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Abstract

Patterns in sediment metal, polycyclic aromatic hydrocarbon (PAH), chlorinated pesticide, and polychlorinated biphenyl (PCB) concentrations at 290 sites within coastal, port, harbor, and marina areas of the Southern California Bight (SCB) were evaluated using cluster analysis and principal components analysis (PCA). Cluster analysis identified five primary site groups, with two large groups representing 96% of the total area of the SCB. One of these two groups contained many of the open coastal sites, characterized by relatively coarse-grained sediments (,30% fines), low organic carbon, and low contaminant concentrations. The second large cluster group included a higher proportion of the embayment, marina, and harbor sites, with finer-grained sediments (,70% fines) and proportionately higher mean concentrations of most metals and trace organics. Both site groups were considered representative of SCB background conditions with minimal alterations from contaminant inputs. The other three site groups exhibited elevated concentrations of one or more contaminants, but accounted for only 4% of the total area of the SCB. In particular, two small cluster groups consisted mainly of port, harbor, and marina sites with elevated mean concentrations of certain metals (e.g., Cu, Pb, Sb, and Zn), as well as elevated chlordane, PAH, and PCB concentrations for one of the two site clusters. The fifth cluster group consisted of Palos Verdes Shelf sites that were characterized by high sediment DDT, PCB, Cd, and Ba concentrations, and clearly different from other open coastal sites in the SCB. PCA identified four principal components that explained 67% of the variance in the data set. The first two components (PC1 and PC2) accounted for 52% of the total variance. PC1 was highly loaded with a suite of metals (Cu, Pb, Hg, Zn, Al, and Fe), with high scores primarily for industrialized port and harbor sites. PC2 had high loadings for DDTs, PCBs, Cd, and Cr with highest scores for sites on the Palos Verdes Shelf. PC3 and PC4 each accounted for less than 10% of the total variance, with high loadings for low- and high-molecular weight PAHs and for a subset of metals (Ba, Ni, and Se) and fines, respectively. Although contaminant sources were not analyzed for this study, PC1 and, to a lesser extent, PC3 likely reflected recent industrial inputs to ports, commercial shipping and boatyard operations, and small marina activities. In contrast, PC2, reflected historical, wastewater-derived inputs to the Palos Verdes Shelf. Distinct sediment contaminant patterns were not evident for other large and small wastewater or riverine discharges.

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