Global distillation or the grasshopper effect is the

geochemical Geochemistry is the science that uses the tools and principles of chemistry to explain the mechanisms behind major geological systems such as the Earth's crust and its oceans. The realm of geochemistry extends beyond the Earth, encompassing the e ...

process by which certain chemicals, most notably persistent organic pollutants (POPs), are transported from warmer to colder regions of the Earth, 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 Ce ...

and mountain tops. Global distillation explains why relatively high concentrations of POPs have been found in the Arctic 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 distillations used to make

liquor Liquor (or a spirit) is an alcoholic drink produced by distillation of grains, fruits, vegetables, or sugar, that have already gone through alcoholic fermentation. Other terms for liquor include: spirit drink, distilled beverage or hard ...

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, some evaporates when ambient temperatures are warm, blows around on winds until temperatures are cooler, and then

condensation Condensation is the change of the state of matter from the gas phase into the liquid phase, and is the reverse of vaporization. The word most often refers to the water cycle. It can also be defined as the change in the state of water vapor to ...

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 and altitude. 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,

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 t ...

, 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 Bark may refer to: * Bark (botany), an outer layer of a woody plant such as a tree or stick * Bark (sound), a vocalization of some animals (which is commonly the dog) Places * Bark, Germany * Bark, Warmian-Masurian Voivodeship, Poland Arts, ...

have been shown to be greater in higher latitudes. The effect is also used to explain why certain

pesticides Pesticides are substances that are meant to pest control, control pest (organism), pests. This includes herbicide, insecticide, nematicide, molluscicide, piscicide, avicide, rodenticide, bactericide, insect repellent, animal repellent, microb ...

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 perform ...

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