Geochemical analysis of Lake Bant sediments to ascertain inorganic and organic indicators for warfare residues

Abstract

Purpose

The immediate time period after the Second World War (1945–1946) was characterised by an urgent need to dispose large amounts of ammunition residues. Although the environmental relevance of explosives released to soils is intensively investigated, to date, their fate and effects in marine ecosystems are not well known. Surface sediments from Lake Bant, Germany, for which deposition of an enhanced amount of ammunition after World War II has been reported, were analysed to identify organic and inorganic indicators for warfare residues. Additionally, samples of ammunition residues collected from the Wadden Sea, Germany, were analysed in order to obtain information on the long-term behaviour of explosives in undamaged ammunition left in the aquatic environment and to obtain first insights into the spectrum of organic substances which are possibly released to the aquatic environment by such ammunition residues.

Materials and methods

Inorganic analyses comprising determination of major elements (energy dispersive X-ray fluorescence) and heavy metals (ICP-OES, graphite furnace AAS and LA-ICP-MS) were applied to surface sediment samples from Lake Bant as well as to metal coatings of ammunition samples. Organic constituents of sediment samples, corresponding pore water and ammunition fillings were analysed by a Gas chromatographic/mass spectrometer-based non-target screening approach.

Results and discussion

Analyses of lake sediment samples depicted a complex pattern of pollution dominantly derived from petrogenic and sewage sources. Comparing the spatial distribution of petrogenic contaminants with petroleum-related emissions sources present till 1945 at Lake Bant, it is likely that the detected petrogenic contamination represents dominantly war-related residues. Contamination from ammunition residues was not clearly evident in the sediment samples. However, indicative nitrogen-containing compounds potentially reflecting ammunition impact were obtained from analyses of pore water samples. The presence of dibenzylamine, N-nitroso dibenzylamine and diethylamino benzopyranone might give evidence that nitrogen-rich compounds have been released by dumped ammunition. Additional investigation of ammunition samples from the same time period derived from the Jade Bay indicated a high-preservation potential and consequently long-term preservation for explosives in undamaged ammunition residues.

Conclusions

War-related residues in sediments of Lake Bant have to be appointed dominantly to petroleum-related emission sources, whereas ammunition residues currently do not contribute significantly. However, the identification of specific nitrogen-containing organic substances in the corresponding pore water pointed to the assumption that (1) pore water might be an appropriate compartment to follow the environmental fate of ammunition constituents in surface water systems and (2) an extended bioavailability has to be presumed for explosive derivatives. Furthermore, based on the observed preservation of ammunition fillings, the corrosion and decomposition of ammunition shells might lead to the emission of unaltered explosives even decades after their deposition in aquatic environments. However, the information on their environmental stability and fate in surface waters is still limited.

Recommendations and perspectives

Since the knowledge on the environmental fate of ammunition residues in the aquatic environment comprising their stability as well as their potential harmful effects is very low, further investigations on the long-term behaviour of ammunition residues in subaquatic sediments and the corresponding water body is recommended.