The Influence of Temperature and pH on Trace Metal Speciation in Seawater

Using available data we have constructed complexation schemes which depict the influence of temperature and pH on metal speciation in seawater. Our calculations show that the extent of complexation of strongly hydrolyzed metals in seawater is strongly temperature and pH dependent. The extent of complexation of the twenty or more metals present in seawater predominantly as carbonate complexes is substantially influenced by pH and temperature, but to a much smaller degree than strongly hydrolyzed metals. For the small group of metals extensively complexed with chloride ions in seawater, temperature and pH appear to be variables of minor significance. We have identified the following concerns. (i) In general, previous experimental work does not provide well defined descriptions of metal hydrolysis under weakly alkaline conditions. (ii) Very few studies have been devoted to characterizing the temperature dependence of carbonate complexation equilibria. (iii) There are major uncertainties in the primary data upon which characterizations of Pd (II), Pt (II), Au (I), Ag (I) and Cu (I) chemistry are based