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Chlorofluorocarbons ( CFCs) and hydrochlorofluorocarbons ( HCFCs) are fully or partly halogenated hydrocarbons that contain carbon (C), hydrogen (H), chlorine (Cl), and fluorine (F), produced as volatile derivatives of methane, ethane, and propane . The most common example is dichlorodifluoromethane (R-12). R-12 is also commonly called Freon ...
t. e. Ozone depletion consists of two related events observed since the late 1970s: a steady lowering of about four percent in the total amount of ozone in Earth's atmosphere, and a much larger springtime decrease in stratospheric ozone (the ozone layer) around Earth's polar regions. [1] The latter phenomenon is referred to as the ozone hole.
Only methyl chloride, which is one of the halocarbons, has a mainly natural source, [36] and it is responsible for about 20% of the chlorine in the stratosphere; the remaining 80% comes from man-made sources. [37] Chlorofluorocarbons, in contrast, are insoluble and long-lived, allowing them to reach the stratosphere.
The ozone– oxygen cycle is the process by which ozone is continually regenerated in Earth 's stratosphere, converting ultraviolet radiation (UV) into heat. In 1930 Sydney Chapman resolved the chemistry involved. The process is commonly called the Chapman cycle by atmospheric scientists. Most of the ozone production occurs in the tropical ...
Ozone layer. The ozone layer visible from space at Earth's horizon as a blue band of afterglow within the bottom of the large bright blue band that is the stratosphere, with a silhouette of a cumulonimbus in the orange afterglow of the troposphere. The ozone layer or ozone shield is a region of Earth 's stratosphere that absorbs most of the Sun ...
Deforestation is a major source of greenhouse gas emissions. A study shows annual carbon emissions (or carbon loss) from tropical deforestation have doubled during the last two decades and continue to increase. (0.97 ±0.16 PgC per year in 2001–2005 to 1.99 ±0.13 PgC per year in 2015–2019) [137] [136]
The five most abundant greenhouse gases in Earth's atmosphere, listed in decreasing order of average global mole fraction, are: [ 5 ][ 6 ] water vapor, carbon dioxide, methane, nitrous oxide, ozone. Other greenhouse gases of concern include chlorofluorocarbons (CFCs and HCFCs ), hydrofluorocarbons (HFCs), perfluorocarbons, SF6, and NF3.
Groundwater pollution (also called groundwater contamination) occurs when pollutants are released to the ground and make their way into groundwater.This type of water pollution can also occur naturally due to the presence of a minor and unwanted constituent, contaminant, or impurity in the groundwater, in which case it is more likely referred to as contamination rather than pollution.