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Project title

Air Quality: Transport Impacts and Monitoring Networks - Nature and Origin of PM10 and Smaller Particulate Matter In Air

Primary Funding Agency

Environmental Protection Agency

Co-Funding Organisation(s)

n/a

Lead Organisation

National University of Ireland Galway (NUIG)

Lead Applicant

Gerard Jennings

Project Abstract

The major source categories contributing to particulate air pollution in urban as well as non-urban areas of Ireland were studied over an 18 month period (July 201 to December 2002) using measurements at five sites including urban roadside (site A) urban centre/background (sites B and E) rural (site D)and coastal (site C) environments. Daily fine and coarse aerosol samples were collected at each site using dichotomous Partisol samplers. The measurements included gravimetric mass (PM10 PMi?2.5 and PM2.5-10) soluble ions (SO42- NO3- Cl- CH3SO3- NH4+ Na+ K+ Mg2+ and Ca2+) elemental carbon (EC) and organic carbon (OC). Measurements of polycyclic aromatic hydrocarbon (PAH) content as well as trace metal concentration of samples were also carried out. In addition more intensive measurements were carried out over a 4 week period at three of the sites (rural city centre and coastal) which included size resolved (12 size categories) impactor sampling as well as condensation particle count (CPC) and SO2 NO NO2 NOx O3 and CO gaseous measurements.An annual averaged PM10 mass of 35.4 g m-3 for 2002 was a maximum at the Dublin city kerbside site with values of 22-24 g m-3 for the Dublin and Cork city centre sites. Corresponding PM2.5 mass concentration values were 21.5 g m-3 and 11.5 i- 12.5 g m-3 respectively. The coastal site had an averaged annual value for PM10 and PM2.5 mass concentration of 20 g m-3and 12.5 g m-3 while the rural background site had values of 10.5 and 6.3 g m-3 respectively.Mass closure procedures using reconstructed chemical components were used to identify major source categories contributing to the aerosol mass namely primary marine aerosol (NaCl) secondary inorganic materials [NH4NO3 + (NH4)2SO4] primary anthropogenic combustion materials (EC) primary and secondary organic materials and re-suspended dusts. Source component contributions differed for fine and coarse particles and at different locations. In urban areas the major components contributing to fine particle mass (together accounting for 79-84% of PM2.5 mass) were in order organic compounds elemental carbon ammonium sulphate/ammonium nitrate whilst in the coarse fraction re-suspended material and sea salt were predominant (56-66%). At the rural and coastal sites PM2.5 mainly consisted of ammonium sulphate/ammonium nitrate and organic materials (65%) whilst sea salt was the largest contributor to coarse particles (39% rural 56% coastal). Unexplained materials accounting for about 7-28% of the mass were attributed mainly to re-suspended materials at urban sites and organic materials at the other sites as well as unmeasured water content. Chemical component analysis (for secondary aerosol components of sulphate nitrate and ammonium) according to air mass origin from data in Chapter 5 indicates that long range transport from an eastwardly direction - mainly from the continent and the UK - to Dublin City (Site B) accounts for up to about 30% of the PM2.5 mass [as a fraction of the total mass] over and above that obtained under westerly or maritime air mass conditions and about 25% of PM10 mass. Results also show that local sources account for at least 50% of PM2.5 and of PM10 mass for the city centre sites. The levels of PAHs were largest at the Dublin roadside (site A) whilst similar concentrations were observed at the urban background sites in Dublin (B) and Cork (E) due to the large number of combustion sources. Very low concentrations of the PAHs were observed at the coastal and rural sites due to the lack of significant sources. The concentrations of the particle-phase PAHs measured at the 5 sites are similar to those observed at other locations around the world. The concentration of benzo(a)pyrene is of particular interest because a threshold value of 1 ng m-3 will be introduced as part of a new EU directive. The average monthly concentration exceeded the threshold value on a number of occasions at all urban sites. This EU Directive 2004/107/EC of the European Parliament and Council of 15 December 2004 relates to arsenic cadmium mercury nickel and polycyclic aromatic hydrocarbons in ambient air and it sets a target for PAHs (using B(a)P as a marker) of 1.0 ng m-3 to be achieved by 31 December 2012.The highest concentrations for all metals except magnesium were detected at the kerbside city centre site A. This was expected mainly due to the large number of vehicles passing the site. Within the urban sites site A had the highest concentration of the crustal elements Ca and Fe. Average Ca levels in site B were almost equal to those at site A. The concentrations at these Dublin sites were almost double those observed in site E (Cork). This difference could be due to higher amounts of resuspended road dust in the Dublin sites probably due to the higher volumes of traffic.The Ca concentrations at sites C D and E were quite similar with higher values for the urban site E. Fe concentrations are highest at site A with sites B and E possessing higher levels than the rural and coastal sites. Since Fe is associated with vehicle emissions then these results are not surprising. Site A showed higher concentrations for the toxic trace metals (Mn Pb Cd Zn Ni Cr V and Cu) than either of the other urban sites. In general rural site D (Co. Galway) shows the lowest level of all metals. This was to be expected as this site was removed from any direct vehicle emissions and had no industry within the vicinity. The coastal site showed the highest concentration of magnesium in the coarse fraction in comparison to all other sites. Normally there are high levels of magnesium in sea spray so these observations are consistent with other results.As with the coarse fraction the higher concentrations of trace metals in the fine fraction were usually observed at site A. Within the urban sites (A B and E) site A had consistently higher concentrations than B and E except for Ni (highest at site B). Sites B and E showed similar concentrations for all metals in this fraction. This was expected since B and E are both urban background sites. The coastal (C) and rural (D) sites generally showed lower fine fraction concentrations of the metals than the urban sites. Intensive measurements were carried out during four weeks in February i- March 2002 [19 February i- 21 March] at 3 sites: rural site D coastal site C and city (Dublin) centre site B. Additional measurements were carried out:i condensation particle number concentration i- total number of particles larger than 10nm in size;i SO2 NO NO2 NOx O3 CO gaseous measurements;i cascade impactor (micro-orifice uniform deposit impactor - MOUDI) for collection and analysis of size resolved particles (12 size categories);i meteorological data: temperature wind speed and direction relative humidity.On average chemical species concentrations measured in the size resolved impactor samples are very similar to those measured for the daily samples. Comparison between chemical mass balance and gravimetric mass allowed for calculation of the percentage of unresolved mass for the different size fractions. Missing sub-micrometre mass was up to 40% for the city centre site (and greater for the other sites) and is attributed to non-analyzed organic carbon. Unresolved mass is of order 30-40% for the diameter range from 1 i- 10 m and is in excess of that for larger sizes.

Grant Approved

�522,517.54

Research Hub

Healthy Environment

Research Theme

Environment and Human Health

Start Date

01/11/2000

Initial Projected Completion Date

n/a