Search

The shells of calcitic arthropod Amphibalanus improvisus; aragonitic bivalves Cerastoderma glaucum, Limecola balthica, and Mya arenaria; and bimineralic bivalve Mytilus trossulus were collected in the brackish waters of the southern Baltic Sea in order to study patterns of bulk elemental concentration (Ca, Na, Sr, Mg, Ba, Mn, Cu, Pb, V, Y, U and Cd) in shells composed of different crystal lattices (calcite and aragonite). The factors controlling the elemental composition of shells are discussed in the context of crystal lattice properties, size classes of organisms and potential environmental differences between locations. Clams that precipitate fully aragonitic shells have a clear predominance of Sr over Mg in shells, contrary to predominant accumulation of Mg over Sr in calcitic shells of barnacles. However, the barnacle calcite shell contains higher Sr concentration than bivalve aragonite. The elemental variability between size-grouped shells is different for each studied species, and the elemental concentrations tend to be lower in the large size classes compared to the smaller size classes. Biological differences between and within species, such as growth rate, feeding strategy (including feeding rate and assimilation efficiency or composition) and contribution of organic material, seem to be important factors determining the elemental accumulation in shells. Because specimens used in this study were obtained from different sampling sites within the gulf, the impact of location-specific environmental factors, such as sediment type, cannot be excluded.

In this study, the concentrations of 12 metals: Ca, Na, Sr, Mg, Ba, Mn, Cu, Pb, V, Y, U and Cd in shells of bivalve molluscs (aragonitic: Cerastoderma glaucum, Mya arenaria and Limecola balthica and bimineralic: Mytilus trossulus) and arthropods (calcitic: Amphibalanus improvisus) were obtained. The main goal was to determine the incorporation patterns of shells built with different calcium carbonate polymorphs. The role of potential biological control on the shell chemistry was assessed by comparing the concentrations of trace elements between younger and older individuals (different size classes). The potential impact of environmental factors on the observed elemental concentrations in the studied shells is discussed. Specimens were collected from brackish waters of the Baltic Sea (the Gulf of Gdansk). For every species, 40 individuals (ten in each size class) were selected. Pre-cleaned shells were analysed by ICP-OES and ICP-MS to determine the concentrations of metals. The distributions of elements both differ between species and exhibit high intraspecific variability. Calcitic shells preferentially incorporated Mg > Sr > Na, aragonitic shells incorporated Na > Sr > Mg, and bimineralic shells accumulated Na approximately two times more intensively, than Mg and Sr which remained at similar levels. Among all species, the calcitic shells of A. improvisus most effectively concentrated the majority of the studied elements, especially Mg > Mn > Ba, which was contrary to the shells of aragonitic molluscs that contained the lowest levels of trace elements. The size-dependent distributions of elements in shells did not exhibit a consistent pattern. The highest significant differences were found for the bimineralic shells of M. trossulus, while the smallest were found for aragonitic shells; if any variability occurred, it was observed in heavy metals (Pb, Cd). Our results indicate that elemental variability, especially that of Mg and Sr, is dominated by the properties of the crystal lattice. The inconsistent variability of trace element concentrations between species and within single populations supports the important role of species-specific biological control of the biomineralization process and indicates that environmental factors have a significant influence on the incorporation of trace elements into the shells.

This study presents the results of dosimetry radiation measurement performed in the Antarctic region at the surface of the sea which was conducted between January and March 2018. Over 2 200 records were collected using a portable Gamma Scout Online radiometer during a 72-day voyage circumnavigating the continent of Antarctica. The mean average of the measured radiation dose rate was 0.091 μSvh-1 and varied from 0.052 to 0.193 μSvh-1. These result are above global average dose rate of radiation at sea level (0.031 μSvh-1) and often higher than those recorded on the Antarctic continent. Yet generally our records fall within well recognized latitudinal trend of radiation being higher toward poles. This is results of troposphere begins at lower altitude in Antarctic in comparison to lower latitudes. The origin of this radiation is natural and results from the presence of higher cosmic rays and secondary radiation induced in the atmosphere. The presence of terrestrial radionuclides in the Antarctic environment has a local, secondary influence on the measured values of radiation. The theoretical calculated annual dose equivalent for humans present in Antarctica could often exceed the limit of 1 mSv as recorded for other Antarctic locations yet our results (0.772 mSv per year) do not confirm that. W pracy przedstawiono wyniki dozymetrycznych pomiarów promieniowania, przeprowadzonych przez załogę jachtu Katharsis II, w trakcie 72-dniowego rejsu wokół Antarktydy. Podczas rejsu trwającego od stycznia do marca 2018 roku, za pomocą przenośnego radiometru Gamma Scout Online rejestrowano dawki promieniowania na poziomie morza w odstępach 10-minutowych. Po wstępnej analizie statystycznej uzyskano dane w postaci 2 200 rekordów, które wykorzystano do wnioskowania o rozkładzie promieniowania w rejonie Antarktyki. Średnia zmierzona moc dawki promieniowania wyniosła 0,091 μSvh-1 i wahała się od 0,052 do 0,193 μSvh-1. Wyniki te są powyżej średniej globalnej mocy dawki promieniowania na poziomie morza (0,031 μSvh-1) i często wyższe niż te zarejestrowane bezpośrednio na Antarktydzie. Jednak, generalnie zarejestrowane przez nas dawki promieniowania mieszczą się w dobrze rozpoznanym równoleżnikowym trendzie, w którym promieniowanie jest wyższe w kierunku biegunów. Związane jest to z cieńszą warstwą troposfery w rejonach biegunowych w porównaniu z niższymi, równikowymi szerokościami geograficznymi. Ogólnie pochodzenie tego promieniowania jest naturalne i związane z silniejszą penetracją troposfery przez promieniowanie kosmiczne oraz obecnością promieniowania wtórnego indukowanego w atmosferze. Obecność radionuklidów naziemnych w środowisku Antarktyki ma lokalny, wtórny wpływ na mierzone wartości promieniowania. Teoretycznie obliczony roczny ekwiwalent dawki dla ludzi, w różnych miejscach Antarktydy, może przekraczać limit 1 mSv, natomiast nasze wyniki (0,772 mSv rocznie) tego nie potwierdzają.