Investigation of particulate matter originating from wood combustion in residential areas

During winter especially in residential villages, wood is used as a renewable fuel to a certain extent for room heating. Smoke emitted from wood buming in such areas can be a significant contributor to regional haze and high PMlO concentrations. Exposure to elevated levels of wood smoke is likely to have both short and long-term negative health effects. This includes the increasing risk of cancer caused by some of wood smoke compounds. Therefore, the objective of this study was to find a method to determine the contribution of wood smoke particles to the total PMlO load in residential areas. The developed method was applied during two winter seasons in two residential areas. From November 2005 to March 2006 particlephase PMlO samples were collected in Dettenhausen near Stuttgart which is surrounded by forests ofthe „Naturpark Schönbuch“. Within an UBA (Federal Environment Agency) project samples were also collected during winter 2006/07 in the residential site Bechtoldsweiler near Hechingen. These ambient air samples were collected on pre-baked quartz fibre filters and analysed by gas chromatography mass spectrometry (GC-MS). Forty-six different organic compounds were detected and quantified in this study including 16 US EPA priority pollutants (PAHs), different organic wood smoke tracers, primarily 21 species ofsyringol and guaiacol derivatives which result from the pyrolysis of wood lignin, a thermal degradation products of wood cellulose (e. g. levoglucosan) and resin acid (e. g. dehydroabietic acid). The concentrations of these compounds in ambient air were compared with the fingerprints of emissions from hardwood and softwood combustion carried out in test facilities at Universität Stuttgart and field investigations at a wood stove during real operation in Dettenhausen. It was observed that in the ambient air PMlO samples the wood combustion PARs were detected in higher concentrations than other PARs. Syringol and its derivatives were found in large amounts in hardwood combustion but were not detected in softwood combustion emissions. On the other hand, guaiacol and its derivatives were found in softwood combustion but were not detected in significant quantities from hardwood combustion. So, these compounds can be used as typical tracer compounds for the different types of wood combustion emissions. In ambient air samples, both syringol and guaiacol derivatives were found which indicates the wood combustion contribution to the PM load in such residential areas. Levoglucosan, which is well known in the literature described as typical tracer for wood combustion was detected in relatively high concentrations in all ambient PM lO samples. From the correlation ofambient concentrations of levoglucosan and dehydroabietic acid with PMlO, it can be qualitatively demonstrated that in the investigated residential site about 36 to 64% of ambient mass concentrations ofPM10 can be attributed to residential wood buming. A source apportionment model, the „Positive Matrix Factorization“ was implemented to quantify the wood smoke contribution to the winter ambient air pollution in the residential area. Wood smoke was found as the largest contributor (49%) to the PMlO-bound organic loadings in the winter ambient air ofthe investigated residential area.