Sources and sinks of urban aerosols

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Objectives

  • measure size-segregated land-atmosphere fluxes of aerosols directly over urban areas at a time scale of 30 minutes
  • quantify the role of surface activities (traffic, constructions etc) and meteorological variables in the control of fluxes
  • provide a model describing the emission fluxes, transport, transformation and deposition footprint of aerosols for general application as a planning tool
  • determine the fate of urban aerosols of different size and chemical composition, together with their transport distance and the influence of land use.

Location

Edinburgh

Approach

In a novel approach, this project will use existing fast response instruments on a high-level construction crane to measure the vertical fluxes of aerosols in the turbulent boundary-layer above the buildings of a major city. The measurements will provide size resolved 30-minute average fluxes of atmospheric particles in the size range 100 nm to 5 Ám, and possibly beyond 5Ám, from a 1 km2 to 10 km2 footprint. Using such methods in the turbulent boundary-layer, the project will quantify the net vertical production of aerosols by mechanical or biological activity within the city and the chemical production within the urban boundary-layer. The relationships between the measured fluxes and the major variables will be examined.

The urban measurements will be contrasted with similar flux measurements within the urban plume from the same city but at a distance of 20 km downwind. The degree to which the chemical nature of the aerosol is modified by gas-to-particle conversions will be assessed by comparing the particle size-spectra at the two sites and correlating them with precursor gas concentrations. In this way, the project will study the underlying physics of aerosol production, transport and deposition to identify the large scale processes of aerosol production in urban areas and will quantify the fate downwind.

Start Date/Duration

April 1998 Two years

Lead Organisations

NERC Centre for Ecology and Hydrology, Edinburgh

University of Manchester Institute of Science and Technology

NERC British Antarctic Survey

Deliverables

  • an extensive dataset of direct measurements of vertical aerosol exchange fluxes averaged over a large urban footprint above a major city in a wide range of conditions
  • an estimate of the contribution of various urban activities to the net exchange flux of the major particle modes, including resuspension and emissions from motor vehicles, heating combustion and construction activities and the effects of the key meteorological variables on fluxes and concentrations
  • an estimate of the spatial distribution of the urban sources and sinks within the fetch of the measurements
  • quantification of the contribution of gas-to-particle conversion to the urban aerosol budget and estimates of the processes and time-scales involved
  • a model describing the urban vertical aerosol fluxes due to emission, resuspension and gas-to-particle production as well as dry deposition within and downwind of a large urban area
  • a means for urban planners to quantify the effects of land use and transport strategies on aerosol production and deposition within and downwind of urban areas
  • a means to quantify the fate of urban aerosols, their travel distance and composition.

Users

Edinburgh Council

Further Details

Further information is available from the following contacts:

Lead Researcher: Prof D Fowler

Tel: 0131 445 4343, Fax: 0131 445 3943, e-mail: d.fowler@ite.ac.uk 

URGENT Programme Manager: Graham Leeks

Tel: 01491 692203, Fax: 01491 692313, e-mail: gjll@ceh.ac.uk