The Gulf of Finland has during the last centuries been loaded with heavy metals of anthropogenic origin. Work with mapping of the chemistry of the sediments have been done in all surrounding countries during several decades, first in the Soviet Union and later in Russia and similarly in Finland. More recent sediment chemistry data from the last two decades was in this study combined into sediment chemistry maps added with some data from the commercial Nord Stream project. The result shows that zinc, copper and chromium are enriched in the eastern part of the Gulf of Finland, while mercury, cadmium and lead are showing the highest concentrations in the north- eastern part of the gulf.

The concentration distribution was studied for dissolved oxygen, phosphorus forms, and particulate matter in Curonian Bay of the Baltic Sea in poorly known consolidated ice cover conditions during the winter seasons of 2010, 2011, and 2013. The surface and near-bottom waters were sampled at 51 stations. The ice cover exerts no significant effect on the typical seasonal variation of all considered parameters in the basin. The concentrations of mineral and organic phosphorus in the bay appeared to be lower by factors of 2–4 compared to summer values. A two- to threefold decrease in the concentrations of organic phosphorus since 2010 to 2011 and then to 2013 was recorded in the bay, which resulted from a decrease in phosphorus production by phytoplankton. Despite water being isolated from air by ice, the absence of wave mixing, and the decrease in oxygen production owing to the seasonal winter decrease in the intensity photosynthetic processes, no oxygen deficiency was found in the basin. This is because oxygen supplied to the bay by river runoff and production by photosynthesis in the bay exceed the utilization for oxidation of organic matter resulting from low bioproductivity of the waters during winter. The winter decrease in the fraction of biogenic particulate matter is seen as a four- to sevenfold drop in its total concentration in the waters compared to summer seasons. The absence of wave roiling of bottom sediments also caused a decrease in the secondary supply of biogenic particulate matter from sediments into near-bottom waters. No negative trends of geoecological conditions in the bay were revealed by the studied parameters under consolidated ice cover conditions.

A comprehensive multi-proxy study of mini-core Ash-2009-08 from the inner shelf of the northeastern Black Sea, allowed us to define recent environmental changes in the area, on a sub-decadal resolution. The age model of the core based on radionuclide (Pb-210 and Cs-137) measurements suggests an average sedimentation rate of 2 mm/y and, consequently, a sedimentary record spanning the last similar to 140 years. Overall, four fossil groups studied from the core indicate subtle environmental changes. The dinocyst assemblages show stable surface water conditions with a possible cooling in the 1930s-1950s and a slight decline in salinity from the 1960s, which corresponds to an increase in precipitation and the fresh water balance of the Black Sea, known from the published instrumental data. A gradually increasing abundance of the heterotroph species suggests a nutrient increase from the 1920s. Ostracods and molluscs demonstrate rather stable bottom-water salinity and biotopes over the last similar to 75 years. Changes in abundance of ostracods and benthic foraminifers, as well as changes in the mollusc diversity, most likely reflect variations in trophic conditions with the higher food supply to the sea floor in the 1940s-1960s and from the late 1990s. Enhanced bottom-water energy is inferred from the mollusc enrichment and a relatively high content of the fine sand grain-size fraction in the 1990s. In the pollen assemblages, trees mainly represented by Pinus strongly prevail over herbs throughout the record. However, the trees to herbs ratio demonstrates a slight decline from the 1920s, most likely resulting from human impact on the vegetation of the nearby land. (C) 2013 Elsevier Ltd and INQUA. All rights reserved.

In the summer 2006, integrated geological, geochemical, hydrological, and hydrochemical studies were performed on the relict anoxic Lake Mogil’noe (down to 16 m depths) located on Kil’din Island in the Barents Sea. The chemical and grain-size composition of the bottom sediments were compared for the lake (a permanently anoxic basin) and the Baltic Sea Deeps (periodically anoxic basins). The vertical location of the hydrogen sulfide layer boundary in the lake (9–11 m depths) was practically the same from 1974 up to now. The concentrations of suspended particulate matter in the lake in June and July 2006 appeared to be close to its summer concentrations in the seawaters of the open part of the Baltic Sea. The mud from Lake Mogil’noe compared to those of the Baltic Sea Deeps are characterized by fluid and flake consistency and by pronounced admixtures of sandy and silty fractions probably of eolic origin. The lacustrine mud contain much plant remains; iron sulfides and vivanite were also found in ooze. The concentrations of 22 elements determined in the lacustrine bottom sediments were of the same levels as those found here 33 years ago. The concentrations also appeared to be close to those in the corresponding grain-size types of the bottom sediments in the Baltic Sea. The low Corg/N value (5% on average) in the mud of Mogil’noe Lake compared to the values for the mud of the Baltic Sea Deeps (10% on average) points to the considerable planktogenic component in the organic matter composition of the lacustrine mud. No indications were reveled for anthropogenic contaminations of the lacustrine bottom sediments with toxic metals.

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. The bottom of the deep is covered by mud with thickness of 1-3 m. The heavy metal contents (iron, manganese, zinc, copper, cobalt, nickel, chromium, cadmium, lead) and arsenic in the bottom sediments of chemical weapons dumpsite area were investigated with 378 samples in order to develop new data assessing the influence of chemical weapons on the environment. The data obtained indicate that an increased concentration of arsenic (111-277 mg/kg) in the mud of the dumpsite area is related to the chemical warfare agents, where the corrosion processes of chemical munitions and leakage of arsenic-containing agents are happening. The arsenic contamination is of local character and is not regarded hazardous for the environment. In most of the sediment samples outside the chemical weapons dumping area the contents of all the studied elements are in levels of background concentrations. Seven maps of the distribution of the toxic metals in the bottom sediments of Bornholm Basin were compiled. The contents of the studied heavy metals decrease in the direction away from the chemical weapons dumpsite area to the border of the Bornholm Deep. Although the release of warfare gases from dumped chemical weapons has persisted for many decades, the specific pollution of sediments is found to be rather small. The prognosis for further degradation from chemical weapons should exclude catastrophic scenarios.

Core MD02-2508 retrieved from the plateau of the continental slope off Baja California recovered a 40-m-thick section of sapropel (up to 15% C-org), calcareous clay, and diatom ooze with the age of 120 ka at the core bottom. The section is subdivided into three units: Unit I (Holocene) consists of the laminated sapropel; Unit II comprising oxygen isotope stages (MIS) 2, 3, and 4 is represented by homogeneous calcareous clay with interbeds of slightly siliceous sapropelic mud; and Unit III (MIS-5) is composed of laminated sapropelic diatom ooze. Laminated intervals are characterized by the intercalation of two lamina types: (1) dark-colored organic-rich laminae containing multi-species "oceanic" diatom assemblages, as well as radiolarians, coccoliths, planktonic and benthic foraminifera; (2) lighter-colored laminae consisting of diatom ooze with the neritic colonial diatom assemblages commonly composed of one to three species of a single genera. The dark laminae are assumed to be generated within a high productivity zone over the slope, whereas light ones likely represent diatom mats produced by short-term boisterous phytoplankton blooms, possibly in the coastal upwelling.

As is less toxic than Hg, Cd, Pb, Se, Zn, and Cu. The As clarke for clays and shales is 10 ppm. Our samples of bottom sediments from Kurshskii Bay were determined to contain from 15 to 26 ppm As and up to 34 ppm As in the vicinity of the Neman River mouth. Elevated As concentrations (50–114 ppm) were detected in four columns of subsurface bottom sediments (at depths of 10–65 cm) from the Vistula Lagoon. Elevated As concentrations (50–180 ppm) were also found in a few surface samples of sand from the Gdansk Deep near oil platform D-6. These sediments are either partly contaminated with anthropogenic As or contain Fe sulfides and glauconite, which can concentrate As and contain its elevated concentrations. The As concentration in columns of bottom sediments from the Gulf of Finland were at the natural background level (throughout the columns) typical of the area (9–34 ppm). We repeatedly detected very high As concentrations (up to 227 ppm As) in pelitic ooze from Bornholm Deep, in the vicinity of the sunken vessel with chemical weapons. The sources of elevated As concentrations in the Baltic Sea are the following: (1) chemical weapon (CW) material buried in the floor of the Baltic Sea; (2) As-bearing pesticides, agricultural mineral fertilizers, and burned coal and other fuels; (3) kerogen-bearing Ordovician rocks exposed on the bottom; and (4) As-rich Fe sulfides brought to the area together with construction sand and gravel. This mixture was used in paper production and for the construction of hydraulic engineering facilities in the Vistula Lagoon in the early 20th century and later caused the so-called lagoon disease.