大気中のハロカーボン,炭化水素,硫黄六フッ化物:世界の分布,発生源,沈殿地
まとめ
グローバルな大気測定は,フッ素炭素の滞在時間を明らかにし,シンクが欠けていないことを示しています. メチルクロロフォームムのデータは,より低いヒドロキシルラジカル濃度を示唆し,平流層のオゾン層を枯渇させる可能性を強調しています.
科学分野:
- 大気化学 大気化学
- 環境科学 環境科学
- オゾン層の研究 オゾン層の研究
背景:
- フッ素炭素-12やフッ素炭素-11のようなフッ素炭素は,大気中の重要な成分である.
- その分布と滞在時間を理解することは,大気モデリングとオゾン層の減少に関する研究にとって極めて重要です.
研究 の 目的:
- フルオロ炭素-12とフルオロ炭素-11の半球間交換率と大気中の滞在時間を決定する.
- 大気中のヒドロキシルラジカル (HO) 濃度とその分布を評価する.
- オゾン層を破壊する物質としてのメチルクロロフォームの役割を評価し,メチル塩化物の源を特定する.
主な方法:
- フッ素炭素-12およびフッ素炭素-11の世界的な分布データの分析.
- 大気中のメチルクロロフォームの測定.
- 観測データと大気モデルを比較する.
主要な成果:
- 酸化炭素の半球間為替レートを1年~1年半に設定した.
- フッ素炭素-12の65~70年,フッ素炭素-11の40~45年の大気中の滞在期間が決定されています.
- モデルによって予測されたより低いグローバル平均ヒドロキシルラジカル (HO) 濃度 (3-4 x 10^5分子/cm3) を示した.
- 北半球と比較して南半球でより高いHOレベルが観察されました.
- 大気中のメチル塩化物 (3 x 10^12 g/年) の主要な源泉として海洋を特定した.
結論:
- フッ素炭化水素の定着時間は,重要な欠落シンクを排除しています.
- メチルクロロフォームムの長期滞在時間と成長率は,平流層のオゾン層に潜在的な脅威をもたらす.
- 四塩化炭素の海洋沈殿地は重要ですが,平流圏沈殿地はより重要です.
- 海洋は大気中のメチル塩化物の主要な供給源である.
関連する概念動画
The Sulfur Cycle
Sulfur, an important element in the chemical makeup of proteins, is recycled through the atmosphere and aquatic and terrestrial environments. Found in the atmosphere as sulfur dioxide (SO2), sulfur is released by decaying organisms, weathered rocks, geothermal vents, volcanos, and burning fossil fuels. It is deposited into the ecosystem, cycled through the biotic community, and either released back into the atmosphere as gas or deposited in marine sediment for long-term storage and eventual...
Microbes and the Sulfur Cycle
Sulfur is a vital element in Earth's biogeochemical systems. It transitions through various inorganic states, including sulfate (SO₄²⁻), elemental sulfur (S⁰), and sulfide (S²⁻). Abiotic and biological mechanisms across oxic and anoxic environments intricately mediate these transformations. Sulfate, the most oxidized form of sulfur, is predominantly stored in rocks, marine sediments, and oceanic waters, acting as a long-term reservoir in the global sulfur cycle.In oxic environments,...
Microbes and Climate Change
Microorganisms are pivotal agents in Earth's biogeochemical cycles, significantly influencing climate dynamics through their metabolic activities. These microbes modulate the levels of key greenhouse gases by both contributing to and helping mitigate climate change.Microbial Contributions to Greenhouse Gas EmissionsRising global temperatures accelerate microbial metabolism, which, in turn, speeds up the decomposition of organic matter. This process releases carbon dioxide (CO₂) through...
The Carbon Cycle
Carbon is the basis of all organic matter on Earth, and is recycled through the ecosystem in two primary processes: one in which carbon is exchanged among living organisms, and one in which carbon is cycled over long periods of time through fossilized organic remains, weathering of rocks, and volcanic activity. Human activities, including increased agricultural practices and the burning of fossil fuels, has greatly affected the balance of the natural carbon cycle.
Global Climate Change
Throughout its ~4.5 billion year history, the Earth has experienced periods of warming and cooling. However, the current drastic increase in global temperatures is well outside of the Earth’s cyclic norms, and evidence for human-caused global climate change is compelling. Paleoclimatology, the study of ancient climate conditions, provides ample evidence for human-caused global climate change by comparing recent conditions with those in the past.
Alkyl Halides
Structural Properties
Alkyl halides are halogen-substituted alkanes wherein one or more hydrogen atoms of an alkane is replaced by a halogen atom such as fluorine, chlorine, bromine, or iodine. The carbon atom in an alkyl halide is bonded to the halogen atom, which is sp3-hybridized and exhibits a tetrahedral shape.
Unlike alkyl halides, compounds in which a halogen atom is bonded to an sp2 -hybridized carbon atom of a carbon-carbon double bond (C=C) are called vinyl halides. Whereas aryl...
Alkyl halides are halogen-substituted alkanes wherein one or more hydrogen atoms of an alkane is replaced by a halogen atom such as fluorine, chlorine, bromine, or iodine. The carbon atom in an alkyl halide is bonded to the halogen atom, which is sp3-hybridized and exhibits a tetrahedral shape.
Unlike alkyl halides, compounds in which a halogen atom is bonded to an sp2 -hybridized carbon atom of a carbon-carbon double bond (C=C) are called vinyl halides. Whereas aryl...


