Conclusions

1.     Carbon Monoxide is measured at two sites: Belfast Centre and Londonderry.  Both currently meet the EC limit value and the Air Quality Strategy objective for CO. There is a significant downward trend in the annual mean CO at Belfast Centre but not at Londonderry.

 

2.     Nitrogen Dioxide is monitored at four automatic sites, and over 150 diffusion tube sites. The four automatic sites meet the EC limit values and the Air Quality Strategy objectives for NO2. A small number of diffusion tube sites (four in 2000, six in 2001) had annual mean NO2 concentrations greater than the EC Directive and AQS objective of 40 µg m-3. In all but one case, these were Type A (Roadside) sites.

 

3.     Two automatic sites (Belfast Centre and Londonderry) have sufficient NO2  data to assess trends: there is a significant downward trend in annual mean NO2 concentration at Belfast Centre only. Diffusion tube data show a significant downward trend for Roadside, Intermediate and Urban Background site types, for the period 1993 to 2001.

 

4.     Sulphur Dioxide is monitored at five automatic sites, and 34 non-automatic sites. The requirements of the 1st Daughter Directive and the objectives of the Air Quality Strategy are met at all automatic sites, except Belfast East. This site exceeded the AQS objective for the 15-minute mean on more than 35 permitted occasions in 2000 and 2001, and the EC limit value and AQS objective for the 24-hour mean on more than three occasions in 2001.

 

5.     Significant downward trends in annual mean SO2 concentration were identified at Belfast Centre and Belfast East, but not Londonderry.

 

6.     In calendar year 2001, three non-automatic SO2 (8-port sampler) sites in Belfast exceeded the EC limit value and AQS objective for the 24-hour mean on more than the permitted three occasions. The historical dataset from this network show a clear decrease in annual mean SO2 concentrations since the 1960s, which is also evident in recent years’ data.

 

7.     Particulate matter as PM10 is measured at six automatic monitoring sites in Northern Ireland. All these sites meet the EC Directive limits and Air Quality Strategy objectives for this pollutant. There is a significant downward trend in annual mean PM10 concentrations at Belfast Centre and Londonderry, although not at Belfast East and Lough Navar. (At the two Newry sites, there is as yet insufficient data to assess trends).

 

8.     Particulate matter as black smoke is measured at 31 sites, of which 29 are part of a long-running network. The historical dataset from this network show a clear and consistent decrease in annual mean smoke concentrations from the 1960s to the mid 1990s; however the downward trend has levelled off in the past five years.

 

9.     Ozone is measured at three automatic sites in Northern Ireland: the AUN sites Belfast Centre and Londonderry and the rural site Lough Navar.  In recent years, the new EC Directive target and the more stringent AQS objective, for ozone have been met at these sites, except for Lough Navar in 1995 and Londonderry in 2000. Ozone concentrations at Belfast Centre show an increasing trend; this may be due to decreasing concentrations of other pollutants which can act as “scavengers” of ozone, keeping levels low in urban areas.

 

10. Hydrocarbons were measured from 1993 to 2000 at the Belfast South site. Concentrations of both benzene and 1,3-butadiene were within the limits set by the Air Quality Strategy at this site throughout its operational period. Annual mean benzene showed a significant downward trend over this period; annual mean 1,3, butadiene showed no significant trend.

 

11. Polycyclic aromatic hydrocarbons (PAHs) have been measured since 2000 at Lisburn, and since 2001 at Belfast Clara Street, as part of the Hazardous Air Pollutants (HAPs) Network. At Lisburn, annual mean concentrations of benzo(a)pyrene in 2000 and 2001 were substantially above the new AQS objective of 0.25 ngm-3 (which at the present time does not apply to Northern Ireland) and very close to the proposed EC limit value of 1.0 ngm-3. Lower concentrations of benzo(a)pyrene (2001 annual mean 0.37 ngm-3) were measured at Belfast Clara Street. Benzo(a)pyrene concentrations at Lisburn in particular were high compared with most other urban sites in the UK. This is believed to be due to the widespread domestic use of solid fuels in this area. A study by netcen has predicted that continued use of such fuels may cause parts of Northern Ireland to fail to meet the AQS objective in 2010.

 

12. A one-year study, carried out on behalf of Defra, monitored ambient levels of the metallic elements lead, arsenic, cadmium, mercury and nickel at three sites near to industrial sources. Annual mean concentrations of lead were well within applicable air quality limits and guidelines. Annual mean concentrations of arsenic, cadmium and nickel were well within proposed EC target values.

 

Acknowledgements

Netcen would like to thank the District Councils and other organisations who carried out the air quality measurements detailed in this report, and CEHOG for collating their data.

 

References

1.     R. Maggs “Monitoring of Lead, cadmium, Arsenic, Nickel and Mercury around Industrial Sites” Casella Stanger report. SSE/AQ/A30160109/RM/1718 , Sep 2001. Available from http://www.aeat.co.uk/netcen/airqual/reports/strategicpolicy/Final_Report_rev4.pdf .

 

 

2.     C Buckingham et al “Greater Belfast Atmospheric Emissions Inventory” report produced for DETR by London Research Centre & RSK Environment, April 1999.

 

 

3.     C Buckingham et al “Atmospheric Emissions Inventories for Four Urban Areas” report produced for DETR by London Research Centre & RSK Environment, December 1997.

 

 

4.     P Coleman et al  “Assessment of benzo(a)pyrene concentrations in the UK to support the establishment of a national PAH objective” AEAT/ENV/R/0620, August 2001. Available from http://www.aeat.co.uk/netcen/airqual/reports/naqs2001/aeat-env-r-0620.pdf .