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Environmental fate & pathways

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Trichloroethane environmental distribution models predicted that the bulk >99% of the material released into the environment will make its way into the atmosphere. Levels in the aquatic environment are predicted to be of the order of <0.25% and in soil and sediment <0.01% as the material rapidly volatilises from both water and soil. The Henry's Law constant is 3.47 indicating that the material is highly volatile with a Kaw of -0.03 to -0.17. In practical terms because of the materials ability to volatilise the DT50 is of the order of the few hours to the few days for water, soil and sediments with the primary mode of loss to the atmosphere.

The physical chemical properties of trichloroethane indicate that it will not bioaccumulate (BCF = 9) as the Kow is of the order of 2.17. The Koc of 2.2 also indicates that it does not adsorb on to organic matter in soils and sediments.

Biodegradation (bacterial) in the aquatic environment can occur under both aerobic and anaerobic conditions with the latter being of greatest importance. Acclimatised sewage sludge can rapidly degrade trichloroethane giving a DT50 of approximately one day indicating that trichloroethane can be classified as inherently biodegradable. A number of studies indicate that it can be degraded in municipal sewage treatment plants that can tolerate concentrations of up to 360mg/L.

Prior to the implementation of the restrictions proposed in the Montreal protocol extensive monitoring of concentrations in rivers, estuaries and the open sea were conducted by national governments in the northern EU. The data from these surveys indicate that concentrations of trichloroethane in rivers were of the of <0.1ug/L with worst-case values of 0.6ug/L. In estuaries 0.024ug/L are considered typical with worst-case concentrations of 0.206ug/L. In the North Sea concentrations were usually <0.1ug/L.