Content of PCB substances in carrot root and its relations to selected soil factors

The influence of the content of polychlorinated biphenyls (PCB) in agricultural soil and its agrochemical properties on bioaccumulation of PCBs by edible part of carrot (Daucus carota L.) was monitored in 18 locations of the Eastern Slovakian lowland (ESL). The congeners Nos. 28, 52, 101, 138, 153 and 180 have been determined in almost all samples and in both soil and plant material. Soil PCB values varied between 0.16 µg/kg, detected in the congener 52, and 53.4 µg/kg for the congener 180. The average value of the sum of all the followed congeners was 17.9 µg/kg. The variation interval of investigated PCB congeners in carrot root ranged from the level below the detection limit of the analytical method until the maximum of 10.6 µg/kg, for the congener 153. Average amounts of PCBs significantly differed among individual congeners. The average value of the sum of all the followed congeners in carrot root was 5.39 µg/kg. Statistical evaluation of relationships between the concentrations of congeners in carrot root and in soil predominantly showed highly significant dependences. Interestingly, the contents of individual congeners in carrot root were more tightly correlated to the contents of the remaining congeners in the root than to the amount of the analogous congener in the soil. This suggested a possible synergistic effect of PCBs regarding their uptake by the plant. The increasing concentration of inorganic nitrogen in soil leads to an increase of the content of lightly chlorinated congeners in carrot root. Concentrations of lightly chlorinated congeners 28 and 52 were more significantly affected by followed chemical parameters than were concentrations of highly chlorinated congeners. Among the chemical parameters studied [available phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) in the soil] only P and K gave statistically significant relationships. Changes in the potassium content were responsible for 7.8% variability in the amount of the congener 28. Similarly, Mg induced 7.6% of alterations in the quantity of the congener 180. Our results suggest that importance of both Ca and Mg concentrations in soil regarding the PCBs uptake were less as compared to the concentration of nitrogen. Statistically significant influence of the humus content in soil varying in range between 0.70 and 8.28% as well as the soil acidity (pH = 4.9-7.3) on the content of some of the investigated congeners in carrot root were not estimated.