Fraction of organic carbon

Because many studies have shown a direct relationship between pesticide sorption and organic carbon content of sod, attempts have been made to develop a universal sorption coefficient based on sorption of the pesticide to sod organic carbon (44). Sorption based on sod organic carbon is expressed as C, where is pesticide sorbed per unit mass sod organic carbon, and C is pesticide solution concentration after equdibration. If. is the fraction of organic carbon, can be obtained from i in the equation. Assumptions in the use of this approach include... 

Chlorinated hydrocarbons and soils content [43,47,48,51,53-63] Ki = Koc Xoc where Koc is the partition coefficient expressed on an organic carbon basis, and Xoc is the mass fraction of organic carbon in sediment a... 

Federal Emergency Management Agency flame ionization detector fraction of organic carbon cubic feet... 

Fig. 3.2 Different carbon compounds in primitive meteorites. Species classified as interstellar on the basis of C-isotopes are shaded. Only a minor fraction of organic carbon is interstellar, (after Ming et al. 1989)...

The solid-water partition eoeffieient (Kp) in each compartment (sediment/suspended matter) ean be ealeulated from the Koe value, and the fraction of organic carbon in the compartment (foe)) by predietions outlined in equation 2. 

A large, sealed fish tank - consisting of 20 m of water, 10 m of air, 1 m of sediment, and 0.2 m of fish and other biological organisms - has 100 g of benzene accidentally spilled into it. What will be the eventual (equilibrium) concentrations and mass in each phase The fraction of organic carbon in the sediments has been determined to be 0.01. The density of the sediments has been determined to be 2g/cm. The octanol-water partitioning coefficient for benzene is 138. 

Returning to the sorption observations (Fig. 9.7), as the mass fraction of organic carbon, foc, present in the solids approaches zero, the Kid values for both compounds become very small. Even at very lowy values. Q.,f0C = 0.001 kg oc-kg 1 solid), sorption to the organic components of a natural sorbent may still be the dominant mechanism (see Chapter 11). 

Results of Lean-Shale Studies. Because of the small fraction of organic carbon in the original sample and the correspondingly small amount of carbon in the residue, it is difficult to be sure of the significance of the differences in the amounts of residual carbon among the products of the runs. Certainly, qualitatively, there are many similarities to the results with the rich shale such as ... 

It may be deduced from KP = Koc x foc that partition coefficients of hydro-phobic organic compounds in general are dependent upon the chemical of interest (compound-specific properties affect the value of Koc) and the matrix properties of the medium in which it resides. In addition to the fraction of organic carbon present in the sorption phase, additional environmental factors affect partitioning. These factors include temperature, particle size distribution, the surface area of the sorbent, pH, ionic strength, the presence of suspended material or colloidal material, and the presence of surfactants. In addition, clay minerals may act as additional sorption phases for organic compounds. Nevertheless, organic carbon-normalized partition... 

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