Environmental impact of the explosion of the Nord Stream pipelines.

Armed conflicts have, in addition to severe impacts on human lives and infrastructure, also impacts on the environment, which needs to be assessed and documented. On September the 26th 2022, unknown perpetrators deliberately ruptured the two gas pipelines Nord Stream 1 and 2 with four coordinated explosions near a major chemical munition dump site near the Danish island of Bornholm in the Baltic Sea. While the massive release of natural gas into atmosphere raised serious concerns concerning the contribution to climate change-this paper assesses the overlooked direct impact of the explosions on the marine ecosystem. Seals and porpoises within a radius of four km would be at high risk of being killed by the shockwave, while temporary impact on hearing would be expected up to 50 km away. As the Baltic Proper population of harbour porpoises (Phocoena phocoena) is critically endangered, the loss or serious injury of even a single individual is considered a significant impact on the population. The rupture moreover resulted in the resuspension of 250000 metric tons of heavily contaminated sediment from deep-sea sedimentary basin for over a week, resulting in unacceptable toxicological risks towards fish and other biota in 11 km3 water in the area for more than a month.

High resolution model for assessment of contamination by chemical warfare agents dumped in the Baltic Sea.

The leakage of any substances at the sea bottom consequently leads to contamination. The polluted area will strongly depend on the type of pollution which can be dissolved, material and the physical state of the bottom layers. Although the systems that monitor the particles or pollution on the sea surface already exists, there is no similar tool for the bottom area. This work aims at developing the High Resolution Dispersion Model (HRDM) that calculates transport of the pollution in case of potential leakage from chemical ammunition dumped into the Baltic Sea. The model has been embedded into existing operational system that covers the whole region of the Baltic Sea. Thus, it consists of the three main elements: operational atmospheric model that makes calculations every day, coupled ice-ocean model covering the whole Baltic Sea area and HRDM. The horizontal resolution of the atmospheric part is about 10 km, the coupled system is driven on 2.3 km grid and HRDM is implemented on 50 m horizontal resolution. The clients are able to make integration since 2014. Access to the system is granted via REpresentational State Transfer (REST) API that separates user interface from the server site. It is possible to make simulations for instantaneous and continuous type of leakage. The results are served in binary form (as a netcdf file) and as a georeferenced tiff picture. The temporal resolution of the output data is 1 h. The HRDM consists of half-life of sulfur mustard and the results for both - with and without half-life calculations are included in the output files. The HRDM has been created as a part of Decision Support System and is not (and will not be) available for public.

Exposure status of sea-dumped chemical warfare agents in the Baltic Sea.

About 50 000 tons of chemical weapons (CW) were dumped to the Baltic Sea after the Second World War. Munitions are located in the deep areas of the Baltic Sea, and there they act as a point source of contamination to the ecosystem. Corroded munitions release chemical warfare agents (CWAs) to nearby water and sediments. In this study we investigated known dumpsites (Bornholm, Gotland and Gdansk Deep) and dispersed chemical munitions, to evaluate the extent of contamination of nearby sediments, as well as to assess the degradation process of released CWA. It was found that CWA-related phenylarsenic chemicals (Clark I, Clark II and Adamsite) and sulfur mustard are released to the sediments and undergo environmental degradation to chemicals, of which some remain toxic. The extent of pollution of released CWAs and their corresponding degradation products reaches more than 250 m from the CW objects, and seem to follow a power curve decrease of concentration from the source. Bornholm Deep is characterised with the highest concentration of CWAs in sediments, but occasional concentration peaks are also observed in the Gdansk Deep and close to dispersed munitions. Detailed investigation of spreading pattern show that the range of pollution depends on bottom currents and topography.

Deep sea habitats in the chemical warfare dumping areas of the Baltic Sea.

The Baltic Sea is a severely disturbed marine ecosystem that has previously been used as a dumping ground for Chemical Warfare Agents (CW). The presence of unexploded underwater ordnance is an additional risk factor for offshore activities and an environmental risk for the natural resources of the sea. In this paper, the focus is on descriptions of the marine habitat based on the observations arising from studies linked to the CHEMSEA, MODUM and DAIMON projects. Investigated areas of Bornholm, Gotland and Gdansk Deeps are similarly affected by the Baltic Sea eutrophication, however, at depths greater than 70m several differences in local hydrological regimes and pore-water heavy metal concentrations between those basins were observed. During the lifespan of presented studies, we were able to observe the effects of Major Baltic Inflow, that started in December 2014, on local biota and their habitats, especially in the Bornholm Deep area. Reappearance of several meiofauna taxa and one macrofauna specimen was observed approximately one year after this phenomenon, however it's ecological effects already disappeared in March 2017. According to our findings and to the EUNIS Habitat Classification, the three reviewed areas should be characterized as Deep Sea Muddy Sands, while the presence of suspicious bomb-like objects both beneath and on top of the sediments confirms their CW dumpsite status.