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.

中文翻译：

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受污染田地树木年轮中六氯环己烷异构体 (HCH) 的吸收和转化

树干内六氯环己烷异构体 (HCH) 的潜在转化可能对植物筛选的使用产生重大影响。然而，六氯环己烷在树干尤其是年轮中的转化机制尚不清楚。因此，我们对六氯环己烷污染的现场进行了实地研究，利用多元素化合物特异性同位素分析（ME-CSIA）和对映体分馏来调查六氯环己烷，特别是树干中的α-六氯环己烷的归宿。结果表明，α-六氯环己烷已转化，不同生长轮部分和树皮中检测到的δ ¹³ C 和 δ ^{37 Cl 值高于淤泥和土壤中的δ 13 C 和 δ 37 Cl 值，证明了这一点。}值得注意的是，在年轮中部部分，δ ¹³六氯环己烷的 C 值仅略高于粪便中的值或与粪便中的值相当，而 δ ³⁷ Cl 值则高于粪便中的值，表明不同的转化机制。此外，与土壤和粪便中的β-六氯环己烷相比，树干中的β-六氯环己烷的δ ^{37 Cl值也有所增加，这意味着β-六氯环己烷发生了转化。}此外，双元素同位素分析表明，中部年轮与其他部分之间存在不同的转化机制。我们的研究结果表明，树干中六氯环己烷的转化可能会影响定量植物筛选方法；然而，ME-CISA 提供了估计退化程度的选项。