Exposure Reduction by Green Vegetation Barriers in Near-Road Environments: The Guildford Iscape Case Study

Traffic generated emissions contribute to increased air pollution exposure in near-road environments where commuters such as pedestrians and cyclists are exposed to higher concentration levels. Near-road microenvironment extends over few hundred meters from highways where a significant number of people get exposed to high pollution exposure. For example, over 45 million people in the USA alone live or work with in 100m from heavy traffic ways in the US (EPA, 2016). This result in a range of health implications such as exacerbation of asthma, impaired lung function, cardiovascular morbidity and mortality, adverse birth outcomes, and cognitive declines (HEI, 2010). Green interventions such as vegetation barriers, trees, hedges and green walls are effective in reducing pollutant concentration near open road regions by up to 60% than a clear area without the vegetation (Abhijith et al., 2017). These infrastructural solutions are effective in reducing pollutant concentration in the most important exposure zone which is 50m from the roadsides. These lower the pollutant exposure by enhancing dispersion and removing them through deposition and absorption. Moreover, scientific planning of vegetation barrier along open roads leads to improvement of downwind air quality (Abhijith et al., 2017). As a part of an ongoing EU funded project iSCAPE (www.iscapeproject.eu), this study aims to quantify the impact of green barriers under a variety of real-world conditions through field measurements in Guildford, a typical UK town close to London. The data obtained from the experiments will be used to support modelling assumptions and determine pollutants deposited/absorbed and dispersed in presence of green interventions. We also aim to assess the effects of vegetation parameters such as height, thickness, and leaf area index on deposition and dilution of pollutants. Combining the results of field and numerical modelling studies, we anticipate to use the findings in formulating evidence-based practical recommendations on planting vegetation barrier under near road conditions.

Acknowledgements

This work has been led by the Global Centre for Clean Air Research (GCARE) team at the University of Surrey (UK) under the iSCAPE (Improving Smart Control of Air Pollution in Europe) project, which is funded through the European Community’s H2020 Programme under the Grant Agreement No. 689954.

References

Abhijith, K.V., Kumar, P., Gallagher, J., McNabola, A., Baldauf, R., Pilla, F., Broderick, B., Di Sabatino, S., Pulvirenti, B., 2017. Air pollution abatement performances of green infrastructure in open road and built-up street canyon environments – A review. Atmospheric Environment 162, 71-86.

EPA, 2016. Health Impacts of Near Roadway Air Pollution and Mitigation Strategies Different types of roadways.

HEI, 2010. Traffic-related air pollution: a critical review of the literature on emissions, exposure, and health effects. Health Effects Institute, pp.1–386.