Some trace metals (also known as ‘heavy’ metals), when in high concentrations, can have toxic effects on aquatic life in both a dissolved state and when attached to sediment particles. Zinc and copper, in particular, are often used as proxies for the presence of other potential contaminants such as hydrocarbons and historically-used persistent pesticides such as DDT. These types of contaminants often end up in estuaries via catchment runoff.

Trace metals are rated against thresholds scaled relative to 2018 Australia and New Zealand Default Guideline Value (DGV) and Guideline Value-High (GV-high) concentrations for sediment quality. A rating of ‘Poor’ exceeds the GV-High value, and can be interpreted as reflecting the potential for ‘probable’ ecological effects. A rating of ‘Fair’ corresponds to values between the DGV and GV-High, reflecting ‘possible’ ecological effects. ‘Good’ and ‘Very good’ correspond to values that are less than the DGV, where significant adverse ecological effects are unlikely.

Trace metals are rated against thresholds scaled relative to 2018 Australia and New Zealand Default Guideline Value (DGV) and Guideline Value-High (GV-high) concentrations for sediment quality. A rating of ‘Poor’ exceeds the GV-High value, and can be interpreted as reflecting the potential for ‘probable’ ecological effects. A rating of ‘Fair’ corresponds to values between the DGV and GV-High, reflecting ‘possible’ ecological effects. ‘Good’ and ‘Very good’ correspond to values that are less than the DGV, where significant adverse ecological effects are unlikely.