Abstract
The elemental carbon (EC)-tracer method was applied to PM10 and PM1 data of three sampling sites in the City of Berlin from February to October 2010. The sites were characterized by differing exposure to traffic and vegetation. The aim was to determine the secondary organic carbon (SOC) concentration and to describe the parameters influencing the application of the EC-tracer method. The evaluation was based on comparisons with results obtained from positive matrix factorization (PMF) applied to the same samples. To obtain site- and seasonal representative primary OC/EC-ratios ([OC/EC]p), the EC-tracer method was performed separately for each station, and additionally discrete for samples with high and low contribution of biomass burning. Estimated SOC-concentrations for all stations were between 11% and 33% of total OC. SOC-concentrations obtained with PMF exceeded EC-tracer results more than 100% at the park in the period with low biomass burning emissions in PM10. The deviations were besides others attributed to the high ratio of biogenic to combustion emissions and to direct exposure to vegetation. The occurrences of biomass burning emissions in contrast lead to increased SOC-concentrations compared to PMF in PM10. The obtained results distinguish that the EC-tracer-method provides well comparable results with PMF if sites are strongly influenced by one characteristic primary combustion source, but was found to be adversely influenced by direct and relatively high biogenic emissions.
Highlights
Fine particulate matter (PM) in the atmosphere is of great importance due to climatic effects [1,2]and health aspects [3,4]
PM10 and PM1 samples were collected at three sites in Berlin with different vegetation influences, namely an urban park in the center of the city, referred to as site with high vegetation stock (HV), a traffic station with low vegetation stock (LV) in the west of the city surrounded by dwellings, and an urban background station in the southeast of Berlin with intermediate vegetation density which is typical for the region
The organic carbon (OC)/elemental carbon (EC)-ratios (Table 1) observed at the HV and regV sites are in a similar range as ratios reported for PM2.5 samples from urban sites in California [34] or Pittsburgh [16]
Summary
Fine particulate matter (PM) in the atmosphere is of great importance due to climatic effects [1,2]. The results of the EC-tracer method are assessed by comparing them to those determined by PMF-analysis in a previous study, which was based on the detection of single, mainly biogenic compounds determined for the same samples [14,22] This approach provides an extensive analysis of SOC-concentrations obtained with the EC-tracer method by (a) considering seasonal variations with regard to biomass burning emissions and vegetation; (b) by comparing site-specific primary ratios and (c) by comparing the applications of two established SOC-calculation techniques, which is a useful instrument to verify the results and the study is unique in this detailedness. SOA-events provide the potential to give suggestions for the application
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