Estimating PM2.5 Speciation Concentrations Using Multiangle Imaging SpectroRadiometer (MISR) Aerosol Properties over Southern California: Implications for Multi-Angle Imager for Aerosols (MAIA)

Research efforts to better characterize the differential toxicity of PM_2.5 speciation are often hindered by the sparse or non-existent coverage of ground monitors. The Multi-angle Imaging SpectroRadiometer (MISR) aboard NASA’s Terra satellite is the only satellite aerosol product providing information of aerosol shape, size and extinction globally that can be used to estimate PM_2.5 speciation concentrations. In the past, MISR only provides a 17.6 km product, a bit too coarse for air pollution health effects research and to capture local spatial variability of PM_2.5 speciation. In this study, generalized additive models (GAMs) were developed using MISR prototype 4.4 km-resolution aerosol data with meteorological variables and geographical indicators, to predict ground-level concentrations of PM_2.5 sulfate, nitrite, organic carbon (OC) and elemental carbon (EC) in Southern California between 2001 and 2015. The GAMs are able to explain 66%, 62%, 55% and 58% of the daily variability in PM_2.5 sulfate, nitrate, OC and EC concentrations, respectively. Predicted concentrations capture large regional patterns as well as fine gradients of the four PM_2.5 species in urban areas of Los Angeles and other counties, as well as in the Central Valley. This study is the first attempt to use MISR prototype 4.4 km-resolution fractional AODs data to predict PM_2.5 sulfate, nitrate, OC and EC concentrations at the sub-regional scale. Our analysis suggests that the MISR 4.4 km fractional AODs provide a promising way to capture hotspots of PM_2.5 speciation, understand the effectiveness of air quality controls, and allow our estimated PM_2.5 speciation data to be linked with common spatial units such as census tract or zip code in epidemiological studies.