Variation in Tree Species Ability to Capture and Retain Airborne Fine Particulate Matter (PM_2.5)

Human health risks caused by PM_2.5 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 PM_2.5-capture and (2) explore species-to-species differences in foliar PM_2.5-recapture capacity following a rain event. The study concluded that overall, the acicular needle shape made conifers more efficient with PM_2.5 accumulation and post-rainfall recapture than broadleaved species. The foliar shape and venation of broadleaved species did not appear to influence the PM_2.5 accumulation. However, the number of the grooves and trichomes of broadleaved species were positively related to foliar PM_2.5 accumulation, suggesting that they could be used as indicators for the effectiveness of tree PM_2.5 capture. Furthermore, the amount of PM_2.5 removal by rainfall was determined by the total foliar PM_2.5. Not all PM_2.5 remained on the foliage. In some species, PM_2.5 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 PM_2.5 in urban environments.