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Understanding the geochemical controls on how phosphorus (P), a limiting or co-limiting nutrient for plants and microorganisms in many ecosystems, adsorbs to iron (oxyhydr)oxides minerals (henceforth called Fe oxides) is vital to predict the bioavailability of P in a system. Orthophosphate (henceforth called phosphate), the major ion of P utilized by biota, binds strongly to Fe oxides and is removed from solution, decreasing its bioavailability. The ability of Fe oxides to adsorb phosphate and act as a geochemical control on phosphate bioavailability depends on the crystallinity and mineralogy of the Fe oxides. Changes in hydrology and resulting shifts in redox conditions, represented by field measurements of redox potential (Eh), can directly impact phosphate bioavailability by either dissolving Fe oxides and releasing phosphate or precipitating low crystallinity Fe oxides adsorbing phosphate. Additional importance of the interaction of Fe oxides and P is their impact on the stability of soil organic carbon (OC) in Arctic permafrost soils. Permafrost ecosystems store a significant amount (~60%) of the worlds soil OC that are vulnerable to emissions to the atmosphere with increasing permafrost thaw. As such I hypothesize that shifts in soil EH caused by climatic variations such as progressing permafrost thaw and will shift Fe speciation in soil towards low crystallinity Fe oxides, such as ferrihydrite, and increase the capacity of phosphate adsorption and over a longer time period decrease bioavailability of phosphate to microorganism stabilizing soil OC. In this dissertation, I investigate 1) how EH responds to hydrological change, 2) the impact of EH and Fe oxide mineralogy on Fe oxide dissolution and transformation, as well as 3) the resulting impact of changing Fe oxide mineralogy on phosphorus bioavailability to the system, and 4) the impact of thawing permafrost on soil EH and Fe crystallinity and speciation, and the resulting impact on phosphorus sorption to Fe oxides . Methods employed to address the above mentioned research goals included 1) continuous, high resolution measurements of EH with platinum electrodes, 2) sequential extractions to quantify extractable Fe and P in soils and in field-incubated minerals, and 3) x-ray absorption fine structure (XAFS) spectroscopy to evaluate changes in Fe speciation. In Chapter 2, I present research on how soil EH responds to hydrological change in and around a vernal pond . I show how Eh can vary within a small pond temporally and spatially, and how Fe reducing conditions can persist without surface water ponding. In Chapter 3 I describe how Fe oxide speciation evolves over time towards lower crystallinity in contrasting redox conditions at the same vernal pond as in Chapter 2. I also show how Fe oxides can retain phosphate and how freshly precipitated Fe oxides adsorb phosphate potentially reducing bioavailability of P. In Chapter 4 I show how Eh differs along a permafrost gradient in Sweden. I also show how Fe speciation shifts towards the poorly crystalline Fe oxide ferrihydrite as permafrost thaw progresses. Additionally, I show the strong association of P to Fe oxides along the permafrost gradient.
Elements move through Earth's critical zone along interconnected pathways that are strongly influenced by fluctuations in water and energy. The biogeochemical cycling of elements is inextricably linked to changes in climate and ecological disturbances, both natural and man-made. Biogeochemical Cycles: Ecological Drivers and Environmental Impact examines the influences and effects of biogeochemical elemental cycles in different ecosystems in the critical zone. Volume highlights include: Impact of global change on the biogeochemical functioning of diverse ecosystems Biological drivers of soil, rock, and mineral weathering Natural elemental sources for improving sustainability of ecosystems Links between natural ecosystems and managed agricultural systems Non-carbon elemental cycles affected by climate change Subsystems particularly vulnerable to global change The American Geophysical Union promotes discovery in Earth and space science for the benefit of humanity. Its publications disseminate scientific knowledge and provide resources for researchers, students, and professionals. Book Review: http://www.elementsmagazine.org/archives/e16_6/e16_6_dep_bookreview.pdf
Bioavailability refers to the extent to which humans and ecological receptors are exposed to contaminants in soil or sediment. The concept of bioavailability has recently piqued the interest of the hazardous waste industry as an important consideration in deciding how much waste to clean up. The rationale is that if contaminants in soil and sediment are not bioavailable, then more contaminant mass can be left in place without creating additional risk. A new NRC report notes that the potential for the consideration of bioavailability to influence decision-making is greatest where certain chemical, environmental, and regulatory factors align. The current use of bioavailability in risk assessment and hazardous waste cleanup regulations is demystified, and acceptable tools and models for bioavailability assessment are discussed and ranked according to seven criteria. Finally, the intimate link between bioavailability and bioremediation is explored. The report concludes with suggestions for moving bioavailability forward in the regulatory arena for both soil and sediment cleanup.
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"The history of Earth's early atmosphere, hydrosphere, and biosphere, from Hadean through Proterozoic time, is one of geology's enduring puzzles. Ore deposits provide important insights into this history because they contain elements and minerals that are highly sensitive to the geochemical environment in which they form. Just what these minerals tell us remains a matter of considerable debate, however. When and how did life develop, an oxygen-rich atmosphere form, and sulfate dominate the ocean? This volume contains reports on these questions from both sides of the aisle for iron and manganese formations, uranium paleoplacers and hydrothermal deposits, and exhalative sulfides and oxides."--Publisher's website.
Phosphorus (P) is a finite resource which is essential for life. It is a limiting nutrient in many ecosystems but also a pollutant which can affect biodiversity in terrestrial ecosystems and change the ecology of water bodies. This book collects the latest information on biological processes in soil P cycling, which to date have remained much less understood than physico-chemical processes. The methods section presents spectroscopic techniques and the characterization of microbial P forms, as well as the use of tracers, molecular approaches and modeling of soil-plant systems. The section on processes deals with mycorrhizal symbioses, microbial P solubilization, soil macrofauna, phosphatase enzymes and rhizosphere processes. On the system level, P cycling is examined for grasslands, arctic and alpine soils, forest plantations, tropical forests, and dryland regions. Further, P management with respect to animal production and cropping, and the interactions between global change and P cycling, are treated.
This comprehensive book provides an up-to-date and international approach that addresses the Motivations, Technologies and Assessment of the Elimination and Recovery of Phosphorus from Wastewater. This book is part of the Integrated Environmental Technology Series.
Alle relevanten Informationen zu Eisenoxiden, von der Struktur und Transformation über Charakterisierungsverfahren bis hin zu den neuesten AnwendungEN. Ein Muss für alle, die in dem Fachgebiet arbeiten.
V.3 ... consists of individual chapters that describe 1) the conceptual background for radionuclides, including tritium, radon, strontium, technetium, uranium, iodine, radium, thorium, cesium, plutonium-americium and 2) data requirements to be met during site characterization.
In this edition of the Long Term Ecological Research Network series, editors John Hobbie and George Kling and 58 co-authors synthesize the findings from the NSF-funded Arctic LTER project based at Toolik Lake, Alaska, a site that has been active since the mid-1970s. The book presents research on the core issues of climate-change science in the treeless arctic region of Alaska. As a whole, it examines both terrestrial and freshwater-aquatic ecosystems, and their three typical habitats: tundra, streams, and lakes. The book provides a history of the Toolik Lake LTER site, and discusses its present condition and future outlook. It features contributions from top scientists from many fields, creating a multidisciplinary survey of the Alaskan arctic ecosystem. Chapter topics include glacial history, climatology, land-water interactions, mercury found in the Alaskan arctic, and the response of these habitats to environmental change. The final chapter predicts the consequences that arctic Alaska faces due to global warming and climate change, and discusses the future ecology of the LTER site in the region. Alaska's Changing Arctic is the definitive scientific survey of the past, present, and future of the ecology of the Alaskan arctic.