Benchmarking source specific isotopic ratios of levoglucosan to better constrain the contribution of domestic heating to the air pollution

We report source specific isotope ratios of levoglucosan, the specific biomass burning tracer, in aerosol particles from the combustion of selected woods used for domestic heating in Europe, of coals containing cellulose (lignites) as well as of corn, a C4 plant. Here, we combine compound specific delta C-13 measurements of levoglucosan with total carbon delta C-13 of parent materials, to assess isotopic fractionations due to biosynthetic pathways or combustion processes. Levoglucosan formed during the combustion of cellulose from coals shows with delta C-13 of-21.1%o and-18.6%o a moderate enrichment in the heavier isotope compared to the C3 plant samples. Contrarily, observed levoglucosan isotope ratios of-25.0 to-21.5%o for C3 plant samples are significantly lower than for the C4 plant sample (-12.4%o), as expected from the stronger C-13 discrimination during the carbon fixation process by C3 compared to C4 plants. Overall, the C4 plant sample shows a C-13 enrichment in all bulk measurements, on average by 12.2%o, 14.2%o and 14.2%o for total carbon (TC) in aerosol particle, whole plant/ coal material and cellulose samples, respectively. Further, delta C-13 measurements of levoglucosan and TC for biomass burning aerosol particles, bulk plant/coal and cellulose in C3 plant samples agree well with the published observations. The combined levoglucosan/TC isotopic analyses can be used to differentiate among C3/ coal/C4 origin of the smoke emissions from the cellulose-containing-fuel combustion. Noticeably, there is a consistent delta C-13 offset between C3 plant material and levoglucosan, which allows deriving emission levoglucosan isotope ratios when the combusted plant types are known.