Quantifying the effectiveness of vegetation to reduce PM2.5 concentrations in urban background

Abstract

An observational approach has been undertaken in order to quantify the effectiveness of vegetation (combination of vegetation barriers, hedges and bushes) in reducing particulates matter of 2.5 mu dimeters in near-roadside locations within urban backgrounds. The other primary purpose of the study is to observe the influence of wind direction on PM2.5 concentration. The campaign of high time resolution measurements located on road-side in Manchester, at Lloyd Street (a non-vegetated spot), the other monitoring took place behind the vegetation belt at the same location (2.3m from the road). Results from the experiment indicate the capabilities of this location and the vegetation as therein configured to filter PM2.5 concentration in range of 15 to 80 percent from kerbside concentration, and also vegetation deceased the frequent concentration spikes at roadside. Nevertheless, there is also a possible drawback to the planted vegetation belt, which we noticed during our analysis of the concentration at the roadside. It might cause wind recirculation in canyon due to the high porosity of the vegetation and this could, in turn, lead to decreasing dispersion and increasing PM2.5 concentration locally. Therefore, it is very important to pay attention to the design of local landscape and other variables if the purpose of planting vegetation is to filter, and reduce, PM2.5 concentrations. With regard to the influence of wind direction on either the levels of local concentration or the reduction of PM2.5, there is not sufficient evidence to prove the influence of wind direction on local concentration. This is an issue that would benefit from future work on the impact of wind direction on PM concentration at local level.