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1.
Much of the research that concerns the impacts of management measures in the eastern Baltic cod fishery has focused on fish stock rather than understanding fishermen's attitudes towards regulations. Hence, there is little information available on fishermen's responses although they are the ones whom the regulations affect most profoundly. This study analyses the views of fishermen towards management measures with an emphasis on fishing closures (marine protected areas, MPAs). Swedish log-book data from 1996 to 2005 were used to describe MPA induced fishing effort displacements. Fishermen argued that MPAs have been inefficient in conservation of cod stock. The enlargement of Bornholm MPA in 2005 caused substantial effort displacement towards areas dominated by smaller sized fish. This contributed to the increased discarding of juvenile cod. Enlarged MPAs also intensified competition between different fleet segments and reallocated fishing areas. To reduce fishing mortality, fishermen suggested days-at-sea (effort) regulation and an effective landings control system for all fleets that exploit cod stocks in the Baltic Sea Main Basin. These measures would better motivate fishermen for mutual rule compliance, which is a prerequisite for a sustainable cod fishery. 相似文献
2.
Nataša Ravbar Juan Antonio Barberá Metka Petrič Janja Kogovšek Bartolomé Andreo 《Environmental Earth Sciences》2012,65(8):2259-2272
In this study a multi-tracer test with fluorescent tracers was combined with time series analyses of natural tracers to characterize
the dynamics of the solute transport through different recharge pathways and to study hydraulic behaviour of a binary karst
system under low-flow conditions. Fluorescent tracer testing included the introduction of uranine, amidorhodamine G, or naphthionate
at three injection points. Sampling and monitoring took place at two karst springs (Malenščica, Unica) and at two underground
rivers (Pivka, Rak) recharging the Unica River at the Polje of Planina, SW Slovenia. Other monitored parameters included precipitation,
spring or underground river discharge, water temperature, and electrical conductivity. Water samples were collected and analyzed
for total organic carbon, Mg2+, SO4
2−, and NO3
− in the laboratory. In the study area, results of the tracer test suggest that contaminant transport in karst may be retarded
for several weeks during low-flow conditions followed by increases in contaminant concentrations after subsequent rainfall
events. Based on interpretation of tracer concentration breakthrough curves, low apparent dominant flow velocities (i.e.,
between 5.8 and 22.8 m/h through the well developed karst conduits, and 3.6 m/h through the prevailing vadose zone with a
dominant influence of a diffuse recharge) were obtained. Together with analyses of hydro-chemographs the artificial tracing
identified different origins of water recharging the studied aquifer. During prolonged low-water conditions the Malenščica
spring is mainly recharged from the karst aquifer and the Unica spring by the sinking Pivka River. After more intensive rainfall
events allogenic recharge from Cerknica prevails in the Malenščica spring, while the Unica spring drains mainly the allogenic
water from the Pivka Valley. These findings of alternating hydraulic connections and drainage areas due to respective hydrological
conditions are important and should be considered when monitoring water quality, implementing groundwater protection measures,
and optimizing future water exploitation. 相似文献
3.
4.
Tamás Mikes Dominik Christ Rüdiger Petri István Dunkl Dirk Frei Mária Báldi-Beke Joachim Reitner Klaus Wemmer Hazim Hrvatović Hilmar von Eynatten 《Swiss Journal of Geoscience》2008,101(1):31-54
Sandwiched between the Adriatic Carbonate Platform and the Dinaride Ophiolite Zone, the Bosnian Flysch forms a c. 3000 m thick, intensely folded stack of Upper Jurassic to Cretaceous mixed carbonate and siliciclastic sediments in the Dinarides. New petrographic, heavy mineral, zircon U/Pb and fission-track data as well as biostratigraphic evidence allow us to reconstruct the palaeogeology of the source areas of the Bosnian Flysch basin in late Mesozoic times. Middle Jurassic intraoceanic subduction of the Neotethys was shortly followed by exhumation of the overriding oceanic plate. Trench sedimentation was controlled by a dual sediment supply from the sub-ophiolitic high-grade metamorphic soles and from the distal continental margin of the Adriatic plate. Following obduction onto Adria, from the Jurassic–Cretaceous transition onwards a vast clastic wedge (Vranduk Formation) was developed in front of the leading edge, fed by continental basement units of Adria that experienced Early Cretaceous synsedimentary cooling, by the overlying ophiolitic thrust sheets and by redeposited elements of coeval Urgonian facies reefs grown on the thrust wedge complex. Following mid-Cretaceous deformation and thermal overprint of the Vranduk Formation, the depozone migrated further towards SW and received increasing amounts of redeposited carbonate detritus released from the Adriatic Carbonate Platform margin (Ugar Formation). Subordinate siliciclastic source components indicate changing source rocks on the upper plate, with ophiolites becoming subordinate. The zone of the continental basement previously affected by the Late Jurassic–Early Cretaceous thermal imprint has been removed; instead, the basement mostly supplied detritus with a wide range of pre-Jurassic cooling ages. However, a c. 80 Ma, largely synsedimentary cooling event is also recorded by the Ugar Formation, that contrasts the predominantly Early Cretaceous cooling of the Adriatic basement and suggests, at least locally, a fast exhumation. 相似文献
5.
Daniel H. Doctor E. Calvin Alexander Jr Metka Petrič Janja Kogovšek Janko Urbanc Sonja Lojen Willibald Stichler 《Hydrogeology Journal》2006,14(7):1171-1191
Karst aquifer components that contribute to the discharge of a water supply well in the Classical Karst (Kras) region (Italy/Slovenia) were quantitatively estimated during storm events. Results show that water released from storage within the epikarst may comprise as much as two-thirds of conduit flow in a karst aquifer following rainfall. Principal components analysis (PCA) and end-member mixing analysis (EMMA) were performed using major ion chemistry and the stable isotopes of water (δ18O, δ2H) and of dissolved inorganic carbon (δ13CDIC) to estimate mixing proportions among three sources: (1) allogenic river recharge, (2) autogenic recharge, and (3) an anthropogenic component stored within the epikarst. The sinking river most influences the chemical composition of the water-supply well under low-flow conditions; however, this proportion changes rapidly during recharge events. Autogenic recharge water, released from shallow storage in the epikarst, displaces the river water and is observed at the well within hours after the onset of precipitation. The autogenic recharge end member is the second largest component of the well chemistry, and its contribution increases with higher flow. An anthropogenic component derived from epikarstic storage also impacts the well under conditions of elevated hydraulic head, accounting for the majority of the chemical response at the well during the wettest conditions. 相似文献
6.
Formation of Brominated Disinfection By-products after Chlorination of Water from Lake Constance Depending on Treatment Steps and Bromide Concentration The formation of halogenated disinfection by-products (DNP) (trihalomethanes (THM), haloacetic acids (HES), haloacetonitriles (HAN), haloketones (HKE) and chloropicrin (TCNM)) was studied after chlorination (0.5 mg/L) of raw water and drinking water from Lake Constance. The objectives of this study were to investigate the effect of bromide ion on the distribution of DNP-species resulting from chlorination and to draw up a bromide mass-balance. The treatment of water from Lake Constance with ozone decreased the formation of DNP about 35% and of total organic halogens (AOX) about 45%. This decline in DNP-formation is mainly due to the formation of chloroform, dichloro- and trichloroacetic acid. Though there is only a small amount of bromide (6.2 μg/L) in water from Lake Constance, about 32% of THM, 16% of HES, and 30% of HAN contained bromine after chlorination of treated water. The addition of bromide ion (up to 1 mg/L) shifted the DNP-composition to more brominated species. The distribution of the DNP-species depends on the initial molar bromide-to-chlorine ratio. A mathematic model showed the same pattern of DNP-species depending on the initial molar bromide-to-chlorine ratio that was observed experimentally in microstrained raw water and drinking water from Lake Constance. After chlorination of microstrained raw water, 27% of the bromide were incorporated in known DNP, 34% in unknown substances, and about 39% of bromide were not converted to organic bromine. After chlorination of treated water, only 16% of the bromide were incorporated in unknown substances, whereas 34% were found in known DNP. About 50% were found as bromide again. After addition of bromide (up to 25 μg/L) to ozonated and treated water from Lake Constance, between 60 and 72% of the bromide that had reacted after chlorination were found in analyzed low-molecular DNP. 相似文献
7.
Lake Constance is one of Europe’s largest oligotrophic lakes and provides a water source for more than 4.5 million people in Germany and Switzerland. We present here a 12 month study on iodine concentrations, speciation and fluxes to and from the lake to gain a quantitative understanding of the limnic iodine cycle. Monthly water samples were obtained from all major tributaries (14) and the outflow to construct a mass-balance model. Sediment traps were also deployed in the lake for two years at two different stations. Total soluble iodine (TSI) in aqueous samples were analysed by ICP-MS and speciation (iodide, iodate and soluble organically bound iodine, SOI) by ion chromatography-ICP-MS. Iodine concentrations in the Alpine tributaries (1-2 μg l−1) decreased over the summer months due to increasing proportions of snow and glacial melt water from the Alps, while iodine levels in the lowland rivers (∼2-10 μg l−1) increased over the summer. Deposition of TSI to the catchment (16,340 kg I yr−1) was similar to the TSI out-flux by rivers (16,000 kg I yr−1). By also including the particulate riverine iodine flux out of the catchment (∼12,350 kg I yr−1) it is shown that the catchment is a net source of iodine, with the highest particulate fluxes coming from the Alpine rivers. The total TSI flux to the lake was 16,770 kg I yr−1, the largest proportion coming from the Alpenrhein (43%), followed by the Schussen (8%) and Bregenzer Ach (7.7%). Overall the mass-balance for TSI in the lake was negative, with more iodine flowing out of the lake than in (−2050 kg I yr−1; 12% of TSI in-flux). To maintain mass-balance, 8.8 μg I m−2 d−1 from the Obersee and 23 μg I m−2 d−1 from the Untersee must be released from the sediments into the water column. Thus, in comparison with the total iodine flux to the sediments measured by the sediment traps (4762-8075 kg I yr−1), up to 39% of the deposited iodine may be mobilised back into the lake. SOI was the dominant iodine fraction entering the lake, with a total flux of 10,290 kg I yr−1 (64% of TSI input), followed by iodate (3120 kg I yr−1) and iodide (2760 kg I yr−1). Net formation of SOI from iodide and iodate was also noted within the lake, with an estimated production of 6560 kg I yr−1, suggesting a strong role for biology in iodine cycling. In conclusion, organically bound iodine was the dominant iodine species in aqueous and solid phases in Lake Constance, despite low DOC concentrations (<2 mg l−1), and thus is expected to play an important role in iodine cycling in most freshwater environments. 相似文献
8.
Benjamin G. Petri Radek Fučík Tissa H. Illangasekare Kathleen M. Smits John A. Christ Toshihiro Sakaki Carolyn C. Sauck 《Ground water》2015,53(5):685-698
The generation of vapor‐phase contaminant plumes within the vadose zone is of interest for contaminated site management. Therefore, it is important to understand vapor sources such as non‐aqueous‐phase liquids (NAPLs) and processes that govern their volatilization. The distribution of NAPL, gas, and water phases within a source zone is expected to influence the rate of volatilization. However, the effect of this distribution morphology on volatilization has not been thoroughly quantified. Because field quantification of NAPL volatilization is often infeasible, a controlled laboratory experiment was conducted in a two‐dimensional tank (28 cm × 15.5 cm × 2.5 cm) with water‐wet sandy media and an emplaced trichloroethylene (TCE) source. The source was emplaced in two configurations to represent morphologies encountered in field settings: (1) NAPL pools directly exposed to the air phase and (2) NAPLs trapped in water‐saturated zones that were occluded from the air phase. Airflow was passed through the tank and effluent concentrations of TCE were quantified. Models were used to analyze results, which indicated that mass transfer from directly exposed NAPL was fast and controlled by advective‐dispersive‐diffusive transport in the gas phase. However, sources occluded by pore water showed strong rate limitations and slower effective mass transfer. This difference is explained by diffusional resistance within the aqueous phase. Results demonstrate that vapor generation rates from a NAPL source will be influenced by the soil water content distribution within the source. The implications of the NAPL morphology on volatilization in the context of a dynamic water table or climate are discussed. 相似文献
9.
B. Petri P. Štípská E. Skrzypek K. Schulmann M. Corsini J. Franěk 《Journal of Metamorphic Geology》2014,32(6):599-626
We combine structural observations, petrological data and 40Ar–39Ar ages for a stack of amphibolite facies metasedimentary units that rims high‐P (HP) granulite facies felsic bodies exposed in the southern Bohemian Massif. The partly migmatitic Varied and Monotonous units, and the underlying Kaplice unit, show a continuity of structures that are also observed in the adjacent Blanský les HP granulite body. They all exhibit an earlier NE?SW striking and steeply NW‐dipping foliation (S3), which is transposed into a moderately NW‐dipping foliation (S4). In both the Varied and Monotonous units, the S3 and S4 foliations are characterized by a Sil–Bt–Pl–Kfs–Qtz–Ilm±Grt assemblage, with occurrences of post‐D4 andalusite, cordierite and muscovite. In the Monotonous unit, minute inclusions of garnet, kyanite, sillimanite and biotite are additionally found in plagioclase from a probable leucosome parallel to S3. The Kaplice unit shows rare staurolite and kyanite relicts, a Sil–Ms–Bt–Pl–Qtz±Grt assemblage associated with S3, retrogressed garnet?staurolite aggregates during the development of S4, and post‐D4 andalusite, cordierite and secondary muscovite. Mineral equilibria modelling for representative samples indicates that the Varied unit records conditions higher than ~7 kbar at 725 °C during the transition from S3 to S4, followed by a P?T decrease from ~5.5 kbar/750 °C to ~4.5 kbar/700 °C. The Monotonous unit shows evidence of partial melting in the S3 fabric at P?T above ~8 kbar at 740–830 °C and a subsequent P?T decrease to 4.5–5 kbar/700 °C. The Kaplice unit preserves an initial medium‐P prograde path associated with the development of S3 reaching peak P?T of ~6.5 kbar/640 °C. The subsequent retrograde path records 4.5 kbar/660 °C during the development of S4. 40Ar–39Ar geochronology shows that amphibole and biotite ages cluster at c. 340 Ma close to the HP granulite, whereas adjacent metasedimentary rocks preserve c. 340 Ma amphibole ages, but biotite and muscovite ages range between c. 318 and c. 300 Ma. The P?T conditions associated with S3 imply an overturned section of the orogenic middle crust. The shared structural evolution indicates that all mid‐crustal units are involved in the large‐scale folding cored by HP granulites. The retrograde P–T paths associated with S4 are interpreted as a result of a ductile thinning of the orogenic crust at a mid‐crustal level. The 40Ar–39Ar ages overlap with U–Pb zircon ages in and around the HP granulite bodies, suggesting a short duration for the ductile thinning event. The post‐ductile thinning late‐orogenic emplacement of the South Bohemian plutonic complex is responsible for a re‐heating of the stacked units, reopening of argon system in mica and a tilting of the S4 foliation to its present‐day orientation. 相似文献
10.
We combine a convectively driven dynamo in a spherical shell with a nearly isothermal density-stratified cooling layer that mimics some aspects of a stellar corona to study the emergence and ejections of magnetic field structures. This approach is an extension of earlier models, where forced turbulence simulations were employed to generate magnetic fields. A spherical wedge is used which consists of a convection zone and an extended coronal region to ???1.5 times the radius of the sphere. The wedge contains a quarter of the azimuthal extent of the sphere and 150° in latitude. The magnetic field is self-consistently generated by the turbulent motions due to convection beneath the surface. Magnetic fields are found to emerge at the surface and are ejected to the coronal part of the domain. These ejections occur at irregular intervals and are weaker than in earlier work. We tentatively associate these events with coronal mass ejections on the Sun, even though our model of the solar atmosphere is rather simplistic. 相似文献