Fine-scale spatial structure of air pollutant concentrations along bus routes

Yang Xing; Peter Brimblecombe; Zhi Ning

doi:10.1016/j.scitotenv.2018.12.001

Fine-scale spatial structure of air pollutant concentrations along bus routes

Sci Total Environ. 2019 Mar 25:658:1-7. doi: 10.1016/j.scitotenv.2018.12.001. Epub 2018 Dec 3.

Authors

Yang Xing¹, Peter Brimblecombe², Zhi Ning³

Affiliations

¹ School of Energy and Environment, City University of Hong Kong, Hong Kong.
² School of Energy and Environment, City University of Hong Kong, Hong Kong; Guy Carpenter Asia-Pacific Climate Impact Centre (GCACIC), School of Energy and Environment, City University of Hong Kong, Hong Kong. Electronic address: p.brimblecombe@uea.ac.uk.
³ Division of Environment and Sustainability, The Hong Kong University of Science and Technology Clear Water Bay, Kowloon, Hong Kong.

PMID: 30572209
DOI: 10.1016/j.scitotenv.2018.12.001

Abstract

Air pollution measurements were made at 5 s intervals along a bus route in Hong Kong, chosen to avoid frequent intersections or traffic jams. This allowed periodic pollutant concentration patterns in bus-derived pollutants to be explored using Fourier analysis. The analysis showed the defining role of the bus stops in terms of NO_X and PM_2.5 concentrations, which have profiles with a sawtooth form. Early in inter-stop segments, concentrations are high, followed by a decline. This arises from high emissions during the acceleration away from the bus stop, then lower emissions during cruise and de-acceleration. This pattern can be enhanced on sections of the route where buses are frequent as pollutants accumulate from the larger number of buses. The high concentrations just beyond bus stops may have implications for planning bus routes and the positioning of bus stops.

Keywords: Bus stops; Diesel pollutants; Fourier analysis; On-road measurements; Roadside pollution; Vehicle emission model.