Investigation of the Nocturnal PM Peaks for Evidence of Association with Population Health Risks in Two Border Cities.
Investigation of the Nocturnal PM Peaks for Evidence of Association with Population Health Risks in Two Border Cities
Jessica Gamez1; Donald J. Baca1; Hector A. Olvera1; Nancy Garcia1; Mario Garcia1; Fernando Astorga2; Jose H. Garcia3; Gerardo Mejia4; Kerry Kelly5; JoAnn Lighty5; Wen-Whai Li1,2
1 Department of Civil Engineering, 2 Environmental Science and Engineering, The University of Texas at El Paso; 3 Professional Department (Campus Ciudad Juárez), 4 Centro de Calidad Ambiental (Campus Monterrey), Instituto Tecnológico y de Estudios Superiores de Monterrey; 5 Institute for Combustion and Energy Studies, University of Utah
This paper presents the results of a study characterizing the physical and chemical properties associated with the nocturnal PM10 and PM2.5 spikes that occur in the calm early evening hours (from 6:00 p.m. to 9:00 p.m.) in the two sister border cities (El Paso and Ciudad Juarez) along the U.S.-Mexico border. It represents an ongoing task under a collaborative research effort among several SCERP universities to investigate the nocturnal PM peaks for evidence of association with population health risks.
The nocturnal PM peaks previously observed at Sunland Park, New Mexico and several other cities along the U.S.-Mexico border were observed at the two new locations. The evening PM peak was observed to occur under low wind conditions (< 2 m/sec) with a strong correlation with preceding afternoon high to moderate wind conditions. The hourly PM particle count varied from less than 10,000 particles/cm3 in the afternoon to greater than 80,000 particles/cm3 in the evening hours during the study period. The total number of PM particles peaked in the morning as well as in the evening while the mode of the particle size changed from 20 nm to ~100 nm, indicating different PM sources may be responsible for the mass and number concentrations and agglomeration of particles in the atmosphere during the day may possibly plays a role. Larger particles (100 – 470 nm) were found to associate better than smaller particles (10 – 100 nm) with PM mass. Wind direction did not have an impact on the PM number concentrations whereas wind speed is negative correlated (although small) to both PM size fractions confirming the occurrence of PM peaks under low wind conditions. Further chemical and statistical analyses are underway.
This research was supported by a grant from the Southwest Consortium for Environmental Research and Policy (SCERP, Grant Number A-05-02). Some of the authors were partially supported by grants from the National Institute for Environmental Health Science (NIEHS-NIH, 5 S11 ESO 1339-02), Health Effects Institute grant (HEI, RFA 05-1B), U.S. EPA Undergraduate Research Experience, U.S. DOT Eisenhower Scholarship, UTEP ORSP, and/or UTEP College of Health Sciences. The contents of this research are solely the responsibilities of the authors and do not necessarily represent the official views of any of the above-mentioned agencies.
The authors also appreciate the assistance received from Mr. Joe Bester and Dr. Manisha Singh of Thermo-Electron Inc. and support from UTEP CERM and Department of Civil Engineering.