Benthic foraminifera assemblages as elemental pollution bioindicator in marine sediments around fish farm (Vrgada Island,Central Adriatic,Croatia)     

Jelena Vidović  Matej Dolenec  Tadej Dolenec  Vatroslav Karamarko  Petra Žvab Rožič 《Marine pollution bulletin》2014

Effects on sediments of fish farming activity near Vrgada Island was analysed through living and total foraminiferal assemblages and concentration of major, minor and trace elements from three sediment cores. Elemental concentrations of sediments are in accordance with carbonate characteristics of the surrounding area and show mostly natural element variations between sampling locations and throughout the cores, with no significant increases due to fish farming activity. Only phosphorus concentration shows elevate values below the fish cage, assigned to fish pellets. Foraminiferal communities are dominated by epifaunal and stress tolerant species, while diversity indices point to normal marine conditions. The type of substrate and phosphorus content in sediments principally influence foraminiferal community composition, while other elemental concentrations have no perceptible effect on the assemblages. Some foraminiferal species Ammoniatepida, Ammoniabeccarii, Elphidiumcrispum, Elphidiummacellum and genus Haynesina are confirmed to be tolerant to elevated nutrient (phosphorus) content, while Ammonia parkinsoniana shows sensitivity to pollution. Postmortem processes cause decrease of foraminiferal density and species richness with core depth. All results point to negligible influence of fish farming and relatively stable environmental conditions at all sampling locations.  相似文献   

AHP-based group decision making approach to supplier selection of irrigation equipment     

Jovana Draginčić  Milica Vranešević 《Water Resources》2014,41(6):782-791

Supplier selection is a complex task which assumes decision making in presence of many conflicting criteria and various parameters. If there are more than one decision maker, the problem shifts into a group context and it requires proper approach in mediating the decision making process and use of supporting multi-criteria methods and tools. This paper proposes group decision making approach for supplier selection based on analytic hierarchy process (AHP) that is combined with consensus convergence model, and two voting methods, non-preferential approval voting and preferential Borda count. Proposed approach utilized strengths of these methods thus enabling their adaption to the specific decision problem of supplier selection. An example of selecting a supplier of irrigation equipment in the company engaged in projecting, installing and maintenance of irrigation systems is used to explain and demonstrate how proposed approach can be implemented. Furthermore, this approach is viable as sufficiently general in supporting different selection processes in a field of water planning, management, and development and it can be adapted and applied on various group decision making problems.  相似文献   

Particle simulations of dispersion using observed meandering and turbulence   总被引：2，自引：0，他引：2  

Dean Vickers  Larry Mahrt  Danijel Belušić 《Acta Geophysica》2008,56(1):234-256

A Lagrangian stochastic particle model driven by observed winds from a network of 13 sonic anemometers is used to simulate the transport of contaminates due to meandering of the mean wind vector and diffusion by turbulence. The turbulence and the meandering motions are extracted from the observed velocity variances using a variable averaging window width. Such partitioning enables determination of the separate contributions from turbulence and meandering to the total dispersion. The turbulence is described by a Markov Chain Monte Carlo process based on the Langevin equation using the observed turbulence variances. The meandering motions, not the turbulence, are primarily responsible for the 1-h averaged horizontal dispersion as measured by the travel time dependence of the particle position variances. As a result, the 1-h averaged horizontal concentration patterns are often characterized by streaks and multi-modal distributions. Time series of concentration at a fixed location are highly nonstationary even when the 1-h averaged spatial distribution is close to Gaussian. The results show that meandering dominates the travel-time dependence of the horizontal dispersion under all atmospheric conditions: weak and strong winds, and unstable and stable stratification.  相似文献