In Situ Measurements of Explosive Compound Dissolution Fluxes from Exposed Munition Material in the Baltic Sea

Abstract

Underwater munitions containing millions of tons of toxic explosives are present worldwide in coastal marine waters as a result of unexploded ordnance and intentional dumping. Dissolution flux of solid explosives following corrosion of metal munition housings controls exposure of biological receptors to toxic munition compounds (MC; including TNT: 2,4,6-Trinitrotoluene, RDX: 1,3,5-Trinitro-1,3,5-triazinane, and DNB: 1,3-Dinitrobenzene). Very little is known about the dissolution behavior of MC in the marine environment. In this work, we exploit a unique marine study site in the Baltic Sea with exposed solid explosives to quantify in situ MC dissolution fluxes using dissolved MC gradients near the exposed explosive surface, as well as benthic chamber incubations. The gradient method gave dissolution fluxes that ranged between 0.001 and 3.2, 0.0001 and 0.04, and 0.003 and 1.7 mg cm -2 d -1 for TNT, RDX, and DNB, respectively. Benthic chamber incubations indicated dissolution fluxes of 0.0047-0.277, 0-0.11, and 0.00047-1.45 mg cm -2 d -1 for TNT, RDX, and DNB, respectively. In situ dissolution fluxes estimated in the current study were lower than most dissolution rates reported for laboratory experiments, but clearly demonstrated that MC are released from underwater munitions to the water column in the Baltic Sea.

“Don’t Blast”: blast-in-place (BiP) operations of dumped World War munitions in the oceans significantly increase hazards to the environment and the human seafood consumer

“…It has been anticipated that very high and toxic concentrations may appear in the sediment and sediment pore water in the close vicinity of a munition fragment, but only a short distance away the concentrations may drop to non-toxic and non-detected levels (Beck et al 2019 ; Rosen and Lotufo 2010 ). This may indeed be true for a complete and/or corroding encased mine as a point source of munitions chemicals.…”

“…Water samples collected manually by scientific divers at close intervals very near and vertical to the exposed munitions surface yielded 3100 μg × l −1 dissolved TNT directly at a piece of solid hexanite, whereas concentrations declined rapidly away from the hexanite surface, to 16 μg × l −1 at a 1 cm distance and finally to 3.3 μg × l −1 at a 50 cm distance (Beck et al 2019 ). This explains why the data derived from our studies generally showed elevated levels of explosive chemicals in mussels exposed near the munitions surface, while the concentrations decline upward of the water column.…”

“…Unfortunately, these low-order detonations left substantial quantities of intact explosive material scattered on the seafloor. A visual inspection by scientific divers proved that multiple larger solids (half mete scale) and smaller pieces (10–30 cm scale) of explosive material had been distributed in this area (Appel et al 2018 ; Beck et al 2019 ; Strehse et al 2017 ). Within the Kolberger Heide site, munition items are not only widely scattered, but are also clustered, such as in a large pile of approximately 70 sea mines (Fig.…”

“…Recently discovered and potentially serious is the fact that, after more than 70 years of laying on the seafloor, the metal shells of the dumped munition items are corroded, and their toxic compounds leak out and get distributed in the marine environment (Appel et al 2018 ; Beck et al 2019 ; Böttcher et al 2011 ; Strehse et al 2017 ). Explosive chemicals like TNT and its derivatives are known for their toxicity and carcinogenicity (Bolt et al 2006 ; Sabbioni and Rumler 2007 ) and pose a great threat to the marine environment (Talmage et al 1999 ).…”

“…Unfortunately, these low-order detonation left substantial quantities of intact explosive material on the seafloor. A visual inspection by scientific divers proved that, although the acute danger from uncontrolled explosions was eliminated, a large number of large and small chunks of explosive material had been distributed in this area (Appel et al 2018 ; Beck et al 2019 ; Strehse et al 2017 ).…”