1. Flanders 4-sites study 2011-2012
Sources of the PM10 aerosol in Flanders, Belgium, and re-evaluation of the contribution from wood burning Willy Maenhaut1, Reinhilde Vermeylen2, Magda Claeys2, Jordy Vercauteren3 and Edward Roekens3 1Dept. Analytical Chemistry, Ghent University, Belgium 2Dept. Pharmaceutical Sciences, University of Antwerp, Belgium 3Flemish Environment Agency (VMM), Antwerpen, Belgium
Flanders 4-sites study

2. Motivation for this re-evaluation study
This re-evaluation study is based on samplings that were done at 4 sites in Flanders (Belgium) during a full year ( )
to evaluate the contribution from wood burning (WB) and other sources: positive matrix factorization (PMF) was applied to a multi-species data set
In a previous study (limited to WB), samplings were done at 7 sites in Flanders during a full year ( )
only a limited number of species were measured, with one of them being levoglucosan (levo), which is a very important wood burning marker
In the study [Maenhaut et al., STE, 2012] the contribution from WB to the PM10 mass and the PM10 organic carbon (OC) was assessed by making use of conversion factors that were obtained by Schmidl et al., AE [2008] in burning experiments with Austrian wood stoves
WB PM10 mass = levo * 10.7
WB PM10 OC = levo * 5.59
One may wonder whether these factors are applicable to WB in Flanders
Flanders 4-sites study

3. Introduction for the 2010-2011 study
In Flanders (Belgium) we are struggling with too many exceedances of the 50 µg/m3 daily PM10 mass limit
in the EU: only 35 exceedances per year allowed at any given location
thus, of interest to examine the cause of possible exceedances
Wood burning may provide a substantial contribution to the PM10 aerosol mass, as appeared from studies in several European countries (e.g., Switzerland, Austria)
Over a decade ago, Simoneit et al., AE [1999] introduced levoglucosan as an indicator for wood burning
Levoglucosan (1,6-anhydro-β-D-glucopyranose, C6H10O5) arises from the pyrolysis of cellulose, the main building material of wood, at temperatures higher than 300 °C
Levoglucosan is accompanied by other minor stereoisomeric monosaccharide anhydrides in atmospheric aerosols, with mannosan (1,6-anhydro-β-D-mannopyranose) and galactosan (1,6-anhydro-β-D-galactopyranose) being the most important ones
the latter compounds result from the pyrolysis of hemicelluloses, but the emitted amounts are substantially lower than those of levoglucosan
Flanders 4-sites study

4. Introduction for the 2010-2011 study (continued)
First use of levoglucosan in Europe to quantify the contribution from wood burning was made by Zdráhal et al., EST [2002]
35% of OC in PM10 attributed to wood burning for a 1998 winter campaign (8 daily samples) in Gent
In recent years a lot of work on the use of levoglucosan as a wood burning marker done by the group of Hans Puxbaum, TU Vienna, e.g.,
Schmidl et al., AE [2008] provided source profiles (ratio levoglucosan/OC and ratio levoglucosan/PM10_mass) for burning of hard woods (beech) and soft woods (spruce) in commonly used wood stoves
ratio levoglucosan/mannosan quite different for beech and spruce
%spruce burned deduced from ratio levoglucosan/mannosan
Caseiro et al., AE [2009] assessed the contribution from wood burning for a number of sites in Austria
Flemish Environment Agengy (VMM) wanted to find out what the contribution from wood burning to PM10 was over a full year for 7 sites in Flanders
92 daily samples per site
Flanders 4-sites study

5. Flanders 4-sites study 2011-2012
Sampling
From 7 February 2010 to 6 February 2011 PM10 aerosol samples simultaneously taken every 4th day at 7 monitoring sites in Flanders, Belgium
on 47-mm diameter Pallflex quartz fibre filters
Two of the sites (i.e., Gent and Borgerhout) are urban background sites; Mechelen is a suburban background site, and the other 4 sites are rural background sites, whereby Hamme and Lier were expected to be particularly impacted by biomass burning
Flanders 4-sites study

6. Flanders 4-sites study 2011-2012
Gent : in the Baudelo park in the North-East of the city
Least polluted of the 2 urban background sites
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7. Flanders 4-sites study 2011-2012
Analyses
PM10 mass determined by weighing of the filters at 20 °C and 50% relative humidity [done by VMM]
Organic, elemental, and total carbon [OC, EC, and TC (= OC + EC)] measured with a dual photo-detector (2PD) thermal-optical instrument from Sunset Lab
using NIOSH temperature protocol
transmission (TOT) and reflectance (TOR) simultaneously measured
TOT data retained for further evaluation
Levoglucosan, mannosan, and galactosan measured by gas chromatography / mass spectrometry (GC/MS) after trimethylsilylation, using method described in Pashynska et al., J. Mass Spectrom. [2002], but
extraction with methanol
use made of a different recovery standard (RS)
and slightly modified GC temperature program employed
Flanders 4-sites study

8. OC/EC analysis by thermal-optical methods
quartz fibre filter punch heated in quartz oven
first phase (in pure He): OM compounds desorb -> CO2 -> CH4
second phase (in He/O2 mixture): EC and PC combusted -> CO2 -> CH4
transmission (TOT) or reflectance (TOR) of laser light through/by the filter punch continuously monitored
Flanders 4-sites study

9. Flanders 4-sites study 2011-2012EC
OC1 PC
OC = OC1 + PC (with PC: pyrolytic carbon) : area below the blue line prior to the OC/EC split point (vertical brown line)
EC : area below the blue line after the OC/EC split point
Flanders 4-sites study

10. Flanders 4-sites study 2011-2012
Full brown line : laser transmission (T) signal
vertical full brown line : OC/EC split point for T
Dashed purple line : laser reflectance (R) signal
vertical dashed purple line : OC/EC split point for R
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11. Flanders 4-sites study 2011-2012

12. Flanders 4-sites study 2011-2012
Total ion current (TIC) chromatogram [relative abundance (R.A.) versus time] obtained for the sample that was collected on 23 February 2010 in Hamme. The numbered peaks are for the following compounds:
1: galactosan: 60.6 ng/cm2;
2: mXP: 510 ng/cm2 (added);
3: mannosan: 145 ng/cm2;
4: levoglucosan: 826 ng/cm2.
Flanders 4-sites study

13. Time series for %OC from wood burning at the 7 sites
High values in winter & fall; low levels in spring & summer
Time series for Hamme quite peculiar
Flanders 4-sites study

14. Time series for %PM from wood burning at the 7 sites
High values in winter & fall; low levels in spring & summer
Time series for Hamme quite peculiar
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15. Flanders 4-sites study 2011-2012
7-site study in Flanders in (Chemkar-3) [Maenhaut et al., STE, 2012]
In winter (blue) for 6 of the 7 sites: around 10% of PM10 mass, on average, from wood burning
At Hamme in winter: 22% of PM10 mass, on average, from wood burning
Flanders 4-sites study

16. Introduction for the new (2011-2012) study
In we conducted a 1-year study at 7 sites in Flanders (Belgium) to assess the contribution from wood burning (WB) to the PM10 mass and the PM10 organic carbon (OC) using levoglucosan (levo) as WB tracer and conversion factors of Schmidl et al., AE [2008], see Maenhaut et al., STE [2012]
WB PM10 mass = levo * 10.7
WB PM10 OC = levo * 5.59
In similar 1-year study at 4 urban background sites in Flanders, i.e., Antwerpen, Gent, Brugge, and Oostende
same species measured as in the study, but in addition: water-soluble inorganic species and elements
to assess WB: same approach used as in the study, but in addition: positive matrix factorization (PMF), EPA PMF 5
Flanders 4-sites study

17. Location of the 4 sampling sites
Brussels
Flanders 4-sites study

18. Flanders 4-sites study 2011-2012
Sampling and analyses
From 30 June 2011 to 1 July 2012 PM10 aerosol samples simultaneously taken every 4th day at 4 sites in Flanders, Belgium
on 47-mm diameter Pallflex quartz fibre filters
PM10 mass determined by weighing of the filters at 20 °C and 50% relative humidity [done by VMM]
Organic, elemental, and total carbon [OC, EC, and TC (= OC + EC)] measured with thermal-optical instrument from Sunset Lab
using NIOSH temperature protocol, transmittance (TOT)
Levoglucosan, mannosan and galactosan determined by gas chromatography / mass spectrometry (GC/MS)
8 water-soluble ions measured by ion chromatography (IC)
15 elements determined by a combination of inductively coupled plasma atomic emission spectrometry and mass spectrometry
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19. Flanders 4-sites study 2011-2012
PMF receptor model
Receptor models are mathematical approaches for quantifying the contribution of sources to samples based on the composition (or fingerprint) of the sources
A speciated data set can be viewed as a data matrix X of i by j dimensions, in which i number of samples and j chemical species were measured, with uncertainties u
The goal of receptor models is to solve the chemical mass balance (CMB) between measured species concentrations and source profiles, as shown in the Equation below, with number of factors p, the species profile f of each source, and the amount of mass g contributed by each factor to each individual sample (see Equation) where eij is the residual for each sample/species
X = G * F + E
Flanders 4-sites study

20. PMF receptor model (continued)
The CMB equation can be solved using multiple models, including EPA CMB, EPA Unmix, and EPA Positive Matrix Factorization (PMF)
PMF is a multivariate factor analysis tool that decomposes a matrix of speciated sample data into two matrices: factor contributions (G) and factor profiles (F)
the factor profiles need to be interpreted by the user to identify the source types that may be contributing to the sample using measured source profile information, and emissions or discharge inventories
The PMF method is described in greater detail by Paatero and Tapper, Environmetrics,1994; Paatero, CILS, 1997]
X = G * F + E
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21. PMF: Selected base results as a function of the number of factors
10-factor base solution retained
contributions from WB to PM10 mass and OC quite robust
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22. Flanders 4-sites study 2011-2012
PMF: 10-factor base solution, factor names and key species in each factor
key species are defined as those species with typically at least one third of their mass, on average, attributed to the factor
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23. Flanders 4-sites study 2011-2012

24. Flanders 4-sites study 2011-2012
PMF: wood burning (WB)
The average contributions of wood smoke for the four sites were quite substantial in winter
for the PM10 mass: from 12.5 to 20%
for the PM10 OC: from 47 to 64%
Wood burning appeared to be also a notable source of As, Cd, and Pb
these three elements had similar or higher annual median percentage apportionments to WB as K+, which is typically used as an indicator element for wood smoke
for Gent and Brugge: between 10 and 20% from WB
Flanders 4-sites study

25. Wood burning: levo approach vs. PMF
the data derived from levoglucosan compared very well with those obtained in our previous study using the same approach
however, the PMF data are substantially larger than those derived from levoglucosan
Flanders 4-sites study

26. Flanders 4-sites study 2011-2012
Scatter plots of PMF-derived WB PM (brown squares) and OC (red diamonds) vs. levo and regression lines, forced through the origin
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27. Flanders 4-sites study 2011-2012
Conclusion
The levoglucosan conversion factors of Schmidl et al. [2008] do not seem to be applicable for WB in Flanders
the uncertainty associated with the use of the Schmidl et al. [2008] conversion factors for Flanders was estimated to be of the order of 30% in our study [Maenhaut et al., 2012]
From scatter plots of the PMF-derived wood smoke PM10 OC and PM versus levoglucosan, we arrive at conversion factors of 9.7 and 22.6, respectively
it is recommended to use these latter factors for deriving the contribution from wood smoke when making use of levoglucosan as single marker in future studies in Flanders
it is estimated that the percentage uncertainty, which is associated with these conversion factors, is smaller than 20%
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28. Flanders 4-sites study 2011-2012
Further conclusions
The impact from wood burning on the PM10 mass and OC levels in Flanders is substantially larger than previously thought
The contribution of the heavy oil burning component showed a clear tendency to decrease with distance from the coast
this was likely caused by the larger impact from ship emissions at the sites closer to the coast
The non-ferrous metals factor, which was characterized by As, Cd and Pb, exhibited by far its highest level at Antwerpen
there is a major non-ferrous metals plant in Hoboken, which is located within greater Antwerpen, and this plant is still a large source of airborne As, Cd, and Pb [VMM, 2014]
Wood burning was also a notable source of As, Cd, and Pb
these three elements had similar or higher annual median percentage apportionments to wood burning as K+, which is typically used as an indicator element for wood smoke
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29. Flanders 4-sites study 2011-2012
This work was published:
Maenhaut et al., Sci. Total Environ. 562 (2016)
Thank you for your attention
Flanders 4-sites study

30. Flanders 4-sites study 2011-2012