Dumped Munitions in the Baltic Sea - Evaluation of the Problem

Dumped Chemical Weapons pose an actual environmental and security hazard in the Baltic Sea Region. Their actual position is unknown, and pollution originating from corroded munitions is only roughly estimated. Several research projects were devoted to evaluate the magnitude of the problem. During three international projects, roughly 2000 km2 were surveyed, and more than 200 ROV missions were performed to investigate found objects. . Results suggest that munitions containing CWAs are more scattered on the seafloor than suspected, and previously undocumented dumpsite was discovered in Gdansk Deep. Chemical Warfare Agents (CWA) degradation products were found in the sediments in immediate vicinity of the objects, and sediment pollution was observed even at 40m distance. Analysis of CWA degradation products in the sediments showed widespread contamination in Bornholm Deep area, and more variable pattern of local hotspots in the Gotland and Gdansk Deeps. The latter seem to contain several contaminated areas, which identifies it rather as an unofficial dumping ground than only containing munitions originating from en-route dumping. Bottom currents observed in the dumpsites were strong enough for sediment re-suspension, and contributed to the transport of polluted sediments. Spreading of CWA was modelled using POP3 hydrodynamic model augmented with sediment erosion and benthic boundary layer modules. It follows from the models, that depending on wind conditions, resuspended contaminated sediemnts may remain in the water column for several days up to few weeks, and be transported over the distances up to 15 km. Biomarkers of environmental stress were measured in fish from the dumpsites and caged mussels, and indicated environmental stress in organisms from dumpsites as compared to control. Toxicity of found CWA degradation products was examined in laboratory studies. . Nonetheless, both species showed significantly elevated molecular and cellular level responses at contaminated sites compared to reference sites. It follows from the studies, that pollution originating from dumped munitions is local, and below acute toxicity levels. However chronic toxicity and adverse impact on the ecosystem may not be excluded, pollution may also spread to adjacent areas as the corrosion of the objects progresses.