Miljörisker sjunkna vrak II. Undersökningsmetoder och miljöaspekter

Rapport, 2015

During 2015 the Swedish Maritime Administration continued the second phase of the governmental task Environmental risks from sunken wrecks which first report was finalized 2014-10-31 (Dnr: 1399-14-01942-6). The main conclusions from the 2014 report remain; for future handling of potentially polluting shipwrecks it is recommended that the Swedish Agency for Water and Marine Management is given a coordinating responsibility in close cooperation with other competent national authorities, such as Swedish Maritime Administration, Swedish Coastguard, Swedish National Maritime Museums, the Geological Survey of Sweden, SMHI, Swedish EPA, and Swedish Civil Contingencies Agency. Through coordination of wreck related operations and activities within the concerned competent authorities’ ordinary areas of responsibility, resource efficiency is improved. The estimated extra cost for implementation of a national strategy for handling of the wrecks are estimated to be 10-15 MSEK which should be allocated to the competent authorities by the Swedish Agency for Water and Marine Management. The conclusions from 2014 was reinforced during 2015, e.g. through the validation of the risk assessment model VRAKA, which is now available in a first operative version. Additional ecotoxicological experiments on the development of tolerance against PAHs in meiofauna and microorganism communities were conducted in a field study in Brofjorden. The main conclusions from this work is that comprehensive analyzes of PAHs should include alkylated PAHs, and that exposure to PAHs over time can lead to tolerance development in ammonium oxidizing bacteria, at the expense of their ability to perform the essential ecosystem service nitrification. Continued measurements of the bottom currents were made at the wrecks Villon and Skytteren, and at the dumping area west of Måseskär. Measurement series yielded important information on how measuring equipment at the wreck can be deployed in an optimized way in future monitoring program; to calculate the possible spreading of pollution from a wreck, current measurements should be performed upstream from the wreck site, while sensors for the detection of, for example, oil should be put into the turbulence downstream of the wreck. The current measurement instruments (RDCP) deployed at the Måseskär dump site was trawled up after only three weeks of measurements, but still gave valuable information on the extensive bottom trawling that resuspend (stir up) sediments. Earlier geochemical surveys have shown significantly elevated arsenic concentrations in the area and sediment resuspension greatly increased the risk for spread of any contaminants in the area. Trawling is not prohibited in the area, and the current lack of knowledge regarding potential effects on human health when consuming seafood from dump areas calls for reflection upon the suitability of trawling in the area. In addition to the current measurements Swedish Maritime Administration and the Swedish Navy conducted hydrographic survey with multibeam and side scan sonar and ROV investigation of the wrecks in the dumping area at Måseskär. 28 wrecks were found, and ROV investigation showed cargo holds with dumped torpedoes or mines and other containers in some Sjöfartsverket Dnr: 1399-14-01942-15 6 of the wrecks. There is some discrepancy between the previously measured elevated arsenic concentrations in the Måseskär area and recently presented data from historical archives that does not support the theory that chemical weapons were dumped in the area. However, there is a very good correlation between the dominant current direction in the area, and the highest measured arsenic concentrations in the area downstream of the wrecks, suggesting some form of arsenic source in the area.