Congener distribution concentration calculations

The individual concentration of only a limited number of selected congeners is often given. The most widely measured congeners are PCB 28, PCB 52, PCB 101, PCB 118, PCB 138, PCB 153, and PCB 180. On the basis of the concentration of the most representative congeners, the total PCB concentration can also be expressed as the equivalent quantity of an Aroclor, Clophen J or the commercial PCB mixture that shows a distribution pattern near to that observed in the sample. The value is calculated on the assumption that the concentration pattern in the sample does not signihcantly change from that of a pure commercial mixture. 

The equilibrium between water and sediments can be described by the equation C = Kf.Cy where Cj = concentration of PCBs in sediments, CjY = concentration of PCBs in water and fCp = equilibrium constant that reflects the character of sediments. To calculate the Kf value, tabulated values of Kqq (soil adsorption coefficient) can be used and Kf values calculated using the equation Kf =Kfy,.TOC (total organic carbon). For a description of the behaviour (or distribution) of individual PCB congeners between water and sediments a linear relationship between K( and tabulated Kq values can be used logfr = 0.85 log Q y -F 0.13. The relationship is valid within the range of values of log Kq = 4.S-7.7. 

---