Spatial and Temporal Trends of Air Pollutants in the South Coast Basin Using Low Cost Sensors
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EPA/600/R-17/463| January 2018 | www.epa.gov/ Spatial and Temporal Trends of Air Pollutants in the South Coast Basin Using Low Cost Sensors photo Office of Research and Development National Exposure Research Laboratory 1 EPA/600/R-17/463 January 2018 Spatial and Temporal Trends of Air Pollutants in the South Coast Basin Using Low Cost Sensors Ron Williams and Rachelle Duvall U.S. Environmental Protection Agency Office of Research and Development National Exposure Research Laboratory Research Triangle Park, NC 27711 Dena Vallano U.S. Environmental Protection Agency, Region 9 Air Quality Analysis Office San Francisco, CA 95105 Andrea Polidori, Vasileios Papapostolou, Brandon Feenstra, Hang Zhang South Coast Air Quality Management District Science and Technology Advancement Office Air Quality Sensor Performance Evaluation Center (AQ-SPEC) Diamond Bar, CA 91765 Sam Garvey Jacobs Technology Inc. Tullahoma, TN 37388 ii Disclaimer This technical report presents the results of work performed by the South Coast Air Quality Management District’s AQ-SPEC Laboratory under contract EP-16-W-000117 and Jacobs Technology, Inc. under contract EP-C-15-008 for the National Exposure Research Laboratory, U.S. Environmental Protection Agency (U.S. EPA), Research Triangle Park, NC. It has been reviewed by the U.S. EPA and approved for publication. Mention of trade names or commercial products does not constitute endorsement or recommendation for use. Abstract The emergence of small, portable, low-cost air sensors has encouraged a shift toward their use and away from traditional approaches to monitoring air quality. The U.S. Environmental Protection Agency (U.S. EPA), in collaboration with t h e South Coast Air Quality Management District’s (SCAQMD) Air Quality Sensor Performance Evaluation Center (AQ-SPEC), deployed custom-built sensor devices (pods) measuring fine particulate matter (PM2.5), ozone (O3), relative humidity, and temperature at nine locations throughout southern California from January 2017 to April 2017 to evaluate their performance under “real-life” conditions. Prior to the deployment, these pods were evaluated within the AQ-SPEC program both in the field and in the laboratory. Southern California is an ideal testing location for air quality sensor technology, as it often experiences elevated air pollutant levels resulting from gasoline and diesel engines, marine ports, and various other industries. The South Coast Air Basin’s particular meteorology (frequent sunny days and little precipitation) and geography also contribute to the elevated pollution levels in the region. The goal of this project was to characterize the performance of these newly developed pods and better understand their potential applications for community monitoring. This report summarizes the AQ- SPEC field and laboratory performance evaluations of the Citizen Science Air Monitor (CSAM) sensor pods designed and developed by the EPA. In addition, this document summarizes the spatial and temporal variability of the PM2.5 and O3 measurements collected during the field deployment of the CSAM pods at nine monitoring locations covering approximately a 200 km2 area in southern California. iii Table of Contents ABSTRACT ............................................................................................................................................... III TABLE OF CONTENTS ............................................................................................................................... IV ACRONYMS AND ABBREVIATIONS .......................................................................................................... XII EXECUTIVE SUMMARY .......................................................................................................................... XIV BACKGROUND ........................................................................................................................................... XIV STUDY OBJECTIVES ..................................................................................................................................... XIV STUDY APPROACH ...................................................................................................................................... XIV CONCLUSIONS ........................................................................................................................................... XVI INTRODUCTION ....................................................................................................................................... 1 1. CO-LOCATION TESTING ...................................................................................................................... 1 1.1. METHODS ......................................................................................................................................... 1 1.2. RESULTS ........................................................................................................................................... 3 1.2.2. AMBIENT OZONE .................................................................................................................................... 13 1.2.3. AMBIENT TEMPERATURE ......................................................................................................................... 20 1.2.4. AMBIENT RELATIVE HUMIDITY .................................................................................................................. 25 1.3. QA SUMMARY FOR CO-LOCATION TESTING ............................................................................................ 31 2. LABORATORY CHAMBER EVALUATION ............................................................................................... 33 2.1. METHODS .......................................................................................................................................... 33 2.1.1. PM2.5 TESTING PROCEDURE ..................................................................................................................... 35 2.1.2. OZONE TESTING PROCEDURE .................................................................................................................... 36 2.1.3. CSAM EVALUATION PARAMETERS............................................................................................................. 37 2.2. RESULTS ......................................................................................................................................... 39 2.2.1. LABORATORY PM2.5 ................................................................................................................................ 39 2.2.2. LABORATORY OZONE .............................................................................................................................. 42 2.3. QA SUMMARY FOR LABORATORY TESTING ................................................................................................ 45 3. FIELD DEPLOYMENT ........................................................................................................................... 46 3.1. METHODS .......................................................................................................................................... 46 3.2. RESULTS ............................................................................................................................................ 51 3.2.1. AMBIENT PM2.5 ........................................................................................................................................ 52 iv 3.2.2. AMBIENT OZONE ....................................................................................................................................... 58 3.2.3. TEMPERATURE AND RH INFLUENCES ............................................................................................................. 65 3.3. QA SUMMARY FOR FIELD DEPLOYMENT .................................................................................................... 68 CONCLUSIONS ....................................................................................................................................... 70 REFERENCES .......................................................................................................................................... 71 v List of Tables TABLE A.1. SENSOR COMPONENTS IN EACH CSAM SENSOR POD DEVELOPED BY EPA ..................................................... XV TABLE 1.1A. DESCRIPTIVE STATISTICS FOR PM2.5 SENSORS IN THE CSAMS AND THE FEM GRIMM REFERENCE INSTRUMENT (5- MINUTE AVERAGE) .................................................................................................................................................. 4 TABLE 1.1B. CORRELATION STATISTICS FOR PM2.5 SENSORS IN THE CSAMS AGAINST THE FEM GRIMM REFERENCE INSTRUMENT (5-MINUTE AVERAGE), [FEM= (SLOPE*SENSOR READING) + INTERCEPT] .................................................... 4 2 TABLE 1.2. CORRELATION COEFFICIENT (R ) MATRIX FOR THE 5-MINUTE AVERAGE PM2.5 MASS CONCENTRATIONS MEASURED BY THE FEM AND CSAM UNITS. ............................................................................................................................... 6 2 TABLE 1.3. CORRELATION COEFFICIENT (R ) MATRIX FOR THE 1-HOUR AVERAGE PM2.5 MASS CONCENTRATIONS MEASURED BY THE FEM AND CSAM UNITS ................................................................................................................................ 8 2 TABLE 1.4. CORRELATION COEFFICIENT (R ) MATRIX FOR THE 24-HOUR AVERAGE PM2.5