Vermiremediation applied to PCB and PCDD/F contaminated soils and its implications for percolating water

PCDD/Fs (polychlorinated dibenzo-p-dioxins/dibenzofurans) and PCBs (polychlorinated biphenyls) are ubiquitous persistent pollutants with reduced bioavailability, which bioremediation using soil fauna is still managed to treat. This research set out to: (i) study the suitability of earthworms (Eisenia fetida), alone and associated with plants (Lepidium sativum), for the decontamination of PCDD/F and PCB polluted soils in Brescia-Caffaro (Italy), at total and congener concentration levels; (ii) simulate the action of earthworms in groundwater contamination process and nutrient mobility. Five treatments were set up: (i) uncontaminated soil with E. fetida (NC); (ii) contaminated soil (C); (iii) contaminated soil with E. fetida (CEf); (iv) contaminated soil with L. sativum (CLs); (v) contaminated soil with E. fetida and L. sativum (CEfLs). PCBs and PCDD/Fs in the soil prior to testing were measured. Analysis was repeated in soil treatments and percolating water at the end of the test period (4 months). Dissolved nutrient concentrations were measured in percolated water. PCB and PCDD/F concentrations, initially 259333.33 ± 10867.89 ng/kg and 176 ± 10.69 ngTE/kg, were significantly reduced after 4 months in all treatments. Treatments did not differ in total PCBs concentration (from 160,000 ng/kg to 194,000 ng/kg), but CEfLs congeners concentrations were less environmentally threatening; CEf and CLs resulted in lower PCDD/Fs concentration (79.43 ± 3.34 ngTE/kg and 73.03 ± 4.09 ngTE/kg, respectively). The action of earthworms could enhance contaminants and soluble reactive phosphorous content in percolating water.