Evaluation of negative effect of Naphthenic acids (NAs) on physiological metabolism and polycyclic aromatic hydrocarbons adsorption of Phragmites australis

Enhanced phytoremediation of 2,4-DNP-contaminated wastewater by Salix matsudana Koidz with MeJA pretreatment and associated mechanism

2,4-Dinitrophenol (2,4-DNP) is recognized as an emerging contaminant due to its high toxicity and poor biodegradability, posing a threat to animals, plants, and human health. The efficient removal of 2,4-DNP remains a challenging issue in phytoremediation research, particularly because of its toxic effects on plants. To address this, a hydroponic simulation experiment was conducted to investigate the impact of adding exogenous methyl jasmonate (MeJA) on the tolerance and purification capabilities of Salix matsudana Koidz (S. matsudana) seedlings exposed to 2,4-DNP. The results indicated that the addition of exogenous MeJA mitigated the damage caused by 2,4-DNP to S. matsudana seedlings by enhancing the activity of antioxidant enzymes, reducing excess reactive oxygen species (ROS), lowering membrane lipid peroxidation, and minimizing membrane damage. Notably, the most effective alleviation was observed with the addition of 50 mg·L-1 MeJA. Furthermore, exogenous MeJA helped maintain the biomass indices of S. matsudana seedlings under 2,4-DNP stress and increased the removal efficiency of 2,4-DNP by these seedlings. Specifically, the addition of 50 mg·L-1 MeJA resulted in a removal percentage of 79.57%, which was 11.88% higher than that achieved with 2,4-DNP treatment. In conclusion, exogenous MeJA can improve the plant resistance and enhance 2,4-DNP phytoremediation.

Microbial degradation of naphthenic acids using constructed wetland treatment systems: metabolic and genomic insights for improved bioremediation of process-affected water

Naphthenic acids (NAs) are a complex mixture of organic compounds released during bitumen extraction from mined oil sands that are important contaminants of oil sands process-affected water (OSPW). NAs can be toxic to aquatic organisms and, therefore, are a main target compound for OSPW. The ability of microorganisms to degrade NAs can be exploited for bioremediation of OSPW using constructed wetland treatment systems (CWTS), which represent a possible low energy and low-cost option for scalable in situ NA removal. Recent advances in genomics and analytical chemistry have provided insights into a better understanding of the metabolic pathways and genes involved in NA degradation. Here, we discuss the ecology of microbial NA degradation with a focus on CWTS and summarize the current knowledge related to the metabolic pathways and genes used by microorganisms to degrade NAs. Evidence to date suggests that NAs are mostly degraded aerobically through ring cleavage via the beta-oxidation pathway, which can be combined with other steps such as aromatization, alpha-oxidation, omega-oxidation, or activation as coenzyme A (CoA) thioesters. Anaerobic NA degradation has also been reported via the production of benzoyl-CoA as an intermediate and/or through the involvement of methanogens or nitrate, sulfate, and iron reducers. Furthermore, we discuss how genomic, statistical, and modeling tools can assist in the development of improved bioremediation practices.

Recent trends in polycyclic aromatic hydrocarbons pollution distribution and counteracting bio-remediation strategies

Polycyclic aromatic hydrocarbons (PAHs) are distributed worldwide due to long-term anthropogenic pollution sources. PAHs are recalcitrant and highly persistent in the environment due to their inherent properties, such as heterocyclic aromatic ring structures, thermostability, and hydrophobicity. They are highly toxic, carcinogenic, immunotoxic, teratogenic, and mutagenic to various life systems. This review focuses on the unique data of PAH sources, exposure routes, detection techniques, and harmful effects on the environment and human health. This review provides a comprehensive and systematic compilation of eco-friendly biological treatment solutions for PAH remediation, such as microbial remediation approaches utilizing microbial cultures. In situ and Ex situ bioremediation of PAH methods, including composting land farming, biopiles, bioreactors bioaugmentation, and phytoremediation processes, are discussed in detail, as is a summary of the factors affecting and limiting PAH bioremediation. This review provides an overview of emerging technologies that use multi-process combinatorial treatment approaches and answers to generating value-added by-products during PAH remediation.