Soil-water partition 2,3,7,8-TCDD

Volatilization of 2,3,7,8-TCDD from soils is expected to be very slow, due to the low vapor pressure and high octanol-water partition coefficient. Mill (47) estimates that the half-life for vaporization of 2,3,7,8-TCDD from soils will range from many months to years, in the absence of intervening transformation processes. 

Environmental Fate. CDDs are subject to atmospheric transport and both wet and dry deposition (Kieatiwong et al. 1990). They are partitioned to air, water, sediment, and soil, and they accumulate in both aquatic and terrestrial biota. CDDs can volatilize to the atmosphere from water and soil surfaces. They adsorb strongly to soils and are not likely to leach into groundwater (Eduljee 1987b). In the aquatic environment, CDDs partition to sediment or suspended particulates. TCDD, HpCDD, and OCDD are subject to photolysis in air, water, and soil (Plimmer et al. 1973). 2,3,7,8-TCDD is biodegraded very slowly in soil and thus is likely to persist in the soil. A better understanding of environmental behavior of CDDs is needed with respect to the importance of vapor-phase versus particulate transport, the... 

Jackson, et al.(6), examined the leaching potential of TCDD-contaminated soils Fom various sites. Soil partition coefficients were large (the mean log for two samples was 5.9 and 6.02), indicating that TCDD is only very slightly soluble and that only very small amounts of TCDD will be released into water. The authors concluded that the rates of TCDD movement in soils are so slow that other transport mechanisms such as wind and water erosion are likely to be more significant. 

The majority of available data on the fate of PCDD pertains only to 2,3,7,8-tretrachlorodibenzo-/7-dioxin (TCDD). Since the data are generally not quantitative, interpretation and extrapolation to natural environmental conditions has to be viewed with some caution. Hence, only a qualitative concept of the behavior of PCDD in the environment is presented. PCDDs tend to be rapidly and strongly sorbed by most soils (Firestone, 1977 Ward and Matsumura, 1978), suggesting relative immobility in most matrices. Using partition coefficient data for an octanol/water mixture and its relationship to the organic matter and its content in sediment and soils. 

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