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.Peer reviewe

Acute aquatic toxicity of arsenic-based chemical warfare agents to Daphnia magna

Sea dumping of chemical warfare (CW) took place worldwide during the 20th century. Submerged CW included metal bombs and casings that have been exposed for 50-100 years of corrosion and are now known to be leaking. Therefore, the arsenic-based chemical warfare agents (CWAs), pose a potential threat to the marine ecosystems. The aim of this research was to support a need for real-data measurements for accurate risk assessments and categorization of threats originating from submerged CWAs. This has been achieved by providing a broad insight into arsenic-based CWAs acute toxicity in aquatic ecosystems. Standard tests were performed to provide a solid foundation for acute aquatic toxicity threshold estimations of CWA: Lewisite, Adamsite, Clark I, phenyldichloroarsine (PDCA), CWA-related compounds: TPA, arsenic trichloride and four arsenic-based CWA degradation products. Despite their low solubility, during the 48 h exposure, all CWA caused highly negative effects on Daphnia magna. PDCA was very toxic with 48 h D. magna LC50 at 0.36 mu g x L-1- and Lewisite with EC50 at 3.2 mu g x L-1 . Concentrations at which no immobilization effects were observed were slightly above the analytical Limits of Detection (LOD) and Quantification (LOQ). More water-soluble CWA degradation products showed no effects at concentrations up to 100 mg x L-1.Peer reviewe

Compressing Deep Image Super-resolution Models

Deep learning techniques have been applied in the context of image super-resolution (SR), achieving remarkable advances in terms of reconstruction performance. Existing techniques typically employ highly complex model structures which result in large model sizes and slow inference speeds. This often leads to high energy consumption and restricts their adoption for practical applications. To address this issue, this work employs a three-stage workflow for compressing deep SR models which significantly reduces their memory requirement. Restoration performance has been maintained through teacher–student knowledge distillation using a newly designed distillation loss. We have applied this approach to two popular image super-resolution networks, SwinIR and EDSR, to demonstrate its effectiveness. The resulting compact models, SwinIRmini and EDSRmini, attain an 89% and 96% reduction in both model size and floating-point operations (FLOPs) respectively, compared to their original versions. They also retain competitive super-resolution performance compared to their original models and other commonly used SR approaches. The source code and pre-trained models for these two lightweight SR approaches are released at https://pikapi22.github.io/CDISM/

Chemical warfare agents and their risk assessment in <i>Daphnia magna</i> and fish in the Baltic Sea - 15 years of measurements

The Baltic Sea is one of the world's largest brackish waters, it is drained through the Danish Straits into the Kattegat, and almost enclosed by nine countries. The Baltic Sea is one of the world's most polluted water bodies thus facing a wide range of environmental threats towards its water resources, such as fish stocks, and coastal environments and economics. Chemical warfare agents (CWAs) that were dumped following the Second World War are known to occur in intact or degraded states in sediments and are documented to affect benthic fauna and fish as well as having injured fishermen having accidentally caught lumps of CWAs in their nets. However, a thorough mapping of remaining CWAs and degradation products and an understanding of the environmental risks does not exist although more than 75 years have passed. This study compiles and analyzes published/peer-reviewed data, generated since 2005 in five selected comprehensive studies, on sediment measurements of known dumped CWAs and degradation products in the Baltic Sea. As a worst-case approach, sediment con-centrations are transformed to concentrations in near-bottom water, which represents Predicted Environmental Concentrations (PECs) to marine biota. To investigate the accuracy and representativeness of toxicological values, which are fundamental in risk assessments, two cases are considered: Case 1 (specificity) uses toxico-logical data (EC50 or NOEC) for Daphnia magna and fish with applied assessment factors (AF) to derive Predicted No-Effect Concentrations (PNECs) for organoarsenical and non-arsenical CWAs; Case 2 (robustness) uses partly Danish Environmental Quality Standards (DK EQS) for arsenicals, and partly a Water Quality Criterion (WQC) for arsenicals, representing the marine environment. From 872 data points risk quotients (RQs=PEC/PNEC) are calculated. In Case 1 exceedances of risk for the sum of chemicals (sumRQ>1) occur 24 and 1 times for Daphnia magna and fish, respectively, without applying AFs. 263 and 120 exceedances are found for Daphnia magna and fish, respectively, when applying AFs. Case 2 shows 0 (WQC) and 25 (DK EQS) exceedances for arsenicals when using more robust toxicological values, however, at the expense of specificity of chemicals and target species. The results underline the importance of obtaining more representative and accurate toxicological data (lowering AFs) in order to increase the accuracy of the risk estimates. This quantitative state of risk towards representative marine species indicates that there are indeed potential risks, and it qualifies the understanding and debate on the challenges and future actions regarding dumped chemical munitions in the Baltic Sea.Peer reviewe