Uptake of α-HCH by wheat from the gas phase and translocation to soil analyzed by a stable carbon isotope labeling experiment

Hexachlorocyclohexane isomers (HCH) are persistent organic pollutants which cause serious environmental pollution. Phytoextraction is one of the strategies of phytoremediation, which was considered as a promising method for the clean-up of HCH contaminated field sites. To understand the uptake and translocation mechanisms of HCH in soil-plant system, the uptake of HCH from the gas phase was investigated in a tracer experiment with C-13-labeled alpha-HCH. The results provide new insights on the uptake mechanism of HCH and allow the elucidation of transport pathways of POPs from the leaves to the rhizosphere. A higher dissipation of alpha-HCH in planted set-ups versus unplanted controls indicated next to intensive biodegradation in the rhizosphere the removal of HCH by root uptake, accumulation and possible transformation within plants. Analyzing the carbon isotopic composition (delta C-13) of alpha-HCH in the soil of unplanted controls revealed a change of 15.8-28.6 parts per thousand compared to the initial delta C-13 value, indicating that a soil gas phase transportation of alpha-HCH occurred. Additionally, higher delta C-13 values of alpha-HCH were observed in bulk and rhizosphere soil in non-labeled treatments compared to unplanted controls, revealing the uptake of alpha-HCH from the gas phase by the leaves and the further translocation to the roots and finally release to the rhizosphere. This uptake by the leaves and the subsequent translocation of alpha-HCH within the plant is further indicated by the observed variations of the delta C-13 value of alpha-HCH in different plant tissues at different growth stages. The uptake and translocation pathways of alpha-HCH from the gas phase need to be considered in phytoremediation. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

This study investigated the uptake and translocation mechanisms of Hexachlorocyclohexane from the gas phase in soil-plant systems, providing new insights on the transport pathways of persistent organic pollutants. The results suggest that plants can remove HCH through root uptake and biodegradation in the rhizosphere, indicating the importance of considering gas phase uptake in phytoremediation strategies.