Heavy Metal Pollution in the Baltic Sea, from the North European Coast to the Baltic States, Finland and the Swedish Coastline to Norway

Title: Heavy metal pollution in the Baltic Sea, from the North European coast to the Baltic states, Finland and the Swedish coastline to Norway. Authors: Sergio Manzetti1,2* 1. Computational Ecotoxicology Group, Computational Biology and Bioinformatics, Department of Cell and Molecular Biology, Uppsala Biomedicinska Centrum BMC, Husarg. 3, Box 596, 751 24 Uppsala, Sweden. 2. Fjordforsk A/S, Bygdavegen 155, 6894 Vangsnes, Norway. 1 Abstract1 Environmental pollution and contamination is a continuous challenge that industrialized and developing countries are facing, affecting entire ecosystems, threatening biodiversity, reducing health and life quality of humans and contributing to the extinction of endangered species. The oceans and seas are the most vulnerable ecosystems to anthropogenic impacts, where heavy metals and other pollutants affect the viability of marine species. In this review, the focus is put on the widespread contamination of heavy metals on the Baltic sea and its marine ecosystems. Three parts are considered: the industrial sources of heavy metals in along the entire Baltic coast and in the Baltic sea, the levels and concentrations of heavy metals found in various phases of the environment (sediments, rivers, lakes and seas) and the accumulation of heavy metals in fish as well as avian species. The results from this review show that the heavy metal-releasing industries impact the marine environment for several decades, and that more efforts are required to restitute the Baltic sea to its original state. 1 Please cite as: Sergio Manzetti. 2020. Heavy metal pollution in the Baltic Sea, from the North European coast to the Baltic states, Finland and the Swedish coastline to Norway. Fjordforsk AS, Technical Reports, 6:8. 1-90. 2 Introduction Heavy metals are a particularly toxic class of inorganic pollutants which have been released to the environment after intense anthropogenic activities on both sides of the Atlantic [1–5], from the early stages of the industrial revolution to the First and Second World Wars and further to the modern industrial age [6–9]. Uncontrolled release of heavy metals is prohibited in most countries [10–13], given their ecotoxicological properties, particularly for aquatic ecosystems, marsh-lands and exposed areas near and at industrial sites [14–19]. The release of heavy metals is therefore subjected to stringent regulations, however many cases of uncontrolled release still occur, making making pollution by heavy metals a priority for environmental legislation and regulations [20]. Recent studies show that a series of revised acts of legislation are at implementation stage for various marine ecosystems, such as for the Baltic sea by the HALCOM Baltic Sea Action plan [20] and the Bremen ministerial Declarations [21], for the coastal waters in Chile (CONAMA plan [22]) and furthermore for other areas [23]. An updated set of acts of legislation [24] have also been published in Norway in 2017 where Hg, Cd, Pb, Cr have been put on the revised list of priority pollutants given considerable contamination in fish and sediments [19,25–28], deriving from outdated and active industrial activity, as well as other major sources of heavy metal contamination such as the sunken German boat “U864” located outside the Norwegian coast north of Bergen containing 65 tons of liquid mercury [29], and contamination from aluminum smelting industries along the Norwegian coastline [19,30–33]. The Baltic sea, which is the focus of this review, has experienced a considerable decline in overall environmental health since the 1950’s, when new industries emerged on its shores after World War II, particularly on the East Baltic coast and further along the south coast-line of the Baltic sea. The Swedish coast line, particularly between the city of Sundsvall and Umeå - on the shores of the Sea of Bothnia, has suffered from a dramatic ecosystem decline by the extensive industrial load on the coastal estuaries, leading to the largest accumulation of pollutants deposited on the shores of any Scandinavian country in history [34]. In this study, we focus therefore on heavy metal pollution in the Baltic Sea and describe the past and present states over several respective sections. The southern parts of the Baltic Sea have been studied more rigorously for heavy metal contamination in recent years [35–37], and studies describe alarming levels of heavy metals in the Polish estuaries, particularly in the seabed of rivers and the coast line where Cs137 isotope has been found in fish along the Southern shoreline of the Baltic (Fig 1) [38]. Concomitantly, the general levels of heavy metals in the Southern Baltic Sea have risen in the last 10 years given the flooding of the river Oder 3 [35], indicating, among other pollution sources from neighboring shores [39–41], that the general state of the estuaries and seas of Baltic marine ecosystem require decade-long efforts to be completely cleared to a sustainable state for the fish species, and to provide a secure marine environment to abolish the dietary risks associated with fish and sea food consumption. The implementation of higher ambitions by the European states is therefore necessary to ensure a complete recovery of the Baltic Sea. Heavy metal contamination in the Baltic Sea The Baltic Sea is a mediterranean sea belonging to the Atlantic Ocean, which has a limited water influx from its parental ocean, fueled by high-tide currents as well as during the events of low pressures systems arising in the North Atlantic impacting the Danish and South Swedish coast. The Baltic Sea is composed of several shallow bays and estuaries, encompassing the Gulf of Finland, the Gulf of Riga, the Bay of Gdansk, the Sea of Botnhia and the Bay of Bothnia (Fig 2), with an average depth of 50 m with a bottom rich in sand and clay minerals. This sea was formed 130.000 years ago, and has gone through several stages of evolution, encompassing an ice age of lasting approx 100.000 years during the Weichselian glaciation period. The Baltic Sea is composed of scattered Jotnian sediments, aleurolites and conglomerates, with a high percentage of lime stone. The Southern parts of the Baltic sea contain small petroleum reserves, while the eastern parts towards Estonia and the Gulf of Finland are rich in kukersite deposits [42,43]. The geology of the Baltic sea has an important effect on the fate of pollutants, as the clay materials found in the Baltic are very similar to clays that are regularly used for decontamination and remediation purposes of polluted waters and soils, given their highly sorptive properties. Indeed, clay binds organic pollutants reversibly as well as irreversibly and can also catalyze particular chemical reactions [44,45]. The Baltic sea has therefore geophysical properties which increase the absorption of pollutants of both organic and inorganic origin, and can act as an accumulator of water-soluble and insoluble pollutants released from the industrial facilities which are widespread along its shorelines [46]. The Gulf of Gdansk The Gulf of Gdansk (Fig 1, 2) is particularly exposed to heavy metal contamination as well as radioactive nucleides [35,36,47–52] deriving from industrial activity in the Polish region and possibly also from the Russian enclave (Oblast of Kaliningrad), resulting in peak levels registered 4 in the last 30 years: 1.3 mg Mn/gram sediment, 0.1 mg V/g sediment, 0.2 mg Sr/g sediment, 6.7 mg Zn/ g sediment, 4 mg Pb / g sediment and 0.35 mg Ni / g sediment [35]. Similar levels are detected in the Vistula river sediments, at the central part of the Gulf of Gdansk where Zinc levels of 0.25-5.3 mg/g soil, Lead levels up to 0.760 mg/g soil, Cu levels to 0.47 mg/g sediment and Cd levels up to 0.14 mg/g soil were registered [35]. The same study reports that levels of 7mg/g soil of Zinc, 1mg/g soil of Lead and 0.3 mg/ g soil of Cd are measured in the sediments of the tributaries of the Vistula river, further contaminating the shoreline of the Gulf of Gdansk. This contaminated region stretches for more than 200 km from Poland east towards Germany (Fig 1), where an additional source of contamination of the southern Baltic sea joins the spread of pollutants, namely the Oder river and its lagoons located nearby the border of Germany. These regions have been exposed to heavy metal contamination over several decades of industrial activity in Germany and central-eastern Europe, where discharges have gradually deposited in the lagoons of the Oder basin. Particularly Cd, Pb, Zn and Ni contaminate these lagoon sediments, which arrest the dispersion of the pollutants from reaching the Baltic sea, however with a limit [50]. Also, the clay sediments of the lagoon mark a general geological trait of the entire northern part of the European continent, and as in the basins of the Baltic sea, such minerals act as sorbers. When the limits of sorption are surpassed, the unsorbed fraction enters the Baltic sea. After several decades of industrial discharges and more frequent flooding given climate changes, the levels of contamination from the Oder river have thus been a principal source of pollution of the south-western Baltic sea, south of the Dano- Swedish strait [53]. Regular flooding of the Oder river contributes also to increasing this effluence from the Oder lagoons, and particularly Cadmium appears as the most mobile heavy metal to be transported over long during flooding [53]. In particular, 84 to 96% of Cadmium appears in the mobile fractions in the sediment layers, Zn can be present in the mobile sediment layers from 45 to 94%, while lead is associated with the least mobile fractions (30–60%) [53].

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