Copper is naturally present in rivers and lakes. It can also originate from anthropogenic emissions, including point and diffuse sources. However, when dissolved copper enters natural waters, it is quickly removed from the water column as a result of natural processes.
Field studies and computational studies provide evidence of this process. Dissolved copper is bound by suspended solids in the water column, and transported to sediments through settling. In the sediments, it is tightly bound and buried. This process generally represents a transfer of copper to less bioavailable and less toxic forms.
A standardised test method was developed to assess binding to a substrate, settling to the bottom, and the potential for remobilisation of metals in aquatic systems. The test method was based on the existing transformation-dissolution protocol, which was extended by adding a substrate to stimulate binding and removal. The test results show that copper is rapidly removed from the standardised system, with removal rates around 90% after 28 days.
This information is relevant for hazard classification purposes. Two reports—downloadable via the buttons on the right-hand side of the screen—provide more detail on this topic:
- Copper removal from surface water: Experimental and modelling studies.
- Copper removal from surface water: Development of a standardised test method to measure copper binding, settling, and remobilisation.