MULTIVARIATE-ANALYSIS OF HEAVY-METAL CONCENTRATIONS IN SEDIMENTS OF THE LAGOON OF VENICE

Concentrations of Hg, Pb, Cd, Ni, Co, Zn, Cr, Cu and Fe in surface sediments sampled in the Lagoon of Venice were processed using two mathematical statistical methods. "Principal Component" analysis and "Cluster" analysis were combined in order to assess the degree of contamination in different areas of the lagoon, to determine the sources, and to trace the diffusion paths. Data were normalized to the "natural" concentrations of metals determined from the deepest sections of the sediment cores. The eigenvalues of the first three Principal Components (PC) accounted for 97% of the total variance. The composition of the first eigenvector is related to the overall metal contamination. The second PC separates two main types of contamination; one due to Hg, the second to Zn and related metals (Cd, Pb, Co, Cu and Ni). A third PC isolates Pb from the zinc association. The relationships among metals highlighted by the cluster analysis and synthesized in the dendrogram helped identify the sources of pollution. The lagoon area facing the Porto Marghera industrial zone has suffered the worst contamination and contaminated sediments have spread from there to peripheral zones. For metals, such as Zn, Cd or Pb, the contamination contributed by fresh water from inland was also considerableConcentrations of Hg, Pb, Cd, Ni, Co, Zn, Cr, Cu and Fe in surface sediments sampled in the Lagoon of Venice were processed using two mathematical statistical methods. "Principal Component" analysis and "Cluster" analysis were combined in order to assess the degree of contamination in different areas of the lagoon, to determine the sources, and to trace the diffusion paths. Data were normalized to the "natural" concentrations of metals determined from the deepest sections of the sediment cores. The eigenvalues of the first three Principal Components (PC) accounted for 97% of the total variance. The composition of the first eigenvector is related to the overall metal contamination. The second PC separates two main types of contamination; one due to Hg, the second to Zn and related metals (Cd, Pb, Co, Cu and Ni). A third PC isolates Pb from the zinc association. The relationships among metals highlighted by the cluster analysis and synthesized in the dendrogram helped identify the sources of pollution. The lagoon area facing the Porto Marghera industrial zone has suffered the worst contamination and contaminated sediments have spread from there to peripheral zones. For metals, such as Zn, Cd or Pb, the contamination contributed by fresh water from inland was also considerable. © 1988