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3.3. Integrated analyses and temporal trends
The results of the PCA analysis are presented in Table 5. The three first axes together explained 84.77% of the overall variance for all campaigns. The first axis clearly represents an association between metals with the deposition of fine sediments through positive correlations with mud, organic FK228 and metals. These data indicate a gradient trend for the stations 1 and 4 (inversely) of the Ceará river estuary, as seen in the PCA (Fig. 2), where stations are ordinated along the first axis. This trend is related to higher levels of metals and toxicity at stations located in the river inner portion, whereas the levels of contamination and toxicity were lower toward the river mouth (Fig. 2). Acute and chronic toxicity did not exhibit a significant correlation with metals that emphasize the influence of other contaminants.
Table 5.
Eigenvectors and correlation coefficient from principal component analysis (PCA) based on environmental variables and sediment toxicity from all sampling sites in campaign A, B and C. Marked (bold) results are >0.65.