Particulate matter pollution: An environmental magnetism study with biological collectors in urban areas of Northern Portugal

• Type: Article in International Scientific Journal
• Date: 2010

Authors

M.J. Lacerda (Author) FCUP; Helena Sant'Ovaia (Author) FCUP; C.R. Gomes (Author) Other

Journal

Title: Geochimica et Cosmochimica Acta

Vol. 74 No. 12, Supplement

ISSN: 0016-7037

Publisher: Elsevier

Indexing

ISI Web of Science

Scientific classification

FOS: Natural sciences > Earth and related Environmental sciences

Other information

Abstract (EN): This work presents an evaluation of the pollution levels in plant leaves from five selected sites, 4 in urban areas (2 zones in Porto, 1 in Valongo and 1 in Braga towns) and one in a rural area. An environmental magnetism study was used with particle biological collectors, leaves from Nerium oleander, Quercus spp., Tilia spp. and Platanus spp. The sampling was conducted in July, August, October, November and December 2009 and January 2010. A total of 34 samples was obtained. Magnetic parameters, low-field magnetic susceptibility (") and isothermal remanent magnetization (IRM) determinations, were used to indicate the source of the magnetic particles. The magnetic susceptibility (") values are comprised between 2.54 and 17.17 E-8 m3kg-1 in Porto, 3.78 and 5.70 E-8 m3kg-1 in Braga, 2.85 and 8.28 E-8 m3kg-1 in Valongo and, finally, between -0.66 and -0.21 E-8 m3kg-1, in the rural area. The town of Porto shows the higher " comparing to Braga and Valongo. The samples of the rural area showed always negative values of " and very low values of IRM1T. The values of IRM1T, measured for the Tilia spp. in Porto and in the rural area have a relationship 9.92:1.00. In Porto, when comparing neighbouring trees of different species (Platanus spp, Quercus spp. and Nerium oleander) in the same area, the highest values of " are always obtained in the Quercus leaves. A comparison of the values of " for the different months shows that in the month of December, these values are, on average, higher. In November, compared with October, there was a decrease of ", which can be explained by the rainfall which had the effect of removing particles from the leaves. In January, it seems to have had an increase of ", although the sampling had been limited to evergreen species. The average values of S-300 was 0.96 (N=26), indicating the presence of ferrimagnetic particles magnetite-like. The values of S-25 (mean=0.27, N=26) were consistent with the presence of particles with a PM10 diameter. The results pointed out the contrast between areas with high traffic and the countryside. We come to the conclusion that Quercus leaves showed a higher efficiency to accumulate particles than the Platanus leaves.

Language: English

Type (Professor's evaluation): Scientific

Notes: Comunicação apresentada na Conferência "Goldschmidt 2010: Earth, Energy, and the Environment"