Low-cost, real-time PM monitors can greatly extend the range of expensive (but more accurate) networks run by regulatory agencies. Both types of networks are useful for determining areas with unhealthy pollution levels and tracking long-term trends, but lack the ability to distinguish sources or the effectiveness of source-specific control efforts , which are usually done with resource-intensive special studies – either air quality modeling (dependent on accurate meteorological and emission input data) or source tracer measurements (dependent on unique chemical signatures for each source type).
Mobile monitors (vehicles instrumented with high accuracy monitoring equipment) collect air quality data with high temporal and spatial resolution to study near-roadway exposures in highly impacted communities and measure pollutant gradients under a variety of conditions. This research tool is an important supplement to regional air quality monitoring networks and new U.S. requirements for near-road monitoring, and can help identify contributing sources.
Satellite-based aerosol optical depth readings (interpreted through comparison with ground-level PM monitors) can provide detailed PM2.5 maps throughout a region, although limited to daylight, cloud-free conditions. The GOES-16 satellite has readings every 15 minutes at a 1-2 km resolution, and my former group is collaborating with Emory University on a NASA-funded project to develop a “decoder” for California to interpret and display the PM2.5 maps in near real-time. Research is needed to apply this tool to other regions and combine with other satellite data streams to distinguish sources and track trends. The Multi-angle Imaging SpectroRadiometer (MISR) provides information on aerosol shape, size, and extinction globally for a continuous period that can be used to estimate PM2.5 speciation concentrations since 2000.
All these approaches are complementary with one another in determining current air quality, pollution hotspots, compliance with regulatory air quality standards, contributing sources, and overall/source-specific trends, as well as useful for health, exposure, and environmental justice studies. We are currently working on a paper to describe a multi-scale framework for community-level air quality analysis in California that takes advantage of these new capabilities.
[World’s) Air Pollution: Real-time Air Quality Index](http://waqi.info%22%5DWorld’s – Compendium of real-time air quality for more than 10,000 stations around the world.
Kozawa et al. (2013) Mobile Measurement Platform: An Innovative Tool for Studying the Impacts of Traffic Emissions – Overview of the California Air Resources Board’s mobile monitoring research program.
Apte et al. (2017) High-Resolution Air Pollution Mapping with Google Street View Cars: Exploiting Big Data – Google Street View vehicles equipped with a fast-response pollution measurement platform used to repeatedly sample every street in a 30-km2 area of Oakland, CA. Resulting maps of annual daytime NO, NO2, and black carbon at 30 m-scale reveal stable, persistent pollution patterns with surprisingly sharp small-scale variability attributable to local sources, up to 5–8× within individual city blocks.
Lee and Son (2016) Spatial Variability of AERONET Aerosol Optical Properties and Satellite Data in South Korea during NASA DRAGON-Asia Campaign – Both transported dust and local combustion contribute to PM2.5 levels in South Korea, although the study is limited to the spring of 2012. This shows the promise of satellite-based aerosol optical depth readings (in combination with strategically placed ground-level PM monitors) to provide detailed air quality maps throughout a region.
Meng et al. (2018) Estimating PM2.5 speciation concentrations using prototype 4.4 km-resolution MISR aerosol properties over Southern California – PM2.5 sulfate, nitrate, OC and EC trends from 2001 to 2015.
CARB (2018) Use of Satellite Remote Sensing Data to Support Air Quality Decision-making – Overview of the California Air Resources Board’s remote sensing research program.