Nanoplastic Particle Emissions from Plastic Smoldering Combustion

HONGRU SHEN, Arthur W. H. Chan, Jonathan Abbatt, University of Toronto

     Abstract Number: 75
     Working Group: Chemicals of Emerging Concern in Aerosol: Sources, Transformations, and Impacts

Abstract
Atmospheric nanoplastic particles (NPP, <1 mm in diameter) are an emerging environmental concern due to their potential adverse effects on human health, global climate, and ecological systems. Recent field studies observed widespread atmospheric NPP presence, with plastic combustion as a potentially important source. However, the physical and chemical properties of NPP emissions from plastic combustion are unknown. Our study focused on the NPP emissions from plastic smoldering, an incomplete combustion stage lasting for a long period and posing high risks. Five types of plastics are selected, including low-density polyethene (LDPE), propylene (PP), polyethylene terephthalate (PET), polyvinyl chloride (PVC), and polystyrene (PS), and smoldered at temperatures up to 350℃ in a small combustion vessel. For all particles, a strong sub-micron mode (200-300 nm) of emitted particles was observed, along with a super-micron-sized particle mode (>20 um). We used a high-resolution time-of-flight aerosol mass spectrometer (AMS) to identify and quantify NPP emissions based on specific fragment ions, for example, C8H9+ for PS and C8H6O4+ for PET. For the NPP from all plastic types, the AMS mass fractions of m/z 60 are low (<0.01) and the ratio of m/z 55 to m/z 57 are larger than 1, allowing NPP to be distinguished from primary emissions from biomass burning aerosol particles. Compared to corresponding virgin plastics, NPP emissions are more oxidized. Using the composition and dynamic trends of gas-phase emissions characterized by online chemical ionization mass spectrometry, we propose potential formation mechanisms of these NPP. We also estimated the emission factors of organic vapors and NPP, with a range of 33-430 g kg-1 and 0.5-828 g kg-1 respectively. This study is the first systematic characterization and quantification of NPP emissions from plastic smoldering combustion, which will aid identification of these particles in the atmosphere and assessment of their health and climate effects.