Abstract

Trees and other vegetation have been advocated as a mitigation measure for urban air pollution mainly due to the fact that they passively filter particles from the air. However, mounting evidence suggests that vegetation may also worsen air quality by slowing the dispersion of pollutants and by producing volatile organic compounds that contribute to formation of ozone and other secondary pollutants. We monitored nanoparticle (>10 nm) counts along distance gradients away from major roads along paired transects across open and forested landscapes in Baltimore (USA), Helsinki (Finland) and Shenyang (China) − i.e. sites in three biomes with different pollution levels − using condensation particle counters. Mean particle number concentrations averaged across all sampling sites were clearly reduced (15 %) by the presence of forest cover only in Helsinki. For Baltimore and Shenyang, levels showed no significant difference between the open and forested transects at any of the sampling distances. This suggests that nanoparticle deposition on trees is often counterbalanced by other factors, including differing flow fields and aerosol processes under varying meteorological conditions. Similarly, consistent differences in high frequency data patterns between the transects were detected only in Helsinki. No correlations between nanoparticle concentrations and solar radiation or local wind speed as affecting nanoparticle abundances were found, but they were to some extent associated with canopy closure. These data add to the accumulating evidence according to which trees do not necessarily improve air quality in near-road environments.
Original languageEnglish
Article number115294
JournalEnvironmental Pollution
Volume266
Issue numberPart 2
Number of pages9
ISSN0269-7491
DOIs
Publication statusPublished - Nov 2020
MoE publication typeA1 Journal article-refereed

Fields of Science

  • 1172 Environmental sciences
  • Air pollution
  • Particulate Matter
  • Particles
  • Nanoparticles
  • particle concentrations
  • Urban forest
  • Forests
  • Urban trees
  • Parks
  • Urban ecology
  • Urban ecosystems
  • URBAN ATMOSPHERE
  • Urban meteorology
  • near-road environment
  • Road traffic
  • Air pollution mitigation
  • Ecosystem services
  • Air quality
  • Urban vegetation
  • particle pollution
  • Nanoparticles
  • Air pollution
  • Air quality
  • Urban forest
  • Urban trees
  • AIR-POLLUTION
  • GREEN INFRASTRUCTURE
  • ECOSYSTEM SERVICES
  • URBAN VEGETATION
  • QUALITY
  • NANOPARTICLES
  • DEPOSITION
  • IMPACT
  • DISPERSION
  • HELSINKI

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