Neighborhood-scale NO2 variations and enhanced capability of human exposure assessment
Year: 2023
Type: conference-abstract
Abstract: This study estimated ambient long-term average NO2 concentrations using TROPOspheric Monitoring Instrument (TROPOMI) tropospheric column NO2 data and land use parameters in California, U.S. for the years 2018–2019. Exploiting unprecedentedly high spatial resolution of TROPOMI NO2 (3.5×7 km prior to August 6, 2019 and 3.5×5.5 km thereafter) and the point statistics function implemented in ArcGIS (Environmental Systems Research Institute, ESRI), the NO2 concentration estimates were downscaled to 500 m, which enabled the neighborhood-scale exposure assessment of ambient NO2. Our satellite-land use hybrid regression model demonstrated cross-validation R2= 0.76, mean absolute error (MAE)= 1.95 ppb, and root mean squared error (RMSE)= 2.51 ppb in a comparison between site-specific average measured and estimated NO2 concentrations. These high-resolution NO2 concentration estimates enhanced the capability of human exposure assessment, enabling (1) the evaluation of ground NO2 monitors to represent population exposures and (2) the attribution of micro-level NO2 exposures. When measured NO2 concentrations were compared to population-weighted NO2 concentrations, calculated by using the satellite-based NO2 estimates, in each county, the differences in NO2 concentrations (i.e., population-weighted average NO2 – arithmetic average NO2 measurements) ranged from -38.6% (San Bernardino) to 82.2% (Humboldt). Though both negative and positive differences represented exposure errors without considering the spatial co-variations of NO2 and populations, monitor-based NO2 higher than the population-weighted NO2 demonstrated the overestimation of population NO2 exposures and was at least protective with current NO2 monitoring locations in the counties. However, the opposite was detrimental, while underestimating population NO2 exposures and likely not motivating NO2 mitigation efforts. In addition, the high-resolution NO2 estimates were further overlaid with parcel-level property data in Los Angeles County to attribute the spatial variation of NO2 exposures to that of the property types. The micro-level NO2 hotspots were identified at high-density residential complexes such as (high-rise) apartments. When the traffic impacts on NO2 were adjusted, the NO2 hotspots at the residential complexes still remained. This finding may suggest residential complexes as an emerging source type of NO2 due to emissions from boilers (space heating and hot water) and other indoor-to-outdoor ventilation systems.
Authors: Hyung Joo Lee, Yang Liu, Robert Chatfield
Language: English
Subfield: Health, Toxicology and Mutagenesis
Field: Environmental Science
Domain: Physical Sciences
Open Access status: gold
OpenAlex ID: W4321995992