Assessment of heavy metal fractionation in surface coastal sediments obtained by different sequential extraction schemes using FAAS and three-way multivariate analysis

Mar del Plata, Pcia. Buenos Aires, Argentina

Simposio; Eleventh Rio Simposium on Atomic Spectrometry; 2010

The sediments and the water bodies associated with them, represent a topic of great interest for designing strategies focused in the study and control of the environmental impact of anthropogenic or natural pollution processes. Sediments are one of the principal reservoirs of heavy metals in the hydrosphere. Heavy metals are associated to the sediments in different ways and exhibit different physical and chemical properties. So, the quantification of the total metal concentrations does not provide enough information about the potential interactions between heavy metals and the biotic and non-biotic components in the environment. The fractionation methods consist of extraction/lixiviation procedures carried out under an operationally defined sequential scheme. In order to evaluate the fractionation among metals associated with amorphous Fe and Mn oxides and those associated with crystalline oxides of Fe, two typical sequential extraction schemes, involving respectively five and seven leaching steps, were applied to coastal surface sediment samples from Bahía Blanca estuary, where an important industrial emplacement is located. Also, three certified reference materials for total metal concentrations were analyzed. The studied metals were cadmium, chromium, copper, lead, nickel and zinc because of their hazardous potential and related abundance in the estuary. The concentration of metals in the liquid extracts was determined by flame atomic absorption spectrometry (FAAS). Precisions for both sequential procedures were comparable. Mass balances showed acceptable agreement. Values of %RSD for the certified reference materials were in the 2 to 8% range. A three-way multivariate analysis was performed in order to obtain a better visualization of the experimental data. The extracted information was used to evaluate the equivalence among the results obtained by the two sequential extraction schemes. The data were analyzed by parallel factor analysis (PARAFAC).