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Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union
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https://doi.org/10.5194/amt-2019-501
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/amt-2019-501
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 28 Jan 2020

Submitted as: research article | 28 Jan 2020

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This preprint is currently under review for the journal AMT.

Mobile-Platform Measurement of Air Pollutant Concentrations in California: Performance Assessment, Statistical Methods for Evaluating Spatial Variations, and Spatial Representativeness

Paul A. Solomon1,a, Dena Vallano2, Melissa Lunden3, Brian LaFranchi3, Charles L. Blanchard4, and Stephanie L. Shaw5 Paul A. Solomon et al.
  • 1independent consultant: Henderson, Nevada, 89052, USA
  • 2U.S. Environmental Protection Agency, Region 9, Air and Radiation Division, 75 Hawthorne St, San Francisco, CA, 94105, USA
  • 3Aclima, Inc., 10 Lombard St,Suite 200, San Francisco, CA, 94111, USA
  • 4Envair, 526 Cornell Avenue, Albany, CA, 94706, USA
  • 5Electric Power Research Institute, 3420 Hillview Ave, Palo Alto, CA, 94304, USA
  • aformerly at: U.S. Environmental Protection Agency, Office of Research and Development, Las Vegas, NV, 89119, USA

Abstract. Mobile platform measurements provide new opportunities for characterizing spatial variations of air pollution within urban areas, identifying emission sources, and enhancing knowledge of atmospheric processes. The Aclima, Inc. mobile measurement and data acquisition platform was used to equip Google Street View cars with research-grade instruments. On-road measurements of air quality were made between May 2016 and September 2017 at high (i.e., 1-second [s]) temporal and spatial resolution at several California locations: Los Angeles, San Francisco, and the northern San Joaquin Valley (including non-urban roads and the cities of Tracy, Stockton, Manteca, Merced, Modesto, and Turlock). The results demonstrate that the approach is effective for quantifying spatial variations of air pollutant concentrations over measurement periods as short as two weeks. Measurement accuracy and precision are evaluated using results of weekly performance checks and periodic audits conducted through the sampler inlets, which show that research instruments in stationary vehicles are capable of reliably measuring nitric oxide (NO), nitrogen dioxide (NO2), ozone (O3), methane (CH4) black carbon (BC), and particle number (PN) concentration with bias and precision ranging from < 10 % for gases to < 25 % for BC and PN at 1-s time resolution. The quality of the mobile measurements in the ambient environment is examined by comparisons with data from an adjacent (< 9 m) stationary regulatory air quality monitoring site and by paired collocated vehicle comparisons, both stationary and driving. The mobile measurements indicate that U.S. EPA classifications of two Los Angeles stationary regulatory monitors’ scales of representation are appropriate. Paired time-synchronous mobile measurements are used to characterize the spatial scales of concentration variations when vehicles were separated by < 1 to 10 kilometers (km). A data analysis approach is developed to characterize spatial variations while limiting the confounding influence of diurnal variability. The approach is illustrated using data from San Francisco, revealing 1-km scale enhancements in mean NO2 and O3 concentrations up to 117 % and 46 %, respectively, during a two-week sampling period. In San Francisco and Los Angeles, spatial variations up to factors of 6 to 8 occur at sampling scales of 100–300 m, corresponding to 1-minute averages.

Paul A. Solomon et al.

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Short summary
The Aclima, Inc. measurement and data acquisition platform was used with Google Street View cars and research-grade instruments to measure air quality between May 2016 and September 2017 at high (1-second) temporal and spatial resolution in Los Angeles, San Francisco, and the San Joaquin Valley, California. The results demonstrate that the approach is effective for quantifying spatial variations of air pollutant concentrations and is expected to yield increasingly accurate estimates of exposure.
The Aclima, Inc. measurement and data acquisition platform was used with Google Street View cars...
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