Measuring the bioavailability of polychlorinated biphenyls to earthworms in soil enriched with biochar or activated carbon using triolein-embedded cellulose acetate membrane

Abstract

Polychlorinated biphenyls (PCBs) are persistent soil contaminants that resist biodegradation and present serious risks to living organisms. The presence of biochar in soils can lower the availability of PCBs to biota. In this study, the effect of biochar enrichment in soils on bioaccumulation of PCBs was investigated. We applied two types of biochar including pine needle biochar (PC) and wheat straw biochar (WC), and an activated carbon (AC) to soil (2 % w/w) and employed two alternative methods to quantified rates of bioaccumulation: a living bioassay (using earthworm, Eisenia fetida, as a model organism) and a triolein-embedded cellulose acetate membrane (TECAM). Our results show that the application of biochar or AC greatly reduced the uptake of PCBs (particularly less-chlorinated PCBs) by earthworms (the reduction in total PCBs concentration was up to 40.0 and 49.0 % for PC and WC treatments, while 71.6 % for AC application). We found that the bioaccumulation factors (BAFs) for PCBs in the earthworms in biochar/AC-enriched soils were strongly correlated with O:C ratio of the biochar/AC (R 2 = 0.998, p < 0.05). We observed that BAFs increased at log K OW below 6.3 and decreased at log K OW values greater than 6.3. We demonstrated that the concentration of PCBs in TECAM membranes were positively correlated with the concentration of PCBs earthworms in soil. TECAM offers an efficient and cost-effective method for predicting the bioavailability of PCBs in field-contaminated soils undergoing sorbent-based remediation.