Effects of forests on particle number concentrations in near-road environments across three geographic regions

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http://hdl.handle.net/10138/318580

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Viippola, V, Yli-Pelkonen, V, Järvi, L, Kulmala, M & Setälä, H 2020, ' Effects of forests on particle number concentrations in near-road environments across three geographic regions ', Environmental Pollution, vol. 266, no. Part 2, 115294 . https://doi.org/10.1016/j.envpol.2020.115294

Title: Effects of forests on particle number concentrations in near-road environments across three geographic regions
Author: Viippola, Viljami; Yli-Pelkonen, Vesa; Järvi, Leena; Kulmala, Markku; Setälä, Heikki
Contributor organization: Urban Ecosystems
Ecosystems and Environment Research Programme
Helsinki Institute of Sustainability Science (HELSUS)
Institute for Atmospheric and Earth System Research (INAR)
Urban meteorology
Helsinki Institute of Urban and Regional Studies (Urbaria)
SUSTAINABLE URBAN DEVELOPMENT EMERGING FROM THE MERGER OF CUTTING-EDGE CLIMATE, SOCIAL AND COMPUTER SCIENCES
Date: 2020-11
Language: eng
Number of pages: 9
Belongs to series: Environmental Pollution
ISSN: 0269-7491
DOI: https://doi.org/10.1016/j.envpol.2020.115294
URI: http://hdl.handle.net/10138/318580
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.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.
Subject: 1172 Environmental sciences
Air pollution
Particles
Nanoparticles
Urban forest
Parks
near-road environment
Forests
Ecosystem services
Urban ecology
Urban ecosystems
URBAN ATMOSPHERE
Urban meteorology
particle concentrations
Air quality
traffic
Urban trees
Field study
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
Peer reviewed: Yes
Rights: cc_by
Usage restriction: openAccess
Self-archived version: publishedVersion


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