engleski

The investigation of planting , water leaching and atmospheric escape on the decrease of PCBs level in thin karst soil layer

Natural contaminated soil with PCBs was used in this study. That soil was excavated from an area around a damaged capacitor of an Electrical Transformer Station in Zadar, Croatia. This study examined the abilities of different plant species and natural attenuation on the dissipation of PCBs in a soil. A lysimeter experiment was conducted for 1 year under natural climatic conditions and designed to measure the concentration of PCBs in soil and leachates. Our research field is composed of four plots and located near ETS. Three lysimeters have been set on each plot. Plot No.1 was sowed with legume alfalfa (Medicago sativa L.) seeds, plot No.2 with a commercial grass seed mixture suitable for an arid Adriatic region, and plot No.3 was sowed with Arabidopsis thaliana (Heynh L.) seeds . Plot No.4 was control plot that was left to grow wild. Soil samples were taken in three depths from each lysimeter (surface layer 0-5cm, middle layer 5-10cm, deeper layer 10-15cm before planting. In June 2005 soil sampling layers were 0-4 cm, 4-8 cm, 8-12 cm and soil around the plant root. We estimated the level of total PCBs within soil layers as Aroclor 1248 equivalents and the sum of 7 “ key” PCBs congeners before and after planting. Results of leaching PCBs into water collected from lysimeters showed that after 12 months (including twelve period of rainfall events), a negligible quantity of Ar 1248 (an average of 0.024 %) and the sum of 7 key PCBs (an average of 0.032 %) were leached from the soils. Although amounts of leached PCBs are relatively small if we take into account that the maximal acceptable level of total PCBs in fishpond waters is only 1 ng l-1, observed levels in leachates ranging between 4000 and 15 000 ng l-1 are more than significant.

PCB; soil; plant; remediation; Zadar

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