Leisure craft sacrificial anodes as a source of zinc and cadmium to saline waters.

Sacrificial anodes are attached to the hulls of boats and marine structures to prevent corrosion. Their use inevitably leads to release of zinc as well as impurities in the zinc alloy such as cadmium to the saline environment. Risk assessments and source apportionment exercises require accurate assessments of the potential loads of chemicals into the environment. This research has surveyed a wide variety of zinc anodes for their composition to compare against a reported industry standard as well as using differing methodologies to determine the dissolution rate of zinc and cadmium from anodes. A zinc dissolution rate of 477 g/yr/kg of anode is proposed. Although most anodes tested had concentrations of cadmium within the prescribed limits set by the reported standard, calculated leaching rates from laboratory dissolution experiments suggested as much as 400 g per year of cadmium could leach from zinc anodes used on leisure vessels within UK waters.

An analysis of variable dissolution rates of sacrificial zinc anodes: a case study of the Hamble estuary, UK.

Sacrificial anodes are intrinsic to the protection of boats and marine structures by preventing the corrosion of metals higher up the galvanic scale through their preferential breakdown. The dissolution of anodes directly inputs component metals into local receiving waters, with variable rates of dissolution evident in coastal and estuarine environments. With recent changes to the Environmental Quality Standard (EQS), the load for zinc in estuaries such as the Hamble, UK, which has a large amount of recreational craft, now exceeds the zinc standard of 7.9 µg/l. A survey of boat owners determined corrosion rates and estimated zinc loading at between 6.95 and 7.11 t/year. The research confirms the variable anode corrosion within the Hamble and highlighted a lack of awareness of anode technology among boat owners. Monitoring and investigation discounted metal structures and subterranean power cables as being responsible for these variations but instead linked accelerated dissolution to marina power supplies and estuarine salinity variations.

Metals in boat paint fragments from slipways, repair facilities and abandoned vessels: an evaluation using field portable XRF.

Paint flaking off abandoned vessels or generated during boat repair is hazardous to human health and wildlife. In this study, a means of screening paint fragments using a field portable-X-ray fluorescence (FP-XRF) spectrometer is described. The technique is capable of delivering rapid, surficial measurements of Ba, Cu, Pb and Zn down to concentrations less than 150 µg g(-1), and Sn and Cr to concentrations of a few hundred µg g(-1). Application of the technique to fragments collected from slipways, yards, hardstandings, abandoned boats and ships undergoing maintenance throughout the EU reveal highly variable concentrations of metals among samples from the same environment or from the same region of a given boat; in many cases, variability is also evident in different areas or on different surfaces of the same fragment. Of particular concern are elevated concentrations of substances that have been restricted or banned (e.g. Sn, an indicator of organotin, and up to concentrations of 40,000 µg g(-1), and Pb up to concentrations of 200,000 µg g(-1)). Although FP-XRF can rapidly screen samples whose composition and origin are unknown and can assist in instantaneous decision making, a full risk assessment will rely on additional analyses of the precise species (including organo-forms) of the metals present.

Metal contamination of sediment by paint peeling from abandoned boats, with particular reference to lead.

Fragments of flaking paint have been sampled from eighteen boats (including sailing barges, houseboats, a trawler and a ferry) abandoned on the intertidal mudflats of two estuaries in eastern England and analysed for Cu, Pb and Zn by X-ray fluorescence (XRF) spectrometry. Median concentrations of Pb on each boat ranged from about 350 to 35,000 µg g(-1), with individual concentrations exceeding 200,000 µg g(-1) in several cases. Median concentrations of Cu and Zn ranged from about 50 to 1900 µg g(-1) and 50 to 10,000 µg g(-1), respectively, with respective maxima of 172,000 µg g(-1) and 239,000 µg g(-1). Because of peeling paint, local sediment (analysed by ICP following acid digestion) was often measurably contaminated by the metals and, based on median, Al-normalised enrichment factors, in the order Pb>Zn>Cu. Due to its abundance and persistence in old paints, Pb is of greatest concern from both environmental and human health perspectives.