Controls of 234Th removal from the oligotrophic ocean by polyuronic acids and modification by microbial activity     

Chen Xu  Peter H. Santschi  Chin-Chang Hung  Saijin Zhang  Kathleen A. Schwehr  Kimberly A. Roberts  Laodong Guo  Gwo-Ching Gong  Antonietta Quigg  Richard A. Long  James L. Pinckney  Shuiwang Duan  Rainer Amon  Ching-Ling Wei 《Marine Chemistry》2011,123(1-4):111-126

To gain new insights into the variability of particulate organic carbon (POC) fluxes and to better understand the factors controlling the POC/²³⁴Th ratios in suspended and sinking particulate matter, we investigated the relationships between POC/²³⁴Th ratios and biochemical composition (uronic acids, URA; total carbohydrates, TCHO; acid polysaccharides, APS; and POC) of suspended and sinking matter from the Gulf of Mexico in 2005 and 2006. Our data show that URA/POC in sediment traps (STs), APS/POC in the suspended particles, and turnover times of particulate ²³⁴Th in the water column and those of bacteria in STs inside eddies usually increased with depth, whereas particulate POC/²³⁴Th (10–50 μm) and the sediment-trap parameters (POC flux, POC/²³⁴Th ratio, bacterial biomass, and bacterial production) decreased with depth. However, this trend was not the case for most biological parameters (e.g., phytoplankton and bacterial biomass) or for the other parameters at the edges of eddies or at coastal-upwelling sites.In general, the following relationships were observed: 1) ²³⁴Th/POC ratios in STs were correlated with APS flux, and these ratios in the 10–50 μm suspended particles also correlated with URA/POC ratios; 2) neither URA fluxes nor URA/POC ratios were significantly related to bacterial biomass; 3) the sum of two uronic acids (G2, glucuronic, and galacturonic acid, which composed most of the URA pool) was positively related to bacterial biomass; and 4) the POC/²³⁴Th ratios in intermediate-sized particles (10–50 μm) were close to those in sinking particles but much lower than those in > 50 μm particles. The results indicate that acid polysaccharides, though a minor fraction (~ 1%) of the organic carbon, act more likely as proxy compound classes that might contain the more refractory ²³⁴Th-binding biopolymer, rather than acting as the original ²³⁴Th “scavenger” compound. Moreover, these acid polysaccharides, which might first be produced by phytoplankton and then modified by bacteria, also influence the on-and-off “piggy-back” processes of organic matter and ²³⁴Th, thus causing additional variability of the POC/²³⁴Th in particles of different sizes.  相似文献   

越南东北部Cat Ba岛泥盆系-石炭系过渡层的初探     

Toshifumi KOMATSU  Reishi TAKASHIMA  TA Hoa PHUONG  Tran Huyen DANG  Duc Phong NGUYEN  Huu Hung NGUYEN  Satoru KATO  Kento HIRATA  Takumi MAEKAWA 《地球学报》2012,33(S1):38-38

The Pho Han Formation is exposed on southern Cat Ba Island, Hai Phong Province in northeastern Vietnam, and intercalates the Devonian and Carbonif-erous (D-C) boundary (Ta and Doan, 2007; Komatsu et al., 2012). The D-C boundary section consists mainly of limestone beds, numbered from 1 to 167, interca-lated with alternating black organic-rich shales. The limestone yields abundant brachiopods, crinoid-stems and conodonts. Preliminary investigations on strati-graphy (conodont biostratigraphy and δ13C) and sedi-mentology of beds 113-133 were undertaken in this study.  相似文献   

Analytical Expression for Vertical Stress within an Inclined Mine Stope with Non-parallel Walls   总被引：1，自引：0，他引：1  

Ching Hung Ting  Nagaratnam Sivakugan  Wayne Read  Sanjay Kumar Shukla 《Geotechnical and Geological Engineering》2014,32(2):577-586

Arching is a phenomenon that occurs in many situations in geotechnical engineering. When underground mine stopes are backfilled, a significant fraction of the self-weight of the backfill is carried by the side walls. As a result, the vertical stress at the bottom of the stope is significantly less than its overburden pressure. Few analytical expressions published in the literature can be used to determine the vertical stresses of stope with parallel walls. The objective of this paper is to extend the analytical solution previously developed by the authors to long plane-strain stopes with non-parallel walls with both slopes leaning to the same side. Different combinations of wall inclination are examined using the new analytical expression developed. To validate the analysis, the proposed results are compared with numerical model results. The results show that the proposed analytical expression is capable of estimating the vertical stress within mine stopes when the inclination of the hangingwall to the horizontal (α) is less than that of footwall (β). An important behavioural trend for the stress distribution is observed, where with the same overburden pressure and base width, the stress magnitude experienced by fill material significantly varies depending on the wall inclination.  相似文献   

Fuzzy-based spatial modeling approach to predict island karst distribution: a conceptual model   总被引：1，自引：0，他引：1  

Hung Chak Ho  John E. Mylroie  Louis R. Infante  John C. Rodgers III 《Environmental Earth Sciences》2014,71(3):1369-1377

Previous studies have shown that island karst could successfully indicate paleoclimate change in the Quaternary Period. However, because of the relative inaccessibility of carbonate islands and their rural settings, the exploration of island karst features has been limited. To enhance future research, remote sensing and geospatial modeling were used in this study to improve the island karst exploration record. The results showed that fuzzy-based spatial modeling could successfully predict the island karst distributions on a simple carbonate island. The accuracy of the model was above 90 %. This method could apply to other coastal karst regions and carbonate islands in the future.  相似文献   

Groundwater geochemical evolution in the northern portion of the Guarani Aquifer System (Brazil) and its relationship to diagenetic features   总被引：1，自引：0，他引：1  

Didier Gastmans  Hung K. Chang  Ian Hutcheon 《Applied Geochemistry》2010

The groundwater flow pattern in the northern portion of GAS (Guarani Aquifer System) is characterized by the existence of four regional recharge areas located in São Paulo, Mato Grosso do Sul and Goiás states. From these areas of recharge the regional flow is radial and directed toward the center of the Paraná Sedimentary Basin. Local discharge occurs in portions of outcrop regions. The groundwater has low mineralization and can be classified as Ca or Ca–Mg–HCO₃ type, Na–HCO₃ type and Na–HCO₃/Cl/SO₄ type, this sequence represents the hydrochemical evolution. The mechanisms responsible for this evolution are dissolution of feldspars and removal of the carbonate cement from the sandstone mineral framework, followed by ion exchange, responsible for the increase in the Na concentration and decrease of Ca, and, finally, enrichment in Cl and SO₄ derived from underlying aquifer units. The hydrochemical evolution is consistent with diagenetic features that are observed in the sandstones, with the presence of siliceous cement in the outcrop areas, and carbonate cement toward the center of Paraná Basin.  相似文献   

Data analysis on the extrasolar planets using robust clustering     

Ing-Guey Jiang  Li-Chin Yeh  Wen-Liang Hung  Miin-Shen Yang 《Monthly notices of the Royal Astronomical Society》2006,370(3):1379-1392

We use both the conventional and more recently developed methods of cluster analysis to study the data of extrasolar planets (exoplanets). Using the data set with planetary mass M , orbital period P and orbital eccentricity e , we investigate the possible clustering in the  ln  M ,  ln  P ,  ln  P –ln  M ,   e   and ln   P – e spaces. There are two main implications: (1) mass distribution is continuous, and (2) orbital population could be classified into three clusters, which correspond to the exoplanets in the regimes of tidal, ongoing tidal and disc interaction, respectively.  相似文献   

Application of a feature-based approach to debris flow detection by numerical simulation     

Chih-Wei Lin  Cheng-Wu Chen  Wen-Ko Hsu  Chia-Yen Chen  Chung-Hung Tsai  Yi-Ping Hung  Wei-Ling Chiang 《Natural Hazards》2013,67(2):783-796

A debris flow is a serious natural disaster which can occur anywhere whether in a valley or on a mountain slope, destroying everything it passes through. Debris flows can occur suddenly and cause residents in the path to suffer casualties and property loss. An early warning system is necessary to reduce the damage in order to protect human life and personal property. However, most debris flow detection systems, like wireless sensors, satellite images and radar, are not suitable for general public use. Vision surveillance systems are generally erected in Taiwan as public devices for security. Therefore, we propose a novel debris early warning system that uses a computer vision technique and build a simulation environment to prove the feasibility.  相似文献   

Removal of Two Pharmaceutically Active Compounds from Aqueous Phase Using an Engineered Floodplain Filtration System     

Shishir Kumar Behera  Eldon R. Rene  Hung‐Suck Park 《洁净——土壤、空气、水》2013,41(8):780-788

This study investigated the removal of two model pharmaceutically active compounds (PhAcs), viz., ibuprofen and triclosan, in lab‐scale engineered floodplain filtration (EFF) system. Biodegradation experiments were performed to acquire knowledge about the degradation of the targeted PhAcs, at an initial concentration of 350 µg/L. Biodegradation results showed that the two compounds were bio‐transformed to >70% after 15 days of incubation. Column tests were performed in a statistically significant manner to determine the adsorptive potential of the suggested filler layer in the EFF (C/C₀), by varying the flow rate and initial concentration of the compound. It was observed based on the F and p‐values that the main effects (F = 3163, p < 0.005) were more significant than the interactive effects (F = 9561, p < 0.05) for both ibuprofen and triclosan removal. Besides, by performing the Student's “t” test, it was concluded that the flow rate plays a major role in determining the rapidness of achieving complete breakthrough than the initial concentration of both the compounds. The data obtained from column studies under biotic conditions indicated that the removal mechanism for PhAcs is mainly biotransformation based, and that an EFF system may be effectively used to remove these emerging compounds during ground water recharge for water recycling.  相似文献   

Adsorption of Complex Pollutants from Aqueous Solutions by Nanocomposite Materials     

Yeoung‐Sheng Wang  Shu‐Huei Hsieh  Chang‐Hung Lee  Jao‐Jia Horng 《洁净——土壤、空气、水》2013,41(8):828-828

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The use of isotopes in evolving groundwater circulation models of regional continental aquifers: The case of the Guarani Aquifer System     

Roberto Eduardo Kirchheim  Didier Gastmans  Hung Kiang Chang  Troy E. Gilmore 《水文研究》2019,33(17):2266-2278

The Guarani Aquifer System (GAS) has been studied since the 1970s, a time frame that coincides with the advent of isotopic techniques in Brazil. The GAS isotope data from many studies are organized in different phases: (a) the advent of isotope techniques, (b) consolidation and new applications, (c) isotope assessments and hydrochemistry evolution, and (d) a roadmap to a new conceptual model. The reasons behind the phases, their methodological approaches, and impacts on the regional flow conceptual models are examined. Starting with local δ²H and δ¹⁸O assessments of values for water fingerprinting and estimates of recharge palaeoclimate scenarios, studies evolved to more integrated approaches based on multiple tracers. Stable isotope application techniques were consolidated during the 1980s, when new dating approaches dealing with radiogenic and heavy isotopes were introduced. Through the execution of an international transboundary project, the GAS was studied and extensively sampled for isotopes. These results have triggered wider application of isotope techniques, reflecting also world research trends. Presently, hydrochemical evolution models along flow lines from recharge to discharge areas, across large‐scale tectonic features within the entire sedimentary basin, are being combined with residence time estimates at GAS outcrop areas and deep confined units. In a complex system, it is normal that many, and even contradictory hypotheses are proposed, but isotope techniques provide a unique chance to test them. Stable isotope assessments are still needed near recharge areas, and they can be combined with groundwater classical dating procedures, complemented by newer techniques (³H‐³He, CFCs, and SF₆)_. Recent noble gas sampling and world pioneer analytical efforts focused on the confined units in the GAS will certainly led to new findings on the overall GAS circulation. The objective of this article is to discuss how isotope information can contribute to the evolution of conceptual groundwater flow models for regional continental aquifers, such as the GAS.  相似文献