摘要:

A major parallel between soils and lake sediments is found in the role of microorganisms decomposing the organic substances. However, the two systems are not fully comparable: the typical horizons of land soil are lacking in sediments under water. Oligotrophic lake sediments differ in various aspects from the sediments in eutrophic lakes. Depending on the amount and type of organic substances provided, different processes of microbiological activity create major changes in redox potential, acidity, and biochemical changes, Mineralization, nitrification, denitrification, methane production, and sulfate reduction contribute to the geochemical situation of the lake sediment. The carbonate cycle, the formation of iron-manganese deposits, and the silica cycle in lakes are discussed in more detail. The calcium carbonate equilibrium is found to be largely controlled by microbial effects on carbon dioxide concentration. Formation of iron-manganese concretions takes place at the contact-surface between the reducing zone of the sediment and an upper oxidizing layer. Oxidation of the more soluble iron and manganese compounds into less soluble oxides takes place through the agency of various microbes. These microbes are found with the aid of a capillary technique only. The silica transported after weathering into the lakes was found to be in a complex association with organic substances; subsequent decomposition of these complexes by microorganisms leads to the precipitation of silica in the form of its polymers (opal, quartz).

ISSN:0038-075X    

出版商:OVID    

年代:1975

数据来源: OVID

摘要:

The vertical distribution of microbial adenosine triphosphate (ATP) was determined seasonally for sediments of the salt marsh at Sapelo Island, Georgia. Two study areas were chosen representing major differences in productivity of the marsh grass,Spartina alterniflora. The streamside zone represented an area of greater production ofS. alterniflorathan did the high marsh zone. In addition, differences in other features were noted.In all cases the concentration of ATP was greatest in the surface 1 cm and decreased with increasing depth. ATP varied seasonally in both regions. A comparison was made of the sediment organic carbon and total nitrogen within the sediments and the calculated carbon and nitrogen associated with the microbial community. The contribution of these elements within the microbial community is at most a few percent of the total pools. The surface sediment ATP values reported here are within the range of those for water-logged sediments from various diverse environments.

ISSN:0038-075X    

出版商:OVID    

年代:1975

数据来源: OVID

摘要:

Modern research on macromolecular humus has revealed the binding capacity of this type of humus towards heavy metal ions. While humic substances are active in the freeing and uptake of such metal ions from disintegrating rocks, deposition of these ions will result from the contact between the metal-humate complexes and microbially generated hydrogen sulfide. Such a process of deposition of metal sulfides in marine sediments could have been the main factor in the creation of certain geological so-called stratiform sulfide ore formations of considerable economic importance. In order to study the mechanisms involved in more detail, artificial metal-humates were made. Two types of natural humus (“aqua humus” and “sulfite humus”) were selected for their sorption capacity. Metal-humate complexes were made by adding pure metal powders in different quantities to various humus suspensions, while air was expelled by bubbling nitrogen gas through the flasks. After thorough contact the suspensions were filtered and measured for their metal concentrations with the aid of X-ray fluorescence. Metal sulfides were created by percolating hydrogen sulfide gas through the metal-humate suspensions under controlled circumstances. Precipitated metal sulfides were collected in media such as filter paper, glass beads, silica gel, quartz sand, porous glass, or clay. X-ray identification to the sulfides formed was employed. Unprecipitated metal humates were measured from the remaining suspensions with X-ray fluorescence analysis. Apart from conclusions in regard to the sorption mechanisms involved, conclusions on environmental factors required for this type of mineral deposition, as well as conclusions on morphological aspects of microscopic sulfide spherules (“framboidal textures”) found in recent and fossil marine sediments, are drawn from the laboratory observations described.

ISSN:0038-075X    

出版商:OVID    

年代:1975

数据来源: OVID

摘要:

Contained in this paper is detailed information on the analysis of accumulation and humification of organic material in marine and lagoonal sediments in various areas of the north-western Mediterranean Sea. Typical geographic and hydrodynamical conditions such as the absence of tides, sudden climatic variations, and discharge by low-water rivers and strong floods govern the geological situation. In contrast to the coastal and lagoonal sediments, the sediments of the open sea are only slowly accumulating without a major contribution by deposition and humification of organic substances. Abundant biological activity directly influencing the geochemical situation in the sediment takes place only in lagoons (such as the Etang de St. Nazaire and the Bages-Sigean complex), and certain parts of the coastal zone (including the Bay of Port Vendres, the Gulf of Marseille, and the Banyuls region). Geochemical analysis on carbon content, sulfur compounds present, nitrogen content, and humus characterization, as well as biomass estimation and bacterial counts from the investigated areas, are reported. Major biopedological factors involved were found to be temperature, presence or absence of oxygen, activity of benthic organisms, and concentration of organic matter. With increasing depths of burial, the biogeochemical alterations were found to slow down.

ISSN:0038-075X    

出版商:OVID    

年代:1975

数据来源: OVID