Q-mode factor analysis classified the estuarine samples from Broad Sound into two main geologically distinct groups representing intertidal and supratidal deposition. This classification was supported statistically by stepwise discriminant analysis, and mathematically by Q-technique canonical correlation analysis. Analysis of variance was useful in identifying significant error with some of the measured variables, and proving the stability of the pH and Eh readings over time. Using R-mode factor analysis, with the associated correlation coefficients, and stepwise regression analysis, the various processes controlling the concentration of P2O5, Cu, Pb and Zn, in the supratidal and intertidal sediments are identified. Although Cu, Pb, and Zn are mainly deposited in both supratidal and intertidal zones adsorbed onto iron hydroxide colloids, the three trace elements (but especially Pb) are released with decreasing pH and Eh in the intertidal zone and form metal sulphides or metallo-organic complexes. The reduced iron is also redeposited as iron sulphide. Under supratidal oxidizing conditions the Cu and Zn remain attached to the iron colloids but Pb is released with increasing acidity. The absorption of P2O5 on clay particles increases with acidity in the intertidal zone, but P2O5 is mainly associated with organic carbon in the supratidal sediments.
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