32 research outputs found
Quantifying black carbon from biomass burning by means of levoglucosan - A one-year time series at the Arctic observatory Zeppelin
Levoglucosan, a highly specific tracer of particulate matter from biomass burning, has been used to study the influence of residential wood burning, agricultural waste burning and Boreal forest fire emissions on the Arctic atmosphere black carbon (BC) concentration. A one-year time series from March 2008 to March 2009 of levoglucosan has been established at the Zeppelin observatory in the European Arctic. Elevated concentrations of levoglucosan in winter (mean: 1.02 ng/m3) compared to summer (mean: 0.13 ng/m3) were observed, resembling the seasonal variation seen for e.g. sulfate and BC. The mean concentration in the winter period was 2-3 orders of magnitude lower than typical values reported for European urban areas in winter, and 1-2 orders of magnitude lower than European rural background concentrations. Episodes of elevated levoglucosan concentration lasting from 1 to 6 days were more frequent in winter than in summer and peak values were higher, exceeding 10 ng/m3 at the most.
Concentrations of elemental carbon from biomass burning (ECbb) were obtained by combining measured concentrations of levoglucosan and emission ratios of levoglucosan and EC for wildfires/agricultural fires and for residential wood burning. Neglecting chemical degradation by OH provides minimum levoglucosan concentrations, corresponding to a mean ECbb concentration of 3.7 +- 1.2 ng/m3 in winter (October-April) and 0.8 +- 0.3 ng/m3 in summer (May-September), or 8.8 +- 4.5% of the measured equivalent black carbon (EBC) concentration in winter and 6.1 +- 3.4% in summer. When accounting for chemical degradation of levoglucosan by OH, an upper estimate of 31-45% of EBC could be attributed to ECbb* (ECbb adjusted for chemical degradation) in winter, whereas no reliable (<100%) upper estimate could be provided for summer for the degradation rates applied. Hence, fossil fuel sources appear to dominate the European Arctic BC concentrations in winter, whereas the very wide range obtained for summer does not allow us to conclude upon this for the warm season.
Calculations using the Lagrangian particle dispersion model FLEXPART show that the seasonal variation of the modeled ECbb (ECbb,m) concentration compared relatively well with observationally derived ECbb from agricultural fires/wildfires during summer, and residential wood burning in winter. The model overestimates by a factor of 2.2 in winter and 4.4 in summer when compared to the observationally derived mean ECbb concentration, which provides the minimum estimate, whereas it underestimates by a factor of 2.3-3.3 in winter and a factor of 4.5 in summer when compared to ECbb*, which provides the upper estimate. There are indications of too-low emissions of residential wood burning in northern Russia, a region of great importance with respect to observed concentrations of BC in the European Arctic
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Light-absorbing carbon in Europe â Measurement and modelling, with a focus on residential wood combustion emissions
The atmospheric concentration of elemental carbon (EC) in Europe during the six-year period 2005â2010 has been simulated with the EMEP MSC-W model. The model bias compared to EC measurements was less than 20% for most of the examined sites. The model results suggest that fossil fuel combustion is the dominant source of EC in most of Europe but that there are important contributions also from residential wood burning during the cold seasons and, during certain episodes, also from open biomass burning (wildfires and agricultural fires). The modelled contributions from open biomass fires to ground level concentrations of EC were small at the sites included in the present study, <3% of the long-term average of EC in PM10. The modelling of this EC source is subject to many uncertainties, and it was likely underestimated for some episodes.
EC measurements and modelled EC were also compared to optical measurements of black carbon (BC). The relationships between EC and BC (as given by mass absorption cross section, MAC, values) differed widely between the sites, and the correlation between observed EC and BC is sometimes poor, making it difficult to compare results using the two techniques and limiting the comparability of BC measurements to model EC results.
A new bottom-up emission inventory for carbonaceous aerosol from residential wood combustion has been applied. For some countries the new inventory has substantially different EC emissions compared to earlier estimates. For northern Europe the most significant changes are much lower emissions in Norway and higher emissions in neighbouring Sweden and Finland. For Norway and Sweden, comparisons to source-apportionment data from winter campaigns indicate that the new inventory may improve model-calculated EC from wood burning.
Finally, three different model setups were tested with variable atmospheric lifetimes of EC in order to evaluate the model sensitivity to the assumptions regarding hygroscopicity and atmospheric ageing of EC. The standard ageing scheme leads to a rapid transformation of the emitted hydrophobic EC to hygroscopic particles, and generates similar results when assuming that all EC is aged at the point of emission. Assuming hydrophobic emissions and no ageing leads to higher EC concentrations. For the more remote sites, the observed EC concentration was in between the modelled EC using standard ageing and the scenario treating EC as hydrophobic. This could indicate too-rapid EC ageing in the model in relatively clean parts of the atmosphere
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A European aerosol phenomenology -4: Harmonized concentrations of carbonaceous aerosol at 10 regional background sites across Europe
Although particulate organic and elemental carbon (OC and EC) are important constituents of the suspended atmospheric particulate matter (PM), measurements of OC and EC are much less common and more uncertain than measurements of e.g. the ionic components of PM. In the framework of atmospheric research infrastructures supported by the European Union, actions have been undertaken to determine and mitigate sampling artefacts, and assess the comparability of OC and EC data obtained in a network of 10 atmospheric observatories across Europe. Positive sampling artefacts (from 0.4 to 2.8 Οg C/m3) and analytical discrepancies (between â50% and +40% for the EC/TC ratio) have been taken into account to generate a robust data set, from which we established the phenomenology of carbonaceous aerosols at regional background sites in Europe. Across the network, TC and EC annual average concentrations range from 0.4 to 9 Οg C/m3, and from 0.1 to 2 Οg C/m3, respectively. TC/PM10 annual mean ratios range from 0.11 at a Mediterranean site to 0.34 at the most polluted continental site, and TC/PM2.5 ratios are slightly greater at all sites (0.15â0.42). EC/TC annual mean ratios range from 0.10 to 0.22, and do not depend much on PM concentration levels, especially in winter. Seasonal variations in PM and TC concentrations, and in TC/PM and EC/TC ratios, differ across the network, which can be explained by seasonal changes in PM source contributions at some sites
Overvüking av langtransportert forurenset luft og nedbør. AtmosfÌriske tilførsler 2012.
NILU utfører overvüking av luft- og nedbørkjemi under ulike overvükingsprogrammer ved en rekke mülesteder i Norge. Denne rapporten beskriver resultatene fra 2012, og disse er sammenlignet med tidligere ür
Overvüking av langtransportert forurenset luft og nedbør. AtmosfÌriske tilførsler 2011.
NILU utfører overvüking av luft- og nedbørkjemi under ulike overvükingsprogrammer ved en rekke mülesteder i Norge. Denne rapporten beskriver resultatene fra 2011, og disse er sammenlignet med tidligere ür