Sulfur biogeochemistry and isotopic fractionation in shallow groundwater and sediments of Owens Dry Lake, California     

Ji-hun Ryu  Randy A. Dahlgren  Suduan Gao 《Chemical Geology》2006,229(4):257-272

Groundwater and sediment samples (∼ 1 m depth) at sites representative of different groundwater pathways were collected to determine the aqueous speciation of sulfur and the fractionation of sulfur isotopes in aqueous and solid phases. In addition, selected sediment samples at 5 depths (from oxic to anoxic layers) were collected to investigate the processes controlling sulfur biogeochemistry in sedimentary layers. Pyrite was the dominant sulfur-bearing phase in the capillary fringe and groundwater zones where anoxic conditions are found. Low concentrations of pyrite (< 5.9 g kg^− 1) coupled with high concentrations of dissolved sulfide (4.81 to 134.7 mg L^− 1) and low concentrations of dissolved Fe (generally < 1 mg L^− 1) and reducible solid-phase Fe indicate that availability of reactive Fe limits pyrite formation. The relative uniformity of down-core isotopic trends for sulfur-bearing mineral phases in the sedimentary layers suggests that sulfate reduction does not result in significant sulfate depletion in the sediment. Sulfate availability in the deeper sediments may be enhanced by convective vertical mixing between upper and lower sedimentary layers due to evaporative concentration. The large isotope fractionation between dissolved sulfate and sedimentary sulfides at Owens Lake provides evidence for initial fractionation from bacterial sulfate reduction and additional fractionation generated by sulfide oxidation followed by disproportionation of intermediate oxidation state sulfur compounds. The high salinity in the Owens Lake brines may be a factor controlling sulfate reduction and disproportionation in hypersaline conditions and results in relatively constant values for isotope fractionation between dissolved sulfate and total reduced sulfur.  相似文献   

Geospatial blending to improve spatial mapping of precipitation with high spatial resolution by merging satellite‐based and ground‐based data          下载免费PDF全文

Baik Jongjin  Park Jongmin  Ryu Dongryeol  Choi Minha 《水文研究》2016,30(16):2789-2803

Estimating accurate spatial distribution of precipitation is important for understanding the hydrologic cycle and various hydro‐environmental applications. Satellite‐based precipitation data have been widely used to measure the spatial distribution of precipitation over large extents, but an improvement in accuracy is still needed. In this study, three different merging techniques (Conditional Merging, Geographical Differential Analysis and Geographical Ratio Analysis) were used to merge precipitation estimations from Communication, Ocean and Meteorological Satellite (COMS) Rainfall Intensity data and ground‐based measurements. Merged products were evaluated with varying rain‐gauge network densities and accumulation times. The results confirmed that accuracy of detecting quantitative rainfall was improved as the accumulation time and network density increased. Also, the impact of spatial heterogeneity of precipitation on the merged estimates was investigated. Our merging techniques reproduced accurate spatial distribution of rainfall by adopting the advantages of both gauge and COMS estimates. The efficacy of the merging techniques was particularly pronounced when the spatial heterogeneity of hourly rainfall, quantified by variance of rainfall, was greater than 10 mm²/accumulation time². Among the techniques analysed, Conditional Merging performed the best, especially when the gauge density was low. This study demonstrates the utility of the COMS Rainfall Intensity product, which has a shorter latency time (1 h) and higher spatio‐temporal resolution (hourly, 4 km by 4 km) than other widely used satellite precipitation products in estimating precipitation using merging techniques with ground‐based point measurements. The outcome has important implications for various hydrologic modelling approaches, especially for producing near real‐time products. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Adsorption of heavy metals and organic contaminants from aqueous stream with chemically enhanced kapok fibers     

Runkai Wang  Chul-Ho Shin  Daeik Kim  Moonhee Ryu  Joon-Seok Park 《Environmental Earth Sciences》2016,75(4):338

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The impacts of climate change on local hydrology and low flow frequency in the Geum River Basin,Korea     

Jae H. Ryu  Joo Heon Lee  Sangman Jeong  Seon K. Park  Kyuha Han 《水文研究》2011,25(22):3437-3447

The climate sensitive analysis of potential climate change on streamflow has been conducted using a hydrologic model to identify hydrologic variability associated with climate scenarios as a function of perturbed climatic variables (e.g. carbon dioxide, temperature, and precipitation). The interannual variation of water resources availability as well as low flow frequency driven by monsoonal time shifts have been investigated to evaluate the likelihood of droughts in a changing climate. The results show that the timing shift of the monsoon window associated with future climate scenarios clearly affect annual water yield change of ? 12 and ? 8% corresponding to 1‐month earlier and 1‐month later monsoon windows, respectively. Also, a more severe low flow condition has been predicted at 0·03 m³/s as opposed to the historic 7Q10 flow of 1·54 m³/s given at extreme climate scenarios. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Estimation of Roughness Parameters Within Sparse Urban-Like Obstacle Arrays   总被引：1，自引：0，他引：1  

Byung-Gu?Kim  Changhoon?LeeEmail author  Seokjun?Joo  Ki-Cheol?Ryu  Seogcheol?Kim  Donghyun?You  Woo-Sup?Shim 《Boundary-Layer Meteorology》2011,139(3):457-485

We conduct wind-tunnel experiments on three different uniform roughness arrays composed of sparsely distributed rectangular cylinders for the estimation of surface parameters. Roughness parameters such as the roughness length z ₀ and zero-plane displacement d are extracted using a best-fit approximation of the measured wind velocity. We also perform a large-eddy simulation (LES) to confirm that four sampling points are sufficient to surrogate a space average above the canopy layer of the sparse roughness arrays. We propose a new morphological model from a systematic analysis of experimental data on the arrays. The friction velocity predicted by the proposed model agrees well with the peak value of the measured Reynolds shear stress ${(-\left<\overline{u'w'}\right>)^{0.5}}${(-\left<\overline{u'w'}\right>)^{0.5}}. The proposed model is further validated in an additional wind-tunnel experiment conducted on a scaled configuration of a real urban area exposed to four wind directions. The proposed model is found to perform very well particularly in the estimation of the friction velocity, readily leading to a better estimation of turbulence, which is essential for an accurate prediction of pollutant dispersion.  相似文献   

Macrobenthos habitat mapping in a tidal flat using remotely sensed data and a GIS-based probabilistic model     

Choi JK  Oh HJ  Koo BJ  Lee S  Ryu JH 《Marine pollution bulletin》2011,62(3):564-572

This paper proposes and tests a method of producing macrofauna habitat potential maps based on a weights-of-evidence model (a probabilistic approach) for the Hwangdo tidal flat, Korea. Samples of macrobenthos were collected during field work, and we considered five mollusca species for habitat mapping. A weights-of-evidence model was used to calculate the relative weights of 10 control factors that affect the macrobenthos habitat. The control factors were compiled as a spatial database from remotely sensed data combined with GIS analysis. The relative weight of each factor was integrated as a species potential index (SPI), which produced habitat potential maps. The maps were compared with the surveyed habitat locations, revealing a strong correlation between the potential maps and species locations. The combination of a GIS-based weights-of-evidence model and remote sensing techniques is an effective method in determining areas of macrobenthos habitat potential in a tidal flat setting.  相似文献   

Qualitative assessment of gas hydrate and gas concentrations from the AVO characteristics of the BSR in the Ulleung Basin, East Sea (Japan Sea)     

Bo Y. Yi  Gwang H. Lee  Senay Horozal  Dong G. Yoo  Byong J. Ryu  Nyeon K. Kang  Sung R. Lee  Han J. Kim 《Marine and Petroleum Geology》2011,28(10):1953-1966

The presence of gas hydrate in the Ulleung Basin, East Sea (Japan Sea), inferred by various seismic indicators, including the widespread bottom-simulating reflector (BSR), has been confirmed by coring and drilling. We applied the standard AVO technique to the BSRs in turbidite/hemipelagic sediments crosscutting the dipping beds and those in debris-flow deposits to qualitatively assess the gas hydrate and gas concentrations. These BSRs are not likely to be affected by thin-bed tuning which can significantly alter the AVO response of the BSR. The BSRs crosscutting the dipping beds in turbidite/hemipelagic sediments are of low-seismic amplitude and characterized by a small positive gradient, indicating a decrease in Poisson’s ratio in the gas-hydrate stability zone (GHSZ), which, in turn, suggests the presence of gas hydrate. The BSRs in debris-flow deposits are characterized by a negative gradient, indicating decreased Poisson’s ratio below the GHSZ, which is likely due to a few percent or greater gas saturations. The increase in the steepness of the AVO gradient and the magnitude of the intercept of the BSRs in debris-flow deposits with increasing seismic amplitude of the BSRs is probably due to an increase in gas saturations, as predicted by AVO model studies based on rock physics. The reflection strength of the BSRs in debris-flow deposits, therefore, can be a qualitative measure of gas saturations below the GHSZ.  相似文献   

Is the Parker Instability a Viable Mechanism for the Formation of Giant Molecular Clouds?     

Jongsoo Kim  Dongsu Ryu  Seung Soo Hong 《Astrophysics and Space Science》2004,292(1-4):255-260

The stratified interstellar medium has been known to be subject to the Parker instability, and the instability has been considered as a plausible mechanism for the formation of giant molecular clouds (GMCs). By presenting our recent efforts to understand the instability through linear analyses and numerical simulations, we raise a negative point of view that the Parker instability alone could not form GMCs.  相似文献   

Effect of anisotropic conductivity on suction and reliability index of unsaturated slope exposed to uniform antecedent rainfall     

Khalid Mahmood  Jeong Ho Ryu  Jin Man Kim 《Landslides》2013,10(1):15-22

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Cosmic Rays Accelerated at Cosmological Shock Waves     

Renyi Ma  Dongsu Ryu  Hyesung Kang 《Journal of Astrophysics and Astronomy》2011,32(1-2):301-302

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