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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

The Global Biogeochemical Cycle of Rhenium

Here, this paper is the first comprehensive synthesis of what is currently known about the different natural and anthropogenic fluxes of rhenium (Re) on Earth's surface. We highlight the significant role of anthropogenic mobilization of Re, which is an important consideration in utilizing Re in the context of a biogeochemical tracer or proxy. The largest natural flux of Re derives from chemical weathering and riverine transport to the ocean (dissolved = 62 × 10 6 g yr -1 and particulate = 5 × 10 6 g yr -1 ). This review reports a new global average [Re] of 16 ± 2 pmol L -1 , or 10 ± 1 pmol L -1 for the inferred pre-anthropogenic concentration without human impact, for rivers draining to the ocean. Human activity via mining (including secondary mobilization), coal combustion, and petroleum combustion mobilize approximately 560 × 10 6 g yr -1 Re, which is more than any natural flux of Re. There are several poorly constrained fluxes of Re that merit further research, including: submarine groundwater discharge, precipitation (terrestrial and oceanic), magma degassing, and hydrothermal activity. The mechanisms and the main host phases responsible for releasing (sources) or sequestrating (sinks) these fluxes remain poorly understood. This study also highlights the use of dissolved [Re] concentrations as a tracer of oxidation of petrogenic organic carbon, and stable Re isotopes as proxies for changes in global redox conditions.

58 GEOSCIENCES↗
DOE OSTI2025

Simulating Marine Ecosystem Dynamics and Biogeochemical Cycling With Multiple Plankton Functional Types

Current representations of marine ecosystems in Earth System Models are greatly simplified, neglecting key interactions between dynamic food webs, biogeochemistry, and climate change. We use the Marine Biogeochemistry Library code base within the Community Earth System Model 2.2.2 to create an expanded ecosystem model with eight phytoplankton groups and four zooplankton size classes (MARBL-8P4Z). Incorporating more specific plankton types and size classes has the potential to capture a wider range of possible behaviors of the ecosystem, its complex interactions with biogeochemistry, and its feedback to climate change. It also permits stronger observational constraints, including in situ group-specific biomass and various observational estimates of plankton community composition. MARBL-8P4Z broadly captures observed global-scale patterns in biomass and community composition for both phytoplankton and zooplankton, with a good performance in simulating broad biogeochemistry fields. The model shows comparable spatial patterns and magnitudes to the observed picophytoplankton biomass (Prochlorococcus, Synechococcus, picoeukaryotes), and captures the seasonal cycle of mesozooplankton biomass. Picophytoplankton groups and microzooplankton dominate biomass and production in oligotrophic, subtropical regions, while nano-phytoplankton, diatoms and the larger zooplankton groups prevail at higher latitudes and within upwelling zones. The model simulates reasonable energy transfer efficiency through the food web, with tight linkages between the phytoplankton community composition, zooplankton grazing, and carbon export, with the potential to link to fisheries models. Thus, MARBL-8P4Z has the potential to account for key climate-driven ecological shifts in the plankton that will modify ocean biogeochemistry in the future.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1984

Inland Aquatic Resources and Biogeochemical Cycles

The biosphere is the entire planetary system that includes, sustains and is influenced by life. The central issue of the science of the biosphere is the extent to which the Earth's surface, atmosphere and hydrosphere is the result of biological rather than abiotic processes. Space science and technology accelerates the understanding of global biological processes by providing repetive synoptic observations on large spatial scales once the relationships between the processes and the remotely sensed quantities are established. Especially promising applications of space technology are the measurement of biological productivity and portions of geochemical cycles in aquatic ecosystems and the evaluation and management of the quality of freshwater resources.

Melack, J. M.↗
NASA NTRS1984

Biogeochemical cycles: Interactions in global metabolism

A science that chooses the globe as it fundamental biogeophysical unit forces extraordinary conceptual difficulties. The roles of energy flow, matter cycles, carbon cycle, air pollution, global effects, air water interactions are discussed.

Moore, B., III↗
NASA NTRS1984

Global biogeochemical cycles: Studies of interaction and change, some views on the strategy of approach

The global biosphere is an exceedingly complex system. To gain an understanding of its structure and dynamic features, it is necessary to increase knowledge about the detailed processes, but also to develop models of how global interactions take place. Attempts to analyze the detailed physical, chemical and biological processes need, in this context, to be guided by an advancement of understanding of the latter. It is necessary to develop a strategy of data gathering that serves both these purposes simultaneously. climate research during the last decade may serve as a useful example of how to approach this difficult problem in a systematic way. Large programs for data collection may easily become rigid and costly. While realizing the necessity of a systematic and long lasting effort of observing the atmosphere, the oceans, land and life on Earth, such a program must remain flexible enough to permit the modifications and even sometimes improvisations that are necessary to maintain a viable program.

Bolin, B.↗
NASA NTRS1991

Terrestrial biogeochemical cycles - Global interactions with the atmosphere and hydrology

A review is presented of developments in ecosystem theory, remote sensing, and geographic information systems that support new endeavors in spatial modeling. A paradigm has emerged to predict ecosystem behavior based on understanding responses to multiple resources. Ecosystem models couple primary production to decomposition and nutrient availability utilizing this paradigm. It is indicated that coupling of transport and ecosystem processes alters the behavior of earth system components (terrestrial ecosystems, hydrology, and the atmosphere) from that of an uncoupled model.

Schimel, David S.↗
NASA NTRS1993

Biogeochemical cycles of carbon, sulfur, and free oxygen in a microbial mat

Complete budgets for carbon and oxygen have been constructed for cyanobacterial mats dominated by Microcoleus chthonoplastes from the evaporating ponds of a salt works. We infer from the data the various sinks for O2 as well as the sources of carbon for primary production. Although seasonal variability exists, a major percentage of the O2 produced during the day did not diffuse out of the mat but was used within the mat to oxidize both organic carbon and the sulfide produced by sulfate reduction. At night, most of the O2 that diffused into the mat was used to oxidize sulfide, with O2 respiration of minor importance. During the day, the internal mat processes of sulfate reduction and O2 respiration generated as much or more inorganic carbon (DIC) for primary production as diffusion into the mat. Oxygenic photosynthesis was the most important process of carbon fixation. At night, the DIC lost from the mat was mostly from sulfate reduction. Elemental fluxes across the mat/brine interface indicated that carbon with an oxidation state of greater than zero was taken up by the mat during the day and liberated from the mat at night. Overall, carbon with an average oxidation state of near zero accumulated in the mat. Both carbon fixation and carbon oxidation rates varied with temperature by a similar amount.

Canfield, Donald E.↗
NASA NTRS1998

Biogeochemical cycling of manganese in Oneida Lake, New York: whole lake studies of manganese

Oneida Lake, New York is a eutrophic freshwater lake known for its abundant manganese nodules and a dynamic manganese cycle. Temporal and spatial distribution of soluble and particulate manganese in the water column of the lake were analyzed over a 3-year period and correlated with other variables such as oxygen, pH, and temperature. Only data from 1988 are shown. Manganese is removed from the water column in the spring via conversion to particulate form and deposited in the bottom sediments. This removal is due to biological factors, as the lake Eh/pH conditions alone can not account for the oxidation of the soluble manganese Mn(II). During the summer months the manganese from microbial reduction moves from the sediments to the water column. In periods of stratification the soluble Mn(II) builds up to concentrations of 20 micromoles or more in the bottom waters. When mixing occurs, the soluble Mn(II) is rapidly removed via oxidation. This cycle occurs more than once during the summer, with each manganese atom probably being used several times for the oxidation of organic carbon. At the end of the fall, whole lake concentrations of manganese stabilize, and remain at about 1 micromole until the following summer, when the cycle begins again. Inputs and outflows from the lake indicate that the active Mn cycle is primarily internal, with a small accumulation each year into ferromanganese nodules located in the oxic zones of the lake.

NASA Discipline Exobiology↗
NASA NTRS1995

Terminal Proterozoic reorganization of biogeochemical cycles

The Proterozoic aeon (2,500-540 million years ago) saw episodic increases in atmospheric oxygen content, the evolution of multicellular life and, at its close, an enormous radiation of animal diversity. These profound biological and environmental changes must have been linked, but the underlying mechanisms have been obscure. Here we show that hydrocarbons extracted from Proterozoic sediments in several locations worldwide are derived mainly from bacteria or other heterotrophs rather than from photosynthetic organisms. Biodegradation of algal products in sedimenting matter was therefore unusually complete, indicating that organic material was extensively reworked as it sank slowly through the water column. We propose that a significant proportion of this reworking will have been mediated by sulphate-reducing bacteria, forming sulphide. The production of sulphide and consumption of oxygen near the ocean surface will have inhibited transport of O2 to the deep ocean. We find that preservation of algal-lipid skeletons improves at the beginning of the Cambrian, reflecting the increase in transport by rapidly sinking faecal pellets. We suggest that this rapid removal of organic matter will have increased oxygenation of surface waters, leading to a descent of the O2-sulphide interface to the sea floor and to marked changes in the marine environment, ultimately contributing to the Cambrian radiation.

Non-NASA Center↗
NASA NTRS2009

Using Coupled Models to Study the Effects of River Discharge on Biogeochemical Cycling and Hypoxia in the Northern Gulf of Mexico

We describe emerging capabilities to understand physical processes and biogeoehemical cycles in coastal waters through the use of satellites, numerical models, and ship observations. Emerging capabilities provide significantly improved ability to model ecological systems and the impact of environmental management actions on them. The complex interaction of physical and biogeoehemical processes responsible for hypoxic events requires an integrated approach to research, monitoring, and modeling in order to fully define the processes leading to hypoxia. Our efforts characterizes the carbon cycle associated with river plumes and the export of organic matter and nutrients form coastal Louisiana wetlands and embayments in a spatially and temporally intensive manner previously not possible. Riverine nutrients clearly affect ecosystems in the northern Gulf of Mexico as evidenced in the occurrence of regional hypoxia events. Less known and largely unqualified is the export of organic matter and nutrients from the large areas of disappearing coastal wetlands and large embayments adjacent to the Louisiana Continental Shelf. This project provides new methods to track the river plume along the shelf and to estimate the rate of export of suspended inorganic and organic paniculate matter and dissolved organic matter form coastal habitats of south Louisiana.

COUPLED MODEL↗
NASA NTRS1983

Earth Observing System, Introduction

Much is known about the Earth, but the unifying concepts are still only beginning to be established. An exposition of the key issues in Earth science is neither simple or concise. From the scientific questions at hand there are many interconnections among them and the view of the Earth as a system is essential to their solution. The Earth science goals for the 1990's are presented for the following areas: hydrologic cycle; biogeochemical cycles; climatological processes; geophysical processes; oceanography; and solid earth.

Source record↗
NASA NTRS1985

Nasa's Land Remote Sensing Plans for the 1980's

Research since the launch of LANDSAT-1 has been primarily directed to the development of analysis techniques and to the conduct of applications studies designed to address resource information needs in the United States and in many other countries. The current measurement capabilities represented by MSS, TM, and SIR-A and B, coupled with the present level of remote sensing understanding and the state of knowledge in the discipline earth sciences, form the foundation for NASA's Land Processes Program. Science issues to be systematically addressed include: energy balance, hydrologic cycle, biogeochemical cycles, biological productivity, rock cycle, landscape development, geological and botanical associations, and land surface inventory, monitoring, and modeling. A global perspective is required for using remote sensing technology for problem solving or applications context. A successful model for this kind of activity involves joint research with a user entity where the user provides a test site and ground truth and NASA provides the remote sensing techniques to be tested.

Higg, H. C.↗
NASA NTRS1989

Mission to Planet Earth - The Earth Observing System

The Earth Observing System (EOS) is a major component of NASA's Mission to Planet Earth initiative. It seeks to achieve a comprehensive understanding of the earth as a system, including its various components (solid earth, atmosphere, hydrosphere, and biosphere) and its various processes (hydrologic cycle, biogeochemical cycles, and climatic processes). This is to be achieved by space-based remote sensing, using a variety of instrumentation and observing techniques, operating simultaneously, and providing continuous and complete global coverage over a long time period. A few of the investigations to be carried out with EOS, in areas of (1) imagery of the earth from space, and (2) investigations of the earth's radiation budget are described. EOS is expected to make major contributions to the basic earth sciences (geology, meteorology, etc.), but its results also will have important immediate or near-term practical applications which will improve the quality of life on earth.

Carruthers, George R.↗
NASA NTRS1985

Phototrophic bacteria and their role in the biogeochemical sulfur cycle

An essential step that cannot be bypassed in the biogeochemical cycle of sulfur today is dissimilatory sulfate reduction by anaerobic bacteria. The enormous amounts of sulfides produced by these are oxidized again either anaerobically by phototrophic bacteria or aerobically by thiobacilli and large chemotrophic bacteria (Beggiatoa, Thiovulum, etc.). Phototrophic bacteria use sulfide, sulfur, thiosulfate, and sulfite as electron donors for photosynthesis. The most obvious intermediate in their oxidative sulfur metabolism is a long chain polysulfide that appears as so called sulfur globules either inside (Chromatiaceae) or outside (Ectothiorhodospiraceae, Chlorobiaceae, and some of the Rhodospirillaceae) the cells. The assimilation of sulfur compounds in phototrophic bacteria is in principle identical with that of nonphototrophic bacteria. However, the Chlorobiaceae and some of the Chromatiaceae and Rhodospirillaceae, unable to reduce sulfate, rely upon reduced sulfur for biosynthetic purposes.

Trueper, H. G.↗
NASA NTRS1984

Earth Observing System. Volume 1, Part 2: Science and Mission Requirements. Working Group Report Appendix

The Earth Observing System (EOS) is a planned NASA program, which will carry out multidisciplinary Earth science studies employing a variety of remote sensing techniques in the 1990's, as a prime mission, using the Space Station polar platform. Its primary goal is the generation of long term Earth science data sets of measurements and processes in the areas of agriculture, forestry, geology, hydrology, oceanography, snow and ice, troposphere and upper atmospheric chemistry, radiation and dynamics pertaining to global studies of Earth as a system, emphasizing the interactions and couplings of the atmospbere-ocean-land-cryosphere system. These results will provide the information needed to qualify our understanding of the global hydrological cycle, global biogeochemical cycles and global climate processes. This report provides the science rationale, recommended observational needs, the broad system configuration and a recommended implementation strategy to achieve the stated mission goals. The report is one volume of a proposed five volume set constituting the Phase A report as the Earth Observing System (EOS).

Goddard Space Flight Center↗
NASA NTRS1984

Integrated remote sensing of the earth from low earth orbit in the 1990's

Trends in the areas of science, data systems, instruments and space technologies and their related infrastructures that will be experienced in earth remote sensing activities from LEO in the 1990s are discussed. Interdisciplinary studies will examine the flow of energy through the earth system, encompassing surveys of atmospheric and ocean circulations, the hydrologic cycle, and biogeochemical cycles. Mainframe computer assimilation of large data inputs will be associated with distributed microcomputer processing and analyses. Single satellite antennas will scan several microwave frequencies simultaneously, e.g., taking data on vegetation, water, and ice. Broadening the range of simultaneous observations will require multiinstrumented free-flying platforms, placed in orbit, repaired and/or retrieved by the Shuttle. Future instrumentation will include visible/IR imagers and the multifrequency microwave sounders with capabilities mainly limited by the availability of sufficient data-handling facilities.

Butler, D. M.↗