Temporal evolution of secondary organic aerosol production from volatile chemical products

Abstract:

One of the key distinctions between volatile chemical products (VCPs) and traditional combustion sources is that the magnitude and composition of VCP emissions can evolve over time. Chemical transport models can reasonably assume that vehicles and power plants have consistent (or at least predictable) fuel-based emission factors (e.g., g-pollutant per kg-fuel). Activity based emission factors are less certain for evaporative emissions from VCPs such as paints, coatings, and sealants that are applied as a liquid and have solvent(s) that evaporate over time. In this study, we monitored the evolution of organic compound (I/S/VOC) emissions from paint samples and floor coverings and quantified secondary organic aerosol (SOA) formation and composition over time.

We conducted experiments where we either painted a 1 square meter board with several paints (e.g., interior latex paint, spray paint) or applied self-adhesive carpet squares to a wood backing. We characterized I/S/VOC emissions with a PTR-MS and sorbent tubes analyzed via GC-MS. We used an oxidation flow reactor to generate SOA from the paint emissions. In each experiment concentrations were monitored until they returned to background levels. We hypothesized that the VCPs would act as long-term sources of IVOC and SVOC compounds, and that SOA formation would persist for days to weeks due to slow and evolving emissions. Instead, the results are consistent with the painting acting as a one-time emissions event. Both vapor concentrations and SOA formation in the OFR return to background levels within a few hours, consistent with emissions of VOCs and IVOCs from a thin film. The composition of the resulting SOA is similar to typical oxygenated organic aerosol (OOA) determined from factor analysis of ambient data, suggesting that previous source apportionment may have misclassified this SOA as coming from other sources.