PCBs: Ex situ short-term vegetation screening of the immobilization effect of differentially activated soil-applied humic preparations

The container trial scope was to screen the immobilisation effect of humic acids on polychlorinated biphenyls (PCBs), verifying a set of soil-applied preparations of HUMAC^® Agro (HA) – Enviro (HE) – Sorbent (HS). A secondary goal was to formulate main closures for subsequent semi-operational in situ experiments focused on the Slovakian infamous case of Chemko Strážske, a facility of the former PCB producer, where the surrounding environment is polluted. Two experiments were established on August 3, 2020, by treating the upper 15 cm layer of soil. A week later, the sown radish Raphanus sativus L. var. sativus cv. Vinara F1 was sown. The crop was harvested in four cumulative harvests according to maturity, with soil samples collected on September 30 at the end of the trial. In trial A, the substrate was contaminated by extremely highly polluted bottom sediment taken from the waste channel of the facility and separately treated with the humic preparation in the ameliorative dose of 3 t/ha. In radish tubers, the sum of PCBs (PCB 28, 52, 101, 138, 153, 180) decreased by 32.73, 39.41 and 29.4% in comparison to the contaminated control, while in the leaves this reduction was 7.0, 15.6, 53.8%, to HA – HE – HS. The content of PCBs released from the soil into the soil leachate decreased by 49.3, 48.8 and 32.2%, respectively. Trial B was designed to test the double-dose effect, where agricultural soil with aged contamination was treated with HE only. Relating to the untreated control, a higher effect of a simple dose was recorded in comparison to double one, the content of PCBs was reduced by 73.2 vs. 60.5% in tubers, and by 23.1% vs 22.2% in leaves, respectively.