bluuebunny/crossref_metadata_2025_split huggingface dataset:
Suspended sediment and phosphorus in proglacial rivers: bioavailability and potential impacts upon the P status of ice‐marginal receiving waters
Authors: Hodson Andy , Mumford Paul , Lister Debbie 
Published: June 2004

AbstractThis paper adopts standard tests developed in temperate catchment research to determine the total phosphorus (TP) and the algal available (base‐extractable) phosphorus (NaOH–P) content of a wide range of glaciofluvial sediments from the Northern Hemisphere. We find that the TP content of these sediments is broadly similar to the P content of major rock types in Earth's crust (230–670 µgP/g) and so the TP yields of glacier basins may be high owing to the efficacy of suspended sediment evacuation by glacial meltwaters. We show that this is best achieved where subglacial drainage systems are present. The NaOH–P pool of the sediments is found to be low (1–23 µgP/g) relative to the TP pool and also to the NaOH–P pool of suspended sediments in temperate, non‐glacierized catchments. This most probably reflects the restricted duration of intimate contact between dilute meltwaters and glacial suspended sediments during the ablation season. Thus, despite the high surface‐area:volume ratio of glacial suspended sediments, the potential for P adsorption to mineral surfaces following release by dissolution is also low. Further, sorption experiments and sequential extraction tests conducted using glacial suspended sediments from two Svalbard catchments indicate that the generation of reactive secondary minerals (e.g. Fe‐ and other hydroxides) with a strong capacity to scavenge P from solution (and thereby promote the continued dissolution of P) may also be limited by the short residence times. Most P is therefore associated with poorly weathered, calcite/apatite‐rich mineral phases. However, we use examples from the Svalbard glacier basins (Austre Brøggerbreen and Midre Lovénbreen) to show that the high sediment yields of glaciers may result in appreciable NaOH–P loading of ice‐marginal receiving waters. Again, the importance of subglacial drainage is highlighted, as it produces a major, episodic release of NaOH–P at Midre Lovénbreen that results in a yield (8·2 kg NaOH–P/km2/year) more than one order of magnitude greater than that at Austre Brøggerbreen (where subglacial drainage is absent and the yield is 0·48 kg NaOH‐P/km2/year). Therefore, as since both detrimental and beneficial effects of sediment‐bound P loading in ice marginal receiving waters are possible (i.e. either reduced primary productivity owing to increased turbidity or P fertilization following desorption) there is a pressing need to assess the ambient P status of such environments and also the capacity for ice‐marginal ecosystems to adapt to such inputs. Copyright © 2004 John Wiley & Sons, Ltd.
Experimental investigation of bedload transport processes under unsteady flow conditions
Authors: Lee Kwan Tun , Liu Yi‐Liang , Cheng Kai‐Hung 
Published: June 2004

AbstractHydraulic engineering is usually based on theoretical analysis and/or numerical modelling simulation. As the dynamic behaviour of sediment movement under unsteady flow is still unclear, and field measurement is comparatively difficult during a large flood, prior investigations through flume experiments are required. A series of flume experiments, conducted using different inflow hydrographs without sediment supply from upstream, was carried out to investigate the sediment transport process under unsteady flow conditions.A series of triangular hydrographs were performed in the experiments. The results indicate that a temporal lag was found between the flow hydrograph peak and the sediment hydrograph peak because large size sand dunes lasted for a short period in the falling limb of the flow hydrograph. The temporal lag was found to be about equal to 6–15% of the flow hydrograph duration. Owing to the temporal lag, the total bedload yield in the rising period was less than that in the falling period. Furthermore, the measured total bedload yield in the unsteady flow experiments was larger than the predicted value, which was estimated by using the results obtained from the equivalent steady flow experiment. The peak bedload transport rate for unsteady flow conditions was also larger than the predicted value. The ratios of the measured to the predicted quantities mentioned above were found to be constant values for different shapes of hydrographs. It is, therefore, expected that the analytical results of sediment transport from equivalent steady flow can be a good reference for sediment transport under unsteady flow conditions. Copyright © 2004 John Wiley & Sons, Ltd.
Determination of two‐dimensional laboratory‐scale dispersivities
Authors: Kim Song‐Bae , Jo Kyu‐Hyeok , Kim Dong‐Ju , Jury William A. 
Published: June 2004

AbstractA tracer test was conducted in a laboratory chamber representing a two‐dimensional aquifer to investigate the longitudinal dispersivity (αL) and the ratio (αT/αL) of transverse to longitudinal dispersivity of sandy aquifer materials. Dispersive parameters were obtained by matching the observed chloride plumes at 9 hours and 16 hours after tracer injection with those simulated by a flow and transport model. The best match was found for αL = 0·2 − 0·25 cm and αT/αL = 0·2. The ratio of αT/αL = 0·2 was within the range of laboratory values reported in the literature. Sensitivity analysis revealed that the tracer plume concentration and shape were more sensitive to variations in longitudinal dispersivity than to the ratio of transverse to longitudinal dispersivity. This result contrasted with findings of others, showing that the dispersivity ratio greatly affects contaminant plume shape. However, our experimental boundary conditions restricted expansion of the plume normal to the direction of flow and thus affected the parameter estimation. Copyright © 2004 John Wiley & Sons, Ltd.
Modelling water infiltration in cracked paddy field soil
Authors: Liu Chen‐Wuing , Chen Shih‐Kai , Jang Cheng‐Shin 
Published: June 2004

AbstractPeriodic paddy field flooding is a major source of groundwater recharge. Many paddy fields thus are used as groundwater recharge ponds after harvesting the first crop of the summer. Following rice harvesting, paddy field surfaces may crack into fissures as a result of drainage and exposure to sunlight. Field observation indicates that applying precipitation to the paddy field can increase the rate of infiltration. To quantitatively evaluate the amount of infiltration in a cracked paddy field, this study sets up a simple soil crack model to simulate the field infiltration process. A three‐dimensional groundwater model FEMWATER is adopted to simulate water movement in the paddy field subjected to various crack conditions. Using the field and laboratory data of irrigation water requirements, soil physical properties, hydraulic conductivities and soil profiles obtained from Ten‐Chung, FEMWATER simulates the water movement in the dry cracked paddy. Simulation results show that if the cracks develop extensively and penetrate the ploughed soil, the infiltration rate may increase significantly. The infiltration fluxes of crack with depths of 80, 60 and 27·5 cm are 18·77, 14·50 and 8·06 times higher than that of 20 cm, respectively. The simulation results of cracks with 80 cm depth correlated closely with field observations. The results of the study elucidate the processes of unsaturated water movement in a dry cracked paddy field. Copyright © 2004 John Wiley & Sons, Ltd.
Techniques for assessing the climatic sensitivity of river flow regimes
Authors: Bower Donna , Hannah David M. , McGregor Glenn R. 
Published: June 2004

AbstractRegimes are useful tools for characterizing the seasonal behaviour of river flow and other hydroclimatological variables over an annual cycle (hydrological year). This paper develops and tests: (i) a regime classification method to identify spatial and temporal patterns in intraannual hydroclimatological response; and (ii) a novel sensitivity index (SI) to assess river flow regimes' climatic sensitivity. The classification of regime shape (form) and magnitude considers the whole annual cycle rather than isolating a single month or season for analysis, which has been the common approach of previous studies. The classification method is particularly useful for identifying large‐scale patterns in regimes and their between‐year stability, thus providing a context for short‐term, small‐scale process‐based research. The SI provides a means of assessing the often‐complex linkages between climatic drivers and river flow, as it identifies the strength and direction of associations between classifications of climate and river flow regimes. The SI has the potential for application to other problems where relationships between nominal classifications require to be found. These techniques are evaluated by application to a test data set of river flow, air temperature and rainfall time‐series (1974–1999) for a sample of 35 UK river basins. The results support current knowledge about the hydroclimatology of the UK. Although this research does not seek to yield new, detailed physical process understanding, it provides perspective at large spatial and temporal scales upon climate and flow regime patterns and quantifies linkages. Having clearly demonstrated the regime classification and SI to be effective in an environment where the hydroclimatology is relatively well known, there appears to be much to gain from applying these techniques in parts of the world where patterns and associations between climate and hydrology are poorly understood. Copyright © 2004 John Wiley & Sons, Ltd.
Forecasting flows in Apalachicola River using neural networks
Authors: Huang Wenrui , Xu Bing , Chan‐Hilton Amy 
Published: June 2004

AbstractForecasting river flow is important to water resources management and planning. In this study, an artificial neural network (ANN) model was successfully developed to forecast river flow in Apalachicola River. The model used a feed‐forward, back‐propagation network structure with an optimized conjugated training algorithm. Using long‐term observations of rainfall and river flow during 1939–2000, the ANN model was satisfactorily trained and verified. Model predictions of river flow match well with the observations. The correlation coefficients between forecasting and observation for daily, monthly, quarterly and yearly flow forecasting are 0·98, 0·95, 0·91 and 0·83, respectively. Results of the forecasted flow rates from the ANN model were compared with those from a traditional autoregressive integrated moving average (ARIMA) forecasting model. Results indicate that the ANN model provides better accuracy in forecasting river flow than does the ARIMA model. Copyright © 2004 John Wiley & Sons, Ltd.
Using a topographic index to distribute variable source area runoff predicted with the SCS curve‐number equation
Authors: Lyon Steve W. , Walter M. Todd , Gérard‐Marchant Pierre , Steenhuis Tammo S. 
Published: June 2004

AbstractBecause the traditional Soil Conservation Service curve‐number (SCS‐CN) approach continues to be used ubiquitously in water quality models, new application methods are needed that are consistent with variable source area (VSA) hydrological processes in the landscape. We developed and tested a distributed approach for applying the traditional SCS‐CN equation to watersheds where VSA hydrology is a dominant process. Predicting the location of source areas is important for watershed planning because restricting potentially polluting activities from runoff source areas is fundamental to controlling non‐point‐source pollution. The method presented here used the traditional SCS‐CN approach to predict runoff volume and spatial extent of saturated areas and a topographic index, like that used in TOPMODEL, to distribute runoff source areas through watersheds. The resulting distributed CN–VSA method was applied to two subwatersheds of the Delaware basin in the Catskill Mountains region of New York State and one watershed in south‐eastern Australia to produce runoff‐probability maps. Observed saturated area locations in the watersheds agreed with the distributed CN–VSA method. Results showed good agreement with those obtained from the previously validated soil moisture routing (SMR) model. When compared with the traditional SCS‐CN method, the distributed CN–VSA method predicted a similar total volume of runoff, but vastly different locations of runoff generation. Thus, the distributed CN–VSA approach provides a physically based method that is simple enough to be incorporated into water quality models, and other tools that currently use the traditional SCS–CN method, while still adhering to the principles of VSA hydrology. Copyright © 2004 John Wiley & Sons, Ltd.
Geochemical and isotopic evidence of a groundwater source in the Corral Canyon meadow complex, central Nevada, USA
Authors: Atekwana Eliot A. , Richardson Dorothea S. 
Published: June 2004

AbstractMajor inorganic ions and stable carbon and oxygen isotopes in stream water, groundwater, groundwater seeps and springs were measured in the Corral Canyon meadow complex and watershed in the Toquima Mountains of central Nevada, USA. The purpose of the study was to determine whether stream water or groundwater was the source of water that supports vegetation in the meadow complex. Water samples from the watershed and meadow complex were mixed cation–HCO3 type. Stream water sampled at different locations in the meadow complex showed variations in temperature, pH and specific conductance. The cation–anion proportions for stream water were similar to groundwater, groundwater seeps and runoff from the meadow complex. Stable oxygen isotope ratios for stream water (−17·1 to −17·6‰ versus VSMOW) and groundwater and groundwater seeps in the meadow site (−17·0 to −17·7‰ versus VSMOW) were similar, and consistent with a local meteoric origin. Dissolved inorganic carbon (DIC) and the δ 13CDIC for stream water (−12·1 to −15·0‰ versus VPDB) were different from that of groundwater from the meadow complex (−15·3 to −19·9‰ versus VPDB), suggesting different carbon evolution pathways. However, a simple model based on cation–δ 13CDIC suggests that stream water was being recharged by shallow groundwater, groundwater seeps and runoff from the meadow complex. This leads to the conclusion that the source of water that supports vegetation in the meadow complex was primarily groundwater. The results of this study suggest that multiple chemical and stable carbon isotope tracers are useful in determining the source of water that supports vegetation in meadow complexes in small alpine watersheds. Copyright © 2004 John Wiley & Sons, Ltd.
Sensitivity to acidification of subalpine ponds and lakes in north‐western Colorado
Authors: Campbell D. H. , Muths E. , Turk J. T. , Corn P. S. 
Published: June 2004

AbstractAlthough acidifying deposition in western North America is lower than in many parts of the world, many high‐elevation ecosystems there are extremely sensitive to acidification. Previous studies determined that the Mount Zirkel Wilderness Area (MZWA) has the most acidic snowpack and aquatic ecosystems that are among the most sensitive in the region. In this study, spatial and temporal variability of ponds and lakes in and near the MZWA were examined to determine their sensitivity to acidification and the effects of acidic deposition during and after snowmelt. Within the areas identified as sensitive to acidification based on bedrock types, there was substantial variability in acid‐neutralizing capacity (ANC), which was related to differences in hydrological flowpaths that control delivery of weathering products to surface waters. Geological and topographic maps were of limited use in predicting acid sensitivity because their spatial resolution was not fine enough to capture the variability of these attributes for lakes and ponds with small catchment areas. Many of the lakes are sensitive to acidification (summer and autumn ANC < 100 µeq L−1), but none of them appeared to be threatened immediately by episodic or chronic acidification. In contrast, 22 ponds had minimum ANC < 30 µeq L−1, indicating that they are extremely sensitive to acidic deposition and could be damaged by episodic acidification, although net acidity (ANC < 0) was not measured in any of the ponds during the study. The lowest measured pH value was 5·4, and pH generally remained less than 6·0 throughout early summer in the most sensitive ponds, indicating that biological effects of acidification are possible at levels of atmospheric deposition that occurred during the study. The aquatic chemistry of lakes was dominated by atmospheric deposition and biogeochemical processes in soils and shallow ground water, whereas the aquatic chemistry of ponds was also affected by organic acids and biogeochemical processes in the water column and at the sediment–water interface. These results indicate that conceptual and mechanistic acidification models that have been developed for lakes and streams may be inadequate for predicting acidification in less‐understood systems such as ponds. Copyright © 2004 John Wiley & Sons, Ltd.
Near‐saturated surface soil hydraulic properties under different land uses in the St Denis National Wildlife Area, Saskatchewan, Canada
Authors: Bodhinayake Waduwawatte , Cheng Si Bing 
Published: June 2004

AbstractSurface soil hydraulic properties are key factors controlling the partition of rainfall and snowmelt into runoff and soil water storage, and their knowledge is needed for sound land management. The objective of this study was to evaluate the effects of three land uses (native grass, brome grass and cultivated) on surface soil hydraulic properties under near‐saturated conditions at the St Denis National Wildlife Area, Saskatchewan, Canada. For each land use, water infiltration rates were measured using double‐ring and tension infiltrometers at −0·3, −0·7, −1·5 and −2·2 kPa pressure heads. Macroporosity and unsaturated hydraulic properties of the surface soil were estimated. Mean field‐saturated hydraulic conductivity (Kfs), unsaturated hydraulic conductivity at −0·3 kPa pressure head, inverse capillary length scale (α) and water‐conducting macroporosity were compared for different land uses. These parameters of the native grass and brome grass sites were significantly (p < 0·1) higher than that of the cultivated sites. At the −0·3 kPa pressure head, hydraulic conductivity of grasslands was two to three times greater than that of cultivated lands. Values of α were about two times and values of Kfs about four times greater in grasslands than in cultivated fields. Water‐conducting macroporosity of grasslands and cultivated fields were 0·04% and 0·01% of the total soil volume, respectively. Over 90% of the total water flux at −0·06 kPa pressure head was transmitted through pores > 1·36 × 10−4 m in diameter in the three land uses. Land use modified near‐saturated hydraulic properties of surface soil and consequently may alter the water balance of the area by changing the amount of surface runoff and soil water storage. Copyright © 2004 John Wiley & Sons, Ltd.
NS398 reduces hypoxia‐inducible factor (HIF)‐1α and HIF‐1 activity: Multiple‐level effects involving cyclooxygenase‐2 dependent and independent mechanisms
Authors: Zhong Hua , Willard Margaret , Simons Jonathan 
Published: June 2004

AbstractTissue hypoxia is a common feature in solid tumors. Hypoxia‐inducible factor 1 (HIF‐1) is a critical transcription factor that regulates the expression of genes encoding factors that influence tumor growth including vascular endothelial growth factor. Previous studies have demonstrated that post‐transcriptional modification events are important for regulation of HIF‐1α protein expression and HIF‐1 transcriptional activity. Prostaglandin E2 (PGE2), a major end product of the cyclooxygenase‐2 (COX‐2) enzyme, induces the basal and hypoxia‐induced nuclear relocalization of HIF‐1α. This is suppressed by NS398, a COX‐2 selective inhibitor. NS398 also inhibits hypoxia‐induced angiogenesis, which may be mediated by the inhibition of HIF‐1 function in a COX‐2‐dependent manner. Here, we show that NS398 reduces HIF‐1α and HIF‐1 transcriptional function in both COX‐2 positive PC‐3 cells and COX‐2 negative HCT116 cells under normoxic and hypoxic conditions. On the one hand, NS398 decreases the expression of HIF‐1α mRNA and reduces HIF‐1α synthesis in a COX‐2/PGE2 dependent way, which can be restored by addition of exogenous PGE2 that activates the phosphatidylinositol 3‐kinase/AKT/p70s6k signaling pathway. On the other hand, NS398 accelerates HIF‐1α degradation by moderately increasing ubiquitination and remarkably promoting the clearance of ubiquitylated protein, an effect most likely independent of COX‐2/PGE2 since exogenous PGE2 fails to reverse it. Finally, NS398 decreases hypoxia‐induced shifted form of HIF‐1α and attenuates HIF‐1 activation in greater extent under hypoxic than normoxic conditions. These data not only confirm the inhibitory effect of NS398 on HIF‐1α and HIF‐1 transcriptional activity but also demonstrate that such an effect occurs at multiple levels involving both COX‐2 dependent and independent mechanisms. © 2004 Wiley‐Liss, Inc.
Combination of low‐dose cisplatin and recombinant xenogeneic endoglin as a vaccine induces synergistic antitumor activities
Authors: Tan Guang‐hong , Tian Ling , Wei Yu‐quan , Zhao Xia , Li Jiong , Wu Yang , Wen Yan‐jun , Yi Tao , Ding Zhen‐yu , Kan Bin , Mao Yong‐qiu , Deng Hong‐xin , Li Hong‐li , Zou Chun‐hua , Fu Chun‐hua 
Published: June 2004

AbstractAngiogenesis is critical to the growth and metastasis of solid tumors, and acquired drug resistance is one of the major hindrances to chemotherapy. Thus, we sought a rational strategy using the combination of antiangiogenic biotherapy and chemotherapy for cancer therapy. We explored the efficacy of a strategy combining low‐dose cisplatin and a recombinant xenogeneic endoglin as a protein vaccine, which we previously demonstrated to have effective antiangiogenic effects in several mouse models. We found that both low‐dosage cisplatin and xenogeneic endoglin vaccine individually resulted in effective suppression of tumor growth in 2 tumor models via inhibition of tumor angiogenesis. Remarkably, the combination therapy resulted in not only significant antiangiogenic effects but also additional promotion of tumor cell apoptosis and inhibition of tumor cell proliferation, without any ensuing increase in host toxicity during the course of treatment, which lasted for 6 months. In addition, the combination demonstrated a synergistic relationship, which was shown in all of the synergistic indexes, i.e., tumor volume, angiogenesis, apoptosis and proliferation. Both antibodies and antibody‐producing B cells against mouse self‐endoglin were observed in all mice immunized by the xenogeneic endoglin vaccine (alone and combination), which suggested that low‐dose cisplatin did not suppress the host immune response but potentiated the antitumor activity of the xenogeneic endoglin vaccine. These observations may provide the basis for an effective alternative strategy for cancer therapy in the near future. © 2004 Wiley‐Liss, Inc.