Low-Wind/High Particulate Matter Episodes in the Calexico/Mexicali Region

• Published in: Journal of the Air & Waste Management Association (1995) 2010-12, Vol.60 (12), p.1476-1486
• Main Authors: Kelly, Kerry E., Jaramillo, Isabel C., Quintero-Núñez, Margarito, Wagner, David A., Collins, Kimberly, Meuzelaar, Henk L.C., Lighty, JoAnn S.
• Format: Article
• Language: English
• Subjects: Air pollution; Air Pollution - analysis; Applied sciences; Atmospheric pollution; Automotive emissions; Bronchial diseases; California; Cardiac arrhythmia; Causes of; Emissions; Environmental Monitoring; Exact sciences and technology; Global environmental pollution; Hydrocarbons - analysis; Mass spectrometry; Mexico; Models, Statistical; Multivariate Analysis; Natural gas; Particle Size; Particles; Particulate Matter - analysis; Pollution; Respiratory diseases; Sample size; Seasons; Studies; Weather; Wind; Winter
• ISSN: 1096-2247; 2162-2906
• DOI: 10.3155/1047-3289.60.12.1476

The U.S. Environmental Protection Agency (EPA) currently classifies Imperial County, CA, as a nonattainment area for PM 10 (particulate matter [PM] ≤ 10 μm in diameter), and this region suffers from high rates of chronic bronchitis and childhood asthma. Although high annual and daily average PM levels can have negative health and economic effects, recent studies have identified an association between adverse health effects and short-term PM spikes of tens of micrograms per cubic meter. This study identified PM episodes in Calexico/Mexicali that involve PM concentration spikes with concentrations up to 10 times greater than those reported to cause adverse health effects. These episodes appear to be relatively common during the winter months, are associated with wind speeds below 2 m/sec and stable boundary level heights below 500 m, and can comprise a large portion of the 24-hr PM levels. The organic composition of the PM 10 samples collected during the low-wind/high-PM episodes differed from that collected at other times. However, a preliminary source attribution identified only one significant difference between the source classes: agricultural burning accounted for 6.7% of organic-fraction PM 10 for low-wind/high-PM episodes versus 0.25% at other times. This preliminary source attribution also revealed that motor vehicles were the most important relative contributor to organic PM 10 .