Generation and Atmospheric Evolution of Light-Absorbing Carbonaceous Aerosol from Thermal Degradation of Plastic

Abstract

Open burning of plastic waste is a significant source of carbonaceous aerosol, including nanoplastics, in the atmosphere. As these particles are carried downwind, they undergo atmospheric aging through irradiation and oxidation, with potential impacts on their optical properties and, in turn, interactions with sunlight. Here, we report measurements of the initial and dynamic light absorption of carbonaceous aerosol from the thermal degradation of plastic, i.e., polyethylene terephthalate glycol (PETG). Four colors (red, yellow, blue, and colorless) of PETG were selected for thermal degradation in a tube furnace across a wide range of temperatures. The generation of submicron particles was confirmed using a scanning mobility particle sizer. Carbonaceous aerosol was collected on filters for characterization and aging experiments. Characterization included infrared and visible spectroscopy for composition and absorption, respectively, and colorimetry. Depending on the combustion conditions, the aerosol ranged from organic to elemental (i.e., black) carbon. The organic aerosol included polymer and nonpolymer species, distinguished using infrared spectroscopy. Selected light-absorbing organic aerosol samples from red and yellow PETG underwent irradiation in a solar simulator and oxidation in a flow tube with ozone at 50 ppb. The organic aerosol lost absorption more through irradiation than ozone oxidation; i.e., 1 d of irradiation led to a significant, 50% decrease for samples from both red and yellow PETG. Together, the results demonstrate that the initial absorption of carbonaceous aerosol from open burning of plastics varies significantly and that the absorption of light-absorbing organic aerosol at moderate temperatures is highly dynamic upon atmospheric aging.