The copper-containing anti-fouling coatings found on ship hulls are a major source of trace metal contamination in the marine environment. These coatings release ionic copper [Cu(I) and Cu(II) ], which is highly reactive and needs to be measured immediately upon collection. Presently, there are no inexpensive, accurate, and simplistic tests to measure ionic copper. Most currently available tests measure only Cu(II). However, the major copper ion leaching from the marine anti-fouling coatings is Cu(I).
The objective of this project was to develop an operationally simple, user-friendly detection system for rapid assessment of the major ionic copper ions in the marine environment. Emphasis was placed on those ionic copper species [Cu(I) and Cu(II)] which could adversely affect the marine environment biota. The overall goal of the project was to develop and test an ionic copper probe that had parts per billion (ppb) detection limits and could be used easily by dockside personnel having little to no formal chemistry analysis training.
The copper sensing probe, known as the Nafion Membrane Probe, uses a polymer impregnated with a color indicator. The polymer was impregnated with a Cu(I) metal ion organic complexing agent, 2,9-dimethyl-4,7-diphenyl-1,10- phenanthroline (Bathocuproine or BCP), and attached to a plastic panel. BCP reacts with Cu(I) to give a very intense, visible, and stable orange-complex with a unique spectroscopic signal. The probe can be immersed in a known volume of water suspected to contain Cu(I). When the probe is removed from the solution and the active test strip (see diagram) is compared to a known color concentration panel, a relative concentration of Cu(I) is determined. By adding a reducing agent to the sample before introducing the probe, Cu(II) can be measured.
The Nafion Membrane Probe was developed and tested at the former Naval Surface Warfare Center in Annapolis, MD. The probe provided a simple and rapid means to quantify both copper ions that are present in the water column. This project was completed in FY 2000.
This project will benefit the Department of Defense by developing a simple-to-use, inexpensive ionic copper monitoring system that will aid in the implementation of the Uniform National Discharge Standards (UNDS) Act. The UNDS Act will mandate the use of some form of sensor/detection system that can address the role of copper speciation in marine environments, and it has identified 25 discharges requiring Marine Pollution Control Devices. Three of these discharges that can be monitored with the Nafion Membrane Probe are (1) hull-coating leachate; (2) seawater cooling overboard discharges; and (3) underwater ship husbandry.