The Fate of Polychlorinated Biphenyls inKarstic Soil

Abstract

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