Baltic Sea

Балтийское море

Abstract Large quantities of German trophy chemical weapons (CW)1 were dumped after World War II in the Bornholm Deep of the Baltic Sea. Four ships wrecks were found on the bottom of the central part of the Bornholm Deep at depths of 90-100 m.

  • References

    Baturin G. N., Emelyanov, E. M., Kunzendorf, H., 1995.
    Authigenous deposits in the sediments. In E. M. Emelyanov,
    Ch. Christiansen, O. Michelsen (eds), Geology of
    the Bornholm Basin, Aarhus Geoscience 5, 189-194.
    CARION NPF, 2005. Technique of performance of measurements
    of a mass fraction of metals in powder tests of
    sea bottom sediments by a method X-Ray Fluorescence
    Spectrometry. M-002/2005. Certificate of Compliance
    № 242/57-2005. Mendeleyev Institute for Metrology
    (VNIIM).

  • Conclusions

    Increased As concentrations (111-277 mg/kg) in the
    surface layer of the bottom sediments were found near
    the ships wreck W.1 and W.3 and mostly, and just in
    areas where the metal objects occur in the mud. The
    sources of arsenic could be thin–wall containers, shells
    and bombs with As–containing agents depressurized
    during they remained at surface of the bottom. Such
    distribution of arsenic could be reckoned as indicator
    of leakage of As– containing warfare agents to the
    marine environment. The state of metal objects
    (probably, shells, bombs, containers) were buried in
    the mud at depth 1-2 m from the surface is unknown.
    It is desirable to conduct special study of these objects
    in future.

  •                  

  • DISCUSSION

    For clay and shale the average background content
    of As is normally 10 mg/kg. Examined samples from
    the Bornholm Basin, based also on the data shown by
    Emelyanov and Kravtsov (2007), contain from 1 to
    277 mg/kg As (see Tables 2, 3). The highest As value
    (277 mg/kg) was found in the mud from “hot spot” of
    the P-181 area in the Bornholm Basin, located about
    500 m to the south from W.3 shipwreck.

  • Results

    Sapropel and sapropel–like mud is common not only
    in the Bornholm Basin but also in many other Baltic
    Sea basins. In the Bornholm Basin this mud contains
    up to 7.87% Corg, 7.08% Fe, 0.86% Mn (Table 2). Two
    mud samples taken near the shipwreck (stations 26S
    and 47) contained 17.7 and 41.5% Fe respectively
    (Table 3). Apparently these sediments might have
    some metal scrap corrosion products. Ignoring these
    outliers, Fe concentration varies in a much narrower
    range–between 0.05-7.08%.

  • Material and Methods

    Material underlying this article is based on samples
    of bottom sediments taken from the Bornholm
    CW dumpsite during implementation of MERCW
    Project: explorations on R/Vs Professor Shtokman
    and Centaurus in 2006 and 2007 and on the chartered
    German vessel Fritz Reuter in 2008. Sampling stations
    in the Bornholm Deep were chosen on the basis of
    earlier data about arsenic distribution and location
    of the shipwrecks that had been obtained during
    1997–2005 and subsequently studied in AB IO RAS
    (Paka 2004; Emelyanov, Kravtsov 2007). 178 samples
    of sediments from the Bornholm Basin were subject to
    chemical analysis in AB IO RAS (Emelyanov 2007;
    Emelyanov, Kravtsov 2007). This included grain
    size analysis of sediments and determination of the
    following 18 elements contained in the sediments:
    Corg, Ntotal, Ptotal, Ca, Mg, K, Na, Fe, Mn, Ti, Cu, Zn, Co,
    Ni, Cr, Cd, Pb, As. The central part of the CW dumps
    site (encircled area at Fig. 1) was further referred to
    as “hot spot”.

  • GEOLOGICAL SETTINGS

    The Bornholm Basin with water depth of about 100
    m is located east of the island of Bornholm, in the
    south–western Baltic Sea. It has its boundaries at
    50030’–55045’N and 14030’–16030’E. The basin is
    assumed to be bordered by 50 m isobaths (Fig.1) thus
    covering the area of 14 000 sq. km. It is surrounded
    by shallow bottom areas with depth ranging between
    25 and 30 m. Saline and dense waters occasionally
    penetrating to the Baltic from the North Sea, find
    their way from the Danish passages first to the Arkona
    Basin with depth of about 46 metres, then entering the
    Bornholm Basin through the Bornholm Gat channel.
    The Słupsk Trench is another considerably deep basin
    to the east of the Bornholm Basin, separated from the
    latter by a moraine ridge, thus forming Słupsk Sill with
    its ridge coming at the depth of 56 m.