Development of a simple extraction procedure using ligand competition for biogeochemically available metals of estuarine suspended particulate matter Original Research Article

Sorption of trace metals by suspended particulate matter (SPM) in estuarine systems has important implications for the fate of dissolved metals in these waters. This paper describes the development of a single extraction procedure for SPM-associated trace metals, using a ligand competition approach with EDTA as the added complexing ligand. The use of EDTA allows the determination of available particulate trace metals using well defined constraints with respect to the competition for trace metals between EDTA and the particles. Incubation experiments showed that equilibrium times between EDTA and particulate material of 72 h were required to reach equilibrium for most of the metals studied (Cu, Zn, Mn, Ni, Co, Al, Fe, Pb and Mg). Optimum conditions included a 0.05 M EDTA concentration and the use of an extractant: particulate matter ratio of 200 : 1 (v : w). Kinetic calculations on data from the incubation experiments were used to calculate the apparent stability constants (KMeS) for the metal-particulate matter interaction and indicated values ranging from 10−2.1 for KMgS to 10−13.5 for KCuS.