Geochemistry of trace metals in estuarine waters: A multi-phase speciation approach

A series of laboratory and field investigations were conducted using ultraclean techniques to study the speciation and estuarine geochemistry of colloidal and particulate trace metals (Ag, Al, Cd, Co, Cu, Fe, Mn, Ni, Pb, Zn), These metals were chosen for this study based on their different chemical properties and their importance as contaminants in Texas estuaries. Colloids were observed to have significantly affected the fate and speciation of these trace metals.;Calibrations of the cross-flow ultrafiltration system used for the collection of colloidally sized trace metals and organic matter resulted in considerable improvements (better recovery, lower system blanks) for the collection of colloidal matter and associated trace elements. All metals exhibited significant colloidal fractions (10;Molecular weight distributions of organic carbon and associated trace metals in Galveston Bay waters and controlled laboratory experiments using radiolabelled colloids showed that two competing processes are of primary importance. Namely, coagulation of colloidal metals resulting in particle formation and production of lower molecular weight species, possibly mediated by photochemical or microbiological reactions. The determination of estuarine distributions of these trace metals also made possible the calculation of their fluxes into and out of the estuary. Filter-passing (...