Spatial and Temporal Distribution of Current-Use Pesticides in Atmospheric Particulate Matter in Houston, Texas

The atmospheric concentrations of seven current-use pesticides in particulate matter were determined at four locations throughout the Houston metropolitan area in TSP and PM2.5 samples from September 2013. Atmospheric concentrations in both TSP and PM2.5 ranged from below method detection limits (MDLs) to nearly 1100 pg m−3. The three compounds most frequently detected above MDLs were chlorothalonil, bifenthrin, and λ-cyhalothrin. Atmospheric chlorothalonil concentrations were above 800 pg m−3 in several TSP samples, but <MDL in PM2.5 samples. Bifenthrin atmospheric concentrations, which were detected above MDLs in all samples, differed between urban and suburban sites, while also being more associated with fine particulate matter. λ-cyhalothrin had high atmospheric concentrations at one of the suburban sites and the industrial site, but was <MDL in the urban site samples. Diurnal trends in atmospheric concentration, as related to wind direction, showed that daytime peaks came from east while nighttime peaks came from northeast directions.