Feb 2022, Volume 16 Issue 1

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    Neha Badola, Ashish Bahuguna, Yoel Sasson, Jaspal Singh Chauhan

    • Physical, chemical and biological methods are explored for MPs removal.

    • Physical methods based on adsorption/filtration are mostly used for MPs removal.

    • Chemical methods of MPs removal work on coagulation and flocculation mechanism.

    • MBR technology has also shown the removal of MPs from water.

    • Global policy on plastic control is lacking.

    Microplastics are an emerging threat and a big challenge for the environment. The presence of microplastics (MPs) in water is life-threatening to diverse organisms of aquatic ecosystems. Hence, the scientific community is exploring deeper to find treatment and removal options of MPs. Various physical, chemical and biological methods are researched for MPs removal, among which few have shown good efficiency in the laboratory. These methods also have a few limitations in environmental conditions. Other than finding a suitable method, the creation of legal restrictions at a governmental level by imposing policies against MPs is still a daunting task in many countries. This review is an effort to place all effectual MP removal methods in one document to compare the mechanisms, efficiency, advantages, and disadvantages and find the best solution. Further, it also discusses the policies and regulations available in different countries to design an effective global policy. Efforts are also made to discuss the research gaps, recent advancements, and insights in the field.

    Joana C. Prata, Ana L. Patrício Silva, Armando C. Duarte, Teresa Rocha-Santos

    • Portugal recycles 34% of the 40 kg/hab year of plastic packaging waste.

    • Recycling of plastics in Portugal produces a final revenue of 167 €/t.

    • Recycling and recovery must be the priority for imported wastes.

    • Beach litter must be reduced from 330 to 20 items/100 m (94%) under EU goals.

    • Consumption, use, and waste management of plastics need to improve.

    As a European Union (EU) member, Portugal must comply with reductions in plastic waste. In Portugal, the 330 items/100 m of beach litter, comprising up to 3.9 million pieces and of which 88% is plastic, is higher than the EU median (149 items/100 m) and must be reduced to 20 items/100 m (94%). Integrative measures are needed to reduce littering and improve plastics’ use and disposal under the circular economy. Of this 414 kt of plastic packaging waste, 163 kt were declared plastic packaging, 140 kt subjected to recycling, and 94 kt to energy recovery. The current recycling rate of plastic packaging (34%) should be improved to reach EU recycling averages (42%) and goals and to provide widespread benefits, considering revenues of 167 €/t. As a net importer of waste, Portugal could benefit from the valorization of imported waste. Besides increased recycling, pyrolysis and gasification could provide short-term alternatives for producing value-added substances from plastic waste, such as hydrogen, consistent with the National Plan of Hydrogen and improving ongoing regulations on single-use plastics. This manuscript provides an integrative view of plastics in Portugal, from use to disposal, providing specific recommendations under the circular economy.

    Jian Lu, Jun Wu, Jianhua Wang

    • Total 174 subtypes of ARGs were detected by metagenomic analysis.

    • Chloramphenicol resistance genes were the dominant ARGs in water and microplastics.

    • The abundances of MRGs were much higher than those of ARGs.

    • Proteobacteria, Bacteroidetes, and Actinobacteria were the dominant phylum.

    • Microplastics in mariculture system could enrich most of MRGs and some ARGs.

    Microplastics existing widely in different matrices have been regarded as a reservoir for emerging contaminants. Mariculture systems have been observed to host microplastics and antibiotic resistance genes (ARGs). However, more information on proliferation of ARGs and metal resistance genes (MRGs) in mariculture system at the presence of microplastics is needed. This study used metagenomic analysis to investigate the distribution of ARGs and MRGs in water and microplastics of a typical mariculture pond. Total 18 types including 174 subtypes of ARGs were detected with the total relative abundances of 1.22/1.25 copies per 16S rRNA copy for microplastics/water. Chloramphenicol resistance genes were the dominant ARGs with the abundance of 0.35/0.42 copies per 16S rRNA copy for microplastics/water. Intergron intI1 was dominant gene among 6 detected mobile genetic elements (MGEs) with the abundance of 75.46/68.70 copies per 16S rRNA copy for water/microplastics. Total 9 types including 46 subtypes of MRGs were detected with total abundance of 5.02 × 102/6.39 × 102 copies per 16S rRNA copy for water/ microplastics while genes resistant to copper and iron served as the dominant MRGs. Proteobacteria, Bacteroidetes, and Actinobacteria accounted for 84.2%/89.5% of total microbial community. ARGs with relatively high abundance were significantly positively related to major genera, MGEs, and MRGs. Microplastics in mariculture system could enrich most of MRGs and some ARGs to serve as potential reservoir for these pollutants. The findings of this study will provide important information on resistance gene pollution at presence of microplastics in the mariculture system for further proposing suitable strategy of environmental management.

    Xianying Ma, Xinhui Zhou, Mengjie Zhao, Wenzhuo Deng, Yanxiao Cao, Junfeng Wu, Jingcheng Zhou

    • PP-MPs reduced the adsorption capacity of the bulk soil for Cd in aqueous medium.

    • The responses of the POM, OMC and mineral fractions to PP-MPs were different.

    • PP-MPs reduced the adsorption of POM and OMC fractions to Cd.

    • PP-MPs increased the adsorption of mineral fraction to Cd.

    • Effect of MPs on soil may be controlled by proportion of POM, OMC and mineral fractions.

    Microplastics (MPs) are widely present in a variety of environmental media and have attracted more and more attention worldwide. However, the effect of MPs on the the interaction between heavy metals and soil, especially in soil fraction level, is not well understood. In this study, batch experiments were performed to investigate the adsorption characteristics of Cd in bulk soil and three soil fractions (i.e. particulate organic matter (POM), organic-mineral compounds (OMC), and mineral) with or without polypropylene (PP) MPs. The results showed that the addition of PP-MPs reduced the Cd adsorption capacity of the bulk soil in aqueous solution, and the effects varied with PP-MPs dose and aging degree. Whereas, the responses of the three fractions to PP-MPs were different. In presence of PP-MPs, the POM and OMC fractions showed negative adsorption effects, while the mineral fraction showed positive adsorption. For the bulk soil, POM and OMC fractions, the adsorption isotherm fitted to the Langmuir model better than the Freundlich model, whereas, the Freundlich isotherm model is more fitted for the mineral fraction. Combined with the comprehensive analysis of the partitioning coefficients, XRD and FTIR results, it was found that OMC fraction extremely likely play a leading role in the bulk soil adsorption of Cd in this study. Overall, the effect of MPs on adsorption capacity of the bulk soil for Cd may be determined by the proportion of POM, OMC, and mineral fractions in the soil, but further confirmation is needed.

    Zuyin Chen, Lihua Li, Lichong Hao, Yu Hong, Wencai Wang

    • Polystyrene microplastic caused hormesis-like effects in Phaeodactylum tricornutum.

    • Low concentration of microplastic promoted growth, otherwise the opposite was true.

    • The change trends of pigment contents were opposite at two initial algae densities.

    • The chlorophyll fluorescence parameters were more sensitive at low algae density.

    The effects of pristine polystyrene microplastics (pMPs) without any pretreatment at different concentrations (0, 10, 20, 50, and 100 mg/L) on Phaeodactylum tricornutum Bohlin at two initial algae densities (105 and 106 cells/mL) were assessed in this study. Hormesis-like effects were found when microalgae grew with pMPs. The results showed that pMPs inhibited microalgae growth under a high concentration of microplastics tolerated by individual algal cell (low initial algae density) (up to −80.18±9.71%) but promoted growth when the situation was opposite (up to 15.27±3.66%). The contents of photosynthetic pigments including chlorophyll a, chlorophyll c and carotenoids showed resistance to pMPs stress under a low initial algae density and increased with time, but the opposite was true under a high initial algae density. Compared with the low initial algae density group, Qp received less inhibition, and NPQ (heat dissipation) also decreased under the high initial algae density. Under the low initial algae density, OJIP parameters such as Sm, N, Area, Pi Abs, ѱo, φEo, TRo/RC and ETo/RC were more perturbed initially and returned to the levels of the control group (without pMPs) over time, but they remained stable throughout the experiment at high initial algae density. These results show that microplastics in the marine environment may have different toxic effects on P. tricornutum at different growth stages, which is of great significance for understanding the impact of microplastics on marine microalgae and aquatic ecosystems.

    Qinghui Sun, Juan Li, Chen Wang, Anqi Chen, Yanli You, Shupeng Yang, Huihui Liu, Guibin Jiang, Yongning Wu, Yanshen Li

    • Microplastics are widely found in both aquatic and terrestrial environments.

    • Cleaning products and discarded plastic waste are primary sources of microplastics.

    • Microplastics have apparent toxic effects on the growth of fish and soil plants.

    • Multiple strains of biodegradable microplastics have been isolated.

    Microplastics (MPs) are distributed in the oceans, freshwater, and soil environment and have become major pollutants. MPs are generally referred to as plastic particles less than 5 mm in diameter. They consist of primary microplastics synthesized in microscopic size manufactured production and secondary microplastics generated by physical and environmental degradation. Plastic particles are long-lived pollutants that are highly resistant to environmental degradation. In this review, the distribution and possible sources of MPs in aquatic and terrestrial environments are described. Moreover, the adverse effects of MPs on natural creatures due to ingestion have been discussed. We also have summarized identification methods based on MPs particle size and chemical bond. To control the pollution of MPs, the biodegradation of MPs under the action of different microbes has also been reviewed in this work. This review will contribute to a better understanding of MPs pollution in the environment, as well as their identification, toxicity, and biodegradation in the ocean, freshwater, and soil, and the assessment and control of microplastics exposure.