Phosphorus and Iron Content, Redox Potential and Phosphorus Fractionation of Lake Sediment-water Interfaces PDF Download
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Author: Dennis Byron Fenn
Publisher:
ISBN:
Category : Phosphorus
Languages : en
Pages : 148
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Author: Dennis Byron Fenn
Publisher:
ISBN:
Category : Phosphorus
Languages : en
Pages : 148
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Author: Md Abdus Sabur
Publisher:
ISBN:
Category : Biogeochemical cycles
Languages : en
Pages : 206
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Book Description
Internal phosphorus loads, from bottom sediments to surface waters, are often comparable in magnitude to external phosphorus loads, particularly in water bodies with a history of high external phosphorus inputs from point and non-point sources. The benthic release of phosphorus can be influenced by several factors including pH, redox potential, temperature, microbial activity and the concentration of competitive anions at or near the sediment-water interface. Dissolved silicate occurs ubiquitously in natural waters and may act as a competitive ion to phosphate. Nonetheless, prior to the work in this thesis, the effect of silicate on internal phosphorus loading remained poorly understood. This thesis addresses several of the mechanisms through which silicate may influence the mobilization of aqueous phosphate from sediments in aquatic environments. The thesis starts with a thorough literature review of phosphorus biogeochemical cycling in relation to eutrophication, sediment-surface water interactions, mineralogy, competitive anions and microbial activity (Chapter 1). Next, adsorption/desorption of phosphate on/from goethite, a model ferric (hydr)oxide mineral, is investigated in the absence and presence of dissolved silicate. The influence of dissolved silicate on phosphate adsorption is evaluated through laboratory experiments and application of the CD-MUSIC model (Chapter 2). The results show that increasing concentrations of silicate decrease phosphate adsorption, leaving more phosphate in the aqueous phase. The competitive effect of dissolved silicate is more pronounced under alkaline conditions. Subsequently, phosphate desorption experiments were conducted under dynamic pH conditions in the presence and absence of silicate (Chapter 3). The experimental results show that the gradual transition from acidic to alkaline conditions induces the desorption of phosphate adsorbed to goethite under acidic conditions. The presence of silicate in the phosphate/goethite system does not affect phosphate desorption, because of the stronger surface complexation of phosphate to goethite. In addition to adsorption and desorption processes, the co-precipitation of phosphate with iron and the potential subsequent dissolution of these co-precipitates as a result of changing physico-chemical conditions may also control the mobility of phosphate in aquatic environments. The effects of dissolved silicate on the co-precipitation of phosphate with iron and the reactivity of the resulting solids are examined (Chapter 4). Ferric (co)-precipitates (i.e., Fe-P-Si) with variable Si:Fe ratios, were synthesized either via oxidation of Fe2+(aq) or by increasing the pH of Fe3+(aq) solution. The solids were characterized by a combination of chemical and spectroscopic techniques including attenuated total internal reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray powder diffraction spectroscopy (XRD). Similar solid phase P:Fe ratios were found in co-precipitates formed from solutions with different dissolved silicate concentrations, regardless of the method of preparation. This suggests that the interactions between phosphate and iron during co-precipitation were not affected by dissolved silicate. The ferric (co)-precipitates were subsequently reductively dissolved abiotically in buffered ascorbate-citrate solution to determine their reactivity under reducing conditions. The kinetic data show that the co-precipitates with higher Si:Fe ratios were more recalcitrant to dissolution. For co-precipitates synthesized via oxidation of Fe2+(aq), reductive dissolution experiments were also conducted in the presence of the facultative anaerobic iron reducing bacteria Shewanella putrefaciens. XRD analyses of the residual solids imply that solids with the higher Si:Fe ratios may be more resistant to microbially mediated reductive dissolution. The relative reactivities of the co-precipitates obtained by the two synthesis methods are also addressed in Chapter 4. In Chapter 5, the effect of silicate on the mobility of phosphate in a natural sediment was evaluated via flow-through experiments. The results show that dissolved silicate enhances the mobility of phosphate at the sediment-water interface. Ferric (co)-precipitates were formed at the oxic surface of sediment columns via the oxidation of ferrous iron supplied with upflowing solutions containing variable silicate concentrations. The subsequent dissolution of these co-precipitates under imposed anoxic conditions at the sediment-water interface indicates that the co-precipitates formed at higher dissolved silicate concentrations were more reactive towards reductive dissolution. These results are therefore in apparent contradiction to those observed in Chapter 4. The ferric (co)-precipitates (i.e., Fe-P-Si) evaluated in Chapter 4 were prepared from solutions containing high concentrations of iron, phosphate and silicate, by imposing either rapid aeration or pH increase. These conditions were selected to maximize the yield from the syntheses. The synthesis methods in Chapter 4 are therefore most representative of aquatic environments where co-precipitation occurs rapidly (e.g., groundwater springs) and the concentrations of these dissolved constituents are fairly high. However, in many other aquatic environments, the diffusion-controlled release of Fe2+(aq) from the deeper sediments results in the gradual oxidation of Fe2+ at the sediment-water interface under oxic conditions. This process is typical in lake sediments with minimal advective exchange between surface water and groundwater. This gradual oxidation (at relatively low concentrations of Fe2+) results in the slow formation of ferric (co)-precipitates which may be dissimilar to those synthesized herein and discussed in Chapter 4. The ferric (co)-precipitates synthesized with the flow-through column system in Chapter 5 may be better analogues of slow forming co-precipitates in diffusion dominated or moderately advection influenced aquatic sediments than those synthesized in Chapter 4. Finally, to elucidate the likely importance of the various influences of dissolved silicate on phosphate mobility investigated in this thesis, concentrations of dissolved phosphate and silicate as well as pH data are extracted from the US National Water Information System (NWIS) network (data shown in Chapter 1 and Chapter 2). The NWIS data along with combined experimental and modeling results suggest that silicate-mediated phosphate mobilization is likely a commonly occurring process at the sediment-water interface of lakes and reservoirs. This thesis also demonstrates the multiple roles of silicate on the mobilization of phosphate in aquatic environments, and improves our fundamental knowledge of iron, phosphorus and silicon cycling in freshwater environments.
Author: Shengrui Wang
Publisher: Springer
ISBN: 9811007217
Category : Science
Languages : en
Pages : 187
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This book focuses on the development of DGT (diffusive gradients in thin films) and the related techniques for measuring and investigating the geochemical process and P transfer across the sediment/water or sediment/root interface in lakes. A series of DGT techniques such as new types of probes, test methods in sediment or the rhizosphere, DIFS (DGT induced fluxes in sediments and soils) model for kinetic P exchange, CID (computer imaging densitometry) for S(-II), and microchelex gel/LA-ICP-MS (laser ablation inductively coupled plasma mass spectrometry) have been developed. The corresponding chapters on the theory and methodology of DGT, the “internal P loading” or P transfer across sediment/root in two lakes, provide insights into the research method and conclusions, including the P release mechanism, the quantification of “internal P loading”, kinetic P exchange in DGT/sediment interface, Fe- or S(-II)-microniches at submillimeter scales in sediments for the prediction of P release, and DGT as a surrogate for the prediction of P uptake by roots. It also offers new perspectives in the fields of P analysis and P process in micro-interfaces in lakes using DGT techniques. The P remobilization from Fe-bound P, the coupled Fe-S(-II)-P geochemical reaction and algae biomass breakdown causing P release, are elucidated using DGT methods in sediment layers. DGT parameters and curves for time or distance derived from DIFS can be used to assess kinetic P release in the sediment microzone. CID and LA-ICP-MS methods deliver Fe- and S(-II) images at submillimeter scales, which can be used for the quantification of flux related to microniche peaks and the prediction of P release from Fe-microniche or Fe-S(-II)-P geochemical reactions. DGT measurements in-situ in rhizosphere or rhizonbox can give CE (effective concentration) and CDGT values for the prediction of P accumulated in plant tissues. This book provides a valuable reference resource for senior graduate students, lecturers and researchers in the fields of the geochemical process of eutrophic elements in lakes, lake eutrophication mechanism and environmental analysis.
Author: Gertrud K. Nürnberg
Publisher: CRC Press
ISBN: 1040133681
Category : Science
Languages : en
Pages : 299
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Book Description
This book explores the interconnections of internal phosphorus loading, cyanobacteria, and climate change and their role in determining water quality in freshwater. It goes on to discuss the sometimes elusive process of internal phosphorus loading with its chemical and biological roots. Reviewing recent observations on present and future climate change, the book explores its effects on lake functioning. It concludes with the abatement and prevention of cyanobacteria proliferation, including techniques that deal with internal phosphorus loading. Some key topics covered are: In-depth exploration of internal phosphorus loading and its quantification in global lakes with diverse morphometry, hydrology, geochemistry, and degree of eutrophication. Determination of climate change effects on physical, chemical, and cyanobacteria-related variables in tables based on more than 100 reviewed journal articles. Evidence for the enhancing influences of climate change on internal phosphorus load and cyanobacteria, and of internal load on cyanobacteria. This book will be of interest to limnologists, environmental and engineering professionals, and natural science students. It will also be an interesting read to government agents, lake managers, and others interested in maintaining lake water quality and understanding algal blooms.
Author: Renato Baudo
Publisher: CRC Press
ISBN: 1000724212
Category : Science
Languages : en
Pages : 432
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Book Description
This important volume-the product of a meeting of a select group of scientists-provides the most recent research results from the world's leaders in the study of toxic pollutants in sediments. It gives practical information on measuring and mapping distributions of concentrations of pollutants and their toxic effects in sediments. Also covered are the use and relative advantages and disadvantages of benthic chambers, sedimentation traps, box corers, "peepers" and other sampling techniques in sediment research and assessment. Important topics covered include: bioassay, elemental speciation, diffuse source problems, nutrient flux, biomethylation, bioavailability, and toxicity assessment. Will help in assessment and monitoring of chemistry, dynamics, bioavailability, and toxicity of pollutants, as well helping to chart courses for remedial action. This book will be of interest to anyone interested in the processes controlling the chemistry and movement of pollutants in sediments, especially: limnologists aquatic toxicologists engineers lake managers ecologists biologists environmental chemists
Author: North American Lake Management Society. Conference
Publisher:
ISBN:
Category : Eutrophication
Languages : en
Pages : 406
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Author: Robert G. Wetzel
Publisher: Gulf Professional Publishing
ISBN: 0127447601
Category : Nature
Languages : en
Pages : 1023
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Book Description
This book gives a comparative treatment of topics accross lake, reservoir, and rive ecosystems. These analysis do indeed indicate differences among the properties of lakes, land-water interface regions, reservoirs, and rivers. Importantly, these analysis also indicate marked commonality in function.
Author: Ian D. Jones
Publisher: Elsevier
ISBN: 0128227109
Category : Science
Languages : en
Pages : 1105
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Book Description
Wetzel's Limnology: Lake and River Ecosystems, Fourth Edition, presents a fully updated revision of the classic textbook Limnology: Lake and River Ecosystems - last published in 2001. The coverage has been thoroughly updated with recent research and theoretical developments. Each chapter of this edited volume has been written by an expert, or team of experts, providing a comprehensive and global perspective, with the editors working closely with the authors to maintain continuity within and between the chapters. This is not only an essential textbook for undergraduate and graduate students in limnology but also a standard reference book for seasoned limnologists and other scientists. - Chapters from the third edition have been updated by an international team of experts, incorporating developments from the past two decades - Several new chapters have been added, reflecting exciting developments in the field of limnology - New color illustrations and images throughout - Detailed summaries at the end of each chapter
Author: Roger T. Bannerman
Publisher:
ISBN:
Category : Lake sediments
Languages : en
Pages : 68
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Author: Raymond E. Wildung
Publisher:
ISBN:
Category : Eutrophication
Languages : en
Pages : 218
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Book Description
