LCKW

CHC is the abbreviation for L eichtflüchtige C hlorierte K ohlen w asserstoffe (or: Volatile chlorinated hydrocarbons ). These are derivatives of methane , ethane and ethene , in which hydrogen - atom by chlorine substituted -atoms. LCKW is less of a group of substances in the strict chemical sense, it is rather a term from environmental sciences, under which substances are summarized that have or had a comparable application-related meaning (solvents, etc.) that show a similar behavior in the environment (e.g. B. comparatively high volatility) and which can be analyzed together (e.g. headspace - gas chromatography ).

Single substances

Methane derivatives

• Chloromethane (CH ₃ Cl, common name: methyl chloride)
• Dichloromethane (CH ₂ Cl ₂ , common name: methylene chloride)
• Trichloromethane (CHCl ₃ , common name: chloroform)
• Tetrachloromethane (CCl ₄ , common name: carbon tetrachloride or tetra)

Derivatives of ethane

• Chloroethane (C ₂ H5Cl, common name: ethyl chloride)
• 1,2-dichloroethane (C ₂ H4Cl ₂ , common name: ethylene dichloride)
• 1,1,1-trichloroethane (C ₂ H ₃ Cl ₃ , common name: methyl chloroform)
• 1,1,2,2-tetrachloroethane (C ₂ H2Cl ₄ , common name: acetylene tetrachloride )

Derivatives of ethene

• Chlorethene (C ₂ H ₃ Cl, common name: vinyl chloride)
• 1,1-dichloroethene (C ₂ H2Cl ₂ , common name: vinylidene chloride)
• cis-1,2-dichloroethene (C ₂ H2Cl ₂ , common name: Cis)
• trans-1,2-dichloroethene (C ₂ H2Cl ₂ , common name: Trans)
• Trichlorethylene (C ₂ HCl ₃ , common name: trichlorethylene or tri)
• Tetrachlorethylene (C ₂ Cl ₄ , common name: Perchlorethylene or Per)

Use, production, education

There are / have been two main areas of application for volatile chlorinated hydrocarbons: They are starting materials for the production of plastics (chloromethane, 1,2-dichloroethane, chloroethene) and serve as solvents or cleaning agents (dichloromethane, 1,1,1-trichloroethane, trichloroethene, Tetrachlorethylene). The world production quantities in the 1980s were over 1000 kt / a, in Germany at 150 kt / a. The production volumes are falling. In Germany, the CFC-Halon Prohibition Ordinance and the Chemical Prohibition Ordinance stipulate prohibitions, production reductions or phase -out times for individual LCKW .

Individual CHCs can also unintentionally occur during combustion processes, e.g. B. PVC , arise or have been identified as natural metabolic products of marine algae, seaweed and terrestrial fungi. Trichloromethane can form during the chlorination of drinking water in the presence of humic acids. Chlorethene and the three isomers of dichloroethene can arise in the background of tri- and tetrachloroethene damage through reductive microbial dechlorination.

LCKW as environmental pollutants

The CHCs used as solvents and cleaning agents mostly evaporated into the atmosphere until well into the 1980s. Due to their long lifespan, LCKW can still be detected ubiquitously in the atmosphere today. In the past, large amounts of CHCs found their way into the subsurface through carelessness, improper handling, the depositing of waste containing CHCs (e.g. grinding, electroplating and oil sludge) or accidents. LCKW damage forms a separate category within the contaminated sites .

Individual evidence

1. ↑ Martin Bittens, Peter Grathwohl: LCKW - volatile chlorinated hydrocarbons . In: Soil-endangering substances: Evaluation - Material data - Ecotoxicology - Remediation . American Cancer Society, 2014, ISBN 978-3-527-67850-1 , pp. 1-26 , doi : 10.1002 / 9783527678501.bgs2004020 .
2. ↑ LCKW in groundwater: Danger from the past. Retrieved January 17, 2020 (English). ISBN 978-3-658-09248-1 .