The Experts below are selected from a list of 48486 Experts worldwide ranked by ideXlab platform
T Yamamoto - One of the best experts on this subject based on the ideXlab platform.
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Nutrient Dynamics and the eutrophication of shallow lakes kasumigaura japan donghu pr china and okeechobee usa
Environmental Pollution, 2001Co-Authors: Karl E Havens, Noriko Takamura, Takehiko Fukushima, Ping Xie, T Iwakuma, R T James, Takayuki Hanazato, T YamamotoAbstract:We compared the Nutrient Dynamics of three lakes that have been heavily influenced by point and non-point source pollution and other human activities. The lakes, located in Japan (Lake Kasumigaura), People's Republic of China (Lake Donghu), and the USA (Lake Okeechobee), all are relatively large(>30 km(2)), very shallow (<4 m mean depth), and eutrophic. In all three lakes we found strong interactions among the sediments, water column, and human activities. Important processes affecting Nutrient Dynamics included nitrogen fixation, light limitation due to resuspended sediments, and intense grazing on algae by cultured fish. As a result of these complex interactions, simple empirical models developed to predict in-lake responses of total phosphorus and algal biomass to external Nutrient loads must be used with caution. While published models may provide 'good' results, in terms of model output matching actual data, this may not be due to accurate representation of lake processes in the models. The variable Nutrient Dynamics that we observed among the three study lakes appears to be typical for shallow lake systems. This indicates that a greater reliance on lake-specific research may be required for effective management, and a lesser role of inter-lake generalization than is possible for deeper, dimictic lake systems. Furthermore, accurate predictions of management impacts in shallow eutrophic lakes may require the use of relatively complex deterministic modeling tools. (C) 2000 Elsevier Science Ltd. All rights reserved.
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Nutrient Dynamics and the eutrophication of shallow lakes Kasumigaura (Japan), Donghu (PR China), and Okeechobee (USA).
Environmental pollution (Barking Essex : 1987), 2001Co-Authors: Karl E Havens, Noriko Takamura, Takehiko Fukushima, Ping Xie, T Iwakuma, R T James, Takayuki Hanazato, T YamamotoAbstract:We compared the Nutrient Dynamics of three lakes that have been heavily influenced by point and non-point source pollution and other human activities. The lakes, located in Japan (Lake Kasumigaura), People's Republic of China (Lake Donghu), and the USA (Lake Okeechobee), all are relatively large(>30 km(2)), very shallow (
Pierre Marmonier - One of the best experts on this subject based on the ideXlab platform.
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Nutrient Dynamics in river bed sediments: effects of hydrological disturbances using experimental flow manipulations
Journal of Soils and Sediments, 2013Co-Authors: Chafik Maazouzi, Cécile Claret, Marie-josé Dole-olivier, Pierre MarmonierAbstract:Purpose River sediments play a crucial role in the storage and transformation of organic matter (OM). Nutrient dy- namics are controlled by the interaction of several key parameters, i.e. river discharge, channel geometry and ver- tical exchanges of water (upwelling vs. downwelling zones). The main aim of this study was to evaluate the effect of channel forms and discharge variation on Nutrient spiralling in the hyporheic zone (HZ) of streams. Materials and methods Four experimental flow manipula- tions (EFM) were carried out at two reaches with different channel forms (straight vs. sinuous) in an oligotrophic sub- tropical river in Australia. Flow manipulation consisted of reducing the river width with a temporary dam, diverting and concentrating the main water flux on two different geomorphological units (riffle vs. gravel bar), in order to simulate flooding conditions. Hyporheic waters were ana- lysed for their physicochemical characteristics and Nutrient (nitrates + nitrites 0 NOx and soluble reactive phosphorus [SRP]) and OM contents at two depths (10 and 50 cm) within the bed sediments, both upstream and downstream of the geomorphological units. Results and discussion The physicochemical parameters clearly demonstrated the existence of hyporheic flow paths, characterized by the alternation of downwelling and upwell- ing areas, with more consistent gradients in gravel bars than in riffles. The HZ acted as source for NOx and SRP, but this role varied between geomorphological units and reaches. The effect of EFM differed between sampling points, irre- spective of the type of geomorphological unit. In gravel bars, a flush out during high discharge was observed for NOx, SRP and particulate organic matter (POM) at the sinuous channel, whereas storage and removal were recorded at the straight channel for SRP and NOx, respec- tively. At the riffle of the sinuous channel, very fine POM accumulated, while removal was noticed for POM. In con- trast, at the riffle of the straight channel, SRP accumulated in the HZ and NOx was removed out of the HZ. Conclusions Nutrient Dynamics in the HZ and the response to flow increases were not governed by the geomorphological unit type. Other parameters that determine water residence time in the sediments, such as local heterogeneity in sediment characteristics (grain size, porosity and hydraulic conductivi- ty), channel sinuosity, reach slope and the size and form of the gravel bar, may be more significant explanatory variables for understanding OM and Nutrient Dynamics in the HZ. This study emphasizes the need for caution in making generalisa- tions about the role of river sediment in Nutrient storage and the impact of floods on Nutrient Dynamics.
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Nutrient Dynamics in river bed sediments: effects of hydrological disturbances using experimental flow manipulations
Journal of Soils and Sediments, 2012Co-Authors: Chafik Maazouzi, Cécile Claret, Marie-josé Dole-olivier, Pierre MarmonierAbstract:Purpose River sediments play a crucial role in the storage and transformation of organic matter (OM). Nutrient Dynamics are controlled by the interaction of several key parameters, i.e. river discharge, channel geometry and vertical exchanges of water (upwelling vs. downwelling zones). The main aim of this study was to evaluate the effect of channel forms and discharge variation on Nutrient spiralling in the hyporheic zone (HZ) of streams.
Karl E Havens - One of the best experts on this subject based on the ideXlab platform.
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Nutrient Dynamics and the eutrophication of shallow lakes kasumigaura japan donghu pr china and okeechobee usa
Environmental Pollution, 2001Co-Authors: Karl E Havens, Noriko Takamura, Takehiko Fukushima, Ping Xie, T Iwakuma, R T James, Takayuki Hanazato, T YamamotoAbstract:We compared the Nutrient Dynamics of three lakes that have been heavily influenced by point and non-point source pollution and other human activities. The lakes, located in Japan (Lake Kasumigaura), People's Republic of China (Lake Donghu), and the USA (Lake Okeechobee), all are relatively large(>30 km(2)), very shallow (<4 m mean depth), and eutrophic. In all three lakes we found strong interactions among the sediments, water column, and human activities. Important processes affecting Nutrient Dynamics included nitrogen fixation, light limitation due to resuspended sediments, and intense grazing on algae by cultured fish. As a result of these complex interactions, simple empirical models developed to predict in-lake responses of total phosphorus and algal biomass to external Nutrient loads must be used with caution. While published models may provide 'good' results, in terms of model output matching actual data, this may not be due to accurate representation of lake processes in the models. The variable Nutrient Dynamics that we observed among the three study lakes appears to be typical for shallow lake systems. This indicates that a greater reliance on lake-specific research may be required for effective management, and a lesser role of inter-lake generalization than is possible for deeper, dimictic lake systems. Furthermore, accurate predictions of management impacts in shallow eutrophic lakes may require the use of relatively complex deterministic modeling tools. (C) 2000 Elsevier Science Ltd. All rights reserved.
-
Nutrient Dynamics and the eutrophication of shallow lakes Kasumigaura (Japan), Donghu (PR China), and Okeechobee (USA).
Environmental pollution (Barking Essex : 1987), 2001Co-Authors: Karl E Havens, Noriko Takamura, Takehiko Fukushima, Ping Xie, T Iwakuma, R T James, Takayuki Hanazato, T YamamotoAbstract:We compared the Nutrient Dynamics of three lakes that have been heavily influenced by point and non-point source pollution and other human activities. The lakes, located in Japan (Lake Kasumigaura), People's Republic of China (Lake Donghu), and the USA (Lake Okeechobee), all are relatively large(>30 km(2)), very shallow (
Chafik Maazouzi - One of the best experts on this subject based on the ideXlab platform.
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Nutrient Dynamics in river bed sediments: effects of hydrological disturbances using experimental flow manipulations
Journal of Soils and Sediments, 2013Co-Authors: Chafik Maazouzi, Cécile Claret, Marie-josé Dole-olivier, Pierre MarmonierAbstract:Purpose River sediments play a crucial role in the storage and transformation of organic matter (OM). Nutrient dy- namics are controlled by the interaction of several key parameters, i.e. river discharge, channel geometry and ver- tical exchanges of water (upwelling vs. downwelling zones). The main aim of this study was to evaluate the effect of channel forms and discharge variation on Nutrient spiralling in the hyporheic zone (HZ) of streams. Materials and methods Four experimental flow manipula- tions (EFM) were carried out at two reaches with different channel forms (straight vs. sinuous) in an oligotrophic sub- tropical river in Australia. Flow manipulation consisted of reducing the river width with a temporary dam, diverting and concentrating the main water flux on two different geomorphological units (riffle vs. gravel bar), in order to simulate flooding conditions. Hyporheic waters were ana- lysed for their physicochemical characteristics and Nutrient (nitrates + nitrites 0 NOx and soluble reactive phosphorus [SRP]) and OM contents at two depths (10 and 50 cm) within the bed sediments, both upstream and downstream of the geomorphological units. Results and discussion The physicochemical parameters clearly demonstrated the existence of hyporheic flow paths, characterized by the alternation of downwelling and upwell- ing areas, with more consistent gradients in gravel bars than in riffles. The HZ acted as source for NOx and SRP, but this role varied between geomorphological units and reaches. The effect of EFM differed between sampling points, irre- spective of the type of geomorphological unit. In gravel bars, a flush out during high discharge was observed for NOx, SRP and particulate organic matter (POM) at the sinuous channel, whereas storage and removal were recorded at the straight channel for SRP and NOx, respec- tively. At the riffle of the sinuous channel, very fine POM accumulated, while removal was noticed for POM. In con- trast, at the riffle of the straight channel, SRP accumulated in the HZ and NOx was removed out of the HZ. Conclusions Nutrient Dynamics in the HZ and the response to flow increases were not governed by the geomorphological unit type. Other parameters that determine water residence time in the sediments, such as local heterogeneity in sediment characteristics (grain size, porosity and hydraulic conductivi- ty), channel sinuosity, reach slope and the size and form of the gravel bar, may be more significant explanatory variables for understanding OM and Nutrient Dynamics in the HZ. This study emphasizes the need for caution in making generalisa- tions about the role of river sediment in Nutrient storage and the impact of floods on Nutrient Dynamics.
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Nutrient Dynamics in river bed sediments: effects of hydrological disturbances using experimental flow manipulations
Journal of Soils and Sediments, 2012Co-Authors: Chafik Maazouzi, Cécile Claret, Marie-josé Dole-olivier, Pierre MarmonierAbstract:Purpose River sediments play a crucial role in the storage and transformation of organic matter (OM). Nutrient Dynamics are controlled by the interaction of several key parameters, i.e. river discharge, channel geometry and vertical exchanges of water (upwelling vs. downwelling zones). The main aim of this study was to evaluate the effect of channel forms and discharge variation on Nutrient spiralling in the hyporheic zone (HZ) of streams.
João Coutinho - One of the best experts on this subject based on the ideXlab platform.
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Wood ash effects on Nutrient Dynamics and soil properties under Mediterranean climate
Annals of Forest Science, 2012Co-Authors: María Xesús Gómez-rey, Manuel Madeira, João CoutinhoAbstract:Aims This study aims to evaluate the effects of wood ash application on Nutrient Dynamics and soil properties of an acidic forest soil (Arenosol).
