Variation in Tree Species Ability to Capture and Retain Airborne Fine Particulate Matter (PM2.5)

Human health risks caused by PM2.5 raise awareness to the role of trees as bio-filters of urban air pollution, but not all species are equally capable of filtering the air. The objectives of this current study were: (1) to determine the foliar traits for effective PM2.5-capture and (2) explore species-to-species differences in foliar PM2.5-recapture capacity following a rain event. The study concluded that overall, the acicular needle shape made conifers more efficient with PM2.5 accumulation and post-rainfall recapture than broadleaved species. The foliar shape and venation of broadleaved species did not appear to influence the PM2.5 accumulation. However, the number of the grooves and trichomes of broadleaved species were positively related to foliar PM2.5 accumulation, suggesting that they could be used as indicators for the effectiveness of tree PM2.5 capture. Furthermore, the amount of PM2.5 removal by rainfall was determined by the total foliar PM2.5. Not all PM2.5 remained on the foliage. In some species, PM2.5 was resuspended during the growing season, and thus reduced the net particular accumulation for that species. These findings contribute to a better understanding of tree species potential for reducing PM2.5 in urban environments.