Although the fate of many trace metals in estuarine and coastal waters is intimately tied to that of dissolved and colloidal organic matter and inorganic colloids, little work has been done to establish the association of trace elements with colloidal organic matter. Colloids often appear to be reactive intermediaries in the sorption process, leading to slower uptake by suspended particles because a substantial fraction of trace metals is first adsorbed by colloids, which coagulate more slowly with suspended matter. Many natural colloids contain substantial amounts of trace elements, including potentially toxic heavy metals such as lead, mercury, silver, and cadmium. Heavy metals are among the most toxic, ubiquitous, and persistent contaminants in estuarine habitats. Toxicity to aquatic organisms, bioavailability and the potential for bioaccumulation and food chain transfer depends critically on the specific physico-chemical forms or species present in the substrate.
Metal ions can bind to inorganic or organic ligands, including organic macromolecules.
Some of these organic complexes have very different properties and chemical reactivities and, therefore, biological availabilities. Since it is paramount for this kind of work to avoid any sources of contamination, special clean techniques needed to be established in the field and lab, and special equipment was needed for analysis in the laboratory. He also found that a major fraction of these metals is associated with colloids in slope waters and in Galveston Bay. This self-cleansing capacity of Texas estuaries is particularly interesting and provides a focus for research efforts. While metal concentrations in Galveston Bay are higher than nearby gulf waters, they are orders of magnitude lower than those reported by various government agencies for the same waters.