The south-western Baltic Sea has about 3,000 kilograms of dissolved toxic chemicals released from unexploded ordnance, according to a new study by the GEOMAR Helmholtz Centre for Ocean Research Kiel.
Most of this originates from deliberate dumping after the end of the Second World War. These dumping sites are well documented, with much of the ordnance lying visibly on the seabed, allowing it to be mapped and documented using underwater robots.
The study highlights the long-term environmental contamination caused by unexploded ordnance in the south-western Baltic Sea.
“Unexploded ordnance contains toxic substances such as TNT (2,4,6-trinitrotoluene), RDX (1,3,5-trinitro-1,3,5-triazine), and DNB (1,3-dinitrobenzene), which are released into the seawater when the metal casings corrode,” explains lead author Dr Aaron Beck, a geochemist at GEOMAR. “These compounds pose a threat to the marine environment and living organisms as they are toxic and carcinogenic.”
Water samples were taken from the region in 2017 and 2018, including from the Bay of Kiel and the Bay of Lübeck. Ammunition-related chemicals were detected in almost every water sample. The concentrations detected were generally well below drinking water limits or toxicological thresholds for marine organisms. In some cases, however, concentrations approached critical levels.
Without removal action, the contamination is expected to increase as metal casings continue to corrode, releasing more and more toxic compounds. This process is projected to continue for at least 800 years.
Due to variations in the types of munitions dumped, regional differences in contamination levels were observed: particularly high concentrations of TNT were measured in the Bay of Kiel, while RDX and DNB were more prevalent in the Bay of Lübeck. Most munitions-related chemicals were found in dissolved form rather than bound to suspended particles or sediments.
The study emphasises that chemical contamination from legacy munitions is an international problem. The researchers recommend that dumped ordnance be classified as “historical contaminants of emerging concern” and addressing them through targeted remediation efforts.
Beck says: “Unlike diffuse pollution sources, unexploded ordinance exists in a concentrated, already packaged form. This means it can be physically removed from the environment.” Germany’s munitions clearance operations could serve as a model for the removal of such hazardous waste around the world.