Remediation technology towards zero plastic pollution: Recent advance and perspectives

Improved YOLOv5 s and transfer learning for floater detection

This study aims to address the detection and classification of floating objects on water surfaces, including items such as bottles, plastic bags, aquatic plants, and dead fish, which pose significant threats to water quality and ecosystems. Traditional detection methods rely on manual observation and cleanup, which are inefficient, costly, and risky. To tackle this challenge, this paper proposes a solution based on an improved YOLOv5 s model by collecting floating object image data and constructing and processing the dataset using manual photography and SAGAN data augmentation techniques. We optimized the YOLOv5 s model by integrating the EfficientNetv2 lightweight network, the content-aware reassembly of features lightweight upsampling module, the bidirectional feature pyramid network structure, and by introducing attention modules such as squeeze-and-excitation and efficient multi-scale attention, along with the scylla intersection over union (SIoU) loss function. Additionally, transfer learning techniques were employed to enhance the model's performance in detecting floating objects on water surfaces, and ablation experiments were conducted to validate the effectiveness of each improvement. The results show that the improved YOLOv5 s model exhibits better performance and generalization ability on the test set, with a 5.27 percentage point increase in model accuracy. The model's parameter count, computational load, and weight size are 53.9%, 21.3%, and 54% of the original YOLOv5 s model, respectively, providing an efficient, accurate, and real-time solution for detecting floating objects on water surfaces. The methodology presented in this paper holds significant importance for the monitoring of aquatic ecological environments and the management of floating debris, offering valuable insights for achieving precise and efficient detection and classification of floating objects on water surfaces.

Remediation on antimony-contaminated soil from mine area using zero-valent-iron doped biochar and their effect on the bioavailability of antimony

Due to the bioavailability and movement of antimony in trophic web, the overexploitation of antimony mine resulted in antimony contamination that harmed the ecology nearby, raising concerns for public health. Whereas, most researches focused on the removal of antimony in the aqueous instead of the immobilization of antimony in the soil. Herein, the immobilized performance of biochar (BC) loaded with nano zero-valent iron (nZVI-BC) on antimony in the soil near the smelting area was researched through pot experiments for the first time, and its stabilization mechanism on antimony was investigated by valent state variation of antimony. The results demonstrated that BC restricted the cation exchange capacity and catalase activity in the soil, while nZVI-BC had a favorable and negative impact on two variables, respectively. The nZVI-BC showed more stable immobilization capacity on antimony over time than BC, whose exchangeable speciation only marginally rose (2%-6%), although the exchangeable speciation of antimony fell both from 15% to 2% after adding the BC and nZVI-BC, The electron attraction force between nZVI-BC and antimony was also intensified owing to the oxidation-reduction process, which was considered as the stabilizing principle of nZVI-BC on antimony in soil. Furthermore, the decreased bioaccumulation factor for the perennial ryegrass (0.46-0.21) and Galinsoga parviflora Cav. (0.26-0.17) stated that the BC effectively mitigated the bioaccumulation risk of antimony.

The power of green: Harnessing phytoremediation to combat micro/nanoplastics

Plastic pollution and its potential risks have been raising public concerns as a global environmental issue. Global plastic waste may double by 2030, posing a significant challenge to the remediation of environmental plastics. In addition to finding alternative products and managing plastic emission sources, effective removal technologies are crucial to mitigate the negative impact of plastic pollution. However, current remediation strategies, including physical, chemical, and biological measures, are unable to compete with the surging amounts of plastics entering the environment. This perspective lays out recent advances to propel both research and action. In this process, phytoaccumulation, phytostabilization, and phytofiltration can be applied to reduce the concentration of nanoplastics and submicron plastics in terrestrial, aquatic, and atmospheric environments, as well as to prevent the transport of microplastics from sources to sinks. Meanwhile, advocating for a more promising future still requires significant efforts in screening hyperaccumulators, coupling multiple measures, and recycling stabilized plastics from plants. Phytoremediation can be an excellent strategy to alleviate global micro/nanoplastic pollution because of the cost-effectiveness and environmental sustainability of green technologies.

Plastic pollution on Moroccan beaches: Toward baselines for large-scale assessment

In Africa, Morocco is the 10th largest producer of plastic. The severity of this plastic has attracted increasing amounts of attention in the Moroccan Atlantic and Mediterranean in recent years. However, at the national level, there is limited knowledge of plastic pollution. To obtain an exhaustive and comprehensive evaluation of plastic pollution levels in Morocco, large-scale monitoring is needed on all the coasts of the country. In this context, this paper examined the composition, abundance, distribution, source and quality of beaches on two Moroccan coasts using four beach quality indices along 29 beaches. During two seasons, a total of 72,105 items were counted. The mean litter abundance was 0.31 items/m2, and the Mediterranean beaches were more dense than the Atlantic beaches. In particular, litter density was greater in spring (0.35 items/m2) than in summer (0.29 items/m2). The data indicate considerable differences in the density of marine debris according to the seasonality, beach typology and presence of rivers. Hazardous litter items were collected along both Moroccan coasts, constituting 8.41 % of the total collected items, with a mean of 0.026 items/m2. The use of environmental indices allowed us to classify Moroccan beaches as "moderate cleanliness", "moderate abundance" of plastics, "moderately safe" presence of hazardous litter and "mediocre" environmental status. The findings of the present study indicate that the sources of litter on both Moroccan coasts come mainly from recreational activities and dumping. The waste management practices recommended for Moroccan beaches include reducing sources, mitigating mitigation measures and changing littering behavior.

Enhanced adsorption for trivalent antimony by nano-zero-valent iron-loaded biochar: performance, mechanism, and sustainability

The discharge of tailing leachate and metallurgical wastewater has led to an increasing trend of water pollution. In this study, nZVI-modified low-temperature biochar was used to adsorb Sb(III) from water. The adsorption capacity and speed of nZVI-BC were better than those of BC, and the best adsorption effect was observed for 4nZVI-BC, with 93.60 mg·g-1 maximum adsorptive capacity, which was 208.61% higher than the original BC. The Langmuir and Temkin models were well fitted (R2 ≥ 0.99), and PSO was more in line with the 4nZVI-BC adsorption process, indicating that the adsorption was a monolayer physico-chemical adsorption. The combination of XRD, FTIR, and XPS characterization demonstrated that the adsorption mechanism predominantly included redox reactions, complexation, and electrostatic interactions. The thermodynamic results demonstrated that 4nZVI-BC adsorption on Sb(III) was a spontaneous endothermic process. Additionally, the order of the influence of interfering ions on 4nZVI-BC was CO32-  > H2PO4-  > SO42-  > Cl-. After three repeated uses and adsorption-desorption, the adsorption ratio of Sb(III) by 4nZVI-BC was still as high as 90% and 65%, respectively. This study provides a theoretical reference for the exploration and development of Sb(III) removal technologies for aquatic environments.

Directed Evolution of Material Binding Peptide for Polylactic Acid-specific Degradation in Mixed Plastic Wastes

In order to preserve our livelihood for future generations, responsible use of plastics in a climate-neutral and circular economy has to be developed so that plastics can be used in an environmentally friendly way by future generations. The prerequisite is that bioplastic polymers such as polylactic acid (PLA) can be efficiently recycled from petrochemical based plastic. Here, a concept in which accelerated PLA degradation in the mixed suspension of PLA and polystyrene (PS) nanoparticles has been achieved through an engineered material binding peptide. After comparison of twenty material binding peptides, Cg-Def is selected due to its PLA binding specificity. Finally, a suitable high-throughput screening system is developed for enhancing material-specific binding toward PLA in presence of PS. Through KnowVolution campaign, a variant Cg-Def YH (L9Y/S19H) with 2.0-fold improved PLA binding specificity compared to PS is generated. Contact angle and surface plasmon resonance measurements validated higher surface coverage of Cg-Def YH on PLA surface and the fusion of Cg-Def YH with PLA degrading enzyme confirmed the accelerated PLA depolymerization (two times higher than only enzyme) in mixed PLA/PS plastics.

Microplastics in soils during the COVID-19 pandemic: Sources, migration and transformations, and remediation technologies

The COVID-19 pandemic has led to a notable upsurge of 5-10 % in global plastic production, which could have potential implications on the soil quality through increased microplastics (MPs) content. The elevated levels of MPs in the soil poses a significant threat to both the environment and human health, hence necessitating the remediation of MPs in the environment. Despite the significant attention given to MPs remediation in aqueous environments, less consideration has been given to MPs remediation in the soil. Consequently, this review highlights the major sources of MPs in the soil, their migration and transformation behaviors during the COVID-19 pandemic, and emphasizes the importance of utilizing remediation technologies such as phytoremediation, thermal treatment, microbial degradation, and photodegradation for MPs in the soil. Furthermore, this review provides a prospective outlook on potential future remediation methods for MPs in the soil. Although the COVID-19 pandemic is nearing its end, the long-term impact of MPs on the soil remains, making this review a valuable reference for the remediation of MPs in the post-pandemic soil.

Assembly strategies for polyethylene-degrading microbial consortia based on the combination of omics tools and the "Plastisphere"

Numerous microorganisms and other invertebrates that are able to degrade polyethylene (PE) have been reported. However, studies on PE biodegradation are still limited due to its extreme stability and the lack of explicit insights into the mechanisms and efficient enzymes involved in its metabolism by microorganisms. In this review, current studies of PE biodegradation, including the fundamental stages, important microorganisms and enzymes, and functional microbial consortia, were examined. Considering the bottlenecks in the construction of PE-degrading consortia, a combination of top-down and bottom-up approaches is proposed to identify the mechanisms and metabolites of PE degradation, related enzymes, and efficient synthetic microbial consortia. In addition, the exploration of the plastisphere based on omics tools is proposed as a future principal research direction for the construction of synthetic microbial consortia for PE degradation. Combining chemical and biological upcycling processes for PE waste could be widely applied in various fields to promote a sustainable environment.