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31.
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   
32.
ABSTRACT

To investigate the uptake and depuration of polycyclic aromatic hydrocarbons associated with the Rena oil spill we sampled the surf clam Paphies subtriangulata at two open coast locations (6?km apart) just prior to oil coming ashore (7 October 2011), then at 1–3 week intervals for the next 4 months. Total polycyclic aromatic hydrocarbons (tPAH) increased at both sites from 1 to 96–124?µg?kg?1 (wet weight) by 18 October before declining to low levels (<4?µg?kg?1) by February 2012. Ongoing sampling throughout 2012–2014 included three additional sites to the north east (up to 30?km away) and a site 5?km to the south east revealing tPAH levels generally <10?µg?kg?1 except in October 2013 where levels ranged between 39–45?µg?kg?1 at all sites. A comparison of PAH component profiles with oil-contaminated beach sediment indicated that the high levels observed in surf clams between October–December 2011 were clearly associated with the Rena spill. However, the October 2013 peak had a PAH profile inconsistent with weathered Rena oil, suggesting an alternative source of contamination. Our results highlight the potential for P. subtriangulata as a PAH monitoring tool but recognise more study is needed to better quantify baseline levels and uptake and depuration dynamics.  相似文献   
33.
The presence of domoic acid (DA) toxin from multiple species of Pseudo-nitzschia is a concern in the highly productive food webs of the northern Gulf of Mexico. We documented the Pseudo-nitzschia presence, abundance, blooms, and toxicity over three years along a transect ~100 km west of the Mississippi River Delta on the continental shelf. Pseudo-nitzschia were present throughout the year and occurred in high abundances (>104 cells l?1) in the early spring months during high Mississippi River (MSR) flow (~20,000 m3 s?1) but were most abundant (>106 cells l?1) when MSR discharge was relatively lower among the spring months. A high particulate toxin production (maximum reaching 13 μg DA l?1) was associated with the high cell abundances and exceeded, by an order of magnitude, prior reports of particulate DA concentrations in Louisiana coastal waters. Differences in Pseudo-nitzschia peak times and its toxicity were correlated mainly with the timing and magnitude of MSR discharge and changes in associated parameters such as nutrient stoichiometry and salinity. A negative relationship between high MSR discharge and Pseudo-nitzschia and particulate DA concentrations was documented. These riverine dynamics have the potential to influence DA contamination in pelagic and benthic food webs in the coastal waters of the northern Gulf of Mexico.  相似文献   
34.
Aplite dikes intruding the Proterozoic 1.42(±?3) Ga Longs Peak-St. Vrain Silver Plume-type peraluminous granite near Jamestown, Colorado, contain F, P, and rare earth element (REE)-rich globular segregations, with 40–46% REE, 3.7–4.8 wt% P2O5, and 5–8 wt% F. A combination of textural features and geochemical data suggest that the aplite and REE-rich globular segregations co-existed as two co-genetic liquids prior to their crystallization, and we propose that they are formed by silicate–fluoride?+?phosphate (+?S?+?CO2) melt immiscibility following ascent, cooling, and decompression of what was initially a single homogeneous magma that intruded the granite. The REE distribution coefficients between the silica-rich aplites and REE-rich segregations are in good agreement with experimentally determined distribution coefficients for immiscible silicate–fluoride?+?phosphate melts. Although monazite-(Ce) and uraninite U–Th–Pb microprobe ages for the segregations yield 1.420(±?25) and 1.442(±?8) Ga, respectively, thus suggesting a co-genetic relationship with their host granite, εNd1.42Ga values for the granites and related granitic pegmatites range from ??3.3 to ??4.7 (average ??3.9), and differ from the values for both the aplites and REE-rich segregations, which range from ??1.0 to ??2.2 (average ??1.6). Furthermore, the granites and pegmatites have (La/Yb)N <50 with significant negative Eu anomalies, which contrast with higher (La/Yb)N >100 and absence of an Eu anomaly in both the aplites and segregations. These data are consistent with the aplite dikes and the REE-rich segregations they contain being co-genetic, but derived from a source different from that of the granite. The higher εNd1.42Ga values for the aplites and REE-rich segregations suggest that the magma from which they separated had a more mafic and deeper, dryer and hotter source in the lower crust or upper mantle compared to the quartzo-feldspathic upper crustal source proposed for the Longs Peak-St. Vrain granite.  相似文献   
35.
36.
37.
Jing Zhang  Mark Ross 《水文研究》2012,26(24):3770-3778
Clay‐settling areas (CSAs) are one of the most conspicuous and development‐limiting landforms remaining after phosphate mining. Many questions are asked by the mining and regulatory communities with regard to the correct modelling (predictive) methods and assumptions that should be used to yield viable hydrologic post‐reclamation landforms within CSAs. Questions as to the correct methodology to use in modelling/predicting long‐term CSA hydrologic performance have historically been difficult to answer because the data and analysis to support popular hypotheses did not exist. The goal of this paper was to substantially improve the data, analysis and predictive methodology necessary to return CSAs to viable hydrologic units, and moreover, to develop better understanding of the hydrology of CSAs and their ability to support wetlands. The study site is located at the Fort Meade Mine in Polk County, Florida. In this paper, continuous model simulation and calibration of study site were conducted for the hydrologic model, Hydrological Simulation Program – FORTRAN, which was generally selected on the basis of its popularity in predicting the hydrologic behaviour of CSAs. The objective of this study was to simulate streamflow discharges and stage to estimate runoff response from these areas on the basis of the observed rainfall within the CSA. A set of global hydrologic parameters was selected and tested during the calibration by the parameter estimation software PEST. A comparison of the simulated and observed flow data indicates that the model calibration adequately reproduces the hydrologic response of the CSAs. The estimated parameters can be used as references for future application of the model. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   
38.
The Lophelia pertusa community at Viosca Knoll (VK826) is the most extensive found to date in the Gulf of Mexico. As part of a multi-disciplinary study, the physical setting of this area was described using benthic landers, CTD transects and remotely operated vehicle observations. The site was broadly characterised into three main habitats: (1) dense coral cover that resembles biogenic reef complexes, (2) areas of sediment, and (3) authigenic carbonate blocks with sparse coral and chemosynthetic communities. The coral communities were dominated by L. pertusa but also contained numerous solitary coral species. Over areas that contained L. pertusa, the environmental conditions recorded were similar to those associated with communities in the north-eastern Atlantic, with temperature (8.5–10.6 °C) and salinity (~35) falling within the known species niche for L. pertusa. However, dissolved oxygen concentrations (2.7–2.8 ml l?1) and density (σΘ, 27.1–27.2 kg m?3) were lower and mass fluxes from sediment trap data appeared much higher (4002–4192 mg m?2 d?1). Yet, this species still appears to thrive in this region, suggesting that L. pertusa may not be as limited by lower dissolved oxygen concentrations as previously thought. The VK826 site experienced sustained eastward water flow of 10–30 cm s?1 over the 5-day measurement period but was also subjected to significant short-term variability in current velocity and direction. In addition, two processes were observed that caused variability in salinity and temperature; the first was consistent with internal waves that caused temperature variations of 0.8 °C over 5–11 h periods. The second was high-frequency variability (20–30 min periods) in temperature recorded only at the ALBEX site. A further pattern observed over the coral habitat was the presence of a 24 h diel vertical migration of zooplankton that may form part of a food chain that eventually reaches the corals. The majority of detailed studies concerning local environmental conditions in L. pertusa habitats have been conducted within the north-eastern Atlantic, limiting most knowledge of the niche of this species to a single part of an ocean basin. Data presented here show that the corals at VK826 are subjected to similar conditions in temperature, salinity, and flow velocity as their counterparts in the north-east Atlantic, although values for dissolved oxygen and density (sigma-theta: σΘ) are different. Our data also highlight novel observations of short-term environmental variability in cold-water coral habitat.  相似文献   
39.
Oxygen isotope analyses of 101 samples from the Marcy Anorthosite Massif (61 from this study, 40 from Taylor 1969), indicate that two major and distinct processes of crustal contamination have affected the massif. Ninety percent of the 93 samples with over 65% plagioclase are enriched in 18O by 2.6 relative to normal anorthosites or gabbros: the average 18O for 83 enriched samples is 9.5 Depletions in 18O occur in 8% of the samples which have values ranging from 3.0 to 5.8 Only 2 of the samples fall within the normal magmatic range for anorthosites.Low 18O values of 3.0 to 5.8 in the anorthosite occur only near contacts, and a gradient in 18O occurs near the contact within the border zone of the massif. Low 18O values in both the anorthosite and adjacent wollastonite skarns (with 18O down to –1.3) were probably caused by isotopic exchange with heated meteoric water when the anorthosite intruded at shallow levels, prior to Grenvilleage ( 1.1 by) granulite facies metamorphism.The 18O-enrichment was ascribed to exchange between anorthosite and 18O-rich marble by means of a pervasive, H2O-CO2 fluid during the regional metamorphism by Taylor (1969). However, a number of lines of evidence argue against this hypothesis: 1) the preservation of premetamorphic low 18O values in anorthosite from the border zone as well as preserved gradients in 18O from a number of localities, 2) mass balance calculations of the amount of marble necessary to produce the 18O enrichment 3) metamorphic phase equilibria which buffer and to low values, and, 4) recent oxygen isotope analyses show homogeneity which indicates that magmatic oxygen isotope compositions have been preserved. We evaluated the importance of magmatic assimilation of country rock at the present level of intrusion as an alternative cause of the 18Oenrichment. Samples from 2 distinct lobes of the massif were analyzed: the NE lobe where xenoliths of metasedimentary country rock are common, and the NW lobe, where xenoliths are scarce and the country rock is dominantly granitic. The mean values of 18O for these two lobes are 9.6 in the NE and 9.3 in the NW. Thus, magmatic assimilation at the present level of exposure probably had only localized and relatively minor effects on the oxygen isotope composition of the massif. This conclusion is supported by Rb/Sr data: variations in Rb content and (87Sr/ 86Sr)i show that such crustal contamination is localized, generally occurring only in samples near the border zone. All of the available results suggest that the 18O-enrichment is a magmatic feature, acquired prior to intrusion at the present level of exposure.  相似文献   
40.
The effects of sub-blocking temperature metamorphism on the K/Ar system in hornblende, as revealed by 40Ar/39Ar release spectra, have been studied in a polymetamorphic knocker from the Franciscan Complex (FC), California. A primary amphibolite assemblage of horn-blende +rutile+epidote+apatite±garnet±sphene is variably overprinted by a blueschist facies assemblage of blue amphibole +lawsonite+chlorite+white mica+pumpellyite±sphene. The secondary assemblage formed at a temperature of 370° C, below that at which rapid Ar diffusion is expected in hornblende. Hornblendes from three, variably-altered samples of garnet amphibolite yield total gas ages of 147 to 161 Ma, but the corresponding plateau ages of 163.0±2.8, 160.6±2.2, and 161.8±2.2 Ma are identical within error. Hornblende separates with lower total gas ages come from more highly overprinted rocks, have excess K compared to that expected on the basis of electron probe analyses, and exhibit anomalously high K/Ca ratios in the low-temperature fractions of their incremental heating spectra. The reduced total gas ages result from the presence of thin (2 m) sheets of younger white mica in hornblendes from the moderately and highly altered amphibolites. The secondary micas are difficult to detect because of their small size and low abundance (2%), but because their K content is 50 to 100 times that of the host hornblende, they contribute significantly to the K and Ar budgets of the sample. The mica intergrowths are not removed by normal sample preparation, but because the mica inclusions degas at lower temperatures than hornblende during vacuum extraction, incremental heating analyses can provide precise cooling ages for the hornblendes as well as useful estimates of the age of the mica inclusions. The hornblende separate from the most altered sample contained 20±10% younger blue amphibole replacing hornblende, but its plateau age was not significantly affected. This is consistent with a replacement process in which K and Ar loss from the hornblende are coupled, leaving the K/Ar system undisturbed in relict primary grains. The K and Ar budgets of the sample are not strongly affected by the blue amphibole because of its very low K content. Because partial replacement of primary amphibole by high-K phyllosilicates occurs in many geological environments, effects like those described here could be widespread.  相似文献   
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