نتایج جستجو برای: anoxic ocean
تعداد نتایج: 70018 فیلتر نتایج به سال:
in this study, oxic and anoxic microcosms were constructed with aquifer sediment collected from the vicinity of a municipal solid waste composting site.phenanthrene was used as a model pah compound. the changes of bacterial and archaeal communities in microcosms were characterized with terminal restriction fragment length polymorphism. 16s rrna gene clone library analysis was also used to inves...
Novel methods were developed for the determination of 12 of the 14 Rare Earth Elements (REE) in seawater. Initial extractions of the REE by chelating ion exchange chromatography is followed by cation exchange for removal of co-extracted U and remaining traces of major ions. Finally traces of U are removed by anion exchange before irradiation for 8 hours at a flux of 5 x 1013 neutrons.cm-2 .sec~...
G rasping the big picture of the early ocean used to be easy: no oxygen, and then oxygen. The crux of that popular model hinged on the almost universally accepted Great Oxidation Event, or GOE, during which appreciable free oxygen (O2) first accumulated in the atmosphere about 2.4 billion years ago. At the same time, as the old argument goes, the O2-free, iron-rich earlier ocean gave way to one...
The Oceanic Anoxic Event 2, at the Cenomanian-Turonian boundary (∼93.9 Ma), was an episode of widespread burial organic matter in marine sediments, underlined by a positive carbon-isotope (δ 13 C) excursion observed worldwide. Within this O 2 -depleted conditions, short interval cooling, termed as Plenus Cold Event, has been recorded many sites and sections northern hemisphere (Tethyan domain, ...
The early Toarcian (~183 Ma) was characterized by a prominent volcanism-induced warming event associated with massive addition of 12C-enriched carbon to the ocean-atmosphere system. This likely contributed marked ocean deoxygenation during this time, giving its name: Oceanic Anoxic Event (T-OAE). Although T-OAE has been recognized globally, clear geographic differences in character and environm...
Oceanic anoxic events (OAEs) are large-scale events of oxygen depletion in the deep ocean that happened during pre-Cenozoic periods of extreme warmth. Here, to assess the role of major continental configuration changes occurring during the Late Cretaceous on oceanic circulation modes, which in turn influence the oxygenation level of the deep ocean, we use a coupled ocean atmosphere climate mode...
The Ediacaran Period (635 to 542 million years ago) was a time of fundamental environmental and evolutionary change, culminating in the first appearance of macroscopic animals. Here, we present a detailed spatial and temporal record of Ediacaran ocean chemistry for the Doushantuo Formation in the Nanhua Basin, South China. We find evidence for a metastable zone of euxinic (anoxic and sulfidic) ...
Marine oxygen minimum zones (OMZs) are widespread regions of the ocean that are currently expanding due to global warming. While inhospitable to most metazoans, OMZs are hotspots for microbial mediated biogeochemical cycling of carbon, nitrogen and sulphur, contributing disproportionately to marine nitrogen loss and climate active trace gas production. Our current understanding of microbial com...
Oceanic Anoxic Event 2 (OAE 2), occurring ∼94 million years ago, was one of the most extreme carbon cycle and climatic perturbations of the Phanerozoic Eon. It was typified by a rapid rise in atmospheric CO2, global warming, and marine anoxia, leading to the widespread devastation of marine ecosystems. However, the precise timing and extent to which oceanic anoxic conditions expanded during OAE...
نمودار تعداد نتایج جستجو در هر سال
با کلیک روی نمودار نتایج را به سال انتشار فیلتر کنید