Particulate matter in the Milan area
Submitted by soltec-admin on Thu, 04/29/2010 - 11:20
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E. Bolzacchini, J. Hjorth, V. Gianelle, B. Rindone, G. Sesana, S.Villa, V. Maggi, S.Guidi
| Department of Environmental Sciences, University of Milano-Bicocca, Piazza della Scienza 1, I-20126 Milano, Italy. ARPA Milano-Città, Centro di Microscopia Elettronica, Via Mangiagalli 3, 20129 Milano, Italy. ARPA U.O. Chimica di Parabiago, Via Spagliardi 19, I-20015 Parabiago, Milano, Italy. |
JRC Ispra, Institute for Environment and Sustainability, I-21020 Ispra, Varese, Italy. SOLTEC, Via Castelbarco 17, 20136 Milano Italy. |
Particulate matter PM2.5 is a complex mixture of thousands of chemical compounds and many of these, though present only in small quantities, are of great interest due to their potential toxicity.
Attention has been focused on polycyclic aromatic hydrocarbons (PAH), ubiquitous air pollutants that play a role in the development of cancer. During a summer and a winter campaign, in the years 2000 and 2001, atmospheric samples were collected using 16.7 L/min inertial impactors with particle cut points of 2.5 and 10 mm, a sequential sampler and 4, 6, 24, 48 h sampling time.
Preliminary studies conducted in co-operation with industry showed an ultrasonic extraction technique to produce high recovery and good reproducibility, and to have the further benefit of not being time consuming. All the fine particulate matter filters were extracted by ultrasonic agitation with CH3CN solvent and the samples, following extraction, were analysed for PAH in HPLC with a fluorescence detector.
The PAH concentrations in PM10 and PM2.5 correspond to approximately 100% and 80% of the PAH concentrations in the total particulate.
The following table shows PAH mean concentrations in PM2.5, obtained during the summer campaign (August-September 2000) and the winter campaign (February 2001).
| COMPOUND | SUMMER CAMPAIGN (ng m -3 ) |
WINTER CAMPAIGN (ng m -3 ) |
|---|---|---|
| Fluoranthene | 0.07 ± 0.03 | 1.10 ± 0.37 |
| Pyrene | 0.10 ± 0.06 | 1.24 ± 0.36 |
| Chrysene | 0.10 ± 0.06 | 2.02 ± 0.77 |
| Benz[a]anthracene | 0.06 ± 0.03 | 1.29 ± 0.59 |
| Benzo[b]fluoranthene | 0.22 ± 0.13 | 3.19 ± 1.04 |
| Benzo[k]fluoranthene | 0.07 ± 0.04 | 1.32 ± 0.45 |
| Benzo[a]pyrene | 0.10 ± 0.07 | 2.42 ± 0.99 |
| Dibenz[a,h]anthracene | 0.06 ± 0.03 | 1.07 ± 0.41 |
We investigated the use of PAH for an estimation of the contribution, by gasoline and diesel vehicles, to the emissions of PM2.5. Earlier studies had demonstrated that the emissions of these two types of vehicles have different characteristic PAH ratios and in order to verify whether these findings can be applied to field studies a third sampling campaign took place in March 2001. This sampling was carried out at a site where the traffic consists mainly of diesel vehicles, and we are now able to make a comparison of the ratios obtained at this site, those from the site of the February campaign (mainly gasoline traffic) and the values of the sources.
| RATIO | Gasoline vehicles | Diesel vehicles | Gasoline site | Diesel site |
|---|---|---|---|---|
| fl/(fl±pyr) | 0.41 | 0.51 | 0.46±0.05 | 0.49±0.05 |
| b[a]ant/(b[a]ant±chrys) | 0.41 | 0.21 | 0.38±0.04 | 0.31±0.06 |
fl: fluoranthene; pyr: pyrene; b[a]ant: benz[a]anthracene; chrys: chrysene.
The values of the ratios at the two sites are in good agreement with those of the sources. Therefore the method can be used to estimate the influence of the different composition of traffic in two or more urban sites.
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