%

27%

29%

Reiden ZürichECfossil

ECbiomass burning

OCfossil

OCbiogenic

OCbiomass burning