A wavelet-based approach applied to suspended particulate matter time series in Portugal

This study intends to analyse the particulate matter (PM) levels in Portugal (mainland and islands) throughout a 3-year period. Although a decreasing trend has been observed, the WHO guidelines for the PM 10 and PM 2.5 annual mean concentrations have been exceeded in all monitoring stations. Most in...

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Bibliographic Details
Published in:	Air quality, atmosphere and health Vol. 9; no. 8; pp. 847 - 859
Main Authors:	Cruz, Ana M. J., Alves, Célia, Gouveia, Sónia, Scotto, Manuel G., Freitas, Maria do Carmo, Wolterbeek, Hubert Th
Format:	Journal Article
Language:	English
Published:	Dordrecht Springer Netherlands 01-12-2016 Springer Nature B.V
Subjects:	Air masses Air pollution Airborne particulates Atmospheric Protection/Air Quality Control/Air Pollution Carcinogens Cluster analysis Clustering Earth and Environmental Science Emissions Environment Environmental Health Environmental monitoring Health Promotion and Disease Prevention Metropolitan areas Mortality Outdoor air quality Particulate matter Pollutants R&D Research & development Seasonal variations Studies Summer Time series Traffic Wavelet transforms Portugal ANE, Portugal Madeira, Madeira I ASE, Atlantic, Madeira Wavelets Air mass trajectories Clustering PM Air quality monitoring stations Classification
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Summary:	This study intends to analyse the particulate matter (PM) levels in Portugal (mainland and islands) throughout a 3-year period. Although a decreasing trend has been observed, the WHO guidelines for the PM 10 and PM 2.5 annual mean concentrations have been exceeded in all monitoring stations. Most inland urban, rural and suburban sites follow a pronounced seasonal variation with much higher values in winter than in summer. Lower levels and a weak seasonal variability were registered in the two urban background stations of Madeira Island, which are permanently under the influence of clean air masses over the Atlantic. Receiving long-range transported pollution, rural stations located in mountain sites presented an opposite seasonal pattern, with higher levels in summer. Diurnal profiles were also analysed and compared between stations. A mining process was also carried out, consisting in the application of multi-scale wavelet transforms, data pattern identification using cluster analysis and examination of the contribution to the total variance/covariance of the time series per wavelet scale for all stations. Groups of stations exhibiting similar variance/covariance profiles were identified. One group contains urban and rural stations with diurnal and daily time scales. Urban background stations located in the island of Madeira constitute another cluster, corresponding to higher wavelet scales (lower periodicity phenomena). One traffic station in the Oporto metropolitan area was grouped with a suburban/industrial station of central Portugal, suggesting the need for reclassification in what concerns the type of environmental influence.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	1873-9318 1873-9326
DOI:	10.1007/s11869-016-0393-4