Evaluating the Impact of a Wall-Type Green Infrastructure on PM10 and NOx Concentrations in an Urban Street Environment

Maria Gabriella Villani,Antonio Piersanti,Luisella Ciancarella,Gianni Tinarelli,Mario Adani,Peter Sänger,Stefano Decesari,Claudio Carbone,Matteo Rinaldi,Lina Vitali,Felicita Russo,Gabriele Zanini,Antonio Donateo

doi:10.3390/atmos12070839

Abstract

Nature-based solutions can represent beneficial tools in the field of urban transformation for their contribution to important environmental services such as air quality improvement. To evaluate the impact on urban air pollution of a CityTree (CT), an innovative wall-type green infrastructure in passive (deposition) and active (filtration) modes of operation, a study was conducted in a real urban setting in Modena (Italy) during 2017 and 2018, combining experimental measurements with modelling system evaluations. In this work, relying on the computational resources of CRESCO (Computational Centre for Research on Complex Systems)/ENEAGRID High Performance Computing infrastructure, we used the air pollution microscale model PMSS (Parallel Micro-SWIFT-Micro SPRAY) to simulate air quality during the experimental campaigns. The spatial characteristics of the impact of the CT on local air pollutants concentrations, specifically nitrogen oxides (NOx) and particulate matter (PM10), were assessed. In particular, we used prescribed bulk deposition velocities provided by the experimental campaigns, which tested the CT both in passive (deposition) and in active (filtration) mode of operation. Our results showed that the PM10 and NOx concentration reductions reach from more than 0.1% up to about 0.8% within an area of 10 × 20 m2 around the infrastructure, when the green infrastructure operates in passive mode. In filtration mode the CT exhibited higher performances in the abatement of PM10 concentrations (between 1.5% and 15%), within approximately the same area. We conclude that CTs may find an application in air quality hotspots within specific urban settings (i.e., urban street canyons) where a very localized reduction of pollutants concentration during rush hours might be of interest to limit population exposure. The optimization of the spatial arrangement of CT modules to increment the “clean air zone” is a factor to be investigated in the ongoing development of the CT technology.

Highlights

With the proportion of the European population living in urban areas expected to rise to over 80% by 2050 [1], making European cities sustainable for human health has become a key challenge
When we take into consideration the pollutant abatement caused by the CT in passive mode, we observe that reductions of nitrogen oxides (NOx) and PM10 concentrations are smaller than 1% in an area of about of 10 × 20 m2 around the CT and at the same height as that of the green wall
We presented an application of the modelling suite Micro-SWIFT-SPRAY (PMSS) as a reasonable tool for an estimate of the impact of a single CityTree (CT) on the abatement of air pollution concentrations, such as PM10 and NOx, in viale Verdi, Modena (Italy)

Summary

Introduction

With the proportion of the European population living in urban areas expected to rise to over 80% by 2050 [1], making European cities sustainable for human health has become a key challenge. This challenge includes efforts to improve air quality by reducing emissions, and by modifying the urban morphology to reduce the exposure of the population to air pollution [2,3]. The results in [6] identified six specific policy interventions, underpinned by research, allowing green infrastructures to improve air quality with unambiguous benefits. It is crucial to develop design guidelines, vital for promoting and optimizing greening benefits

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