Comparison of four active and passive sampling techniques for pesticides in air

Four sampling systems were evaluated for their ability to determine the concentrations of pesticides in the atmosphere of rural southern Ontario. Two active air samplers (AAS, high-volume and low-volume pumps) and two passive air samplers (PAS, polyurethane foam disks and XAD-resin) were deployed between March 2006 and September 2007 using different sampling frequencies (biweekly to annually) and durations (24 h to 1 yr). Concentrations of nine pesticides in air determined by the different systems were compared at time scales of two weeks, two months, and one year. Agreement in the average concentrations obtained by different techniques improved with increasing length of the comparison period, especially for pesticides with high short-term temporal concentration variability. Such variability was high for the most volatile and reactive pesticides (trifluralin and pendimethalin). Except for these two pesticides, the annually averaged air concentrations determined by the different systems are within a factor of 2.5 for all pesticides and are not statistically different. Even though the PUF-PAS may have approached equilibrium with the atmosphere during deployment, the air concentrations are not statistically significantly different from those determined by AAS when averaged over longer time scales. Two month XAD-PAS deployments during the second summer resulted in sufficient sampling volumes to reliably establish air concentrations. If the sole purpose of collecting air samples is the assessment of long-term air concentration trends, this can be achieved most cost-effectively, i.e., with the least number of samples with year-long XAD-PAS.