Nitrogen Dioxide
Up until 2002, although NO2 concentrations were above the air
quality objective of 40 µg m-3, concentrations of the gas remained
relatively stable at each site and showed a general decrease in
concentrations. However, since 2002, annual average NO2
concentrations have increased quite dramatically at all diffusion
tube sampling locations.
During 2006 the concentrations dropped to below that of 2005
levels, however, it should be noted that the results for 2006 prior
to applying the bias factor were actually of greater concentrations
than those in 2005.
Fine Particles (PM10)
PM10 is measured at three locations across the City.
The air quality in 2003 with respect to PM10 was the
worst year recorded since monitoring began at Beech Street in 1999.
Since 2003 the 24 hour PM10 objective has been exceeded
at all sites, apart from at John Cass School during the years 2004
and 2006.
Benzene
Concentrations of benzene have declined since monitoring began
in 1997. As can be seen in the following graph, benzene
concentrations in the City are below the 2003 and 2010 objectives
set by the Government.
