The Fate of Polychlorinated Biphenyls inKarstic Soil

During the Croatian Homeland war in 1991, the capacitor batteries of the Zadar electric power substation (TS 110/35 kV) were damaged, resulting in the severe pollution of the soil with polychlorinated biphenyls (PCBs). Due to porosity of karstic soil PCBs represent great environmental and human health risks that need some action. The polluted soil was collected and an experimental field was formed. This paper reports the behaviour of PCBs in karstic soil over an extended period of time under field conditions. Vertical movement of PCBs through the soil profiles was also observed. The soil was sampled four times. The initial median levels of Aroclor 1248 in the surface soil layer were 76.5 μg g-1. The levels of PCB in the soil layers collected after initial stage were quite variable. In general, PCB patterns were dominated by low-chlorinated homologue groups (<5 Cl groups). The dominant indicator PCB congeners initially present in the soil were PCB 28 and PCB 52. At the end of the experiment, in surface soil layer, the levels of PCB 28 decreased significantly (38%), while the levels of PCB 52 decreased at a smallier rate with time 15%). In the observed time periods the levels of higher PCBs (n>6) were relatively stable. The results show that the total PCB concentration in the soil around the roots significantly dropped by 36% while in the deeper soil layer decreased for 18%.