Dissolution and movement experiments conducted with solid explosive material recovered from dumped munitions in Lübeck Bay

The explosive fill in sea-dumped munitions can become exposed to seawater when munition metal housings corrode. Exposure leads to the release of toxic explosive chemicals to the environment, followed by accumulation in organisms, including those consumed by humans as seafood. In addition, solid explosive fragments can be transported by waves and currents, posing a risk to beachgoers. Munitions typically contain a mixture of explosive types, and with more than 400 known mixtures, it is difficult to predict the dissolution and movement behavior without direct knowledge of the explosive composition.

As part of the test munition clearance work in the Immediate Action Program, the Explosive Ordnance Disposal (EOD) companies Eggers GmbH and Hansataucher GmbH recovered small fragments of exposed explosive material from the WWII-era Pelzerhaken munition dumpsite in Lübeck Bay and transferred them to the Schleswig-Holstein state EOD specialists (Kampfmittelräumdienst; KRD S-H). The KRD S-H provided space at their secure facility for scientists from the GEOMAR Helmholtz Centre for Ocean Research Kiel and the University of Rostock (URO) to conduct laboratory tests on the recovered material to determine the explosive composition, dissolution rate in water, and susceptibility to movement at difference current speeds.

Data from these experiments are currently being analyzed at GEOMAR and URO, and the results will support both the MMinE-SwEEPER and CONMAR-II projects. The results will help us understand the chemical source from dumped munitions and allow us to predict the release of explosive chemicals to the environment. Results from the flume experiments will help us better understand the physical transport of solid explosive pieces and the potential for this material to reach public coastlines and beaches.

Figure 1: Fragments of a corroded 20 mm projectile. The copper driving bands are visible, as is much of the dark-colored solid explosive fill.(A. Beck, GEOMAR)

Figure 2: A beaker from the dissolution experiment with a fragment of solid explosive. The dark yellow color comes from dissolved explosive compounds, especially TNT. (A. Beck, GEOMAR)

Figure 3: Maria Khon (l.; GEOMAR) and Ansgar Leefken (r.; URO) sampling a current flume experiment at the KRD S-H facility. The flume allows precise control and measurement of current speeds over a solid explosive fragment, and water samples are simultaneously collected over time to calculate dissolution rates. (A. Beck, GEOMAR)

Figure 4: Image sequence of a rolling chunk of explosives (KMRD 04-02). The flow is seeded with 100 µm polyamide particles in order to measure the velocity field with particle image velocimetry. (A. Leefken, URO)

Figure 5: Velocity field from particle image velocimetry representing critical flow conditions, i.e. onset of rolling motion of the explosive chunks. The velocity field was averaged over 319 instantaneous velocity fields covering a period of 2 s. (A. Leefken, URO)