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M. Yang N. Her J. Ryu Y. Yoon 《International Journal of Environmental Science and Technology》2014,11(3):565-570
Perchlorate and iodide concentrations were determined in brown (Undaria pinnatifida and Laminaria japonica) and red (Porphyra sp.) edible seaweeds, which are commonly consumed by Korean people, with the use of ion chromatography, coupled with a tandem mass spectrometer. Seaweeds (i.e., good sources of iodine) are among the most important plant life in the ocean and commonly consumed as food and nutritional supplement in South Korea. All seaweed samples were purchased from different regions in South Korea. The detected concentrations of perchlorate were as follows: 19.7–620.7 μg kg?1 dry weight (n = 11, mean concentration = 149.2 μg kg?1 dry weight) for L. japonica and 7.3–21.7 μg kg?1 dry weight (mean concentration = 10.6 μg kg?1 dry weight) for U. pinnatifida. Of the 11 samples of Porphyra sp., only 1 sample showed 6.7 μg kg?1 dry weight perchlorate. The concentrations of iodide in all seaweed samples varied from 0.44 to 6,800 mg kg?1 dry weight. L. japonica samples (n = 11) had significantly higher iodide concentrations, with a mean of 5,261 mg kg?1 dry weight. The bioconcentration factor values for perchlorate and iodide in the three different seaweeds varied widely and showed similar variation trends. The trend for perchlorate and iodide was Porphyra sp. < U. pinnatifida < L. japonica. The results have provided growing evidence that perchlorate frequently occurs in food products. 相似文献
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L’Her Alexandre Reinert Markus Prants Sergey Carton Xavier Morvan Mathieu 《Ocean Dynamics》2021,71(5):601-612
Ocean Dynamics - The Eastern Kamchatka Current (EKC) is the western boundary current of the North Pacific subpolar gyre. Southeast of the Kamchatka Peninsula lies a large anticyclonic eddy, the... 相似文献
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Analysis of global hybrid simulations of Mercury’s magnetosphere-solar wind interaction is presented for northward and southward interplanetary magnetic field (IMF) orientations in the context of MESSENGER’s first two encounters with Mercury. The global kinetic simulations reveal the basic structure of this interaction, including a bow shock, ion foreshock, magnetosheath, cusp regions, magnetopause, and a closed ion ring belt formed around the planet within the magnetosphere. The two different IMF orientations induce different locations of ion foreshock and different magnetospheric properties: the dayside magnetosphere is smaller and cusps are at lower latitudes for southward IMF compared to northward IMF whereas for southward IMF the nightside magnetosphere is larger and exhibits a thin current sheet with signatures of magnetic reconnection and plasmoid formation. For the two IMF orientations the ion foreshock and quasi-parallel magnetosheath manifest ion-beam-driven large-amplitude oscillations, whereas the quasi-perpendicular magnetosheath shows ion-temperature-anisotropy-driven wave activity. The ions in Mercury’s belt remain quasi-trapped for a limited time before they are either absorbed by Mercury’s surface or escape from the magnetosphere. The simulation results are compared with MESSENGER’s observations. 相似文献
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Two‐dimensional continuous simulation of spatiotemporally varied hydrological processes using the time‐area method 
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下载免费PDF全文 Distributed, continuous hydrologic models promote better understanding of hydrology and enable integrated hydrologic analyses by providing a more detailed picture of water transport processes across the varying landscape. However, such models are not widely used in routine modelling practices, due in part to the extensive data input requirements, computational demands, and complexity of routing algorithms. We developed a two‐dimensional continuous hydrologic model, HYSTAR, using a time‐area method within a grid‐based spatial data model with the goal of providing an alternative way to simulate spatiotemporally varied watershed‐scale hydrologic processes. The model calculates the direct runoff hydrograph by coupling a time‐area routing scheme with a dynamic rainfall excess sub‐model implemented here using a modified curve number method with an hourly time step, explicitly considering downstream ‘reinfiltration’ of routed surface runoff. Soil moisture content is determined at each time interval based on a water balance equation, and overland and channel runoff is routed on time‐area maps, representing spatial variation in hydraulic characteristics for each time interval in a storm event. Simulating runoff hydrographs does not depend on unit hydrograph theory or on solution of the Saint Venant equation, yet retains the simplicity of a unit hydrograph approach and the capability of explicitly simulating two‐dimensional flow routing. The model provided acceptable performance in predicting daily and monthly runoff for a 6‐year period for a watershed in Virginia (USA) using readily available geographic information about the watershed landscape. Spatial and temporal variability in simulated effective runoff depth and time area maps dynamically show the areas of the watershed contributing to the direct runoff hydrograph at the outlet over time, consistent with the variable source area overland flow generation mechanism. The model offers a way to simulate watershed processes and runoff hydrographs using the time‐area method, providing a simple, efficient, and sound framework that explicitly represents mechanisms of spatially and temporally varied hydrologic processes. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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Impact of the numbers of observations and calibration parameters on equifinality,model performance,and output and parameter uncertainty 总被引：1，自引：0，他引：1 下载免费PDF全文
下载免费PDF全文 The level of model complexity that can be effectively supported by available information has long been a subject of many studies in hydrologic modelling. In particular, distributed parameter models tend to be regarded as overparameterized because of numerous parameters used to describe spatially heterogeneous hydrologic processes. However, it is not clear how parameters and observations influence the degree of overparameterization, equifinality of parameter values, and uncertainty. This study investigated the impact of the numbers of observations and parameters on calibration quality including equifinality among calibrated parameter values, model performance, and output/parameter uncertainty using the Soil and Water Assessment Tool model. In the experiments, the number of observations was increased by expanding the calibration period or by including measurements made at inner points of a watershed. Similarly, additional calibration parameters were included in the order of their sensitivity. Then, unique sets of parameters were calibrated with the same objective function, optimization algorithm, and stopping criteria but different numbers of observations. The calibration quality was quantified with statistics calculated based on the ‘behavioural’ parameter sets, identified using 1% and 5% cut‐off thresholds in a generalized likelihood uncertainty estimation framework. The study demonstrated that equifinality, model performance, and output/parameter uncertainty were responsive to the numbers of observations and calibration parameters; however, the relationship between the numbers, equifinality, and uncertainty was not always conclusive. Model performance improved with increased numbers of calibration parameters and observations, and substantial equifinality did neither necessarily mean bad model performance nor large uncertainty in the model outputs and parameters. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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