Agata Zaborska

Distribution and origin of organic matter in the Baltic Sea sediments dated with 210Pb and 137Cs

Organic carbon deposited in marine sediments is an important part of the global carbon cycle. The knowledge concerning the role of shelf seas (including the Baltic Sea) in the carbon cycle has increased substantially, however organic carbon accumulation rates in the Baltic sediments still require clarification.This paper describes methods used for assessing organic carbon and nitrogen accumulation rates in six sediment cores collected in the sediment accumulation areas in the Baltic Sea. Mass sediment accumulation rates were based on 210Pb method validated by 137Cs measurements. The organic carbon accumulation rates ranged from 18 to 75 g·C·m−2·yr−1. The C/N ratios and δ13C were used to access sedimentary organic matter provenance. The C/N ratios in the investigated cores vary in the range from 7.4 to 9.6, while δ13C ranged from −24.4‰ to −26.4‰. Results of the terrestrial organic matter contribution in the sedimentary organic matter were calculated basing on δ13C using the end member approach. Large proportion (41–73%) of the sedimentary organic carbon originates on land.The obtained results indicate the Baltic Sea sediments as an important sink for organic carbon. Substantial fraction of the sedimentary load originates on land.

Sources and distributions of 137Cs, 238Pu, 239,240Pu radionuclides in the north-western Barents Sea

Sediment deposits are the ultimate sink for anthropogenic radionuclides entering the marine environment. The major sources of anthropogenic radionuclides to the Barents Sea are fallout from nuclear weapons tests, long range transport from other seas, and river and non-point freshwater supplies. In this study we investigated activity concentrations, ratios, and inventories of the anthropogenic radionuclides, 137Cs, 238Pu, 239,240Pu in dated sediment cores collected along a north-south transect in the northwestern Barents Sea. The data were used to evaluate the influence of different sources on the derived spatial and temporal patterns of anthropogenic radionuclides in seafloor sediment deposits. Activity concentrations of 137Cs ranged from <0.1 Bq/kg to 10.5 Bq/kg while 239,240Pu ranged from <0.01 Bq/kg to 2.74 Bq/kg and 238Pu activity concentrations ranged from <0.01 Bq/kg to 0.22 Bq/kg. Total inventories of 137Cs ranged from 29.5+/-1.5 Bq/m2 to 152.7+/-5.6 Bq/m2 and for 239,240Pu inventories (6 sediment layers only) ranged from 9.5+/-0.3 Bq/m2 to 29.7+/-0.4 Bq/m2. Source contributions varied among stations and between the investigated radionuclides. The 238Pu/239,240Pu ratios up to 0.18 indicate discharges from nuclear fuel reprocessing plants as a main contributor of plutonium. Based on 238Pu/239,240Pu ratio, it was calculated that up to 19-27% of plutonium is supplied from sources other than atmospheric global fallout. Taking into account Atlantic current flow trajectories and that both activity concentrations and inventories of plutonium negatively correlate with latitude, Sellafield is a major source for the Barents Sea. Concentrations and inventories of 137Cs correlate positively with latitude and negatively with distance from the Svalbard archipelago. The 137Cs concentrations are highest in an area of intensive melting of sea ice formed along the Siberian coast. Thus, sea ice and supplies from Svalbard may be important source of 137Cs to the Barents Sea seafloor.

Anthropogenic lead concentrations and sources in Baltic Sea sediments based on lead isotopic composition

The Gulf of Gdańsk is influenced by heavy metals of anthropogenic origin. In this study, temporal concentration changes of Pb, Zn, Cd, and Cu were studied in six, 50 cm long sediment cores. The main aim of the study was to concentrate on the history of Pb fluxes and Pb isotopic composition ((206)Pb/(207)Pb and (208)Pb/(206)Pb) to trace Pb sources. The lowest Pb concentrations (19 μg g(-1)) were measured in sediments deposited circa 1860, while the highest Pb concentrations (63-147 μg g(-1)) were measured in sediments deposited between 1960s and 70s. Pre-industrial Pb fluxes were 7 Pb m(2)year(-1), while after WWII they reached 199 Pb m(2)year(-1). Highest (206)Pb/(207)Pb ratios (∼1.22) were measured in the oldest sediment layers, and the lowest (206)Pb/(207)Pb ratios (∼1.165) were measured in the sediments deposited in 1970s-90s. During the period of highest Pb contamination, the anthropogenic Pb fraction reached up to 93%. A general discussion of the Pb sources, emissions, and loads for Poland is included.

Sediment carbon sink in low‐density temperate eelgrass meadows (Baltic Sea)

Seagrass meadows are highly productive habitats that can act as “blue carbon sinks” in coastal ecosystems by facilitating sedimentation and trapping particles. However, the magnitude and occurrence of these effects may be species and density dependent. The present study is the first estimation of seagrass sediment carbon sink in the temperate Zostera marina beds in the Baltic Sea. Several descriptors of organic matter characteristics, along with possible organic matter sources in the sediment were compared at vegetated and unvegetated bottoms. The 210Pb dating of the sediment has been used for accumulation rate assessment. The photopigments and POC concentrations in sediments were higher in vegetated bottoms. The SIAR (Stable Isotopes in R) mixing model based on nitrogen and carbon stable isotope values, indicated that higher percentages of organic matter originated from seagrass production in vegetated sediments (40–45%) compared to unvegetated ones (5–21%). The carbon stock in the upper 10 cm of the vegetated sediments ranged from 50.2 ± 2.2 to 228.0 ± 11.6 (g m−2), whereas the annual C accumulation amount from 0.84 ± 0.2 to 3.85 ± 1.2 (g m−2 yr−1). Our study shows that even the relatively weakly developed vegetation of the small temperate seagrass species enhance organic carbon concentration in the sediments. Estimated carbon stock was much lower than those reported for most of the seagrass meadows elsewhere, and the carbon burial rate was the lowest ever reported. Evidently, the global calculations of sediment carbon stock should be reconsidered by taking into account density and species-related variability.

Distribution of sedimentary mercury off Svalbard, European Arctic.

The European Arctic, including the Svalbard archipelago, receives mercury loads due to long range atmospheric transport, local contamination, melting of glaciers and as a result of bedrock weathering. Few studies have been devoted to the contamination history and sources of sedimentary mercury in the Svalbard area. This knowledge gap is addressed in this study. Concentrations of total mercury (10-80ng/g), fractions of mercury differing with affinity to the sediment matrix (88-97% refractory, 3-12% mobile), organic and methyl mercury (100-500pg/g) were measured in surface and subsurface sediments in the Spitsbergen fjords and in the Barents Sea off Svalbard. The atmospheric mercury signal can be observed in the Barents Sea, while in the Svalbard fjords it is strongly modified by supply of mercury from natural sources that may include weathering of rocks and glaciers melting, all modified by organic matter supply. Sedimentary methyl mercury concentrations seem to be dependent on environmental factors affecting mercury methylation rather than on location of sampling stations.

Climate Change Influence on Migration of Contaminants in the Arctic Marine Environment

The Arctic is particularly vulnerable to environmental changes connected to climate change. Most of assessments of the climate change impact to the Arctic environment concentrate on direct effects to the marine and terrestrial ecosystems. There is little understanding of numerous indirect effects of global change and their impact on cycle of different compounds e.g. man-made substances. The global change effects will not always be predictable but may be abrupt. Environmental changes connected to climate change will influence contaminant transport and migration within the Arctic marine ecosystem. Main effects of global change will be visible through changes of large scale contaminant transport pathways e.g. air mass transport, ice transport, marine currents transport and the changes of in situ environmental conditions e.g. changes of pH, temperature, oxygen content. In this review article we describe major environmental factors that may influence global transport of contaminants and migration of contaminants within the arctic ecosystem elements. We also discuss possible further changes in contaminant sources and distribution within the Arctic related to global changes.

Polychlorinated Dibenzo-P-Dioxins (PCDD), PolychlorinatedDibenzofurans (PCDF) and Dioxin-Like Polychlorinated Biphenyls (Dl-PCB)in the Baltic and Arctic Fish and the Further Trophic Transfer of thesePollutants to Seabirds

The study presents the analysis of polychlorinated dibenzo-p-dioxins, dibenzofurans (PCDD/F) and dioxin-like polychlorinated biphenyls (dl-PCB) in fish and seabirds from the Baltic Sea area and the Arctic region (the Svalbard Archipelago). Long-time studies revealed no significant temporal trends in PCDD/F and dl-PCB concentrations in fish from the Baltic Sea. Trace amounts of PCDD/F were detected in the Arctic fish as an evidence of their anthropogenic sources from the temperate zone, however congener profile in the cod was entirely different than in the Baltic fish. On the contrary, both concentrations and profiles of dl-PCB were comparable in cod from the Baltic Sea and from the polar region. PCDD/F`s congener profile in African penguin`s tissues breed in captivity and fed only by herring exhibited a clear resemblance to the profiles measured in herring. This indicates a relevant impact of diet (fish) on PCDD/F`s level in seabirds. Diet impact on the further transfer of these xenobiotics in the trophic chain, evidenced in the presented study, appears to be of the particular relevance due to the human health.