Description and interpretation of the composition of fluid and alteration mineralogy in the geothermal system,at Svartsengi,Iceland

The bulk composition and mineralogy of hydrothermally altered tholeiite, along with the composition and speciation of fluid, have been determined for a well-defined alteration zone at 240°C and 110 bars at Svartsengi, Iceland. Mass balances between the geothermal fluid and altered tholeiite, relative to a seawater/fresh water mixture and unaltered tholeiite, indicate the overall reaction per 1000 cm³ is: 1325 gm plagioclase + 1228 gm pyroxene + 215 gm oxide-minerals break down to form 685 gm chlorite + 636 gm albite + 441 gm quartz + 249 gm epidote + 266 gm calcite + 201 gm oxide-minerals + 15 gm pyrite, requiring an influx of 123 gm CO₂, 10 gm H₂S and 4 gm Na₂O and a release of 57 gm SiO₂, 35 gm FeO, 21 gm CaO, 8 gm MgO and 4 gm K₂O.Principal reactions, deduced from textural evidence, include Na-Ca exchange in plagioclase, precipitation of quartz, calcite and anhydrite, and formation of chlorite and epidote by reactions between groundmass minerals and fluid.Thermodynamic analyses of authigenic minerals and downhole fluid indicate that the fluid maintains a state close to equilibrium with the secondary mineral phases chlorite, epidote, albite, quartz, calcite, prehnite, anhydrite, pyrite and magnetite, whereas remnant primary labradorite and augite are out of equilibrium with the fluid.Water/rock ratios for the system are determined under a variety of assumptions. However, the open nature of the system makes comparisons with experimental and theoretical closed system studies ambiguous.     

Flash flood susceptibility mapping using a novel deep learning model based on deep belief network,back propagation and genetic algorithm

Flash floods are responsible for loss of life and considerable property damage in many countries.Flood susceptibility maps contribute to flood risk reduction in areas that are prone to this hazard if appropriately used by landuse planners and emergency managers.The main objective of this study is to prepare an accurate flood susceptibility map for the Haraz watershed in Iran using a novel modeling approach(DBPGA) based on Deep Belief Network(DBN) with Back Propagation(BP) algorithm optimized by the Genetic Algorithm(GA).For this task, a database comprising ten conditioning factors and 194 flood locations was created using the One-R Attribute Evaluation(ORAE) technique.Various well-known machine learning and optimization algorithms were used as benchmarks to compare the prediction accuracy of the proposed model.Statistical metrics include sensitivity,specificity accuracy, root mean square error(RMSE), and area under the receiver operatic characteristic curve(AUC) were used to assess the validity of the proposed model.The result shows that the proposed model has the highest goodness-of-fit(AUC = 0.989) and prediction accuracy(AUC = 0.985), and based on the validation dataset it outperforms benchmark models including LR(0.885), LMT(0.934), BLR(0.936), ADT(0.976), NBT(0.974), REPTree(0.811), ANFIS-BAT(0.944), ANFIS-CA(0.921), ANFIS-IWO(0.939), ANFIS-ICA(0.947), and ANFIS-FA(0.917).We conclude that the DBPGA model is an excellent alternative tool for predicting flash flood susceptibility for other regions prone to flash floods.     

Physiological and behavioral responses of Bathynerita naticoidea (Gastropoda: Neritidae) and Methanoaricia dendrobranchiata (Polychaeta: Orbiniidae) to hypersaline conditions at a brine pool cold seep

Bathynerita naticoidea (Gastropoda: Neritidae) and Methanoaricia dendrobranchiata (Polychaeta: Orbiniidae) are two of the most abundant invertebrates associated with cold‐seep mussel beds in the Gulf of Mexico. At the methane seep known as Brine Pool NR‐1 (27 °43.415 N, 91 °16.756 W; 650 m depth), which is surrounded by a broad band of mussels (Bathymodiolus childressi), these species have distinctly different patterns of abundance, with the gastropod being found mostly at the outer edge of the mussel bed (average density in November 2003: 817 individuals·m⁻² in outer zone, 20·m⁻² in inner zone) and the polychaete being found almost exclusively near the inner edge (average density in November 2003: 3155 individuals·m⁻² in inner zone, 0·m⁻² in outer zone), adjacent to the brine pool itself. The salinity of the brine pool exceeds 120, so we hypothesized that M. dendrobranchiata should be more tolerant of high salinities than B. naticoidea. The opposite proved to be true. The gastropods were capable of withstanding salinities at least as high as 85, whereas the polychaetes died at salinities higher than 75. Both species were osmoconformers over the range of salinities (35–75) tested. Behavioral responses of B. naticoidea to salinities of 50, 60, and 70 were investigated in inverted vertical haloclines. Gastropods generally did not enter water of salinity greater than 60, but tolerated short periods at 60. Behavioral avoidance of brine should limit the vertical distribution of B. naticoidea in the inner zone to the top 2.5–5 cm of the mussel bed. Behavior is also a likely (though unproven) mechanism for controlling horizontal distribution of this species across the mussel bed. Methanoaricia dendrobranchiata can tolerate short excursions into the brine, but probably avoids hypersaline conditions by aggregating on the tops of the mussels.     

Metabolic conversion of cyclohexane by Pacific salmon microsomal preparations

Hydrocarbons are being introduced into the marine environment from a variety of sources including combustion processes, crude oil spills, fuel oil spills, and controlled disposal such as processed ballast water. Even in the relatively clean waters of Alaska hydrocarbons are being released at an alarming rate. The purpose of this study was to determine the optimum conditions for the metabolism of a representative hydrocarbon by Coho Salmon Oncorhynchus kisutch liver microsomes. The product of cyclohexane metabolism in the salmon microsomal system was identified by gas chromatography-mass spectrometry as cyclohexanol. Conditions of the microsome incubation were varied systematically to determine the optimum temperature, pH, and ionic strength for cyclohexanol production. Cyclohexanol was quantified by capillary column gas chromatography. Maximum cyclohexanol formation was achieved at 20°C, a pH of 8·0–8·5 and an ionic strength of 0·026. A linear rate of cyclohexanol formation is seen from 0–60 min of incubation and there is an apparent decrease in the rate from 60–90 min. Poor stability of the microsomal preparation from the species studied was also identified and several stability studies have been undertaken using cyclohexane metabolism as a monitor.     

Simultaneous exposure of English sole (Parophrys vetulus) to sediment-associated xenobiotics: Part 1—uptake and disposition of 14C-polychlorinated biphenyls and 3H-benzo[a]pyrene

English sole (Parophrys vetulus) were exposed to environmentally realistic levels of sediment-associated ³H-benzo[a]pyrene (3 μg BaP/g sediment, dry weight) and ¹⁴C-Aroclor 1254 (1 μg PCBs/g), separately and together, for up to 10 days. BaP and its metabolites in tissues reached steady-state concentrations by the first day of the exposure, whereas PCBs did not approach steady-state concentrations until the tenth day of exposure. Simultaneous exposure of sole to BaP and PCBs, relative to separate exposure to the xenobiotics, significantly increased the concentrations of BaP-derived radioactivity and decreased the concentrations of PCB-derived radioactivity in some tissues and bile. Accumulation of PCB-derived radioactivity, estimated as the burden in tissues, was significantly greater (4- to 13-fold) than that of BaP-derived radioactivity throughout the experiments and regardless of the type of exposure. The rank of the concentrations of PCB-derived radioactivity in tissues and bile was: bile ～ liver > brain > kidney ～ gill > skin ～ blood ～ muscle and for BaP-derived radioactivity the order was: bile > liver > gill > kidney > skin ～ blood > muscle > brain. BaP-derived radioactivity in liver and bile was present primary (85–99%) as metabolites, whereas PCB-derived radioactivity was present equally as parent compounds and metabolites in bile and primarily (98 %) as parent compounds in liver. Hydrolysis of bile from PCB/BaP-exposed sole with β-glucuronidase/arylsulfatase released 35 % of the BaP-derived radioactivity and 32 % of the PCB-derived radioactivity as primary metabolites. A much higher proportion of the BaP-derived radioactivity (64 %) than the PCB-derived radioactivity (13 %) in bile was unaffected by the enzyme treatment, indicating differences in the conjugation of the primary metabolites of PCBs and BaP. The results suggest that in contaminated environments the tissue to sediment concentration ratios for PCBs would exceed that for BaP and its metabolites; however, BaP would be continually absorbed and metabolized by sole to potentially carcinogenic and mutagenic compounds. In addition, the tissue levels of these toxic compounds may be increased by simultaneous exposure to PCBs.     

Government response to marine pollution from ships

The Marine Pollution Control Unit (MPCU) is the competent national authority for discharging the Secretary of State for Transport responsibility for pollution from ships under the Prevention of Oil Pollution Act 1971 and subsequent legislation covering other hazardous substances. It is an integral part of The Coastguard Agency, an executive agency of The Department of Transport. MPCU is responsible for maintaining the National Contingency Plan, for monitoring and assessing all pollution incidents within UK waters including dealing with pollution from ships and for advising on/co-ordinating shoreline counter pollution operations, and for fostering and maintaining international relationships for mutual support.     

Tracking the last sea-level cycle: seafloor morphology and shallow stratigraphy of the latest Quaternary New Jersey middle continental shelf

Seafloor geomorphology and surficial stratigraphy of the New Jersey middle continental shelf provide a detailed record of sea-level change during the last advance and retreat of the Laurentide ice sheet (120 kyr B.P. to Present). A NW–SE-oriented corridor on the middle shelf between water depths of 40 m (the mid-shelf “paleo-shore”) and 100 m (the Franklin “paleo-shore”) encompasses 500 line-km of 2D Huntec boomer profiles (500–3500 Hz), an embedded 4.6 km² 3D volume, and a 490 km² swath bathymetry map. We use these data to develop a relative stratigraphy. Core samples from published studies also provide some chronological and sedimentological constraints on the upper <5 m of the stratigraphic succession.The following stratigraphic units and surfaces occur (from bottom to top): (1) “R”, a high-amplitude reflection that separates sediment >46.5 kyr old (by AMS ¹⁴C dating) from overlying sediment wedges; (2) the outer shelf wedge, a marine unit up to 50 m thick that onlaps “R”; (3) “Channels”, a reflection sub-parallel to the seafloor that incises “R”, and appears as a dendritic system of channels in map view; (4) “Channels” fill, the upper portion of which is sampled and known to represent deepening-upward marine sediments 12.3 kyr in age; (5) the “T” horizon, a seismically discontinuous surface that caps “Channels” fill; (6) oblique ridge deposits, coarse-grained shelly units comprised of km-scale, shallow shelf bedforms; and (7) ribbon-floored swales, bathymetric depressions parallel to modern shelf currents that truncate the oblique ridges and cut into surficial deposits.We interpret this succession of features in light of a global eustatic sea-level curve and the consequent migration of the coastline across the middle shelf during the last 120 kyr. The morphology of the New Jersey middle shelf shows a discrete sequence of stratigraphic elements, and reflects the pulsed episodicity of the last sea-level cycle. “R” is a complicated marine/non-marine erosional surface formed during the last regression, while the outer shelf wedge represents a shelf wedge emplaced during a minor glacial retreat before maximum Wisconsin lowstand (i.e., marine oxygen isotope stage 3.1). “Channels” is a widespread fluvial subarial erosion surface formed at the late Wisconsin glacial maximum 22 kyr B.P. The shoreline migrated back across the mid-shelf corridor non-uniformly during the period represented by “Channels” fill. Oblique ridges are relict features on the New Jersey middle shelf, while the ribbon-floored swales represent modern shelf erosion. There is no systematic relationship between modern seafloor morphology and the very shallowly buried stratigraphic succession.