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Objectives
The objectives of this project are
to calculate the benefits of large-scale urban tree planting programmes
as a means of reducing human exposure to air pollutants. This will
involve:
- Mapping existing vegetation cover in the
conurbation.
- Discussing with planning authorities and other
local government departments possible scenarios for large-scale tree
planting on both public and private land in the conurbation.
- Estimating the removal rates of air pollutants
by trees under present tree cover conditions and under various
future planting programme scenarios. The pollutants to be considered
include SO2, NO, NO2, PM10, O3
and volatile organic compounds (VOCs) including benzene.
- Calculating the emission rates of VOCs from
trees under present and future scenarios.
- Calculating the incremental amount of ozone and
aerosol likely to be formed as a result of these enhanced VOC
emission rates arising from large-scale tree planting.
Location
West Midlands
Approach
The West Midlands will be used as
a case study because of the data and knowledge base that will arise from
the URGENT PUMA project which will provide an essential input to this
project. There will also be interaction with one other URGENT project, Thermal
climatology of the West Midlands. The models derived will, however,
be applicable elsewhere.
The atmospheric transport and
chemistry model that will be used will extend previous urban plume
models, particularly with respect to those parts of the chemistry,
emission and deposition schemes that are most sensitive to changes in
tree population. A simple Lagrangian treatment of transport in the
planetary boundary layer will be used. This will be coupled to a complex
chemistry scheme which is compatible with state-of-the-art explicit
structure-reactivity relationships and also compatible with global
modelling studies.
Start date and duration
January 1999 Three years, plus 6
months extension
Lead Organisations
Lancaster University
CEH Edinburgh
Deliverables
- Quantitative information on the present and
possible future tree cover in the West Midlands conurbation,
together with estimates of the financial costs of a large-scale tree
planting programme.
- Estimates of the possible reductions in air
pollutant concentrations, and hence, reductions in human exposure to
air pollutants achievable by large-scale tree planting.
- Estimates of the detrimental effects of tree
planting to VOC emissions and the resultant likely increases in
downwind ozone and aerosol particle concentrations under a number of
possible future emission control and planting scenarios.
- Surveying, measurement and modelling
methodologies that can be applied to other conurbations and to other
similar problems of environmental cost-benefit analysis.
- Major publication in the peer-reviewed
literature.
Progress to date
- An urban classification has been derived for the
900 km2 of West Midland conurbation using principal
component analysis and cluster analysis based on 27 attributes
describing the land cover of each km2. Thus each km2
has been allocated one of 8 urban classes (villages and farms, open
water and farms, woodlands, very light suburban, light suburban, dense
suburban urban, dense urban).
- Urban morphology types have been mapped onto
urban land class using the definitions in the "Trees in
Towns" report (HMSO, 1994). From this mapping, a first estimate
has been made of tree cover in the West Midlands area.
- First estimates of biogenic VOC and anthropogenic
PM10 emission potentials from the West Midlands area have been made at
1 km2 resolution. These estimates were made using the urban
classification tree cover estimate, data from existing biogenic VOC
emissions and biomass databases (Stewart et al., 1995), and
anthropogenic pollutant concentrations and emissions inventories for
the West Midlands (LRC, 1996; Veal et al., 1997). A first
estimate has also been made of PM10 deposition and removal by trees in
the West Midlands area.
- A tree survey methodology has been devised and
surveying of trees in the West Midland area is underway. Twelve
one-hectare plots are being surveyed in km2 samples for
each of the 8 urban classes. Each tree within the survey plots are
recorded with details of height, age, condition, aspect, crown spread
etc. More than 5,000 trees in 79 ha have been surveyed to date. This
will provide current tree data for more accurate estimates of biogenic
VOC emissions, and pollution deposition.
- Meetings have been held with each of the 7 West
Midland Metropolitan Borough Councils to discuss their existing tree
data and tree planting policies and to encourage councillors to
consider their requirements from our project. A systematic mining of
each council’s existing tree data is currently underway. This will
supplement and complement the field survey data.
- Workshops are planned for councils and other
end-users in early 2001 to discuss future planting scenarios and to
determine how we can accommodate end-user requirements.
Users
Birmingham City Council
Other local authorities
Further Details
Further information is available
from the following contacts:
Lead Researcher: Prof C N Hewitt
Tel: 01524 593931, Fax: 01524 593985, e-mail: n.hewitt@lancaster.ac.uk
URGENT Programme Manager: Graham
Leeks
Tel: 01491 692203, Fax: 01491
692313, e-mail: gjll@ceh.ac.uk |
