7 Benzo(a)pyrene (BaP)
Monitoring of ambient air concentrations of BaP in New Zealand is limited to a small amount of sampling carried out in Auckland during 1997-1998 and Christchurch in 1999. Results of these sampling programmes are compared to the annual average ambient air quality guideline value of 0.0003 µgm-3 (MfE and MoH, 2002).
7.1 Auckland
Air quality monitoring for benzo(a)pyrene was carried in Auckland during 1997 and 1998. Other contaminants monitoring included: naphthalene, acenaphthylene, acenaphthene, fluorine, phenanthrene, anthracene, fluoranthene, pyrene, benz[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, indeno[1,2,3-cd]pyrene, dibenz[a,h]anthracene and benzo[ghi]perylene.
The analysis was carried out on the particulate phase only and included samples from the PM2.5, PM10 and TSP size fractions. A total of 148 particulate filters were analysed. However, only 12 samples (8%) recorded BaP concentrations above the detection limit of around 0.8 ngm-3. The maximum BaP concentration measured was 4.4 nanograms per cubic metre (ngm-3) at the Mt Eden site (PM10 size fraction). An annual average estimate of BaP concentrations was unable to be derived from the study because the detection limit for the method used (around 0.8 ngm-3) was higher than the guideline value (0.3 ngm-3).
Figure 7.1: Concentrations of BaP measured in Auckland in 1997 and 1998
See figure 7.1 at its full size (including
text description).
7.2 Christchurch
Concentrations of BaP were measured in Christchurch during the winter of 1999 at two sites in central Christchurch. Samples were collected over four different monitoring periods: 24-hour averages collected from 4 pm to 4 pm, evening peak monitoring from 4 pm to 8 pm, night time monitoring from 8 pm to 6 am and daytime sampling from 6 am to 4 pm. Results from all four monitoring periods are shown in Figure 7.2. This shows a maximum peak concentration of 79 ngm-3. The 24-hour average concentrations range from around 3 ngm-3 to 39 ngm-3.
Environment Canterbury has made an estimate of the annual average BaP concentration for central Christchurch based on the results of the monitoring and strong associations between the BaP concentrations and concentrations of PM10 (Gunatilaka, 2001). This indicates an annual average concentration for BaP of at least 4 ngm-3. This is over 10 times the guideline value of 0.3 ngm-3 (0.0003 µgm-3).
Figure 7.2: Concentrations of BaP measured in 1999 at Coles Place and Packe Street, Christchurch
See
figure 7.2 at its full size (including text description).