Test of the relationships between the content of heavy metals in sewage sludge and source of their pollution by chemometric methods

Abstract

The content of various metals (Cd, Cr, Cu, Ni, Pb and Zn) in sewage sludge was analysed by ICP-OES technique. The study was performed on 14 samples from the Wielkopolska region and 4 from the neighbouring provinces. The results were used to perform chemometric analysis. Two chemometric methods were used to test the relationships between the content of heavy metals in sewage sludge and the sources of their pollution. The application of cluster analysis displayed important information about the identification of similar locations of sewage sludge sampling stations. This chemometric method showed that all the monitoring locations are grouped into three main clusters. Separated clusters present similarities between locations of the sewage treatment plants, which have the same kind of industrial plants in their catchment area. Principal component analysis enabled interpretation of the complex relationships between determined elements. Application of principal component analysis to the whole data set helped to distinguish only two sewage sludge stations (Ostrow Wlkp. and Poznan-Kozieglowy) that could be interpreted, each in different principal component thereby suggesting that element's concentration differ considerably. The interpretation of relationships between the rest of the stations was possible by performing PCA for the second time, but on the reduced data set (two above-mentioned stations were excluded). It distinguished two groups: (1) Gniezno, Srem, Kalisz, Inowrocław and Sroda Wlkp, and (2) Gostyn, Gniezno and Kalisz, which differ with regard to element's concentration.

Keywords:

• inductively coupled plasma optical emission spectrometry (ICP-OES)
• sewage sludge
• heavy metals
• chemometric methods

Notes

*Analytes concentration in certified reference material CRM-BCR 146 R: Cd 18.8 ± 0.5;Cr 196 ± 7;Cu 838 ± 16; Ni 69.7 ± 4.0;Pb 609 ± 14;Zn 3061 ± 59 [mg kg⁻¹].

*SS – squares sum.

*PC1 – principal component 1.