SEDIMENT POLLUTANTS FROM A RIVER MEANDER REINSTATEMENT SITE - CONCENTRATIONS AND MANAGEMENT IMPLICATIONS

Since European settlement in the early 1800s, 66 artificial meander cu t-offs have been created in the lower Latrobe River, Victoria. Contemp orary waterway management practices include the reinstatement of a sel ection of these cut-off meanders to slow water flows and reduce river bed and bank instability. Infill sediments were collected from a range of depths from one of these meanders prior to its reinstatement to es timate the potential for remobilization of any sediment pollutants int o the waterway. The characteristics of collected sediments were descri bed and sediments were analysed for a range of pollutants including he avy metals, total petroleum hydrocarbons, monoaromatic hydrocarbons, o rganochlorine pesticides, polychlorinated biphenyls (PCBs) and polycyc lic aromatic hydrocarbons (PAHs). Metal concentrations in the fine (<6 3 mu m) sediment fraction increased with increasing sample depth; howe ver, only increases in cadmium, chromium and mercury concentrations we re statistically significant. Statistically significant increases in m ercury concentrations with depth were also present in the entire sedim ent fraction. With the exception of mercury, concentrations of all met als assessed in meander sediments were similar to those reported as be ing at background concentrations. Mercury concentrations, although ele vated, were below concentrations reported to adversely effect riverine biota. Concentrations of organochlorine pesticides, polychlorinated b iphenyls, total petroleum hydrocarbons, monoaromatic hydrocarbons and polycyclic aromatic hydrocarbons were all below detection limits in th e entire sediment fraction. As a consequence, reinstatement of the mea nder as part of a waterway management programme is unlikely to release significant quantities of sediment-partitioned pollutants into the ma instream waterway.