Uptake of halogenated organic compounds (HOCs) into peanut and corn during the whole life cycle grown in an agricultural field

Abstract

Here, we elucidated the uptake and translocation of numerous halogenated organic compounds (HOCs) into corn and peanut throughout their life cycle cultivated in an agricultural field of an electronic waste recycling area, where plants were simultaneously exposed to contaminants in soil and ambient air. The geometric mean concentrations of polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) were 22.3 and 11.9 ng/g in peanut and 16.6 and 13.6 ng/g in corn, respectively. Decabromodiphenyl ethane (DBDPE, 6.07 ng/g) and dechlorane plus (DPs, 6.22 ng/g) also showed significant concentrations in peanuts. The plant uptake was initiated from root absorption at the emergence stage but it was subsequently surpassed by leaves absorption from the air since the late seedling stage or early reproductive stage. There was a rapid uptake of lower halogenated HOCs at the early vegetative stages in both species. However, robust uptake of highly halogenated compounds at the reproductive stages suggests a delayed accumulation of them by the plants. PBDE and PCB congener profiles suggest more noticeable tendency for inter-compartment translocation in peanut than in corn during the plant development. The DP and HBCD isomeric compositions in peanut (enriched with syn-DP and γ-HBCD) were different from those in the rhizosphere soils and air, suggesting a more stereoisomer-selective uptake and/or biotransformation in this species compared to corn. The bioaccumulation factors for root-soil and stem-root of these HOCs in most cases were <1. The tissue-distributions demonstrated that leaves serve as a significant reservoir of absorbed HOCs under the field conditions, whereas the low concentrations in peanut and corn kernels indicated translocation of most HOCs into this compartment was significantly hindered (especially for highly halogenated compounds).

Keywords: Accumulation; Flame retardants; Plants; Polychlorinated biphenyls (PCBs); Translocation.