Chemical and conventional ammunition in the Baltic Sea

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- Status quo, related risk potentials, possible securing and remediation


At the end of World War II it was necessary to find a fast and economical way of disposal for the enormous quantities of no more required conventional and chemical ammunition from German and allied stocks. Usual methods of destruction like detonation, burning or even simple emptying soon emerged as very time-consuming and dangerous. Dumping at sea seemed to be the much more efficient and – concerning the general security – the less problematic solution attempt. Environmental aspects and the issue of protection of the sea were completely ignored at that time.

Details about type and amount of sea dumped conventional and chemical ammunition vary considerably. Trends indicate that the biggest part of conventional ammunition were dumped in the German coastal waters within the 12-nautical miles zone, while the both biggest dumping sites for chemical ammunition are located in the Skagerrak and the Bornholm Basin.

Based on diverse accidents, especially concerning fishery, a discussion about possible risk potentials of dumped ammunition for humans and environment arose mid of the 1980’s in which context first assessments finished that a fairly long-term threat for the marine environment can not be ruled out and that the existing, quite considerable lacks of knowledge – especially concerning ecotoxicology – have to be filled by specific investigations.

Sea dumping of conventional and chemical ammunition

Overall, 16 areas at the German Baltic coast are marked as “unrein Munition” (polluted by ammunition) on maritime shipping charts (Koch & Nehring 2007[1]) (Figure 1). Amounts of dumped ammunition in these areas are – in contrast to the dumping activities in the North Sea – completely unknown. However, a total amount of more than 100,000 tons of ammunition can be assumed, comprising for the most part conventional ammunition (SHL 2001[2]).

Figure 1: Dumping sites and areas of suspicion concerning dumped ammunition at the German Baltic Sea coast

Between 1935 and 1945 about 65,000 tons (net!) of chemical warfare agents were just produced by Germany, 25,000 tons of them – about 39% of the total amount – were mustard gas (BSH 1993[3], HELCOM 1994[4], 1995[5]). After the Second World War, these chemical warfare agents were found filled in ammunition or partly unfilled in the allied occupation zones and amounted to a total quantity of chemical ammunition of 296,103 tons (HELCOM 1994[4]). Despite of partial storing or rather removal into war-participating countries as well as initial destruction by conventional attempts as burning, detonation or simple emptying as well as burying – that were not only very costly but also very dangerous and further very time-consuming – the most part of chemical ammunition and containers were dumped into the North- and Baltic Sea immediately after the end of the second world war. The main dumping sites for chemical warfare agents are the Little Belt, the Bornholm Basin, Gotland and – to be considered as the border area between North- and Baltic Sea – the Skagerrak (Figure 2).

Figure 2: Dumping zones and recommended risk areas for chemical warfare agents

The so called “en route dumping” represents a further significant factor of uncertainty concerning the actual dumping sites. This is about the uncontrolled dumping of ammunition already on the transport routes to the officially identified dumping sites. Based on this quite common practice, significant amounts of conventional and chemical ammunition have never reached their initial destination and are from time to time stored in immediate vicinity of the coast (BSH 1993[3], Missiaen & Henriet 2002[6]).

The amounts of dumped chemical ammunition and unfilled chemical warfare agents in the Baltic Sea amount to 42,000 to 65,000 tons (BSH 1993[3], HELCOM 1994[4], 1995[5]) based on first concrete assessments in which dumping actions of the former soviet republic – that archives are still inaccessible – are only partly taken into consideration. Based on unconfirmed press reports the soviet republic is supposed to have dumped more than 300,000 tons of chemical ammunition amongst other risky things into the Baltic Sea after 1947 (Nehring & Ilschner 2005[7]).

German authorities repeatedly emphasize that there haven’t been any official dumping activities concerning chemical warfare agents at the German Baltic Sea coast (BSH 1993[3], SHL 2001[2]). These statements do indeed surpise: In 1961, 13 gas cylinders with overall 520 l of chlorine and one cylinder with 10 l phosgene and another one with 10 l of laughing gas were dumped in the Luebeck Bight in a water depth of 20 m and only 8 km from the shore with authorization of the German authorities (Pape 1970[8]). The precise origin of the both chemical warfare agents chlorine and phosgene as well as the narcotic laughing gas is unknown. These activities have initially been reported to the HELCOM as dumping of chemical warfare agents (HELCOM 1992[9]). But German authorities did shortly later decide to declare these dumping activities as simple dumping measures of chemicals. In the following analyses and reports concerning dumping activities of warfare agents, these measures have therefore no longer been considered (BSH 1993[3], HELCOM 1994[4], 1995[5]). Presently, the German authorities examine to search for the warfare agents in the Luebeck Bight and - if necessary – to remove and dispose them.

Risk potentials based on dumped ammunition

The progressive corrosion and related leakage of ammunition located in oxygen containing water- and sediment layers result in a diffuse release of contained explosives and chemical warfare agents. In this context, 93 individual substances have just to be considered concerning explosives (Haas 1996[10]), 53 substances for the chemical warfare agents (Kopecz 1996[11]). Related to conventional ammunition, especially the by far mostly used trinitrotoluene (TNT) has to be considered that is toxic for micro organisms and aquatic plants (Spyra 1997[12], Ek 2005[13]) and – despite its rather low solubility in water of about 100 to 130 mg/l – already toxic for fish at a concentration of 0.7 to 3.7 mg/l (Haas 1996[10]).

With regard to chemical warfare agents, nine of twelve main substances (in particular adamsite, hydrocyanic acid, clark I&II as well as mustard gas) are regarded as very dangerous aquatic pollutants, in which again six are strongly to extreme toxic for aquatic organisms. Four of twelve substances contain arsenic compounds and create arsenic containing – and therefore in the environment persistent – degradation products. Three of twelve main substances (hydrocyanic acid, sarin, tabun) are able to create medium- to long-term persistent contamination zones in the water with highly toxic concentrations on the basis of their high water solubility and low velocity of hydrolysis (in dependence of dilution effects for hours or days to weeks) (Koch 2006[14]). Some degradation products of chemical warfare agents are even more persistent and several times more toxic than their original substance (e.g. mustard gas and lewisite) (Kaffka 1996[15]), in addition there is hardly any knowledge about long-term toxicological and ecotoxicological effects. Some substances have provably carcinogen, teratogen or genetically harmful effects (Haas 1996[10], Kopecz 1996[11]).

Further, the following factors have to be considered exemplarily as potential threats:

  • Possibility of access to the ammunition also in the context of terrorist and right-wing extremist activities based on the low water depths (0-30m) of a lot of dumping sites (CITS 1997[16], CSIS 2005[17]).
  • Catching of ammunition and its content by commercial fishing with resulting contamination of the catches, equipment and partly the crew. Up to now such incidents are statistically collected only in Denmark - between 1985 until 2005 at least 443 incidents in Danish fisheries have become public (e.g. Theobald 2002[18]). However, incidents are also known in the fishing fleet of other Baltic countries, but the precise numbers are unknown. A first German analysis has shown, that since the end of WW II until now at least 91 German fishermen became injured, mainly by mustard gas in the area east of Bornholm (Nehring 2007[19]). Furthermore the danger of detonation of fished out ammunition is still within the realm of possibility. In 2005 three Dutch fishermen were killed in such an accident in the North Sea (Nehring & Koch 2006[20]).
  • Basically constant endangering of the civil and commercial shipping by direct contact or rather too close convergence e.g. to still fully operative sea mines, by anchoring and eventual accidents (recent example: in 2001 a German containership run aground in immediate proximity to the Belgian ammunition dumping site “Paardenmarkt” (phosgene, clark, mustard gas (Missiaen & Henriet 2002[6])). The destruction of a large number of ammunition-containers would have – based on the sudden release of significant quantities of contained chemical warfare agents and the close proximity to the residential buildings (< 2 km) as well as the nearby port of Zeebrugge – not assessable consequences for humans, environment and economy).
  • Landing of containers and ammunition as well as already flushed out contents on coasts and beaches (currently, especially the “amber problem” on the German Baltic island Usedom has to be considered in this context; white phosphorus in sea water looks like amber and is collected e.g. by tourists with dramatic effects when the phosphorus dries and automatically starts burning with temperatures of up to 1,300 °C (Nehring 2005[21])).
  • “Sudden release” of significant quantities of ammunition contents with not assessable consequences for the environment (Kaffka 1996[15]).
  • Self-detonations that are currently increasingly observed in the North Sea e.g. by investigations of the British ministry of defence (BGS 2005[22]). The precise range of self-detonations in the Baltic Sea is unknown, but a first German analysis has shown, that since the end of WW II until now at least six self-detonations were registered in German coastal waters of the Baltic Sea (Nehring 2007[19]).

Basic remediation scenarios

Concerning marine ammunition dumping sites and the resulting potentials of threat, there are the following basic remediation scenarios:

  • No remediation of areas with dumped ammunition (“Permanent disposal scenario”)
  • Partial remediation of areas with dumped ammunition (“By the way scenario”)
  • Complete remediation only of areas with high risks and/or significant quantities of ammunition (“Hot spot scenario”)
  • Complete remediation of all known areas with dumped ammunition (“Full clean up scenario”)

“Permanent disposal scenario”

This scenario corresponds to the status of a permanent disposal site for dumped ammunition that stays untouched in situ at the site without securing and remediation attempts. Amongst other things the leakage, related to the progressive corrosion processes in the oxygen containing environment, results in an uncontrolled release of unknown quantities of partly highly toxic pollutants into the surrounding sediment and the free water column with still unknown mechanisms of effectiveness from a toxicological and ecotoxicological point of view (Missiaen & Henriet 2002[6], SRU 2004[23]). Effects can only be investigated by means of a very extensive monitoring that completely covers the related area. In case of a confirmed significant concentration – based on the well mapped-out monitoring – concrete securing and remediation measures have then to be taken.

“By the way scenario”

A related partial remediation might be realised e.g. by regular collections of stranded ammunition and ammunition contents on the beach, especially equipped fishing boats (Rapsch & Fischer 2000[24]) as well as by normal construction works accompanying remediation measures. This attempt results in a continuous but diffuse remediation and securing progress. Concrete measures are not based on a setting of priorities by a risk assessment of a specific dumping site in comparison to others but solely on a collection of ammunition or contents by chance or rather accompanying tackling of dumping sites in the context of concrete building projects. This scenario represents a quite economical but – in the general context of basic risk potentials or rather related emissions – only less effective solution attempt.

“Hot spot scenario”

This remediation attempt is – concerning its resulting securing and remediation measures – based on detailed considerations of individual cases and the related resulting assessments of threat of individual pinpoint dumping sites. The concentration on single pinpoint dumping sites may – considering the totality of dumping activities – eventually lead to the so called “drop in the ocean” but enables – under consideration of threat potentials and the emissions on the bases of previous evaluations – highly efficient and quite economical securing and remediation measures.

“Full clean up scenario”

The here intended full remediation and securing measures related tackling of all known and – by area covering investigations – still to be detected ammunition and ammunition contents containing areas represents at least from the emission related point of view – based on corresponding securing and remediation technologies – the most effective solution. However this attempt results in partly highly ineffective working measures and an enormous financial burden by extensive securing and remediation measures. An actual feasibility of this attempt seems not to be practical and also not to be convertible.

Conclusion and recommendations

From the authors’ point of view, the solution attempt of the “Hot spot scenario” with the related securing and remediation of confirmed pinpoint dumping sites seems to be the most likely realisable alternative from a technical, emission related and economical point of view. The proposed concentration on the so called hot spots leads to a reduced but in the general context highly efficient solution attempt that does further result in a significant cost reduction compared to less efficient but more extensive measures. A remediation or rather partial remediation at least of hot spots is – from an ecotoxicological and general risk related point of view – considered as inevitable by the authors.

Basically can be stated that there is still a significant need of action and scientific investigation in the general topic of marine ammunition dumping sites (especially concerning locating, evaluation of the quantities of dumped ammunition, ecotoxicology, long-term effects etc.) and that related measures have to be taken immediately – especially concerning our sense of responsibility for future generations.


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The main author of this article is Marc Koch
Please note that others may also have edited the contents of this article.

Citation: Marc Koch (2020): Chemical and conventional ammunition in the Baltic Sea. Available from [accessed on 25-05-2024]

The main author of this article is Stefan Nehring
Please note that others may also have edited the contents of this article.

Citation: Stefan Nehring (2020): Chemical and conventional ammunition in the Baltic Sea. Available from [accessed on 25-05-2024]

The main author of this article is Wolfgang Ruck
Please note that others may also have edited the contents of this article.

Citation: Wolfgang Ruck (2020): Chemical and conventional ammunition in the Baltic Sea. Available from [accessed on 25-05-2024]