A study carried out for the Roads and Traffic Authority
(RTA) in October
and November 1994 looked at the composition of exhaust gas emissions from the NSW motor
vehicle fleet. The data gained from this study was to be used to validate the motor
vehicle component of the Metropolitan Air Quality Study emissions inventory as well as
information on the mass emission rates to enable models to be established for road side
pollutant concentration estimations.
The ventilation exhaust system of the harbour tunnel enabled pollutant concentrations
of carbon monoxide, sulphur dioxide, oxides of nitrogen, benzene, total hydrocarbons and
other air toxins to be measured while the breakdown bays of each tunnel were used to
measure total suspended particles (TSP), particles contributing to PM IO, lead in TSP and
dioxins.
The average lead concentrations found were 4.2* and 5.7 µg/M³ in the
Southbound and Northbound tunnels respectively. The average T'SP concentration in the
Southbound tunnel averaged 218 µg/M³ (ranging from 160-260 µg/M³) while the levels in
the Northbound tunnel were higher, averaging 372 µg/M³ (ranging from 178-497 µg/M³).
The higher values found in the Northbound tunnel are due to the position of the sampler on
an uphill gradient where vehicles are under load.
