Page 261 - Manual for Activities directed at the Underwater Cultural Heritage
P. 261
260
silt, such processes are not in themselves negative for the environment. This may be different with the degradation of other materials that may have a negative impact on the environment.
Heritage with a negative impact
on the environment
Stones and ceramics are relatively inert and harmless, but other materials are not. Metal ships from the last century have formed wreck sites of huge size. Iron or steel is their main component and in the long run that is not resistant to (sea) water. Depending on their specific character, such wrecks will tend to continuously produce iron oxides. This is not generally considered a menace for the environment. Heavy metals and alloys that are also present are another matter. Sometimes their corrosion will come to a balanced standstill when a protective layer has formed. But if several metals are present, electrolytic processes will continue to produce materials in solution that are called minerals if they have a positive effect on bio production, and contaminants if their effect is assessed negatively.
For the sake of cultural heritage protection, sa- crificial anodes have occasionally been mounted to stop corrosion processes. In such cases, the argument for cultural significance had better be very strong, because environmentally speaking, it is just replacing one contaminant with another. Management strategies that isolate archaeological materials from the environment by covering or packing them will not suffer from such critique, but will on the other hand allow for a lesser experience during recreational visits.
Many wrecks are likely to induce oil spills that are certainly hazardous. But due to gradual corrosion of tanks such a spill may also occur after many years. The wreck in question may however still be considered significant heritage. An example of a high-risk wreck is the USS Neosho, which lies off the Great Barrier Reef, off Australia, and still holds four million gallons of fuel oil.
Environment
