Heavy phase

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In ecology, a heavy phase is a water-insoluble liquid with a greater density than water (ρ> 1), which is why the abbreviation DNAPL ( d ense n on a queous p hase l iquid) is used in Anglo-American parlance . Immiscible liquids lie on top of one another in clearly separated phases , e.g. B. water and oil.

Almost all chlorinated hydrocarbons (CHC) are such heavy phases and especially for the volatile representatives of the halogenated hydrocarbons (CHC), abbreviated as LHC , the DNAPL behavior plays an important role in connection with groundwater pollution.

Depending on the material properties and the nature of the soil, they reach the groundwater. The organic phases dissolve there, but at concentrations of a few 100 to a few 1,000 mg / l it takes decades to centuries. When dissolved in the water, the CHCs do not sink, but are spread more widely and, under certain environmental conditions, critical breakdown products such as vinyl chloride are created and accumulate.

In practice, DNAPL only seldom spreads into the rock below the groundwater bed and only penetrate more than 10 meters into the soil if large amounts of CHC are released. The horizontal spread is more massive and volatile halogenated hydrocarbons (CHC) seep permanently from the higher layers , resulting in a high contamination density. In addition, CHC phase bodies settle in the rock, which makes targeted removal impossible. The remedial measures are limited to procedures such as pump and treat , excavation or reactive systems.

The DNAPL behavior of the LCKW is largely responsible for their high groundwater pollution potential, as they spread only slowly and widely. In addition, they are difficult or even impossible to remove from the substrate. The groundwater can be polluted for decades or centuries.

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