D ispersion of A ir P ollutants & their P enetration into the L ocal E nvironment EPSRC...
13
Dispersion of Air Pollutants & their Penetration into the Local Environment EPSRC Infrastructure & Environment Programme Dr Samantha Arnold (C.Geog.) DAPPLE Fieldwork Manager Dept. of Env. Sci. & Tech., Imperial College London & Dept. of Meteorology, University of Reading Thursday 26 th August 2004, Clean Air Congress, London. Marylebone Rd Gloucester Pl
-
Upload
jasmin-simpson -
Category
Documents
-
view
240 -
download
7
Transcript of D ispersion of A ir P ollutants & their P enetration into the L ocal E nvironment EPSRC...
Dispersion of
Air
Pollutants & their
Penetration into the
Local
Environment
EPSRC Infrastructure & Environment Programme
Dr Samantha Arnold (C.Geog.)DAPPLE Fieldwork Manager
Dept. of Env. Sci. & Tech., Imperial College London& Dept. of Meteorology, University of Reading
Thursday 26th August 2004, Clean Air Congress, London.
Marylebone Rd
Gloucester Pl
Thursday 26th August 2004, Clean Air Congress, London.
To enhance understanding of dispersion processes,
over short distances, at a street canyon intersection.
To use this information to make improvements in
predictive ability that will enable better planning
and management of urban air quality, accidental
and non-accidental releases, and the development of
safer more sustainable cities.
Aims:
Consortium:
Supported by:London - ALG/APRIL/EA/Local Government/TfL/WCC
DEFRA, AEQ Division, DSTL, HSE, Home Office, Met Office
Thursday 26th August 2004, Clean Air Congress, London.
University of Surrey Wind Tunnel
University of Cambridge Numerical Modelling
Imperial College Personal Exposure
University of Leeds Traffic, Pollution & Met.
University of Reading Meteorology
University of Bristol Tracer Release
Thursday 26th August 2004, Clean Air Congress, London.
Field Site:
Thursday 26th August 2004, Clean Air Congress, London.
During oblique rooftop winds (a) the flow in the constrained streets can be explained by the linear superposition of the parallel (b) and perpendicular (c) rooftop components (with relation to the streets); the parallel component giving the direction of channelling and the perpendicular component driving in-street recirculation/helical vortex.
In-Street Flow:
(a)
(b)
(c) (b)
(c)
Thursday 26th August 2004, Clean Air Congress, London.
0
0.5
1
1.5
2
2.5
3
00:00
01:00
02:00
03:00
04:00
05:00
06:00
07:00
08:00
09:00
10:00
11:00
12:00
13:00
14:00
15:00
16:00
17:00
18:00
19:00
20:00
21:00
22:00
23:00
Time on 15th May 03
CO
(pp
m)
4 (S)
3 (N)
2 (C)
Light winds Stronger SSW winds
NS
CO, 4 (S)
CO, 2 (C)
CO, 3 (N)
Pollution implied in-street vortex during oblique rooftop winds.
Pollution:
Thursday 26th August 2004, Clean Air Congress, London.
At the intersection winds are relatively unconstrained, hence oblique rooftop winds decompose along the two streets. This is visible in the double peak of the Site 1 wind direction pdf below.
Intersection Winds:
Thursday 26th August 2004, Clean Air Congress, London.
Relative Wind Directions:
Rooftop SSWθ = + 50
Rooftop Wθ = - 20
Marylebone RdWNW θ = 0
S wind Gloucester Pl
N wind Gloucester Pl
θ = - 20
θ = + 50
θ = 0
Thursday 26th August 2004, Clean Air Congress, London.
Tracer - Temporal:
0.00
30.00
60.00
90.00
0 5 10 15 20 25 30Time (Mins)
An
gle
to
Rd
Wind Direction
• Time of flight (tstart-
t50%conc) = 4.5 mins
• Rapid vertical mixing (see WCC)
• Coherent trends in tracer concentrations
WCC
Thursday 26th August 2004, Clean Air Congress, London.
The maximum concentration of the tracer gas decreases with increasing straight line fetch (R = 50-250 m) from the release.
Tracer - Spatial:
Thursday 26th August 2004, Clean Air Congress, London.
Personal Exposure:
Personal exposure is consistently greater than fixed monitoring stations would suggest
Mean personal exposure is highly variable in both space and time – synchronised sampling and visualisation with HSL.
0
10
20
30
40
50
60
70
80
90
Min Mean Max
PM
2.5
Co
nc.
Personal ExpMaryleboneBloomsbury
Thursday 26th August 2004, Clean Air Congress, London.
DAPPLE Summary:
Chemical Release
Where?Orientation of the Roads
When?Wind direction above roof
Relative angle of the approach flowDecompose flow into the streets for direction of transport of release – channelled, vortex
etc.
Define hazard area Based on transport direction, flow speed,
decrease in release conc. with distance, etc
Time & Space
Dependent
Check interpretation using pollution data and incorporate difference between fixed monitoring and actual personal exposure which may be
greater
Thursday 26th August 2004, Clean Air Congress, London.
Despite the complexity of the urban intersection topology the main
features of the mean wind field can be related to those described in
idealised 2-D canyons. This information can be used to interpret in-
street, time averaged, tracer and pollution concentrations. Further
work is required to relate the these data to the non-static, personal
exposure measurements.
Analysis of the data from the two DAPPLE field campaigns and a
road dust release experiment is on going. Additional tracer releases
will be conducted in Oct 2004 at the request of the Home Office.
For more details and publications please see http://www.dapple.org.uk
Conclusions:
![CHARACTERIZATION AND DYNAMICS OF AIR OLLUTANTS IN … · Environmental Scoping Study (LRGVESS)[2] started to provide systematic data on air pollution sources, transboundary transport](https://static.fdocuments.us/doc/165x107/5e200567fdc30a487d4fc267/characterization-and-dynamics-of-air-ollutants-in-environmental-scoping-study-lrgvess2.jpg)
![World Bank Document 1 Air Pollutants Emission For Ratchaburi Power Plant Project.]?ollutants Unit Power Plant Emissionsa Thai Eiiiission Standar(ds World Bank Gni(ieliCresc Remlar11klis](https://static.fdocuments.us/doc/165x107/5b004c137f8b9a84338c6e1b/world-bank-document-1-air-pollutants-emission-for-ratchaburi-power-plant-projectollutants.jpg)