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1.
Variability in levels and sources of polycyclic aromatic hydrocarbons (PAH) in sediments from one large sea area off the coast of northern Norway (“North area”, NA) have been compared to similar data from another large area off the coast of southern Norway (“South area”, SA). Samples from NA were collected at the Norwegian continental shelf in south-western Barents Sea and north-eastern Norwegian Sea. Samples from SA were from the Norwegian Trench and the Skagerrak. Sediment cores have been dated, characterised by grain size distribution (GS) and organic carbon content (TOC), and the composition of PAH and geochemical biomarkers (alkanes and triterpanes) studied to provide an insight into the different sources of PAH. Generally, PAH levels are higher in sediments from SA compared to NA. A mixture of pyrogenic and petrogenic sources contribute to PAH levels in SA, while the contents of petrogenic PAH is negligible in surface sediments in NA. At some locations in NA, petrogenic PAH levels are elevated in the deepest sediment layers from pre-industrial times, indicating a natural input of petroleum through seepage. Occurrence of elevated levels of microbial hopanoids (hopenes) in the deepest sediment layers at some locations both in the north and the south indicate the presence of petroleum.  相似文献   

2.
As part of a lipid biogeochemical study, aliphatic and polyaromatic hydrocarbons were determined in surficial sediments from the Cretan Sea (South Aegean Sea) in the Eastern Mediterranean. Total concentrations of both aliphatic (AHC) and polyaromatic (PAH) hydrocarbons were low (562–5697 and 14.6–158.5 ng/g, respectively) with respect to other coastal sediments worldwide and compare with concentrations found in open sea areas. The composition of AHC was dominated by unresolved complex mixture (UCM) indicating the presence of petroleum-related hydrocarbon inputs as confirmed by the detection of specific α,β-hopanes. PAH consisted mainly of pyrolytic four- to five-ring compounds. UCM and PAH amounts revealed that Cretan Sea receives low supply of anthropogenic material compared to NW Mediterranean. The spatial distributions of AHC and PAH indicated that urban run-off and transport from the continental self are the major input pathway of anthropogenic and biogenic hydrocarbons from terrestrial sources in the near shore area, whereas atmospheric transport might be the significant source of hydrocarbons in the deep area.  相似文献   

3.
A C25 highly branched isoprenoid (HBI) monoene hydrocarbon, designated IP25, has been proposed previously to originate from diatoms living in Arctic sea ice, while the presence of IP25 in sediments has been suggested to be a proxy for the occurrence of former Arctic sea ice. Here, we show that the 13C isotopic composition of IP25 in sea ice, in sediment trap material collected under sea ice, and in high latitude northern sediments, is distinctive (isotopically ‘heavy’) and distinguishable from that of organic matter of planktonic or terrigenous origin. Mean δ13C values for IP25 were − 22.3 ± 0.4‰ (sea ice), − 19.6 ± 1.1‰ (sediment traps) and − 19.3 ± 2.3‰ (sediments). These measurements, therefore, support further the proposed use of IP25 as an Arctic sea ice proxy.  相似文献   

4.
Data are presented on the content of aliphatic and polycyclic aromatic hydrocarbons (AHC and PAH, respectively) in the interstitial waters and bottom sediments of the Kara Sea compared to the distribution of the particulate matter and organic carbon. It was found that the AHC concentrations within the water mass (16 μg/l on average) are mainly formed by natural processes. The AHC distribution represents the variability of the hydrological and sedimentation processes in different regions of the sea. The widest ranges of the concentrations were registered in the Ob Bay-Kara Sea section: in the water (10–310 μg/l for the AHC and 0.4–7.2 ng/l for the PAH) and in the surface layer of the bottom sediments (8–42 μg/l for the AHC and 9–94 ng/g for the PAH). The differentiation of the hydrocarbons (HC) in the different media follows the marginal filter’s regularities; therefore, no oil and pyrogenic compounds are supplied to the open parts of the sea. In the sediment mass, the HC content is determined by the variations in the oxidative conditions in the sediment and its material’s composition.  相似文献   

5.
Concentrations of U and Th isotopes in Okinawa Trough and East China Sea sediment cores were determined by isotope dilution inductively coupled plasma-mass spectrometry (ID-ICP-MS) to investigate the behavior of redox sensitive uranium in suboxic hemipelagic sediments and determine their significance in oceanic uranium balance. 238U concentrations and 238U/232Th activity ratios in the East China Sea sediments showed no remarkable variation with depth. However, 238U and 238U/232Th ratios in the Okinawa Trough sediments were low in the surface oxidizing layer but increased where the suboxic condition was encountered. The distribution profiles of 230Th and 232Th concentrations were relatively constant with depth in both the Okinawa Trough and East China Sea sediment cores. These results suggested that there has been post-depositional precipitation of authigenic uranium within the suboxic Okinawa Trough sediment column. The post-depositional precipitation rates of authigenic uranium were estimated to be 47 ± 5 to >62 ± 8 ng cm−2 yr−1; these rates were comparable to those previously reported for several anoxic sediments. A mechanism controlling precipitation of uranium may be the downward diffusion of uranium U(VI), reduction to U(IV) and finally precipitation onto the solid phase. The accumulation rate of uranium for the Okinawa Trough sediments was approximately eight times higher than the world average rate reported for suboxic sediments. This removal of uranium in the oceanic budget increases the importance of the suboxic sediment sink.  相似文献   

6.
Coastal marine sediment, air and seawater samples were collected at six sampling stations in the Eastern Mediterranean Sea distant from pollutant point sources. All sediment samples were analyzed to determine polycyclic aromatic hydrocarbon (PAH), black carbon (BC) and organic carbon (OC) contents. The PAH contents of gaseous and seawater samples of the study were determined in order to evaluate the role of air–sea exchange as PAH nonpoint source to the marine sediments. The average concentration of the total PAHs (∑PAHs) in the sediments varied from 2.2 to 1056.2 ng g−1 dry weight. The average BC and OC contents varied from 0.3 to 5.6 and from 2.9 to 21.4 mg g−1 dry weight, respectively. ∑PAH concentration in the marine atmosphere varied from 20.0 to 83.2 ng m−3. Air–water exchange flux (FA–W) estimation has indicated air transport as a significant source of PAHs to pristine marine sediments of Eastern Mediterranean. In addition, the significant correlation between the PAHs and the organic and soot carbon content further suggests the importance of atmospheric input of PAHs to the sediments.  相似文献   

7.
We studied diatom assemblages and CaCO3 contents of methane-derived authigenic carbonates from the eastern margin of the Sea of Japan and assessed the formation time of these samples. Radioactive 14C date was determined in selected samples to obtain the maximum age of the time. The results of our study suggest mass formation of carbonate nodules in a glacial period within ∼40 ky, consistent with a published U/Th dating result of carbonate nodules in the study area. Diatom assemblages and contents in the carbonate nodules (abundance of ∼106/g, dominance of neritic-littoral species, warm/cold water species ratio lower than ∼25) differ from the near-seafloor sediments in the study area, which have characteristics of Holocene sediments in the Sea of Japan, and suggest cementation of glacial sediments. Laminated sediments in some nodule samples are glacial sediments because laminations are records of a low sea level period in the semi-enclosed ocean. Similarity of diatom assemblages and contents in all carbonate samples is another evidence of glacial sediments in nodules. Glacial sediments with oceanic cold water species as low as Holocene sediments restricts the sediment age to before 20 cal. ky BP. Carbonate contents higher than 78 wt% suggest the cementation of poorly compacted sediments near the seafloor, and the date of carbonate cementation is, therefore, close to that of the cemented sediments. Most carbonate nodule samples in this study were formed in a glacial period and detection of 14C restricts this period to within ∼40 ky.  相似文献   

8.
The question of polycyclic aromatic hydrocarbon (PAH) bioavailability and its relationship to specific PAH sources with different PAH binding characteristics is an important one, because bioavailability drives PAH accumulation in biota and ultimately the biochemical responses to the PAH contaminants. The industrial harbour at Kitimat (British Columbia, Canada) provides an ideal location to study the bioavailability and bioaccumulation of sediment hydrocarbons to low trophic level biota. Samples of soft shell clams (Mya arenaria) and intertidal sediment collected from multiple sites over six years at various distances from an aluminium smelter and a pulp and paper mill were analysed for 106 PAHs, plant diterpenes and other aromatic fraction hydrocarbons. Interpretation using PAH source ratios and multivariate data analysis reveals six principal hydrocarbon sources: PAHs in coke, pitch and emissions from anode combustion from the aluminium smelter, vascular plant terpenes and aromatised terpenes from the pulp and paper mill, petroleum PAHs from shipping and other anthropogenic activities and PAHs from natural plant detritus. Harbour sediments predominantly contain either pitch or pyrogenic PAHs from the smelter, while clams predominantly contain plant derived PAHs and diterpenes from the adjacent pulp mill. PAHs from the smelter have low bioavailability to clams (Biota-Sediment Accumulation Factors; BSAFs <1 for pitch and coke; <10 for anode combustion, decreasing to ∼0.1 for the mass 300 and 302 PAHs), possibly due to binding to pitch or soot carbon matrices. Decreases in PAH isomer ratios between sediments and clams likely reflect a combination of variation in uptake kinetics of petroleum PAHs and compound specific metabolism, with the importance of petroleum PAHs decreasing with increasing molecular weight. Plant derived compounds exhibit little natural bioaccumulation at reference sites, but unsaturated and aromatised diterpenes released from resins by industrial pulping processes are readily accumulated by the clams (BSAFs >500). Thus while most of the smelter associated PAHs in sediments may not be bioavailable to benthic organisms, the plant terpenes (including retene, totarol, ferruginol, manool, dehydroabietane and other plant terpenes that form the chemical defence mechanism of conifers) released by pulp mills are bioavailable and possess demonstrated toxic properties. The large scale release of plant terpenes by some of the many pulp mills located in British Columbia and elsewhere represents a largely undocumented risk to aquatic biota.  相似文献   

9.
Eighteen short cores were analyzed for major and trace metals (Al, Fe, Ca, Mg, Mn, Si, K, Ti, Pb, Zn, Cu, Ni, Cr), 210Pb, 137Cs, and other sediment characteristics, so as to describe the chronology of pollution and calculate metal concentration factors and fluxes. Substantial evidence was found that trace metal profiles are influenced by anthropogenic sources and by changes in sediment composition. Only Zn presents concentrations (up to 13.1 μmol g−) and concentration factors (1.3 to 13.2) that can be attributed to heavy contamination. Pb, Cu and Ni, in this order, are less significant. The areal distribution of concentrations and inventories reflects the importance of direct sources, in particular the industrial area of Porto Marghera and the Dese river. The inventories of excess metals, above pre-industrial levels, were determined for each core and the three different parts of the study area, the amounts of Zn accumulated in sediments are 11.0 Mmol, 5.1 Mmol and 0.37 Mmol in the Campalto, S. Erasmo, and Palude di Cona areas, respectively. Ruxes were also calculated and compared with those suggested for the atmospheric delivery by Cochran et al. [(1995)b. Atmospheric fluxes of heavy metal contaminants to the Venice Lagoon, Rapp. Comm. Int. Mer Médit., 34, 136.], the atmospheric contribution is predominant or significant in many cases, especially at sites far from the major local inputs. Concentrations and fluxes show a significant increase in the anthropogenic metal supply starting from the second decade of this century, with maximum inputs in the period between the (1930)s and the (1970)s. At some stations a decrease in heavy metal contamination of surficial sediments was found and this could be ascribed to a reduced input of pollutants in recent years.  相似文献   

10.
The temporal variability of estuarine sedimentation has been investigated in the northernmost part of the Wadden Sea (Denmark), using an estuarine sedimentary sequence at Ho Havn. The sedimentary sequence appears to have been deposited within the last ∼ 2000 yr based on detailed luminescence dating of the estuarine mud, whose ages range between 225 ± 40 and 2050 ± 300 yr. The age-depth profile reveals that the sedimentation rate has varied considerably in the past. Estuarine sedimentation was very rapid ∼ 1400 yr ago; the ages over almost 1 m of sediment are indistinguishable. After this accretion rate of ∼ 9 mm a− 1, the rate dropped abruptly to ∼ 0.3 mm a− 1 some time between 1340 and 970 yr ago. This slow rate of accretion continued until ∼ 350 yr ago, when it accelerated to ∼ 1.3 mm a− 1. These abrupt changes in the accretion rate are possibly related to local sea level fluctuations, thus the period with low accretion rate most probably reflects a situation with a stable or decreasing relative sea level. The rapid deposition of ∼ 0.9 m of sediment within about one century some 1400 yr ago shows that large amounts of fine-grained sediment were available for deposition in the region at that time, and an increasing relative sea level was most probably responsible for the creation of the accommodation space for sedimentation. Recent studies on mudflats and salt marshes in the region also tend to show high accretion rates, indicating that the coastal lagoons could be less vulnerable and threatened by a future sea level rise than generally believed.  相似文献   

11.
Subsurface sediments from a pockmark area in South-Western Barents Sea have been earlier found to contain elevated levels of petroleum-related polycyclic aromatic hydrocarbons. This work describes a comprehensive analysis of various biomarkers, including the highly source-specific hopanes, in a 4.5?m long gravity core from the same area, together with subsurface sediment samples from other areas in the region without pockmarks present ("background samples"). A clear difference between the pockmark gravity core and the background sediment cores was found, both with regard to genesis and the level of transformation of organic matter. A number of indicator parameters, such as methylphenanthrene index (MPI-1), point towards a significantly higher maturity of hydrocarbons in the pockmark core throughout its length as compared to the other sampled locations. Higher contents of microbial hopanoids (hopenes) may indicate the former presence of petroleum. These findings confirm the hypothesis of a natural hydrocarbon source in the deeper strata present in the studied location with pockmarks.  相似文献   

12.
The sources and distributions of polycyclic aromatic hydrocarbons (PAH) and aliphatic hydrocarbons are characterized in seventeen sediments from a highly river-influenced sedimentary environment off the southwestern coast of Washington. The major hydrocarbons are land-derived, introduced as preformed compounds and display long-term stability in sediment cores. A series of PAH of anthropogenic origin and two naturally derived compounds, retene and perylene, dominate the PAH composition in these sediments. Plantwax n-alkanes are the major aliphatic hydrocarbon constituents. Aliphatic hydrocarbons of marine origin, pristane and a series of four acyclic, multibranched C25 polyolefins, are also observed in many sediments. The concentrations of these marine-derived hydrocarbons decrease to negligible levels rapidly with sediment depth from the sea-sediment interface, suggesting degradation.In general, the major land-derived hydrocarbons are concentrated in the midshelf silt deposit which extends northwestward along the continental shelf from the Columbia River mouth. A quantitatively more minor, natural series of phenanthrene homologs, also of terrestrial origin, is preferentially advected further offshore and deposited in continental slope sediments. These distributions are consistent with recognized particle associations for these compounds and sediment dispersal processes in this coastal environment. Sediment core records suggest the present pattern of dispersal has persisted for at least the past century and possibly since the Late Pleistocene.  相似文献   

13.
Preservation of organic matter in estuarine and coastal areas is an important process in the global carbon cycle. This paper presents bulk δ13C and C/N of organic matter from source to sink in the Pearl River catchment, delta and estuary, and discusses the applicability of δ13C and C/N as indicators for sources of organic matter in deltaic and estuarine sediments. In addition to the 91 surface sediment samples, other materials collected in this study cover the main sources of organic material to estuarine sediment. These are: terrestrial organic matter (TOM), including plants and soil samples from the catchment; estuarine and marine suspended particulate organic carbon (POC) from both summer and winter. Results show that the average δ13C of estuarine surface sediment increases from −25.0 ± 1.3‰ in the freshwater environment to −21.0 ± 0.2‰ in the marine environment, with C/N decreasing from 15.2 ± 3.3 to 6.8 ± 0.2. In the source areas, C3 plants have lower δ13C than C4 plants (−29.0 ± 1.8‰ and −13.1 ± 0.5‰ respectively). δ13C increases from −28.3 ± 0.8‰ in the forest soil to around −24.1‰ in both riverbank soil and mangrove soil due to increasing proportion of C4 grasses. The δ13CPOC increases from −27.6 ± 0.8‰ in the freshwater areas to −22.4 ± 0.5‰ in the marine-brackish-water areas in winter, and ranges between −24.0‰ in freshwater areas and −25.4‰ in brackish-water areas in summer. Comparison of the δ13C and C/N between the sources and sink indicates a weakening TOM and freshwater POC input in the surface sedimentary organic matter seawards, and a strengthening contribution from the marine organic matter. Thus we suggest that bulk organic δ13C and C/N analysis can be used to indicate sources of sedimentary organic matter in estuarine environments. Organic carbon in surface sediments derived from anthropogenic sources such as human waste and organic pollutants from industrial and agricultural activities accounts for less than 10% of the total organic carbon (TOC). Although results also indicate elevated δ13C of sedimentary organic matter due to some agricultural products such as sugarcane, C3 plants are still the dominant vegetation type in this area, and the bulk organic δ13C and C/N is still an effective indicator for sources of organic matter in estuarine sediments.  相似文献   

14.
The Little Ice Age (∼1600–1900 AD) and 20th century sediment accumulation rates in Billefjorden, a subpolar fjord on Svalbard, were reconstructed by applying 210Pb, 137Cs and AMS 14C datings. The modern sediment accumulation rate decreases from more than 0.39 cm y−1 at the fjord head to 0.08 cm y−1 close to the fjord mouth. However, during the Little Ice Age the sediments accumulated at a much lower rate of 0.02 cm y−1 in the central fjord basin. This difference is most likely related to the rapid retreat of glaciers during the 20th century, when most of them withdrew up to 2 km. The post-Little Ice Age increases in temperature and a negative glacier mass balance resulted in a larger meltwater discharge transferring substantial amounts of sediments released from the glaciers, as well as those eroded from previously stored unconsolidated glacial sediments. A comparison of data from the subpolar fjords of Svalbard suggests that the increase in the sediment accumulation rate is a common trend, and further increases might be expected if climate warming continues. The properties of the fjord sediments (grain size, IRD, coarse-fraction composition, clay mineralogy) from the Little Ice Age and the 20th century showed no distinct differences. The change in the accumulation rate may be the most evident sedimentary record of this climatic change.  相似文献   

15.
Temporal variations in sediment carbon content were tracked by sampling every 2 weeks for 6 to 33 months at 6 tidal flat stations with different carbon content levels (0.05–1.64%) in a single estuary. Three temporal series of current velocity at 5 cm above the sediment were also obtained. Non-cohesive and cohesive sediment stations differed in patterns of temporal variation in sediment carbon content, suggesting the difference in processes controlling sediment carbon content. In the stations of non-cohesive sandy sediment with relatively low carbon content (0.05–0.15%), sediment carbon content fluctuated within ranges specific to each station. In these stations, current velocity data suggested that frequency of sand resuspension washing out sediment carbon controls sediment carbon content level. In the stations of cohesive sediment with relatively high carbon content (0.77–1.64%), sediment carbon contents showed some unusual upward and downward peaks, recovered to usual levels specific to the stations, and was always kept higher than that in the non-cohesive sediment stations. We speculate that in the cohesive sediment stations, sand inputs may significantly control processes establishing the consolidated sediments with various carbon content levels. Spatial transitions from non-cohesive to cohesive sediments and from low to high sediment carbon contents likely occur as sand resuspension at spring tides become more irregular and less frequent. Based on these results, conceptual models describing physical processes controlling sediment carbon content at the studied stations were proposed.  相似文献   

16.
Studies on the biogeochemical cycling of organic contaminants in the Mediterranean have demonstrated the importance of polychlorinated biphenyls (PCBs) as relatively stable markers of recent anthropogenic influence in ocean systems. This paper presents results of hydrocarbon analyses of deep water profiles, sediments and their associated surface flocculent layers, and zooplankton samples collected in the western basin. Seawater concentrations were higher than those previously reported for the eastern basin and were consistent with the presence of industrial sources in the northwestern segment. In the water column, the percent of PCBs associated with filterable particles was related to the ambient concentrations of total suspended matter, distance from coastal input sources and on depth. The occurrence of deep water residues primarily in the dissolved phase and observations of subsurface maxima in seawater concentrations during a season of high surface productivity were consistent with the predictions of vertical transport models based on residues associated with sinking particles and equilibrium partitioning. Flocculent layers at the sea/sediment interface contained two and three orders of magnitude, respectively, more PCBs and petroleum hydrocarbons (PHCs) than their associated surface sediments. The flocculent particles also contained several biogenic hydrocarbons presumably originating from plankton and relatively soluble and labile contaminants such as hexachlorohexane isomers (HCH) and hexachlorobenzene (HCB), thus confirming that the majority of the flux of hydrocarbons to sediments is carried on rapidly settling large particles. By combining the sediment and flocculents data with published sedimentation rates for the deep basins of the Mediterranean, a yearly flux rate of PCBs to the open sea sediments was estimated as 13 μg m−2 yr−1 or less than half of the rate measured in a coastal sediment trap experiment. Analytical results are placed in the context of other distribution data for PCBs and long-term flux studies to construct a partial mass balance budget for this semi-enclosed sea. The computed coastal inventory showed that about 35% remains suspended in the water column while the majority of residues are deposited in coastal sediments. However in the open sea, the deep water column may contain up to 70% of the total inventory and may be a continually increasing reservoir of stable organic contaminants reaching the ocean. The budget shows that priority for improved research and monitoring efforts in ocean systems should be given to continued advancement in techniques for the precise measurement of deep water concentrations and for measuring current atmospheric inputs and sedimentation rates in order to develop more accurate ocean flux models.  相似文献   

17.
Surface sediments from the Saronikos Gulf were analyzed for their aliphatic hydrocarbon (AHC) and polycyclic aromatic hydrocarbon (PAH) content by gas chromatography – mass spectrometry (GC/MS). The concentrations of Fe, Cr, As, Sb, Co and Sc were also determined by neutron activation analysis (NAA). The survey was performed at the beginning of the operation of Athens’ sewage primary treatment unit and the results can be used to monitor the unit's long-term effects in the area. The composition of aliphatic hydrocarbons indicated a chronic oil-pollution in the Saronikos Gulf sediments. The industrially impacted Elefsis Bay sediments suffered from heavy petroleum pollution, while the sediments near the sewage outfall had a moderate degree of pollution. Mixed source patterns of polycyclic aromatic hydrocarbons with dominant pyrolytic inputs have been identified in the sediments. Total concentrations of Fe, As and Sb along with their Sc normalized values presented elevated values in Elefsis Bay sediments. Chromium was found enriched in the sediments near the Athens sewage outfall. Factor analysis results showed that a part of As and Sb in Elefsis Bay sediments could be associated with organic or sulphidic phases. In addition, the lithogenic fraction of the sediments and the Fe oxides/hydroxides were important trace element carriers. Chromium and PAH inputs from the sewage outfall were also detected. Comparison of PAH and trace element concentrations with internationally-used sediment quality guidelines (SQG) revealed that Elefsis Bay sediments had the greatest potential of causing adverse effects in benthic organisms.  相似文献   

18.
The food web structure and functioning of two north-western Mediterranean lagoons exhibiting contrasting degrees of eutrophication and marine influences were compared through δ13C and δ15N analysis of major potential food sources and consumers. The Lapalme Lagoon is well preserved and has kept a natural and temporary connection with the open sea. Conversely, the Canet Lagoon is heavily eutrophicated and its water exchange with the open sea has been artificially reduced. In Lapalme, all potential food sources and consumers exhibited δ15N values indicative of pristine coastal areas. Suspended particulate organic matter (POM) and sediment organic matter (SOM) pools seemed to constitute the main food sources of most primary consumers. Both primary producers and all consumers were much more 15N-enriched (by  10‰) and more 13C-depleted in Canet than in Lapalme. This reflected: (1) the assimilation of important amounts of anthropogenic nitrogen in the food web, and (2) a marked and uniform influence of 13C-depleted allochtonous sources of carbon. Based on the mean δ15N of primary consumers, we found rather similar food web lengths in both lagoons with top consumers at trophic levels 3.6 and 4.0 in Canet and Lapalme, respectively. However, the eutrophication of the Canet Lagoon resulted in a simplification of the food web structure (i.e., a single trophic pathway from a 15N-enriched fraction of the SOM pool to top predators) compared to what was observed in Lapalme Lagoon where additional 13C-enriched food sources played a significant trophic role. Moreover, some consumers of Canet tended to exploit primary producers to a larger extent (and thus to exhibit lower trophic levels) than in Lapalme.  相似文献   

19.
ABSTRACT

The October 2011 sinking of the container ship MV Rena on Astrolabe Reef, New Zealand, provided a rare opportunity to examine the fate of shipwreck-derived contaminants on an offshore rocky reef and food chain. Analyses of trace metals, polycyclic aromatic hydrocarbons (PAHs) and organotins indicated significant but localised contamination of Astrolabe Reef but not of nearby Mōtītī Island. Three years after the grounding, PAH concentrations were greater in sediments at Astrolabe (up to 131?mg kg?1) than at control locations, while organotins from the ship's antifouling hull paint were found exclusively in Astrolabe Reef sediments and biota. Over 80% of Astrolabe sediment samples contained tributyltin at concentrations above guideline sediment levels (>0.07?mg kg?1). Tributyltin and its decomposition products were also recorded in sea urchins, gastropods, lobster and fishes at concentrations up to 0.2?mg kg?1. Wreck and cargo-derived metals, particularly copper, tin and zinc, were present in some Astrolabe sediment samples above Australia and New Zealand Environment and Conservation Council guideline concentrations. However, there appeared to be only limited transmission of metals through the food chain. Copper, tin and zinc were recorded at greater concentrations in Astrolabe sea urchins and gastropods compared to control specimens, while metal concentrations in other biota were comparable across impact and control sites. Despite over 3 years having passed since the Rena grounding, the data series does not show any upward or downward trends in contaminant concentrations on Astrolabe Reef. Consequently, there is uncertainty about the long-term implications of the Rena grounding for the ecology of Astrolabe Reef.  相似文献   

20.
Discovery Bay, a carbonate-dominated embayment in north Jamaica, has been subject to inputs for 40 years of iron-rich bauxite sediment associated with the local mining and transport of processed bauxite. As such, this site is an ideal natural laboratory to study the records and impacts of iron oxide inputs upon geochemical, diagenetic, and microbial processes in tropical carbonate sediments.Total Fe contents in sites in the bay not receiving bauxite inputs are negligible and porewater Ca2+, SO42− and Cl− indicate that bacterial sulphate reduction is an important process. In contrast, surface sediments receiving bauxite inputs contain significant total Fe, from 44 μmol/g in shallow (5 m water depth) sites to 110 μmol/g in deeper (20 m water depth) sites. Up-core increases in total Fe record increased temporal inputs into the bay. Within these Fe-rich sediments porewater data shows the presence of FeII released by bacterial FeIII reduction. There is no direct evidence for significant bacterial sulphate reduction in these sediments. Iron oxides within all bauxite-impacted sediments display a high potential reducibility, from 40% to 80% of the total Fe present as dithionite-extractable FeIII. Experimental analysis of the potential susceptibility to, and rates of, bacterial FeIII reduction, utilising Discovery Bay sediment and Shewanella putrefaciens CN32 (a known FeIII-reducer) has confirmed the high bacterial reducibility of iron oxides within the sediment. Up to 75% of initial dithionite-extractable FeIII in the sediments was reduced over 15 days.The presence of iron oxides within the Discovery Bay shallow marine carbonate systems has markedly altered the chemical diagenetic processes taking place, with a shift from apparent dominance of bacterial sulphate reduction at non-impacted (Fe-poor) sites, to highly significant bacterial FeIII reduction in Fe-rich bauxite-impacted sediments. Given the perceived global increases in terrigenoclastic sediment inputs into tropical carbonate systems as a result of land-use and climate changes, coupled with the documented role that iron oxide reduction plays in nutrient and contaminant cycling in sediment systems, more research into the perturbation of early diagenesis by iron oxide inputs is required.  相似文献   

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