Investigation of time-resolved atmospheric conditions and indoor/outdoor particulate matter concentrations in homes with gas and biomass cook stoves in Nogales, Sonora, Mexico

Abstract

This paper reports findings from a case study designed to investigate indoor and outdoor air quality in homes near the United States–Mexico border. During the field study, size-resolved continuous particulate matter (PM) concentrations were measured in six homes, while outdoor PM was simultaneously monitored at the same location in Nogales, Sonora, Mexico, during March 14–30, 2009. The purpose of the experiment was to compare PM in homes using different fuels for cooking, gas versus biomass, and to obtain a spatial distribution of outdoor PM in a region where local sources vary significantly (e.g., highway, border crossing, unpaved roads, industry). Continuous PM data were collected every 6 seconds using a valve switching system to sample indoor and outdoor air at each home location. This paper presents the indoor PM data from each home, including the relationship between indoor and outdoor PM. The meteorological conditions associated with elevated ambient PM events in the region are also discussed. Results indicate that indoor air pollution has a strong dependence on cooking fuel, with gas stoves having hourly averaged median PM₃ concentrations in the range of 134 to 157 μg m⁻³ and biomass stoves 163 to 504 μg m⁻³. Outdoor PM also indicates a large spatial heterogeneity due to the presence of microscale sources and meteorological influences (median PM₃: 130 to 770 μg m⁻³). The former is evident in the median and range of daytime PM values (median PM₃: 250 μg m⁻³, maximum: 9411 μg m⁻³), while the meteorological influences appear to be dominant during nighttime periods (median PM₃: 251 μg m⁻³, maximum: 10,846 μg m⁻³). The atmospheric stability is quantified for three nighttime temperature inversion episodes, which were associated with an order of magnitude increase in PM10 at the regulatory monitor in Nogales, AZ (maximum increase: 12 to 474 μg m⁻³).

Implications:

Regulatory air quality standards are based on outdoor ambient air measurements. However, a large fraction of time is typically spent indoors where a variety of activities including cooking, heating, tobacco smoking, and cleaning can lead to elevated PM concentrations. This study investigates the influence of meteorology, outdoor PM, and indoor activities on indoor air pollution (IAP) levels in the United States–Mexico border region. Results indicate that cooking fuel type and meteorology greatly influence the IAP in homes, with biomass fuel use causing the largest increase in PM concentration.

Acknowledgments

The AQINO field study was completed with assistance from University of Utah students Scott Speckart and Daniel Alexander. In addition, the authors are grateful to Dr. Diane Austin from University of Arizona and her colleagues in Nogales, Sonora, for assistance in finding study participants and Dr. Rodney Larson at the University of Utah for assistance with the survey; to Dr. John Veranth and David Wagner from University of Utah and Dr. David L. Johnson from University of Oklahoma for loaning equipment for use during the experiment; and to Bill Roe from Grimm Technologies, Inc., for calibrating instruments on short notice. Also, they are grateful to the Arizona Department of Environmental Quality for providing data from the Nogales, AZ, monitoring site.

Funding

The authors acknowledge the support of the Southwestern Consortium for Environmental Research and Policy (SCERP).

Additional information

Notes on contributors

Heather A. Holmes

Heather A. Holmes is an assistant professor in the Department of Physics at the University of Nevada, Reno.

Eric R. Pardyjak

Eric R. Pardyjak is a professor in the Department of Mechanical Engineering at the University of Utah.