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1.
In the present work, we built a mathematical model of polychlorinated biphenyl (PCB) bioaccumulation in Perna viridis, namely, a one-compartment model with a time dependent incorporation rate R (μg g−1 lipid per ppb water per day), with positive substrate cooperativity as the underlying physical mechanism. The temporal change of the PCB concentration Q (μg g−1 lipid) in the soft tissues of the mussel depends on the competition of the input rate RW and the output rate kQ, where W is the concentration of PCB in water (ppb water) and k is the elimination rate (per day). From our experimental data, k=0.181±0.017 d−1. The critical concentration in water Wc for positive substrate cooperativity was found to be 2.4 ppb. Below Wc, R is a constant. For a water concentration of 0.5 ppb Aroclor 1254, R=24.0±2.4 μg g−1 lipid ppb−1 d−1. Above Wc, positive substrate cooperativity comes into effect and R becomes a function of time and dependent on the concentration Q in a form R=γQ/(Q+δ). This is the case for a water concentration of 5 ppb Aroclor 1254, where γ=15.1 μg g−1 lipid ppb−1 d1 and δ≈200 μg g−1 lipid. From this model, the uptake is exponentially increasing when the PCB concentration in the mussel is small compared to 200 μg g−1 lipid, and hyperbolically increasing when the concentration is large compared to 200 μg g−1 lipid, which are consistent with the experimental data. The model is useful for understanding the true processes taking place during the bioaccumulation and for risk assessment with higher confidence. Future experimental data which challenge the present model are anticipated and in fact desirable for improvement and perfection of the model. 相似文献
2.
CHRISTOPH SPÖTL 《Sedimentology》1990,37(5):837-845
Complex aluminium phosphate-sulphate minerals of the hinsdalite group have been identified as early diagenetic precipitates in Late Permian sandstones of the Northern Calcareous Alps, western Austria. According to their chemical composition they can be regarded as solid solutions between woodhouseite, svanbergite, crandallite and goyazite. The model proposed for their origin involves the dissolution of detrital apatite in a low-pH environment and subsequent precipitation of aluminium phosphate-sulphate minerals, which clearly pre-date syntaxial quartz cementation of the sediment. Their occurrence probably has been overlooked in other sandstones showing diagenetic apatite dissolution. The recognition of such minerals could provide a significant insight into early phosphate diagenesis. 相似文献
3.
Dark grey, bituminous dolostones interbedded with marine-derived anhydrite horizons occur in the Triassic Reichenhall Formation of western Austria. Fossils are rare and indicate a hostile, hypersaline depositional environment. The dolomites are finely crystalline, fairly stoichiometric, well ordered and non-ferroan. Closely spaced samples (94 in total) of individual dolomite units have been analysed for their carbon and oxygen isotopic composition. The data indicate surprisingly low δ18O values (-5.7 to -2.1%0 PDB), whereas the δ13C values are comparable to the contemporary Triassic seawater (+0.2 to +2.6%0 PDB). Sedimentological evidence, including (i) lack of any evidence for extensive dissolution, (ii) distinct oxygen and carbon isotope ratios of individual dolomite units, (iii) covariance of carbon and oxygen isotopes within some dolomite layers and (iv) inclusions of celestite in dolomite, indicates a nearly closed system after early diagenesis. Combining this information with water-rock interaction calculations suggests that the lightest oxygen isotope compositions are the result of freshwater influx into the basin during very early dolomite formation. A secondary factor may be dolomite recrystallization at elevated temperatures during burial. 相似文献
4.
Mohamad Zam Zuriyati Yang Fong Chee Charles Ramendran S. P. R. Rehman Mobashar Nee Au Yong Hui Yin Yip Chee 《GeoJournal》2022,87(1):167-181
GeoJournal - Two phases of study are involved in this research: first, the sales strategies for affordable houses embedded with eco-friendly and smart technology features; and second, the impact of... 相似文献
5.
Tsunami is one of a few kinds of natural disasters that leave people some time for escape. This escape time, which is essentially the time for the giant wave to propagate from the epicentre to a coast, has to be estimated without delay upon the occurrence of the incident. With the advancement of water wave theories, much work has been done to model the propagation of tsunamis from deep oceans to shallow water. The authors argue that while much emphasis has been put on the expansion of the high-tech early warning system and the development of complicated tsunami models, a simple-to-use yet accurate predictive model is still wanting. This paper presents a handy linear wave model, which is capable of estimating the arrival time of a tsunami with very good accuracy, as has been verified by comparison with past incidents. With the availability of such a simple model, even local communities without access to a high-tech warning system can readily estimate the time left for emergency evacuation. 相似文献
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7.
Magnesite diagenesis in redbeds: a case study from the Permian of the Northern Calcareous Alps (Tyrol, Austria) 总被引：1，自引：0，他引：1
The Upper Permian Gröden Formation of the Northern Calcareous Alps (Austria) is composed of alluvial fan and playa lake sediments that were deposited in intramontane basins. A conspicuous feature of these redbeds is the abundance of magnesite in the form of nodules and discrete layers in mudstones as well as intergranular cement in sandstones. Sedimentological observations indicate that the bulk of these carbonates formed during early diagenesis and were probably syndepositional. Petrographically, most magnesites consist of micrite or, less commonly, microspar. An early non-ferroan magnesite is post-dated by later stage ferroan magnesites. Nodules consisting of recrystallized, sparry magnesite were observed only at one location. The general absence of relics of a non-magnesite precursor mineral and the occurrence of shrinkage features suggest that the fine grained magnesites formed by transformation of a hydrated magnesium carbonate mineral, e.g. hydromagnesite. Carbon, oxygen, sulphur and strontium isotope ratios in conjunction with sedimentological criteria support a model of (hydro)magnesite precipitation in an inland playa lake system, which was fed by run-off from the surrounding hinterland. The scarcity of evaporites and the dominance of magnesite over calcite and dolomite suggest that the playa lake brines were low in sulphate and had high Mg/Ca ratios. The source for the high magnesium concentrations is thought to be the weathering of Devonian dolostones and associated massive magnesite deposits in the catchment area. 相似文献
8.
The aftermath of the Carnian carbonate platform demise: a basinal perspective (Dolomites, Southern Alps) 总被引：1，自引：0，他引：1
In the Dolomites of northernmost Italy the carbonate‐platform growth came to a standstill late in the Early Carnian (Late Triassic). The response to this shutdown of shallow‐water carbonate production in the interplatform basins is largely unknown because erosion has removed most of the soft basinal sediments, giving rise to today's scenic landscape of the Dolomites. Mapping in the central part of the Dolomites and newly available core material has recently revealed a well‐preserved succession of basinal rocks within the Heiligkreuz Hospiz Basin (ital. Ospizio di Santa Croce Basin). In this paper, the regional depositional nature of arrested carbonate platform production is reconstructed by tracing its sedimentological record across the slope and into the basin. The uppermost St. Cassian Formation, the time‐equivalent basinal rocks to the prograding carbonate platforms, is overlain by the Heiligkreuz Formation, whose basal succession was deposited in a restricted and oxygen‐depleted environment immediately post‐dating the platform demise. The succession consists mainly of mudrocks, marlstones, and peloidal packstones, with abundant low‐diversity ostracod and pelecypod fauna and early diagenetic dolomite. C and O isotope values of the basal Heiligkreuz Formation, post‐dating platform demise, average + 2·4 and ? 2·4‰, respectively, and largely overlap the isotopic composition of St. Cassian carbonates. A shift toward slightly lower δ13C values in the Heiligkreuz Formation may reflect incorporation of isotopically depleted C released during bacterial sulphate reduction in the Heiligkreuz sediments. Sedimentological, palaeobiological and geochemical indices suggest that near‐normal marine conditions persisted long after the shutdown of shallow water carbonate‐platform growth, although there are clear indications of severely reduced oxygen levels in the restricted Heiligkreuz Hospiz interplatform basin. The Early Carnian platform demise induced a distinct switch in the locus of carbonate production from the shallow‐water platform and slope to the basin floor and a decrease in the availability of dissolved oxygen in the basinal waters. It is inferred that anoxia extended at least temporarily to the top of the carbonate slope, as indicated by the onlap of normal‐marine mounds by dark marlstones of the basal Heiligkreuz Formation. 相似文献
9.
While much work has been done in investigating determinants of oil spillage attributed to vessel accidents, little research has been conducted on the effectiveness of ship hull design in reducing marine pollution. This paper addresses whether the double-hull requirement reduces vessel-accident oil spillage. The volume of oil spillage due to oil-cargo vessel accidents was investigated using tobit regressions and an empirical data set of individual vessel accident pollution incidents investigated by the US Coast Guard from 2001 to 2008. The results indicate that the double hull design on average reduces the size of oil spills by 20% and 62% in tank barge and tanker ship accidents, respectively. 相似文献
10.
The start of the Upper Würmian in the Alps was marked by massive fluvioglacial aggradation prior to the arrival of the Central Alpine glaciers. In 1984, the Subcommission on European Quaternary Stratigraphy defined the clay pit of Baumkirchen (in the foreland of the Inn Valley, Austria) as the stratotype for the Middle to Upper Würmian boundary in the Alps. Key for the selection of this site was its radiocarbon chronology, which still ranks among the most important datasets of this time interval in the Alps. In this study we re‐sampled all available original plant specimens and established an accelerator mass spectrometry chronology which supersedes the published 40‐year‐old chronology. The new data show a much smaller scatter and yielded slightly older conventional radiocarbon dates clustering at ca. 31 14C ka BP. When calibrated using INTCAL13 the new data suggest that the sampled interval of 653–681 m in the clay pit was deposited 34–36 cal ka BP. Using two new radiocarbon dates of bone fragments found in the fluvioglacial gravel above the banded clays allows us to constrain the timing of the marked change from lacustrine to fluvioglacial sedimentation to ca. 32–33 cal ka BP, which suggests a possible link to the Heinrich 3 event in the North Atlantic. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献