title: Degradation in urban air quality from construction activity and increased traffic arising from a road widening scheme.
abstract: Road widening schemes in urban areas are often proposed as a solution to traffic congestion and as a means of stimulating economic growth. There is however clear evidence that new or expanded roads rapidly fill with either displaced or induced traffic, offsetting any short-term gains in eased traffic flows. What has not been addressed in any great detail is the impact of such schemes on air quality, with modelled impact predictions seldom validated by measurements after the expansion of road capacity. In this study we made use of a road widening project in London to investigate the impact on ambient air quality (particulate matter, NOX, NO2) during and after the completion of the road works. PM10 increased during the construction period up to 15 μg m(-3) during working hours compared to concentrations before the road works. A box modelling approach was used to determine a median emission factor of 0.0022 kg PM10 m(-2) month(-1), three times larger than that used in the UK emission inventory (0.0007 kg PM10 m(-2) month(-1)). Peaks of activity released 0.0130 kg PM10 m(-2) month(-1), three and eight times smaller than the peak values used in the European and US inventories. After the completion of the widening there was an increase in all pollutants from the road during rush hour: 2-4 μg m(-3) for PM10; 1 μg m(-3) for PM2.5; 40 and 8 μg m(-3) for NOX and NO2, respectively. NO2 EU Limit Value was breached after the road development illustrating a notable deterioration in residential air quality. Additionally, PM10, but not PM2.5, glutathione dependent oxidative potential increased after the road was widened consistent with an increase in pro-oxidant components in the coarse particle mode, related to vehicle abrasion processes. These increased air pollution indices were associated with an increase in the number of cars, taxis and LGVs.
authors.affiliation: MRC PHE Centre for Environment and Health, King's College London, 150 Stamford Street, London SE1 9NH, United Kingdom. Electronic address: anna.font_font@kcl.ac.uk.
authors.forename: Anna
authors.initials: A
authors.lastname: Font
authors.affiliation: MRC PHE Centre for Environment and Health, King's College London, 150 Stamford Street, London SE1 9NH, United Kingdom.
authors.forename: Timothy
authors.initials: T
authors.lastname: Baker
authors.affiliation: MRC PHE Centre for Environment and Health, King's College London, 150 Stamford Street, London SE1 9NH, United Kingdom.
authors.forename: Ian S
authors.initials: IS
authors.lastname: Mudway
authors.affiliation: MRC PHE Centre for Environment and Health, King's College London, 150 Stamford Street, London SE1 9NH, United Kingdom.
authors.forename: Esme
authors.initials: E
authors.lastname: Purdie
authors.affiliation: MRC PHE Centre for Environment and Health, King's College London, 150 Stamford Street, London SE1 9NH, United Kingdom.
authors.forename: Christina
authors.initials: C
authors.lastname: Dunster
authors.affiliation: MRC PHE Centre for Environment and Health, King's College London, 150 Stamford Street, London SE1 9NH, United Kingdom.
authors.forename: Gary W
authors.initials: GW
authors.lastname: Fuller
mesh_terms: D000393:Air Pollutants / Q000032:analysis*; D000397:Air Pollution / Q000706:statistics & numerical data*; D004784:Environmental Monitoring; D008131:London; D008962:Models, Theoretical; D014186:Transportation / Q000706:statistics & numerical data*
chemical_list: D000393:Air Pollutants
keywords: Air quality impacts; Construction PM(10) emission factor; Induced traffic; Oxidative potential; Road widening schemes; Source apportionment