A continuous photo-oxidation flow reactor for a defined measurement of the SOA formation potential of wood burning emissions

We present a compact photo-oxidation continuous flow reactor as a conditioning system for real time monitoring of the secondary organic aerosol (SOA) production potential of combustion installations. The reactor was first tested using well known SOA precursor substances. We show that a short residence time of just a few seconds is enough to oxidize the organic gaseous carbon (OGC) and form SOA. The production rate of SOA only seems to be limited by the intensity of the UV radiation and the availability of oxygen in the gas sample. A second set of experiments was conducted using the gas phase emissions from different residential wood burning installations. The SOA production of our reactor, expressed as SOA mass per emitted CO2, closely matches the values found in the literature for smog chamber experiments. The exceptions were episodes when the OGC concentration was too high to be completely transformed by the reactor. The operation range of the reactor can be extended by adjusting the residence time, light intensity and/or the dilution of the sample. The question of correctly dimensioning these parameters is not trivial and failure to do so could result in an underestimation of the SOA production potential at certain OGC concentrations. Current legislation limits the emission of particulate matter, but does not regulate the substances that form SOA. A photo-oxidation continuous flow reactor could be incorporated in type approval testing and emission control measurements as a way of including SOA in the emission legislation for combustion installations.

► Continuous flow reactor for monitoring emissions from wood combustion in real time. ► The photo-oxidation of gas species forms secondary organic aerosols (SOA) within seconds. ► Tested using model substances and actual emissions from wood burning installations. ► Calculated emission factors in agreements with aging experiments in smog chambers. ► Device eligible as a standard for SOA measurements in emission-control legislation.