PARENT SESSION
TA8 Ecological risk assessment for the marine environment
9:00 AM to 12:30 PM, Tuesday, 08 May 2001
Session Chair: J.V. Tarazona
Room 8

(211) Copper antifouling coating release rate measurements to estimate biocide loading in San Diego Bay.

Seligman, Peter¹, Valkirs, Aldis ², Haslbeck, Elizabeth³, Wang, p.¹, ^{1 2 3}

ABSTRACT- Increasing interest in environmental loading of antifouling (AF) biocides, including copper, used to prevent marine growth on vessel hulls, has been stimulated as a result of observed adverse effects on non-target organisms from tributyltin (TBT)leaching off boat hulls and the impending International Maritime Organization ban on TBT-containing coatings. A major component of copper loading into many harbors and estuaries is from the release of cuprous oxide biocide into surrounding waters. Cu release rates from several AF paint formulations were measured by laboratory and in-situ methods from static and dynamic field-exposed panels in San Diego Bay. Direct Cu release rate measurements were made on the hulls of both Navy vessels and pleasure craft with a novel diver-deployed dome system used to obtain realistic loading rates. Cu release rate measurements revealed a large range of values for different formulations and measurement techniques varying from 1g/cm²/d to 35g/cm²/d with order of magnitude differences between any given formulation. The most important environmental variable is the biofilm or slime layer which can reduce Cu release by an order of magnitude or more over coatings with little or no biofilm. Direct on-the-hull measurements of typical Navy AF formulations, with in-tact slime layer are(3-6g/cm²/d) and are typically 2-3- fold lower than laboratory measurements of the same paint system. The next most important variable is temperature. In laboratory studies, a 20°C change (7°-27°C) yielded a 2-3-fold increase in Cu release rate. Changes in salinity and pH also can effect rate of release. With environmentally realistic loading estimates, hydrodynamic models can be used to project copper concentrations and dispersion using various loading scenarios to support risk assessment requirements. Using TRIM, a two-dimensional hydrodynamic/contaminant transport model, accurate predictions of harbor concentrations of Cu in San Diego Bay were made and various loading scenarios run to estimate reductions in water concentrations and risk with hypothetical loading reductions.

Key words: copper, loading, modeling, antifouling coatings