Does Soil Amendment Affect the Assessment of Bioavailability of Pentachlorobenzene Using Hydroxypropyl-β-cyclodextrin Extraction Method?

This study evaluated the effects of the soil amendments biochar, activated carbon (AC), and attapulgite (APG) on the assessment of pentachlorobenzene (PeCB) bioavailability to earthworms (Eisenia foetida) using the hydroxypropyl-beta-cyclodextrin (HPCD) extraction method. The results showed that the amendment of soil with biochar and AC, rather than APG, significantly reduced the bioavailability of PeCB in soil being uptaken by earthworms (p < 0.05). After 1 week aging, the HPCD extraction efficiency of PeCB in biochar - or AC - amended soils decreased relative to that in unamended soils. This reduction was greater compared with the declining extent of PeCB uptaken by earthworms in biochar - or AC - amended soils relative to unamended soils. This could underestimate the bioavailability of PeCB in the amended soils using HPCD extraction method. However, when aging period exceeded 24 weeks, there were diminished differences between earthworm uptake and chemical method results. This suggests a better assessment of the bioavailability of PeCB in the amended soil using HPCD extraction method. Therefore, HPCD extraction method could result in an underestimation of the bioavailability of PeCB in soils amended with biochar - or AC - during a short-term aging period. However, during a long term aging period with these soil amendments, HPCD extraction method was still a suitable tool to assess the bioavailability of PeCB in soil to the uptake by earthworms.