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The hydrogen cycle consists of hydrogen exchanges between biotic (living) and abiotic (non-living) sources and sinks of hydrogen-containing compounds. Hydrogen (H) is the most abundant element in the universe. [1] On Earth, common H-containing inorganic molecules include water (H 2 O), hydrogen gas (H 2), hydrogen sulfide (H 2 S), and ammonia ...
Hydrogen (H) is the most abundant element in the universe. [38] On Earth, common H-containing inorganic molecules include water (H 2 O), hydrogen gas (H 2), methane (CH 4), hydrogen sulfide (H 2 S), and ammonia (NH 3). Many organic compounds also contain H atoms, such as hydrocarbons and organic matter.
The sulfur–iodine cycle (S–I cycle) is a series of thermochemical processes used to produce hydrogen. The S–I cycle consists of three chemical reactions whose net reactant is water and whose net products are hydrogen and oxygen. All other chemicals are recycled. The S–I process requires an efficient source of heat.
The diagram also shows how human water use impacts where water is stored and how it moves. [1] The water cycle (or hydrologic cycle or hydrological cycle) is a biogeochemical cycle that involves the continuous movement of water on, above and below the surface of the Earth. The mass of water on Earth remains fairly constant over time.
In most hydrogen-fusing stars, including the Sun, a chemical cycle involved in stellar nucleosynthesis occurs which is known as a carbon-nitrogen-oxygen or . In addition to this cycle, stars also have a helium cycle. [1] Various cycles involving gas and dust have been found to occur in galaxies. [2]
Photosynthesis in cyanobacteria and green algae splits water into hydrogen ions and electrons. The electrons are transported over ferredoxins. [19] Fe-Fe-hydrogenases (enzymes) combine them into hydrogen gas. In Chlamydomonas reinhardtii Photosystem II produces in direct conversion of sunlight 80% of the electrons that end up in the hydrogen ...
Shielding gas: Hydrogen is used as a shielding gas in welding methods such as atomic hydrogen welding. [164] [165] Cryogenic research: Liquid H 2 is used in cryogenic research, including superconductivity studies. [166] Buoyant lifting: Because H 2 is only 7% the density of air, it was once widely used as a lifting gas in balloons and airships ...
Isotope hydrology applications are highly diverse, and used for informing water-use policy, mapping aquifers, conserving water supplies, assessing sources of water pollution, investigating surface-groundwater interaction, refining groundwater flow models, and increasingly are used in eco-hydrology to study human impacts on all dimensions of the ...