Top-Down Evaluation of Volatile Chemical Product Emissions Using a Lagrangian Framework

In this study, we evaluate volatile chemical product (VCP; e.g., adhesives, personal care products) emissions in the McDonald et al. inventory using sector-specific tracers and the FLEXPART-WRF Lagrangian particle dispersion model. Observations of decamethylcyclopentasiloxane (D5-Siloxane) are used for optimizing emissions from personal care products, para-dichlorobenzene (PDCBZ) for insecticides, and parachlorobenzotrifluoride (PCBTF) for emissions from the construction (coatings + adhesives) subsector. Continuous ground-site measurements obtained in Las Vegas and Los Angeles (LA) during summer 2021 are used to optimize the temporal emission profiles of the area sources. Additionally, in situ aircraft-based observations (June 2021) over the LA region are used to evaluate emission factors for the basin. The configuration of the weather research and forecasting (WRF) model is optimized using vertical wind profile measurements obtained from the Pick-Up truck-based Mobile Atmospheric Sounder (PUMAS) deployed in the LA basin to minimize the uncertainty of the inversion due to meteorology. While the diurnal amplitude in emission rates from personal care products and insecticides is reduced after optimization, that of construction VCPs (coatings + adhesives) is enhanced. From the aircraft inversion, we find that the inventory underestimates the emissions originating from construction by a factor of 5.3 (95% confidence interval 4.3-6.3) in the LA basin. Emissions from consumer products (personal care + cleaning) and insecticides were reduced by a factor of 2.1 (1.7-2.5) and 5.2 (3.9-6.4), respectively, following optimization.