Application of the General Finite Line Source Model to the prediction of

Benzene concentrations adjacent to a motorway in Ireland.

Rajiv Ganguly

Brian M. Broderick

Department of Civil, Structural and Environmental Engineering

Trinity College Dublin

Overview

v  Objectives

v  General Finite Line Source Model (GFLSM)

v  Comparison of Monitored and GFLSM data (M50)

v  Comparison of GFLSM with CALINE4 (M50) v  Conclusions

Overall Research Objectives

Ø  To identify suitable modelling techniques for motorway and urban street canyon.

Ø  To develop models suitable for implementation in integrated transport environmental modelling.

Overall Research Objectives

Ø  To investigate the sensitivity of model outputs to meteorological, traffic and background concentration inputs.

Ø  To recommend best practice for air quality modelling of traffic emissions in Ireland.

Ø  To determine the accuracy of the models through comparison of predicted and ambient air quality data .

Expression for GFLSM (Luhar and Patil)

( )( ) ( )

( ) ( )⎥⎥⎦

⎤

⎢⎢⎣

⎡

⎟⎟

⎠

⎞

⎜⎜

⎝

⎛ +++⎟⎟

⎠

⎞

⎜⎜

⎝

⎛ −−

⎥⎥⎦

⎤

⎢⎢⎣

⎡⎟⎟⎠

⎞⎜⎜⎝

⎛ +−+⎟

⎟⎠

⎞⎜⎜⎝

⎛ −−

+=

yy

zzz

xyperfxyperfx

HzHzuu

QC

σ

θθ

σ

θθ

σσθσπ

2cossin

2cossin

,2

exp2

expsin22 2

2

2

2

0

1

Schematic representation of GFLSM

L

x

y R

θ

Road.

Study on M50 motorway.

Schematic Diagram of Sampling Location.

Receptors

Receptors

Secondary road

-240m -120m

-25m

25m 120m

240m

N M50 Motorway Inner suburbs and city centre

Input Data

l  Traffic volume l  Meteorological Conditions (wind speed, wind direction) l  Emission factors l  Briggs Horizontal and Vertical dispersion coefficients.

Output Data.

§  Traffic source related concentration estimates for hydrocarbons were obtained at the receptor locations.

§  Results for benzene are shown below as they are more relevant for traffic emissions.

Results on M50 Motorway for Benzene.

Variation of monitored and predicted data at 25m

0

0.1

0.2

0.3

0.4

0 5 10 15 20

sampling days

conc

entr

atio

n (p

pb)

monitored dataCALINE4

GFLSM

Results on M50 Motorway for Benzene.

variation of monitored and predicted data at 120m

0

0.1

0.2

0.3

0.4

0 5 10 15 20

sampling days

conc

entr

atio

n (p

pb)

monitored dataCALINE4

GFLSM

Results on M50 Motorway for Benzene.

variation of monitored and predicted data at 240m

0

0.03

0.06

0.09

0.12

0.15

0 5 10 15 20

sampling days

conc

entr

atio

n (p

pb)

monitored dataCALINE4

GFLSM

Results on M50 Motorway for Benzene.

variation of mean concentration with receptor distance (benzene)

0

0.05

0.1

0.15

0.2

0 50 100 150 200 250

distance from road(m)

mea

n co

ncen

trat

ion

(ppb

) monitored data

CALINE4GFLSM

Results on M50 motorway for Benzene.

scatter plots for measured and predicted data at 25m

0

0.1

0.2

0.3

0.4

0.5

0 0.1 0.2 0.3 0.4 0.5

measured data (ppb)

pred

icte

d da

ta (p

pb)

CALINE4GFLSMM=PM=2PM=0.5P

Results on M50 motorway for Benzene.

scatter plots of measured and predicted data at 120m

0

0.02

0.04

0.06

0.08

0.1

0 0.02 0.04 0.06 0.08 0.1

measured data (ppb)

pred

icte

d da

ta (p

pb)

CALINE4GFLSMM=PM=2PM=0.5P

Results on M50 motorway for Benzene.

scatter plots of predicted data at 25m

0

0.1

0.2

0.3

0.4

0.5

0 0.1 0.2 0.3 0.4 0.5

CALINE4

GFL

SM

Results on M50 motorway for Benzene.

scatter plots of predicted data at 120m

0

0.02

0.04

0.06

0.08

0.1

0 0.02 0.04 0.06 0.08 0.1

CALINE4

GFL

SM

Results on M50 motorway for Benzene.

§  Statistical Analysis of Monitored and Predicted data (a) At 25 meters.

Monitored CALINE GFLSM Mean 0.15 0.19 0.19 IA 1.00 0.43 0.57 R 1.00 0.11 0.31 F2 100% 65% 95% FB 0.00 0.3 0.3 NMSE 0.00 0.43 0.44

Results on M50 motorway for Benzene.

variation of IA with receptor distance

0

0.2

0.4

0.6

0.8

1

0 100 200 300

receptor distance(m)

IA v

alue

s Monitored dataCALINE4

GFLSM

Results on M50 motorway for Benzene.

variation of F2 with receptor distance

0

20

40

60

80

100

0 100 200 300

receptor distance(m)

F2 v

alue

s Monitored dataCALINE4

GFLSM

Results on M50 motorway for Benzene.

variation of NMSE with receptor distance

0

0.5

1

1.5

2

2.5

0 100 200 300

receptor distance(m)

NM

SE

val

ues

Monitored dataCALINE4

GFLSM

Ø  For the M50 motorway site the performance of GFLSM has been found to be quite satisfactory when compared with CALINE4, an USEPA reference model

Conclusions

Ø  Further studies have been conducted for in depth evaluation of GFLSM model and it has been found that it can be readily incorporated within integrated environment transport modelling.

Ø  An analytical model, GFLSM has been discussed and has been applied at motorway conditions.

Acknowledgement.

l  This work is a part of the Environment Transport Interface (ETI) project funded by the ERTDI Research Programme.

Thank You