Diurnal and seasonal variation of volatile organic compounds in the atmosphere of Monterrey, Mexico

Volatile organic compounds (VOCs) were characterized in Monterrey, the third largest city in Mexico. In total, 53 VOCs were characterized, of which 29 were analyzed. Three sampling campaigns were performed during the spring of 2011 and the spring and the fall of 2012, using 4-h time intervals from 6:00 am to 10:00 pm. Measurements were performed on the premises of a monitoring station located in downtown Monterrey. The highest concentrations were found in the fall; the two spring measurements exhibited no statistically significant differences. VOC concentrations exhibited a marked diurnal behavior with higher concentrations during the morning intervals. Solar radiation peaked during the noon interval, allowing for greater secondary pollutant production. VOCs reached their lowest levels in the 14:00–18:00 time interval. Correlation analysis found evidence of mobile sources, fugitive fuel emissions, and the use of solvents as possible sources of the majority of the compounds. Additionally, the VOC–O3–NOx relationship was studied. The results indicate that the atmosphere in Monterrey, Mexico is sensitive to the concentration of VOCs.