The potential transformation of hexachlorocyclohexane
isomers (HCHs)
within tree trunks could have a significant impact on the use of phytoscreening.
However, the transformation mechanisms of HCH in trunks particularly
in growth rings are not yet well understood. Therefore, a field study
on an HCH-contaminated field site was conducted to investigate the
fate of HCH, particularly α-HCH in tree trunks using multielement
compound-specific isotope analysis (ME-CSIA) and enantiomer fractionation.
The results indicate that α-HCH was transformed, as evidenced
by higher δ13C and δ37Cl values
detected across different growth ring sections and in the bark compared
to those in muck and soil. Remarkably, in the middle growth ring section,
δ13C values of HCH were only marginally higher or
comparable to those in muck, whereas δ37Cl values
were higher than those of the muck, indicating a different transformation
mechanism. Moreover, the δ37Cl values of β-HCH
also increased in the tree trunks compared to those in soil and muck,
implying a transformation of β-HCH. Additionally, dual-element
isotope analysis revealed that there are different transformation
mechanisms between the middle growth rings and other sections. Our
findings suggest that the transformation of HCHs in trunks could bias
quantitative phytoscreening approaches; however, ME-CISA offers an
option to estimate the degradation extent.