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

Field investigations for evaluating green infrastructure effects on air quality in open-road conditions

“…All close-road sites exhibited positive differences in PM2.5, ranging from 2% to 7% in the cross-vegetation wind category (Table S2). Past studies investigating different GI (Brantley et al, 2014;Chen et al, 2016;Tong et al, 2015;Viippola et al, 2018;Morakinyo et al, 2016) recorded a mixed (increase or decrease) trend for PM2.5 (Table 1), as was also noticed in this study. Hedges and trees with hedges were effective in reducing PM2.5.…”

“…The highest deterioration (22%) in ΔPM10 behind GI was noticed in the hedge only (HCB) scenario of close-road sites. Almost all previous awayroad studies (Chen et al, 2016;Islam et al, 2012;Shan et al, 2007;Tiwary et al, 2008) have reported a high reduction of PM10 compared to close-road (Chen et al, 2015;Viippola et al, 2018).…”

“…These concentrations could be due to a relatively low height of HCB (<1m) that is insufficient to create a barrier effect. Similarly, past investigations have reported mixed results of pollutant concentrations behind trees that emerged from a lack of barrier effect at breathing height and lower density (Brantley et al, 2014;Chen et al, 2016;Hagler et al, 2012;Viippola et al, 2018;Yli-Pelkonen et al, 2017). In addition, major reasons for higher pollutant concentrations behind trees (TCB; single tree row) compared with TIB (multiple tree rows, up to 4) was due to the difference in thickness of tree rows and lower canopy to ground distance.…”

“…Both instruments measured PM mass concentrations in 31 different size channels at a resolution of 6 seconds. These instruments have been widely used for PM concentration measurements (Azarmi and Kumar, 2016;Rivas et al, 2017;Viippola et al, 2018). The mass of bulk particles was collected on a PTFE filter in the GRIMM monitors, which were analysed using SEM-EDS to allow chemical and morphological exploration (Azarmi and Kumar, 2016;Rivas et al, 2017) (Section 2.4).…”

Urban Vegetation in Air Quality Management: A Review and Policy Framework

“…On-site air quality measurements, also if coupled with field vegetation inventories, and data analysis [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] On-site air quality measurements or soil sampling, measurements of pollution removal by means of laboratory techniques, including instrumental analysis on plant samples (e.g., microscopic analysis, spectroscopy, gravimetry, gas exchange measurements, wind tunnel experiments on leaves or branches etc.) and data analysis [31][32][33][34][35] Measurements of pollution removal by means of laboratory techniques, including instrumental analysis on plant samples and data analysis [11][12][13] Estimates of pollution removal by vegetation or statistical analysis based on field plant inventories or remote sensing data and existing literature/databases or air quality data [60][61][62][63][64][65][66] Modelling Approaches…”