Abstract
To better understand the impact of plastic burning on atmospheric fine particulate matter (PM2.5), we evaluated two methods for the quantification of 1,3,5-triphenylbenzene (TPB), a molecular tracer of plastic burning. Compared to traditional solvent-extraction gas chromatography mass spectrometry (GCMS) techniques, thermal-desorption (TD) GCMS provided higher throughput, lower limits of detection, more precise spike recoveries, a wider linear quantification range, and reduced solvent use. This method enabled quantification of TPB in fine particulate matter (PM2.5) samples collected at rural and urban sites in the USA and Bangladesh. These analyses demonstrated a measurable impact of plastic burning at 5 of the 6 study locations, with the largest absolute and relative TPB concentrations occurring in Dhaka, Bangladesh, where plastic burning is expected to be a significant source of PM2.5. Background-level contributions of plastic burning in the USA were estimated to be 0.004-0.03 μg m-3 of PM2.5 mass. Across the four sites in the USA, the lower estimate of plastic burning contributions to PM2.5 ranged 0.04-0.8%, while the median estimate ranged 0.3-3% (save for Atlanta, Georgia, in the wintertime at 2-7%). The results demonstrate a consistent presence of plastic burning emissions in ambient PM2.5 across urban and rural sites in the USA, with a relatively small impact in comparison to other anthropogenic combustion sources in most cases. Much higher TPB concentrations were observed in Dhaka, with estimated plastic burning impacts on PM2.5 ranging from a lower estimate of 0.3-1.8 μg m-3 (0.6-2% of PM2.5) and the median estimate ranging 2-35 μg m-3 (5-15% of PM2.5). The methodological advances and new measurements presented herein help to assess the air quality impacts of burning plastic more broadly.