Global distillation or the grasshopper effect is the geochemical process by which certain chemicals, most notably

persistent organic pollutants Persistent organic pollutants (POPs), sometimes known as "forever chemicals", are organic compounds that are resistant to environmental degradation through chemical, biological, and photolytic processes. They are toxic chemicals that adversel ...

(POPs), are transported from warmer to colder regions of the

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...

, particularly the

poles Poles,, ; singular masculine: ''Polak'', singular feminine: ''Polka'' or Polish people, are a West Slavic nation and ethnic group, who share a common history, culture, the Polish language and are identified with the country of Poland in C ...

and mountain tops. Global distillation explains why relatively high concentrations of POPs have been found in the

Arctic The Arctic ( or ) is a polar region located at the northernmost part of Earth. The Arctic consists of the Arctic Ocean, adjacent seas, and parts of Canada (Yukon, Northwest Territories, Nunavut), Danish Realm (Greenland), Finland, Iceland, N ...

environment and in the bodies of animals and people who live there, even though most of the chemicals have not been used in the region in appreciable amounts.

Mechanism

The global distillation process can be understood using the same principles that explain

distillation Distillation, or classical distillation, is the process of separating the components or substances from a liquid mixture by using selective boiling and condensation, usually inside an apparatus known as a still. Dry distillation is the heat ...

s used to make liquor or purify chemicals in a laboratory. In these processes, a substance is vapourised at a relatively high temperature, and then the vapour travels to an area of lower temperature where it condenses. A similar phenomenon occurs on a global scale for certain chemicals. When these chemicals are released into

the environment The natural environment or natural world encompasses all living and non-living things occurring naturally, meaning in this case not artificial. The term is most often applied to the Earth or some parts of Earth. This environment encompasses t ...

, some evaporates when ambient temperatures are warm, blows around on winds until temperatures are cooler, and then condensation occurs. Drops in temperature large enough to result in deposition can occur when chemicals are blown from warmer to cooler climates, or when seasons change. The net effect is atmospheric transport from low to high

latitude In geography, latitude is a coordinate that specifies the north– south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from –90° at the south pole to 90° at the north pol ...

and

altitude Altitude or height (also sometimes known as depth) is a distance measurement, usually in the vertical or "up" direction, between a reference datum and a point or object. The exact definition and reference datum varies according to the context ...

. Since global distillation is a relatively slow process that relies on successive evaporation/condensation cycles, it is only effective for semi-volatile chemicals that break down very slowly in the environment, like

DDT Dichlorodiphenyltrichloroethane, commonly known as DDT, is a colorless, tasteless, and almost odorless crystalline chemical compound, an organochloride. Originally developed as an insecticide, it became infamous for its environmental impacts. ...

polychlorinated biphenyls Polychlorinated biphenyls (PCBs) are highly carcinogenic chemical compounds, formerly used in industrial and consumer products, whose production was banned in the United States by the Toxic Substances Control Act in 1979 and internationally by ...

, and

lindane Lindane, also known as ''gamma''-hexachlorocyclohexane (γ-HCH), gammaxene, Gammallin and benzene hexachloride (BHC), is an organochlorine chemical and an isomer of hexachlorocyclohexane that has been used both as an agricultural insecticide and ...

Effect of global distillation

Several studies have measured the effect, usually by correlating the concentrations of a certain chemical in air, water, or biological specimens from various parts of the world with the latitude from which the samples were collected. For example, the levels of PCBs,

hexachlorobenzene Hexachlorobenzene, or perchlorobenzene, is an organochloride with the molecular formula C6Cl6. It is a fungicide formerly used as a seed treatment, especially on wheat to control the fungal disease bunt. It has been banned globally under the Sto ...

, and lindane measured in water, lichens, and tree bark have been shown to be greater in higher latitudes. The effect is also used to explain why certain pesticides are found in Arctic and high altitude samples even though there is no agricultural activity in these areas, and why

indigenous peoples Indigenous peoples are culturally distinct ethnic groups whose members are directly descended from the earliest known inhabitants of a particular geographic region and, to some extent, maintain the language and culture of those original people ...

of the Arctic have some of the highest

body burden In analytical chemistry, biomonitoring is the measurement of the body burden of toxic chemical compounds, elements, or their metabolites, in biological substances. Often, these measurements are done in blood and urine. Biomonitoring is performe ...

s of certain POPs ever measured. Recent studies conclude that for most pollutants slower degradation in colder temperatures is a more important factor in accounting for their accumulation in cold region than global distillation. Exceptions include highly volatile, persistent substances such as

chlorofluorocarbon 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 pro ...

s.Fabio Bergamin:
The result of slow degradation
', ETH News, 2014.

References

External links

The Grasshopper Effect and Tracking Hazardous Air Pollutants
Environment Canada. {{Pollution Global environmental issues Environmental effects of pesticides Environment of the Arctic Pollution Air pollution

Mechanism

Effect of global distillation

See also

References

Further reading

External links