The effects of trees on air pollutant levels in peri-urban near-road environments

Research output: Contribution to journalArticleScientificpeer-review

Abstract

It is often stated that plants remove air pollutants from the urban atmosphere with their large leaf area, thus providing benefits − i.e. ecosystem services − for citizens. However, empirical evidence showing that local-scale air quality is uniformly improved by urban forests is scarce. We studied the influence of conifer-dominated peri-urban forests on the springtime levels of NO2 and particle pollution at different distances from roads, using passive samplers and high time resolution particle counters in a northern climate in Finland. Passive samplers provided average values over a one month period, while active particle counters provided real time measurements of air pollution to mimic human inhalation frequency. NO2 concentrations were slightly higher in forests than in adjacent open areas, while passive particle measurements showed the opposite trend. Active particle monitoring campaigns showed no systematic forest effect for PM2.5, but larger particles were reduced in the forest, corroborating the passive sampling result.

Attenuation rates of the mean values of the studied pollutants did not differ between the forest and open habitats. However, high time resolution particle data revealed a distance effect that was apparent only in the forest transect: peak events at the forest edge were higher, while peaks furthest from the road were lower compared to the open transect. Furthermore, the magnitude of PM2.5 peak events was distinctly higher at forest edge than equivalent distance in the open area.

Vegetation characteristics, such as canopy cover and tree density, did not explain differences in pollutant levels in majority of cases. Our results imply that evergreen-dominated forests near roads can slightly worsen local air quality regarding NO2 and PM2.5 in northern climates, but that coarser particle pollution can be reduced by such forest vegetation. It seems that the potential of roadside vegetation to mitigate air pollution is largely determined by the vegetation effects on airflow.
Original languageEnglish
JournalUrban Forestry & Urban Greening
Volume30
Pages (from-to)62-71
Number of pages10
ISSN1618-8667
DOIs
Publication statusPublished - 21 Feb 2018
MoE publication typeA1 Journal article-refereed

Fields of Science

  • 1172 Environmental sciences

Cite this

@article{17dde89672a14672aafe16b39a2db712,
title = "The effects of trees on air pollutant levels in peri-urban near-road environments",
abstract = "It is often stated that plants remove air pollutants from the urban atmosphere with their large leaf area, thus providing benefits − i.e. ecosystem services − for citizens. However, empirical evidence showing that local-scale air quality is uniformly improved by urban forests is scarce. We studied the influence of conifer-dominated peri-urban forests on the springtime levels of NO2 and particle pollution at different distances from roads, using passive samplers and high time resolution particle counters in a northern climate in Finland. Passive samplers provided average values over a one month period, while active particle counters provided real time measurements of air pollution to mimic human inhalation frequency. NO2 concentrations were slightly higher in forests than in adjacent open areas, while passive particle measurements showed the opposite trend. Active particle monitoring campaigns showed no systematic forest effect for PM2.5, but larger particles were reduced in the forest, corroborating the passive sampling result.Attenuation rates of the mean values of the studied pollutants did not differ between the forest and open habitats. However, high time resolution particle data revealed a distance effect that was apparent only in the forest transect: peak events at the forest edge were higher, while peaks furthest from the road were lower compared to the open transect. Furthermore, the magnitude of PM2.5 peak events was distinctly higher at forest edge than equivalent distance in the open area.Vegetation characteristics, such as canopy cover and tree density, did not explain differences in pollutant levels in majority of cases. Our results imply that evergreen-dominated forests near roads can slightly worsen local air quality regarding NO2 and PM2.5 in northern climates, but that coarser particle pollution can be reduced by such forest vegetation. It seems that the potential of roadside vegetation to mitigate air pollution is largely determined by the vegetation effects on airflow.",
keywords = "1172 Environmental sciences, Ecosystem services, NO2, Particulate Matter, Passive samplers, PM2.5, Urban vegetation",
author = "Viippola, {Juho Viljami} and Thomas Whitlow and Wenlin Zhao and Yli-Pelkonen, {Vesa Johannes} and Mikola, {Juha Tapio} and Richard Pouyat and Set{\"a}l{\"a}, {Heikki Martti}",
year = "2018",
month = "2",
day = "21",
doi = "10.1016/j.ufug.2018.01.014",
language = "English",
volume = "30",
pages = "62--71",
journal = "Urban Forestry & Urban Greening",
issn = "1618-8667",
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}

The effects of trees on air pollutant levels in peri-urban near-road environments. / Viippola, Juho Viljami; Whitlow, Thomas; Zhao, Wenlin; Yli-Pelkonen, Vesa Johannes; Mikola, Juha Tapio; Pouyat, Richard; Setälä, Heikki Martti.

In: Urban Forestry & Urban Greening, Vol. 30, 21.02.2018, p. 62-71.

Research output: Contribution to journalArticleScientificpeer-review

TY - JOUR

T1 - The effects of trees on air pollutant levels in peri-urban near-road environments

AU - Viippola, Juho Viljami

AU - Whitlow, Thomas

AU - Zhao, Wenlin

AU - Yli-Pelkonen, Vesa Johannes

AU - Mikola, Juha Tapio

AU - Pouyat, Richard

AU - Setälä, Heikki Martti

PY - 2018/2/21

Y1 - 2018/2/21

N2 - It is often stated that plants remove air pollutants from the urban atmosphere with their large leaf area, thus providing benefits − i.e. ecosystem services − for citizens. However, empirical evidence showing that local-scale air quality is uniformly improved by urban forests is scarce. We studied the influence of conifer-dominated peri-urban forests on the springtime levels of NO2 and particle pollution at different distances from roads, using passive samplers and high time resolution particle counters in a northern climate in Finland. Passive samplers provided average values over a one month period, while active particle counters provided real time measurements of air pollution to mimic human inhalation frequency. NO2 concentrations were slightly higher in forests than in adjacent open areas, while passive particle measurements showed the opposite trend. Active particle monitoring campaigns showed no systematic forest effect for PM2.5, but larger particles were reduced in the forest, corroborating the passive sampling result.Attenuation rates of the mean values of the studied pollutants did not differ between the forest and open habitats. However, high time resolution particle data revealed a distance effect that was apparent only in the forest transect: peak events at the forest edge were higher, while peaks furthest from the road were lower compared to the open transect. Furthermore, the magnitude of PM2.5 peak events was distinctly higher at forest edge than equivalent distance in the open area.Vegetation characteristics, such as canopy cover and tree density, did not explain differences in pollutant levels in majority of cases. Our results imply that evergreen-dominated forests near roads can slightly worsen local air quality regarding NO2 and PM2.5 in northern climates, but that coarser particle pollution can be reduced by such forest vegetation. It seems that the potential of roadside vegetation to mitigate air pollution is largely determined by the vegetation effects on airflow.

AB - It is often stated that plants remove air pollutants from the urban atmosphere with their large leaf area, thus providing benefits − i.e. ecosystem services − for citizens. However, empirical evidence showing that local-scale air quality is uniformly improved by urban forests is scarce. We studied the influence of conifer-dominated peri-urban forests on the springtime levels of NO2 and particle pollution at different distances from roads, using passive samplers and high time resolution particle counters in a northern climate in Finland. Passive samplers provided average values over a one month period, while active particle counters provided real time measurements of air pollution to mimic human inhalation frequency. NO2 concentrations were slightly higher in forests than in adjacent open areas, while passive particle measurements showed the opposite trend. Active particle monitoring campaigns showed no systematic forest effect for PM2.5, but larger particles were reduced in the forest, corroborating the passive sampling result.Attenuation rates of the mean values of the studied pollutants did not differ between the forest and open habitats. However, high time resolution particle data revealed a distance effect that was apparent only in the forest transect: peak events at the forest edge were higher, while peaks furthest from the road were lower compared to the open transect. Furthermore, the magnitude of PM2.5 peak events was distinctly higher at forest edge than equivalent distance in the open area.Vegetation characteristics, such as canopy cover and tree density, did not explain differences in pollutant levels in majority of cases. Our results imply that evergreen-dominated forests near roads can slightly worsen local air quality regarding NO2 and PM2.5 in northern climates, but that coarser particle pollution can be reduced by such forest vegetation. It seems that the potential of roadside vegetation to mitigate air pollution is largely determined by the vegetation effects on airflow.

KW - 1172 Environmental sciences

KW - Ecosystem services

KW - NO2

KW - Particulate Matter

KW - Passive samplers

KW - PM2.5

KW - Urban vegetation

U2 - 10.1016/j.ufug.2018.01.014

DO - 10.1016/j.ufug.2018.01.014

M3 - Article

VL - 30

SP - 62

EP - 71

JO - Urban Forestry & Urban Greening

JF - Urban Forestry & Urban Greening

SN - 1618-8667

ER -