Complex rhizoremediation is the main mechanism of phytoremediation in organic-contaminated soil. Low molecular weight organic acids (LMWOAs) in root exudates have been shown to increase the ...bioavailability of contaminants and are essential for promoting the dissipation of contaminants. The effects of root exudates on the dissipation of organophosphate esters (OPEs) in soil are unclear. Consequently, we studied the combined effects of root exudates, soil enzymes and microorganisms on OPEs (tri (1-chloro-2-propyl) phosphate (TCPP) and triphenyl phosphate (TPP)) dissipation through pot experiments. Oxalic acid (OA) was confirmed to be the main component of LMWOAs in root exudates of ryegrass. The existence of OA increased the dissipation rate of OPEs by 6.04%–25.50%. Catalase and dehydrogenase activities were firstly activated and then inhibited in soil. While, urease activity was activated and alkaline phosphatase activity was inhibited during the exposure period. More bacteria enrichment (e.g., Sphingomonas, Pseudomonas, Flavisolibacter, Pontibacter, Methylophilus and Massilia) improved the biodegradation of OPEs. In addition, the transformation paths of OPEs hydrolysis and methylation under the action of root exudates were observed. This study provided theoretical insights into reducing the pollution risk of OPEs in the soil.
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•Oxalic acid was the main component of ryegrass root exudates.•OPEs stress enhanced the secretion of oxalic acid.•The root exudates of ryegrass promoted the degradation of OPEs in soil.•Microbial communities were significantly affected by root exudates.
Tetrabromobisphenol A (TBBPA) and its derivatives are widely used as brominated flame retardants. Because of their high production and wide environment distribution, TBBPA derivatives have increased ...considerable concern. Previous studies have primarily focused on TBBPA, with limited information available on its derivative. In this study, we investigated the uptake, biotransformation and physiological response of two derivatives, Tetrabromobisphenol A bis(allyl ether) (TBBPA BAE) and Tetrabromobisphenol A bis(2,3-dibromopropylether) (TBBPA BDBPE), in Helianthus annus (H. annus) through a short-term hydroponic assay. The results revealed that H. annus could absorb TBBPA BAE and TBBPA BDBPE from solution, with removal efficiencies of 98.33 ± 0.5% and 98.49 ± 1.56% after 10 days, respectively, which followed first-order kinetics. TBBPA BAE was absorbed, translocated and accumulated while TBBPA BDBPE couldn't be translocated upward due to its high hydrophobicity and low solubility. The concentrations of TBBPA derivatives in plants peaked within 72 h, and then decreased. We identified twelve metabolites resulting from ether bond breakage, debromination, and hydroxylation in H. annus. The high-level TBBPA BAE suppressed the growth and increased malondialdehyde (MDA) content of H. annus, while TBBPA BDBPE didn't pose a negative effect on H. annus. TBBPA BAE and TBBPA BDBPE increased the activity of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), with higher levels of these enzymes activity found in high concentration treatments. Contrastingly, TBBPA BAE exhibited higher toxicity than TBBPA BDBPE, as indicated by greater antioxidant enzyme activity. The findings of this study develop better understanding of biotransformation mechanisms of TBBPA derivatives in plants, contributing to the assessment of the environmental and human health impacts of these contaminants.
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•H. annus could uptake TBBPA derivatives, but translocation of TBBPA BDBPE was limited.•TBBPA derivatives' ether breakage, debromination and hydroxylation in H. annus.•High-level of TBBPA BAE inhibited the growth and development of H. annus.•TBBPA derivatives induced SOD, POD and CAT activities in H. annus.•TBBPA BAE has higher toxicity than TBBPA BDBPE.
Biotransformation is a major dissipation process of tetrabromobisphenol A and its derivatives (TBBPAs) in soil. The biotransformation and ultimate environmental fate of TBBPAs have been widely ...studied, yet the effect of root exudates (especially low-molecular weight organic acids (LMWOAs)) on the fate of TBBPAs is poorly documented. Herein, the biotransformation behavior and mechanism of TBBPAs in bacteriome driven by LMWOAs were comprehensively investigated. Tartaric acid (TTA) was found to be the main component of LMWOAs in root exudates of Helianthus annus in the presence of TBBPAs, and was identified to play a key role in driving shaping bacteriome. TTA promoted shift of the dominant genus in soil bacteriome from Saccharibacteria_genera_incertae_sedis to Gemmatimonas, with a noteworthy increase of 24.90–34.65% in relative abundance of Gemmatimonas. A total of 28 conversion products were successfully identified, and β-scission was the principal biotransformation pathway for TBBPAs. TTA facilitated the emergence of novel conversion products, including 2,4-dibromophenol, 3,5-dibromo-4-hydroxyacetophenone, para-hydroxyacetophenone, and tribromobisphenol A. These products were formed via oxidative skeletal cleavage and debromination pathways. Additionally, bisphenol A was observed during the conversion of derivatives. This study provides a comprehensive understanding about biotransformation of TBBPAs driven by TTA in soil bacteriome, offering new insights into LMWOAs-driven biotransformation mechanisms.
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•Biotransformation of TBBPAs in soil mediated by root exudates was first investigated.•A total of 28 biotransformation products were successfully identified.•Tartaric acid promoted the debromination and oxidative skeletal cleavage pathways.•Some single-ring products were first identified under mediation of tartaric acid.
Phytoremediation mediated by microorganisms in the rhizosphere is a promising technology for the effective management of petroleum hydrocarbons-contaminated soil. However, it is essential to explore ...the dynamics of the micro-environment in the rhizosphere during phytoremediation process. A pot xperiment was conducted to investigate the ecological response of rhizospheric environmental of landscaping plant (Helianthus annus) to the petroleum hydrocarbon compounds (PHCs) contamination. The results showed that the species had a high ability to remove PHCs, and the removal of n-alkanes largely depended on symbiotic microorganisms in the root zone. The remediation efficiency of Helianthus could be regulated by rhizosphere microbes through the enhancement of nutrients and energy cycling, remodeling of the beneficial bacterial abundance, and improvement of enzyme activities. In addition, the ecological response of rhizosphere soil was closely related to the root exudation effect of plant and PHCs exposure. The present study provides information about the succession pattern and response of the microbial community of rhizosphere soil in the PHCs phytoremediation of Helianthus annus, and demonstrated the feasibility of Helianthus annus in the effective management of PHCs in contaminated soil.
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