A chemical speciation of trace metals for fine urban particles

Abstract

The chemical speciation of 11 metals in aerosols has been studied in 12 areas of the city of Seville (Spain). Urban particles were collected with a high-volume sampling system equipped with a cascade impactor, which effectively separates the particulate matter into six size ranges. Forty-one samples were collected in the spring of 1996. The chemical speciation was studied in the finest particles of the impactor system (<0.61 μm), those that can penetrate into the alveolar region of the lung. This speciation scheme is specific for urban particles and consisted of four fractions: 1. soluble and exchangeable metals; 2. carbonates, oxides and reducible metals; 3. bound to organic matter, oxidisable and sulphidic metals; and 4. residual metals. The sample extractions were analysed for 11 metals by inductively coupled plasma atomic emission spectrometry (ICP-AES). The chemical speciation of metals showed that the metals with highest percentages in the different fractions are vanadium (50.4%) in the soluble and exchangeable fraction, calcium (39.7%) in the carbonates, oxides and reducible fraction, magnesium (59.2%) in the bound to organic matter, oxidisable and sulphidic fraction, and iron (54.6%) in the residual fraction. Correlations between all the variables have been studied and the results showed common sources to the metal fractions correlated in relation to the industrial activities and mainly the vehicular traffic.