| Title: | Effects of forests on particle number concentrations in near-road environments across three geographic regions |
| Author(s): | Viippola V; Yli-Pelkonen V; Jarvi L; Kulmala M; Setala H; |
| Address: | "University of Helsinki, Ecosystems and Environment Research Programme, Faculty of Biological and Environmental Sciences, Niemenkatu 73, FI, 15140, Lahti, Finland. Electronic address: viljami.viippola@helsinki.fi. University of Helsinki, Ecosystems and Environment Research Programme, Faculty of Biological and Environmental Sciences, P.O. Box 65, FI, 00014, Finland. University of Helsinki, Institute for Atmospheric and Earth System Research / Physics, P.O. Box 68, FI, 00014, Finland; University of Helsinki, Helsinki Institute of Sustainability Science, Yliopistonkatu 3, FI, 00014, Finland. University of Helsinki, Institute for Atmospheric and Earth System Research / Physics, P.O. Box 68, FI, 00014, Finland. University of Helsinki, Ecosystems and Environment Research Programme, Faculty of Biological and Environmental Sciences, Niemenkatu 73, FI, 15140, Lahti, Finland" |
| DOI: | 10.1016/j.envpol.2020.115294 |
| ISSN/ISBN: | 1873-6424 (Electronic) 0269-7491 (Linking) |
| 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" |
| Keywords: | Air Pollutants/*analysis Air Pollution/*analysis Baltimore China Environmental Monitoring Finland Forests Particulate Matter/analysis Trees Air pollution Air quality Nanoparticles Urban forest Urban trees; |
| Notes: | "MedlineViippola, Viljami Yli-Pelkonen, Vesa Jarvi, Leena Kulmala, Markku Setala, Heikki eng England 2020/08/18 Environ Pollut. 2020 Nov; 266(Pt 2):115294. doi: 10.1016/j.envpol.2020.115294. Epub 2020 Aug 1" |
