Transport processes 2,3,7,8-TCDD

Successful modeling of 2,3,7,8-TCDD photolysis in soils requires additional basic information on the significance of photolysis in relation to other fate and transport processes. 

TrCDD). Thus, volatilization from the water column is not expected to be a very significant loss process for the TCDD through OCDD congeners as compared to adsorption to particulates. In general, the Henry s law constants decrease with increasing chlorine number as a result of the decrease in vapor pressure and water solubility (Shiu et al. 1988). Volatilization half-lives for 2,3,7,8-TCDD were calculated for ponds and lakes (32 days) and for rivers (16 days) (Podoll et al. 1986). The primary removal mechanism for CDDs from the water column is sedimentation, with 70-80% of the CDDs being associated with the particulate phase (Muir et al. 1992). The remainder was associated with dissolved organic substances. CDDs bound to sediment particles may be resuspended in the water column if the sediments are disturbed. This could increase both the transport and availability of the CDDs for uptake by aquatic biota (Fletcher and McKay 1993). 

In the top several centimeters of soil, photolysis, volatilization, mass transport in water either dissolved, sorbed on particles, or complexed with other molecules, and bioturbation are potential processes that affect chemical behavior. Freeman and Schroy (22) have developed a model for movement of 2,3,7,8-TCDD in soils based... 

In 1980, Syntex, Inc., utilized a process based on photolysis to destroy approximately 13 pounds of 2,3,7,8-TCDD contained in 4300 gallons of oily trichlorophenol still-bottom residues ( ). In 1984, EPA began to use a transportable rotary kiln incinerator to detoxify solid and liquid waste which were contaminated with 2,3,7,8-TCDD (i6). Concurrent with the incineration activities, EPA began removing soils and other contaminated materials from a number of sites including a mobile home park near Grays Summit, Missouri. These activities required the application of extensive compositing techniques and statistical treatment of the data to assure the removal of... 

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