Response characteristics of indigenous microbial community in polycyclic aromatic hydrocarbons (PAHs) contaminated aquifers under polyethylene microplastics stress: A microcosmic experimental study

Co-occurrence of microplastics, PFASs, antibiotics, and antibiotic resistance genes in groundwater and their composite impacts on indigenous microbial communities: A field study

There is a major gap in the occurrence of mixed emerging contaminants, which hinders our efforts in exploring their behaviors and transport in environmental media, as well as their toxicity to human and ecosystem. This study assessed the occurrence and their correlations of mixed contamination by microplastics (MPs), per- and polyfluoroalkyl substances (PFASs), antibiotics, and antibiotic resistance genes (ARGs) in groundwater collected from a pharmaceutical and chemical industrial park. MPs, PFASs, antibiotics and ARGs were detected at all monitoring wells. The total concentration range of MPs and 20 PFASs were 693-1032 pieces/L and 577.47-2982.45 ng/L, respectively, with perfluorooctanoic acid (PFOA) being the most prevalent compound among PFASs in groundwater. The abundance of detected target antibiotics and ARGs ranged from 1.97 to 30.65 ng/L and from 2.65 × 102 to 7.53 × 105 copies/mL, respectively. MPs and PFASs have a significant positive correlation, yet interestingly, no correlation was found between antibiotics and ARGs. In addition, the relatively high abundance of integron intI1 detected in the study area illustrated the potential horizontal transfer risk of ARGs in the subsurface. Furthermore, the effects of these mixed emerging contaminants on the indigenous microbial communities were elucidated. The coexistence of MPs, PFASs, antibiotics, and ARGs led to the enrichment of species that were tolerant to pollutants. Specifically, MPs, PFASs and ARGs were found to be positively correlated with Acinetobacter, unclassified_f__Comamonadaceae, Pseudomonas, Simplicispira and Proteiniphilum, while antibiotics were positively associated with Paenisporosarcina and Arthrobacter. Moreover, geochemical parameters such as oxidation-reduction potential and nitrate also played a key role in shaping the microbial community structure. The co-occurrence of mixed emerging contaminants highlighted in this study underscores the urgent need for comprehensive environmental monitoring, systematic toxicity assessments, and stricter regulatory frameworks. In addition, it offers insights in the development of effective bioremediation strategies to mitigate their impacts on both ecosystems and public health.

Aging properties of polyethylene and polylactic acid microplastics and their adsorption behavior of Cd(II) and Cr(VI) in aquatic environments

In this study, we examined the aging characteristics of polyethylene (PE) and polylactic acid (PLA) microplastics (MPs), examining the adsorption behaviors and mechanisms concerning Cd(II) and Cr(VI) under both single and binary systems. The results revealed that aging treatment changed the physicochemical properties of MPs. The aging mechanisms of PLA and PE MPs were shown to be similar by the 2D-FTIR-COS study. These mechanisms involve the formation of oxygen-containing functional groups through the combination of carbon chain breakdown and oxygen. Aged MPs had a greater ability to adsorb metal ions than pristine MPs, with PLA MPs outperforming PE MPs. After 30 days of aging, Cd(II) adsorption increased by 40.61 % and 25.49 % for PE and PLA MPs, respectively, while Cr(VI) adsorption increased by 37.50 % and 69.29 %, respectively. The adsorption ability of PE and PLA MPs with Cd(II) or Cr(VI) under binary systems was less than that under single systems, with Cd(II) exhibiting more adsorption competitiveness than Cr(VI). Humic acid (HA), ionic species and strength, solution pH, and adsorption of Cd(II) and Cr(VI) were found to be significantly correlated. Further investigation into the adsorption mechanisms of Cd(II) and Cr(VI) on PE and PLA MPs revealed that pore-filling, electrostatic interactions, complexation, and hydrogen bonding play important roles in the adsorption process. The study's conclusions are crucial for assessing the risk associated with concurrent contamination by metal ions and microplastics.

Biosurfactants-based mixed polycyclic aromatic hydrocarbon degradation: From microbial community structure toward non-targeted metabolomic profile determination

Biosurfactants-based bioremediation is considered an efficient technology to eliminate environmental pollutants including polycyclic aromatic hydrocarbons (PAHs). However, the precise role of rhamnolipids or lipopeptide-biosurfactants in mixed PAH dissipation, shaping microbial community structure, and influencing metabolomic profile remained unclear. In this study, results showed that the maximum PAH degradation was achieved in lipopeptide-assisted treatment (SPS), where the pyrene and phenanthrene were substantially degraded up to 74.28 % and 63.05 % respectively, as compared to rhamnolipids (SPR) and un-aided biosurfactants (SP). Furthermore, the high throughput sequencing analysis revealed a significant change in the PAH-degrading microbial community, with Proteobacteria being the predominant phylum (>98 %) followed by Bacteroidota and Firmicutes in all the treatments. Moreover, Pseudomonas and Pannonibacter were found as highly potent bacterial genera for mixed PAH degradation in SPR, SPS, and SP treatments, nevertheless, the abundance of the genus Pseudomonas was significantly enhanced (>97 %) in SPR treatment groups. On the other hand, the non-targeted metabolomic profile through UHPLC-MS/MS exhibited a remarkable change in the metabolites of amino acids, carbohydrates, and lipid metabolisms by the input of rhamnolipids or lipopeptide-biosurfactants whereas, the maximum intensities of metabolites (more than two-fold) were observed in SPR treatment. The findings of this study suggested that the aforementioned biosurfactants can play an indispensable role in mixed PAH degradation as well as seek to offer new insights into shifts in PAH-degrading microbial communities and their metabolic function, which can guide the development of more efficient and targeted strategies for complete removal of organic pollutants such as PAH from the contaminated environment.

A biodegradable chitosan-based polymer for sustained nutrient release to stimulate groundwater hydrocarbon-degrading microflora

Petroleum hydrocarbon-contaminated groundwater often has a low indigenous microorganism population and lacks the necessary nutrient substrates for biodegradation reaction, resulting in a weak natural remediation ability within the groundwater ecosystem. In this paper, we utilized the principle of petroleum hydrocarbon degradation by microorganisms to identify effective nutrients (NaH2PO4, K2HPO4, NH4NO3, CaCl2, MgSO4·7H2O, FeSO4·7H2O, and VB12) and optimize nutrient substrate allocation through a combination of actual surveys of petroleum hydrocarbon-contaminated sites and microcosm experiments. Building on this, combining biostimulation and controlled-release technology, we developed a biodegradable chitosan-based encapsulated targeted biostimulant (i.e., YZ-1) characterized by easy uptake, good stability, controllable slow-release migration, and longevity to stimulate indigenous microflora in groundwater to efficiently degrade petroleum hydrocarbon. Results showed that YZ-1 extended the active duration of nutrient components by 5-6 times, with a sustainable release time exceeding 2 months. Under YZ-1 stimulation, microorganisms grew rapidly, increasing the degradation rate of petroleum hydrocarbon (10 mg L-1) by indigenous microorganisms from 43.03% to 79.80% within 7 d. YZ-1 can easily adapt to varying concentrations of petroleum hydrocarbon-contaminated groundwater. Specifically, in the range of 2-20 mg L-1 of petroleum hydrocarbon, the indigenous microflora was able to degrade 71.73-80.54% of the petroleum hydrocarbon within a mere 7 d. YZ-1 injection facilitated the delivery of nutrient components into the underground environment, improved the conversion ability of inorganic electron donors/receptors in the indigenous microbial community system, and strengthened the co-metabolism mechanism among microorganisms, achieving the goal of efficient petroleum hydrocarbon degradation.