Assessment of the primary and secondary contributions from wood burning to the PM10 OC for a rural site in Belgium by making use of molecular markers and PMF Willy Maenhaut1, Reinhilde Vermeylen2, Magda Claeys2, Ariane Kahnt2 and Jordy Vercauteren3 1Dept. Analytical Chemistry, Ghent University, Belgium 2Dept. Pharmaceutical Sciences, University of Antwerp, Belgium 3Flemish Environment Agency (VMM), Antwerpen, Belgium Hamme study 2010-2011 extended

Introduction In 2010-2011 a 1-year study conducted 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 the primary WB tracers levoglucosan (L), mannosan (M), and galactosan (G) [Maenhaut et al., STE, 2012] In a follow-up study other molecular markers measured for one of the 7 sites, i.e., for the rural background site of Hamme, which was particularly impacted by WB [Kahnt et al., AE, 2013]; these other WB markers were: the resin acid dehydroabietic acid (DHAA) nitroaromatic compounds (secondary) nitrophenols (NP; MW 139) 4-nitrocatechol (4-NC; MW 155) methyl-nitrocatechols (MNC; MW 169) dimethyl-nitrocatechols (DMNC; MW 183) α-pinene related nitrooxy-organosulfates (NOS) with MW 295 The combined data of the two studies now used to assess the primary and secondary contributions from WB to the PM10 OC for the site of Hamme hereby making use of positive matrix factorization (PMF), EPA PMF 5 Hamme study 2010-2011 extended

Sampling From February 2010 to February 2011 PM10 aerosol samples simultaneously taken every 4th day at 7 monitoring sites in Flanders, Belgium on 47-mm diam. Pallflex quartz fibre filters The site of Hamme (red circle) particularly impacted by biomass burning Hamme study 2010-2011 extended

Hamme : in a rural area with individual houses In the neigbourhood of the site are several inhabitants who use wood as fuel Hamme study 2010-2011 extended

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 thermal-optical instrument from Sunset Lab using NIOSH temperature protocol, transmittance (TOT) Levoglucosan, mannosan and galactosan determined by gas chromatography / mass spectrometry (GC/MS) Dehydroabietic acid (DHAA), nitroaromatic compounds [i.e., nitrophenols (NP), 4-nitrocatechol (4-NC), methyl-nitrocatechols (MNC) and dimethyl-nitrocatechols (DMNC)] and α-pinene related nitrooxy-organosulfates (NOS) measured by liquid chromatography / mass spectrometry (LC/MS) Hamme study 2010-2011 extended

Some more info on the LC/MS compounds Biomass burning aerosol (BBA) contains a significant fraction of nitrocatechols (MW 155) and methyl-nitrocatechols (MW 169), which were proposed as tracer compounds for processed (secondary) BBA [Iinuma et al., EST, 2010] Further studies identified also other homologues of methyl-nitrocatechols (i.e., dimethyl-nitrocatechols) as abundant compounds in ambient filter samples [Kitanovski et al., RCM, 2012; JCA, 2012] Nitrocatechols and their methyl homologues were shown to correspond to the abundant yellow-coloured compounds of humic-like substances that were isolated from BBA [Claeys et al., Environ. Chem., 2012] Elemental formulae of the species that were targeted in the LC/MS analysis isomers of NP (nitrophenols, C6H5NO3, MW 139) 4-NC (4-nitrocatechol, C6H5NO4, MW 155) MNC (methyl-nitrocatechols, C7H7NO4, MW 169) DMNC (dimethyl-nitrocatechols, C8H9NO4, MW 183) α-pinene related NOS (nitrooxy-organosulfates, C10H17O7SN, MW 295) DHAA (dehydroabietic acid, C20H28O2, MW 300) Hamme study 2010-2011 extended

Structures of the LC/MS compounds Hamme study 2010-2011 extended

Further info on the LC/MS analysis Sections of the filter samples were spiked with 2 internal recovery standards (see Table below), extracted with methanol and analysed by liquid chromatography combined with negative ion electrospray ionisation mass spectrometry (LC/(–)ESI-MS) Quantification was performed using different authentic or surrogate standards and applying an internal calibration method (see Table below) Hamme study 2010-2011 extended

Further info on the LC/MS analysis (continued) Extracted Ion Chromatograms (EICs) of the targeted compounds (m/z 138, 154, 168, 182, 294, 299) and the internal recovery standards (m/z 138, 237) from a filter sample are shown in the Figure below; the isomers are indicated by numbers Hamme study 2010-2011 extended

Time series of Levo and LC/MS compounds for Hamme highest conc. in winter, followed by fall, but occasionally also high levels in spring and summer NOS poorly correlated with Levo and with most nitro-aromatics high levels observed in spring and summer Hamme study 2010-2011 extended

Medians and interquartile ranges as a function of season Hamme study 2010-2011 extended

Medians and interquartile ranges as a function of season Hamme study 2010-2011 extended

PMF Included in the PMF: data for the 92 samples from Hamme PM10 mass OC, EC 9 individual or summed molecular markers, i.e., L, M, G DHAA NP, 4-NC, MNC, DMNC NOS Constrained 4-factor solution retained as final solution (Qtrue/Qexp: 2.53); the 4 factors (with their overall average percentage contributions to the experimentally measured PM10 mass) were primary wood burning (PWB; 16%) secondary wood burning related to the nitro-aromatic compounds (SWB-NA; 1.4%) NOS-related aerosol (NOS-A; 23%) other carbonaceous aerosol (OCA; 51%) Hamme study 2010-2011 extended

4-factor constrained PMF solution: factor names, key species in each factor, source attribution Factor name Key species Source attribution PWB OC, L, M, G, DHAA wood burning (primary) SWB-NA NP, 4-NC, MNC, DMNC wood burning (sec. NA) NOS-A NOS mixed OCA OC, EC anthropogenic (non-WB) key species are defined as those species with typically at least one third of their mass, on average, attributed to the factor Hamme study 2010-2011 extended

Annual and seasonal mean concentrations of the experimental OC mass and of the OC in the 4 factors although the NOS were poorly correlated with the primary and the nitroaromatic secondary WB tracers, it is interesting to note that NOS-A shows a similar seasonal pattern as PWB and SWB-NA, which suggests that it contains a substantial contribution from wood burning Hamme study 2010-2011 extended

Discussion on the source attribution of the 4 factors PWB (with OC, L, M, G, DHAA) primary wood burning SWB-NA (with NP, 4-NC, MNC, DMNC) secondary formation (oxidation) from VOCs that are emitted during biomass burning (e.g., m-cresol) NOS-A (with α-pinene related NOS) during spring and summer: photo-oxidation of α-pinene in the presence of NOx or its oxidation through NO3 radical reactions (thus natural, biogenic SOA) during fall and winter: to a large extent due to oxidation of α-pinene that is emitted from burning softwood logs in domestic fireplaces and/or stoves (thus anthropogenic WB SOA) OCA (with OC, EC) likely mostly anthropogenic (and primary) with as main source: fossil fuel combustion (traffic) Hamme study 2010-2011 extended

Annual and seasonal mean % contributions from the 4 factors to the experimental OC mass OCA provides the largest contribution, with the exception of Winter when PWB provides the largest contribution mean % contribution in Winter from PWB + SWB-NA : 52% mean % contribution In Winter from PWB + SWB-NA + NOS-A: 75% Hamme study 2010-2011 extended

Scatter plots of PMF-derived SWB-NA PM and OC vs Scatter plots of PMF-derived SWB-NA PM and OC vs. Sum (4-NC + MNC + DMNC) SWB-NA PM and OC vs. 4-NC PM_SWB-NA = 95 * 4-NC [R2 = 0.86] OC_SWB-NA = 47 * 4-NC [R2 = 0.86] SWB-NA PM and OC vs. 4-NC PM_SWB-NA = 95 * 4-NC [R2 = 0.86] OC_SWB-NA = 47 * 4-NC [R2 = 0.86] Hamme study 2010-2011 extended

Scatter plots of PMF-derived “wood burning” PM and OC (in each case sum of PWB + SWB-NA) vs. Levo Hamme study 2010-2011 extended

Estimation of WB PM and OC from molecular markers Various WB PM and OC PM_PWB = 12.7 * Levo [R2 = 0.87] PM_PWB + SWB-NA = 14.0 * Levo [R2 = 0.93] PM_PWB + SWB-NA + OS-A = 29 * Levo [R2 = 0.48] PM_WB = 10.7 * Levo [Schmidl et al., AE, 2008; Austrian wood stoves] PM_WB = 22.6 * Levo [Maenhaut et al., STE, 2016; PMF 4 UB sites in Flanders] OC_PWB = 4.72 * Levo [R2 = 0.87] OC_PWB + SWB-NA = 5.37 * Levo [R2 = 0.94] OC_PWB + SWB-NA + OS-A = 6.76 * Levo [R2 = 0.95] OC_WB = 5.59 * Levo [Schmidl et al., AE, 2008 ; Austrian wood stoves] OC_WB = 9.7 * Levo [Maenhaut et al., STE, 2016; PMF 4 UB sites in Flanders] Hamme study 2010-2011 extended

Conclusions The mean % contributions from WB to the expt. OC in Winter were: PWB 42% SWB-NA 10% OS-A 21% Sum (PWB + SWB-NA + OS-A) : 75% OCA 26% The contribution from secondary WB OC to the total WB OC is clearly substantial SWB-NA is one quarter of PWB OS-A represents half of PWB Inclusion of other secondary WB tracers in future studies is suggested to arrive at a more complete assessment of the secondary contribution from WB Hamme study 2010-2011 extended

Further conclusions From scatter plots of the PMF-derived wood smoke OC_PWB + SWB-NA and PM_PWB + SWB-NA versus levoglucosan, we arrive at conversion factors of 5.4 and 14.0, respectively these are substantially lower than the 9.7 and 22.6 derived from the PMF on the data from 4 UB sites in Flanders [Maenhaut et al., STE, 2016] they are similar to the 5.6 and 10.7 for Austrian wood stoves [Schmidl et al., AE, 2008] it is concluded that factors derived from UB sites are not applicable to a rural site, which is heavily affected by nearby WB sources conversion factors that are generally applicable for Flanders do not exist Hamme study 2010-2011 extended

Thank you for your attention Hamme study 2010-2011 extended

Hamme study 2010-2011 extended

Hamme study 2010-2011 extended

Scatter plots of PMF-derived “wood burning” PM and OC (in each case sum of PWB, SWB-NA & NOS-A) vs. Levo Hamme study 2010-2011 extended

Scatter plots of PMF-derived “wood burning” PM and OC (in each case sum of PWB, SWB-NA & NOS-A) vs. Levo with 1 data point for PM excluded Hamme study 2010-2011 extended