Trace metal fluxes to nearshore Long Island Sound sediments

Sediments are very important as trace metal ‘sinks’ in coastal areas. In this paper we present data on the concentrations and calculated fluxes of the trace metals, Fe, Mn, Cu, Pb, Zn, Cd and Ag at nearshore sites in Long Island Sound. In both areas a percentage of the metal accumulation can be ascribed to local human activities with the highest anthropogenic metal fluxes occurring closest to their source.     

Trace metal concentrations in sediments from Long Island Sound

It is important to determine trace metal concentrations in marine sediments because these could be important sources of contamination of marine organisms that reside there. In this study we measured the concentrations of thirteen metals in sediments obtained from Long Island Sound. We found great variations in metal levels for various geographic areas in the Sound; but, generally the highest concentrations found were in the extreme western end of the Sound. Comparison is made between metal levels in sediments from the Sound to seven other areas located in the U.S. and U.K.     

Baseline metal concentrations in coastal Labrador sediments

Levels of Cr, Cu, Fe, Pb, Ni, and Zn in surface sediment from the Voisey's Bay area of coastal Labrador showed no evidence of recent anthropogenic input of metals. Metal concentrations in surface sediments, normalized to Li, fell within the 95% confidence limits of the background levels. Further analysis showed that the Li-metal regression lines from the surface sediments and sediments from 30-cm depth had the same slope and intercepts, suggesting that there was no difference in the metal content of the sediments at the two depths. Li-metal relationships can be used as a measure of the natural variability of the metal concentrations for the region and will serve as a baseline against which future anthropogenic affects may be assessed.     

Trace metal distributions in Saint John Harbour sediments

The concentration and areal distribution of selected trace metals (Cu, Zn, Pb, Cd, Mo, Ni, Mn and Hg) in surficial sediments of Saint John Harbour, New Brunswick, Canada, were studied to determine the extent of anthropogenic input and to estimate the effects of dumping dredged material in the outer harbour. Hg and Cd are of especial concern, since the disposal of dredge material containing these two elements is regulated under the Ocean Dumping Control Act.The concentrations of all metals are low: Cu 16, Zn 53, Pb 24, Cd 0.16, Mo 3, Ni 16, Mn 296 and Hg 0.04 μg g^?1. Hg and Cd levels in sediments are well below the permissible limits of 0.75 and 0.6 μg g^?1, respectively, set by the Ocean Dumping Control Act.The mean concentrations of trace elements are similar to the low mean values in the unpolluted Bay of Fundy. There is an overall decline in concentrations of metals in the sediments from the inner to the outer harbour. Comparison of the metal levels in the sediments from different areas within the harbour indicate that there is a detectable anthropogenic input in the Courtenay Bay area. Trace metal levels at the dumpsite are significantly lower than in the Courtenay Bay area, where the bulk of the dredged material originates.     

Trace metal concentrations in Fucus from the Bristol channel

Brown seaweeds are unable to regulate their uptake of trace metals and can therefore be used to provide a running average of metal contamination in the surrounding waters. There are many sources of error, however, and misleading results can be obtained if attention is not paid to factors that influence the metal concentrations in the weed. This becomes particularly important when comparing the results of different investigators.     

Trace metal remobilization in the interstitial waters of red clay and hemipelagic marine sediments

Interstitial water samples from the Guatemala Basin and the coast of Baja California have been analyzed for manganese, iron, copper, nickel and nitrate. The data provide a systematic look at changes in trace metal diagenesis proceeding from red clay to highly reducing nearshore sediments.In red clay sediments, the nitrate concentrations suggest that only aerobic respiration is occurring. Manganese and iron are below detection. Nickel concentrations remain the same as in bottom seawater but copper shows a pronounced maximum just at the sediment/water interface. Proceeding to hemipelagic sediments, denitrification becomes increasingly important and manganese and iron remobilization occur in the sediments.The linear manganese and nitrate profiles suggest regions of production or consumption separated by zones of diffusion. This differs from the conventional picture of a continuous series of reactions within the sediments. Manganese reduction always occurs before iron reduction. The pore water nickel correlates well with manganese in these sediments, suggesting that nickel is associated with MnO₂ in the solid phase. The pore water flux ratio of manganese and nickel agrees well with the ratio in solid phase authigenic oxides. Copper still displays a core top concentration maximum as well as a second maximum associated with the remobilized manganese. The calculated ratio of the Cu/C flux ratios support the argument for copper remobilization during organic carbon oxidation. Comparison of the upward and downward diffusive fluxes with the rate of copper buried by sedimentation shows that at least half of the copper buried must be of diagenetic origin and less than 25% of the copper reaching the sediments is buried.     

Trace metal concentrations in Antarctic sea spiders (Pycnogonida, Pantopoda)

Trace metals were analysed in sea spiders collected on two Polarstern cruises in the Weddell Sea. We found a substantial interspecific heterogeneity of Cd, Cu, Ni, and Zn, indicating varying accumulation strategies and metabolic demands for essential elements. Means and 95%-confidence intervals for all 44 samples analysed are 26+/-7 mg Cd kg(-1), 38+/-22 mg Cu kg(-1), 62+/-13 mg Ni kg(-1) and 990+/-130 mg Zn kg(-1) DW. Only for Pb do we find values less than 1.0 mg kg(-1) for most collectives analysed, in good agreement with other Antarctic arthropods such as crustaceans. Our study provides further evidence for the frequently reported "Cd anomaly" in many polar arthropods. While Cu concentrations in pantopods are within the reported range for Antarctic amphipods and decapods, Ni concentrations are exceptionally high and might be part of predation defence mechanisms. These possibilities should be investigated in more detail in future studies.     

Noble gas isotopic abundances and noble metal concentrations in sediments from the Cretaceous-Tertiary boundary

Noble gases in four sediment samples from the Cretaceous-Tertiary boundary collected near Stevns in Denmark were investigated to test the possibility of the presence of noble gases indicative for meteorites. All samples were also analyzed for the noble metals Os and Ir and twelve other elements. The observed enrichments of³He,⁴He and of Ar, Kr, and Xe relative to atmospheric abundances can be explained without invoking the addition of extraterrestrial material. The ²⁰Ne/²²Ne ratio and the Kr and Xe isotopic compositions are identical with the isotopic ratios in the terrestrial atmosphere. In contrast, the high noble metal concentrations indicate the presence of material with elemental abundances similar to chondritic matter. Compared to noble metals the noble gases are less sensitive tracers of an admixture of extraterrestrial matter in sediments.     

Metal concentrations, fluxes, inventories and chronologies in sediments from Sepetiba and Ribeira Bays: A comparative study

Three sediment cores were sampled at Sepetiba Bay and four cores at Ribeira Bay, Rio de Janeiro State, Brazil. Sediment accumulation rates and chronologies were obtained from ²¹⁰Pb activity-depth profiles. Sediment accumulation rates in Ribera Bay ranged from 1.2 mm y⁻¹ in the inner bay to 2.6 mm y⁻¹ close to its entrance. In Sepetiba Bay two sediment accumulation rates were observed: a lower rate of 0.35 cm y⁻¹ before the 1960s and 0.76 cm y⁻¹ since then. The cause of this change is due to the construction of the Santa Cecília impoundment (1955) that brings water from the Paraíba do Sul Basin into the Guandu River, which increased its flow from the original 20 m³ s⁻¹ to 160 m³ s⁻¹. Concentration of 44 elements was obtained by ICP-MS after total dissolution of samples from two selected cores. The relative differences between the concentrations of crustal elements, such as Al, Fe and Ti are only about 20% (p < 0.05). Cd and Zn are 15 and four times larger in Sepetiba Bay than in Ribeira Bay, respectively. Other major and minor elements show lower statistically significant differences. The enrichment factors and metal inventories show that Sepetiba Bay can be considered polluted with Bi, Cd, Cr, Cu, Sb and Zn. Particularly, Cd and Zn present concentrations three and four times higher than the Brazilian existing limits.     

Trace metal concentrations in offshore,deep-water seaweeds in the western North Atlantic ocean

Ambient, natural levels of selected heavy metals were assayed from deep, offshore populations of attached seaweeds from 1980 through 1983 from Pigeon Hill, 37 km from the nearest shoreline in the Gulf of Maine, and from Block Island, 23 km from the nearest mainland in Rhode Island Sound. Concentration levels of barium, cadmium, chromium, copper, mercury, lead and zinc were low when compared with concentration values published for a variety of seaweeds from the eastern and western North Atlantic. Values from Pigeon Hill and Block Island provide baseline data for long term monitoring of a relatively pristine, offshore, benthic community in the western North Atlantic.     

Trace metals in Solway Firth sediments

Although the hinterland of the Solway Firth contains deposits of a variety of non-ferrous metals, and coal and steel industries grew there during the industrial revolution, the trace metal content of sediments in the firth is low, and the Solway is the last major unpolluted estuary in Britain.     

Trace metals in carbonate and organic rich sediments

A great variety of man's activities on the coast result in metal contamination of the sea. Investigations at three sites, two in Florida and one in Bermuda reveal trace metals in sediments. In all three cases these accumulations can be ascribed to local human activities, though their nature varies widely from one site to another.