Nature-based solution for mitigation of pedestrians’ exposure to airborne particles of traffic origin in a tropical city

Abstract

This study investigated the effectiveness of vegetation barriers (VBs) planted along roadsides in a highly urbanized tropical Asian city-state to mitigate pedestrians’ exposure to airborne particles (PM) of traffic origin for the first time. Mobile and fixed-site measurements of black carbon (BC) and ultrafine particles (UFPs) were conducted with three types of VBs (green walkway covered with creepers; hedgerow; and three-layer hedges with varying heights) using portable PM devices. The three-layered hedges showed higher BC and UFPs reductions (the average reduction of about 60%) than the other two configurations (20–40%). Deposition of PM with diverse size, morphology and elemental composition onto VBs leaves plays an important role in reducing PM exposure concentration, providing health benefits to pedestrians involved in active mobility on roads. Our findings provide a scientific basis for formulating appropriate guidelines for selecting and installing VBs to reduce the inhalation exposure of pedestrians to PM of traffic origin.