Title : Markers of PM produced by biomass combustion and development of a sampling and analysis technique
Abstract:
Biomass combustion is a relevant source of atmospheric particulate matter (PM), contributing to the emission of inorganic species, organic micropollutants and specific molecular markers associated with the thermal degradation of lignocellulosic materials. Among these compounds, levoglucosan, together with its isomers mannosan and galactosan, is widely recognized as a suitable tracer for PM produced by biomass burning, since it originates from the combustion and pyrolysis of cellulose and hemicellulose. However, the reliability of levoglucosan as a marker strongly depends on the sampling strategy adopted, particularly because of its semi-volatile behavior. This work focuses on the development and evaluation of a fixed-source sampling and analytical technique for the determination of total levoglucosan emitted during biomass combustion. The proposed approach combines an isokinetic sampling probe equipped with a quartz fiber filter, used to collect the particle-bound fraction, with a series of refrigerated impingers filled with Milli-Q water, designed to trap the volatile fraction passing through the filter. The method was applied to combustion tests performed on two agricultural residual biomasses, rice straw and wheat straw, selected for their global availability and relevance as potential biofuels. The results showed that a significant fraction of levoglucosan was not retained on the filter but was instead recovered in the impingers. In particular, the volatile fraction represented approximately 30–50% of the total levoglucosan emitted, demonstrating that filter-only sampling can lead to a substantial underestimation of biomass burning markers. Total levoglucosan emission factors ranged from 53.7 to 65.8 mg kg-1 fuel for rice straw and wheat straw, respectively. The backup impinger contained less than 5% of the levoglucosan recovered in the first two impingers, confirming the effectiveness of the sampling configuration. These findings highlight the importance of considering both particle-bound and volatile fractions when assessing PM markers from biomass combustion. The proposed technique represents a methodological improvement for fixed-source emission monitoring and may support a more accurate evaluation of the contribution of biomass combustion to air quality.
