Efficiency and mechanism of the phytoremediation of decabromodiphenyl ether-contaminated sediments by aquatic macrophyte Scirpus validus

Bromine contamination and risk management in terrestrial and aquatic ecosystems

Bromine (Br) is widely distributed through the lithosphere and hydrosphere, and its chemistry in the environment is affected by natural processes and anthropogenic activities. While the chemistry of Br in the atmosphere has been comprehensively explored, there has never been an overview of the chemistry of Br in soil and aquatic systems. This review synthesizes current knowledge on the sources, geochemistry, health and environmental threats, remediation approaches, and regulatory guidelines pertaining to Br pollution in terrestrial and aquatic environments. Volcanic eruptions, geothermal streams, and seawater are the major natural sources of Br. In soils and sediments, Br undergoes natural cycling between organic and inorganic forms, with bromination reactions occurring both abiotically and through microbial activity. For organisms, Br is a non-essential element; it is passively taken up by plant roots in the form of the Br- anion. Elevated Br- levels can limit plant growth on coastal soils of arid and semi-arid environments. Br is used in the chemical industry to manufacture pesticides, flame retardants, pharmaceuticals, and other products. Anthropogenic sources of organobromine contaminants in the environment are primarily wastewater treatment, fumigants, and flame retardants. When aqueous Br- reacts with oxidants in water treatment plants, it can generate brominated disinfection by-products (DBPs), and exposure to DBPs is linked to adverse human health effects including increased cancer risk. Br- can be removed from aquatic systems using adsorbents, and amelioration of soils containing excess Br- can be achieved by leaching, adding various amendments, or phytoremediation. Developing cost-effective methods for Br- removal from wastewater would help address the problem of toxic brominated DBPs. Other anthropogenic organobromines, such as polybrominated diphenyl ether (PBDE) flame retardants, are persistent, toxic, and bioaccumulative, posing a challenge in environmental remediation. Future research directives for managing Br pollution sustainably in various environmental settings are suggested here.

Phytoremediation of contaminated sediment combined with biochar: Feasibility, challenges and perspectives

The accumulation of contaminants in sediments is accelerated by human activities and poses a major threat to ecosystems and human health. In recent years, various remediation techniques have been developed for contaminated sediments. In this review, a bibliometric analysis of papers on sediment remediation indexed in the WOS database between 2009 and 2023 was conducted using VOSviewer. We describe the development of biochar and plants for sediment contaminant removal. However, the single processes of biochar remediation and phytoremediation can be impeded by (i) low efficiency, (ii) poor tolerance of plants towards pollutants, (iii) difficulty in biochar to degrade pollutants, and (iv) biochar aging causing secondary pollution. Fortunately, combination remediation, realized through the combination of biochar and plants, can overcome the shortcomings of their individual applications. Therefore, we suggest that the remediation of contaminants in sediments can be accomplished by combining biochar with macrophytes and considering multiple limiting factors. Here, we explore the challenges that co-remediation with biochar and macrophytes will face in achieving efficient and sustainable sediment remediation, including complex sediment environments, interaction mechanisms of biochar-macrophyte-microorganisms, emerging pollutants, and integrated life cycle assessments, which can provide references for combined biochar and plant remediation of sediments in the future.

Cellular changes of microbial consortium GY1 during decabromodiphenyl ether (BDE-209) biodegradation and identification of strains responsible for BDE-209 degradation in GY1

Microbial consortium remediation has been considered to be a promising technique for BDE-209 elimination in water, soil and sediment. Herein, we studied malondialdehyde (MDA), membrane potential (MP), and reactive active species (ROS) of a microbial consortium GY1 exposed to BDE-209. The results indicated that the microbial antioxidant defense system was vulnerable by BDE-209. Both early and late apoptosis of microbial consortium induced by BDE-209 were observed. The sequencing results revealed that Stenotrophomonas, Microbacterium and Sphingobacterium in GY1 played major roles in BDE-209 degradation. Moreover, a novel facultative anaerobic BDE-209 degrading strain named Microbacterium Y2 was identified from GY1, by which approximately 56.1% of 1 mg/L BDE-209 was degraded within 7 days, and intracellular enzymes of which contributed great to the result. Overall, the current study provided new insights to deeply understand the mechanisms of BDE-209 degradation by microbial consortium.

Biodegradation of decabromodiphenyl ether (BDE-209) using a novel microbial consortium GY1: Cells viability, pathway, toxicity assessment, and microbial function prediction

GY1, a novel microbial consortium with efficient ability to degrade decabromodiphenyl ether (BDE-209) has been isolated and the sequencing analysis has been conducted. The results revealed that Hyphomicrobium, Pseudomonas, Aminobacter, Sphingopyxis, Chryseobacterium, Bacillus, Pseudaminobacter, Stenotrophomonas, Sphingobacterium and Microbacterium were the dominant genera, and the function genes involved in BDE-209 conversion were predicted by PICRUSt. When BDE-209 concentration increased from 0.5 to 10mg/L, its degradation efficiency declined from 57.2% to 22.3%. Various kinds of debrominated metabolites were detected during the biodegradation process, including BDE-208, BDE-207, BDE-206, BDE-205, BDE-190, BDE-181, BDE-155, BDE-154, BDE-99, BDE-47, BDE-17 and BDE-7. Also, the proportion of necrotic cells was observed during GY1 mediated degradation of BDE-209 to reveal the changes of cells viability under BDE-209 stress. Subsequent analysis showed that the reaction of BDE-209 with GY1 was a detoxification process and bioaugmentation with GY1 effectively enhanced BDE-209 degradation in actual water and water-sediment system.