Excessive loads of sediments delivered to rivers, estuaries and bays can have significant implications for their ecological health. In addition, there may be pollutants (e.g., heavy metals, pesticides) attached to sediments that pose a risk to aquatic ecosystems. Sources of sediment are typically varied but can include agricultural practices and urban developments if not adequately managed. This project focused on understanding the levels and potential ecological impacts of pollutants in sediments generated from new urban residential developments.
Stormwater wetlands and associated receiving waters within representative urban developments in south-eastern Melbourne were sampled to measure sediment-bound pollutants (metals and pesticides) over a period of four years. Passive samplers were also deployed across each of the sites for a period of four weeks on four sampling occasions. Additionally, dust samples were collected and analysed for synthetic pyrethroids that are routinely applied for termite control during house construction. Initial findings have shown low levels of metals across all the sampling sites. The synthetic pyrethroid bifenthrin was detected in all wetlands and downstream in the receiving waterway of the development, in some instances at concentrations that have the potential to cause toxic effects to aquatic invertebrates. The passive samplers also found herbicides, fungicides and insecticides within the adjacent receiving waterway.
The implications of pollutants found within both the wetlands and receiving waters will be discussed in the context of ecological health, as well as potential management interventions such as alternative chemical application practices (e.g., industry codes of practice) and sediment control guidelines.