A Review on Heavy Metal Ion Adsorption on Synthetic Microfiber Surface in Aquatic Environments

Liquidlike, Low-Friction Polymer Brushes for Microfibre Release Prevention from Textiles

During synthetic textile washing, rubbing between fibres or against the washing machine, exacerbated by the elevated temperature, initiates the release of millions of microplastic fibres into the environment. A general tribological strategy is reported that practically eliminates the release of microplastic fibres from laundered apparel. The two-layer fabric finishes combine low-friction, liquidlike polymer brushes with "molecular primers", that is, molecules that durably bond the low-friction layers to the surface of the polyester or nylon fabrics. It is shown that when the coefficient of friction is below a threshold of 0.25, microplastic fibre release is substantially reduced, by up to 96%. The fabric finishes can be water-wicking or water-repellent, and their comfort properties are retained after coating, indicating a tunable and practical strategy toward a sustainable textile industry and plastic-free oceans and marine foodstuffs.

Deciphering morphology patterns of environmental microfibers: Insights into source apportionment

Microfibers, a prevalent form of microplastics, undergo diverse environmental interactions resulting in varied morphological changes. These changes can offer insights into their environmental trajectories. Despite its importance, comprehensive studies on microfiber morphology are scarce. This study collected 233 microfibers from the East China Sea and South China Sea. Based on morphological features observed in microscopic images of microfibers, such as curvature, cross-sectional shapes, diameter variations, and crack shapes, we identified a general morphological pattern, classifying the environmental microfibers into three distinct morphological types. Our findings highlight noticeable differences in morphological metrics (e.g., length, diameter, and surface roughness) across three types, especially the diameter. Microfibers of Type I had an average diameter of 19.45 ± 4.93 μm, significantly smaller than Type II (263.00 ± 75.15 μm) and Type III (299.68 ± 85.62 μm). Within the three-dimensional (3D) space fully defined by these quantitative parameters, the clustering results of microfibers are also consistent with the proposed morphology pattern, with each category showing a potential correlation with specific chemical compositions. Type I microfibers correspond to synthetic cellulose, while 94.79 % of Types II and III are composed of polymers. Notably, we also validated the great applicability of the morphology categories to microfibers in diverse environmental compartments, including water and sediments in nearshore and offshore areas. This classification aids in the efficient determination of microfiber sources and the assessment of their ecological risks, marking a significant advancement in microfiber environmental studies.

Alleviation of microplastic toxicity in soybean by arbuscular mycorrhizal fungi: Regulating glyoxalase system and root nodule organic acid

Microplastic accumulation in the soil-plant system can stress plants and affect products quality. Currently, studies on the effect of microplastics on plants are not consistent and underlying molecular mechanisms are yet unknown. Here for the first time, we performed a study to explore the molecular mechanism underlying the growth of soybean plants in soil contaminated with various types of microplastics (PS and HDPE) and arbuscular mycorrhizal fungi (AMF) (presence/absence). Our results revealed that a dose-dependent decline was observed in plant growth, chlorophyll content, and yield of soybean under MPs stress. The addition of MPs resulted in oxidative stress closely related to hydrogen peroxide generation (H2O2), methylglyoxal (MG) levels, lipid peroxidation (MDA), and lipoxygenase (LOX). In contrast, MPs addition enhanced mycorrhizal colonization and dependency relative to control while the rubisco and root activity declined. All the genes (GmHMA13 and GmHMA19) were downregulated in the presence of MPs except GmHMA18 in roots. AMF inoculation alleviated MPs-induced phytotoxic effects on colonization, rubisco activity, root activity and restored the growth of soybean. Under MPs exposure, AMF inoculation induced plant defense system via improved regulation of antioxidant enzymes, ascorbate, glutathione pool, and glyoxalase system. AMF upregulated the genes responsible for metals uptake in soybean under MPs stress. The antioxidant and glyoxalase systems coordinated regulation expressively inhibited the oxidative and carbonyl stress at both MPs types. Hence, AMF inoculation may be considered an effective approach for minimizing MPs toxicity and its adverse effects on growth of soybean grown on MPs-contaminated soils.

Research progress on the role of biofilm in heavy metals adsorption-desorption characteristics of microplastics: A review

Microplastics (MPs) have been found to be widely distributed in aquatic environments, where they will interact with toxic heavy metals and result in more serious adverse effects on the aquatic environments and organisms. However, after entering the aquatic environments, MPs are quickly covered by biofilms, which significantly modify MPs properties and relevant heavy metals adsorption-desorption characteristics In order to better understand the adsorption behavior of heavy metals on biofilm developed MPs (BMPs), we comprehensively reviewed representative studies in this area. First, we summarized the formation process of biofilms on MPs. Subsequently, we reviewed the current understanding on the influence of biofilm formation on the properties of MPs and discussed the metal adsorption-desorption characteristics of MPs affected by these changes. Finally, based on the systematic literature review, some future research needs and strategies were proposed to further understand the interactions between MPs and heavy metals.

Impact of treatment chemicals on the morphology and molecular structure of microfibers and microplastic films in wastewater

This study investigated the impact of commonly used treatment chemicals on the morphology and molecular structure of microfibers (MFs) and microplastic films (MPFs) to determine whether significant changes could occur during wastewater treatment. MFs and MPFs were exposed to sodium hypochlorite (NaOCl), hydrogen peroxide (H2O2), calcium hydroxide (Ca(OH)2, pH 11), sodium hydroxide (NaOH, pH11), and hydrochloric acid (HCl, pH 3) at typical doses and exposure times used at wastewater treatment plants. Scanning electron microscopy (SEM) analysis and attenuated total reflectance-Fourier-transform infrared (ATR-FTIR) were used to examine any morphological or chemical changes after the treatment. Morphological changes were observed in the form of cracks, and increased roughness was revealed in the SEM and 3-D surface images. The results showed that MFs were more resistant to surface degradation than MPFs. Moreover, intensity peaks of ATR-FTIR revealed some partial dislodgement of the bonds in both MFs and MPFs after chemical treatment, but the overall polymer structure remained intact. The changes that occur on the surface of MFs and MPFs during chemical treatment can impact their fate, removal, and transportation behavior both at the treatment plant and after discharge to the environment.

Detection, characterization and possible biofragmentation of synthetic microfibers released from domestic laundering wastewater as an emerging source of marine pollution

Synthetic microfibers are universally recognized as an emerging pollutant in all ecosystems. The present investigation focuses on the evaluation and quantification of synthetic microfiber released from domestic laundering wastewater from different regions of Bhubaneswar city of Odisha state of India. The estimated number of microfibers collected from 500 ml of sample varied from 200 to 500 in numbers with an average amount of biomass in the range of 0.4-4 g. The surface morphology of the samples was assessed by Scanning Electron Microscopic analysis which revealed that the fibers were having a length of approximately 10-30 mm and diameter of 10-20 μm. Carbonyl (CO) stretching band at 1711 cm^-1 and Aldehyde (CH) Weak bond at 2917.38 cm^-1 absorption were recorded from Fourier transform infrared spectroscopic analysis. As microfibers released from synthetic apparels are major source of environmental microplastic pollution their precise detection could help in controlling this problem.

Microbial remediation of plastic pollutants generated from discarded and abandoned marine fishing nets

A wide range of plastic debris dumped into the ocean has recently gained concern of the marine ecosystems. Discarded and abandoned fishing nets, also known as ghost nets, are lost in the marine water and has no commercial significance. Additionally these fishing gear left out in the aquatic environment pose a severe risk to marine environment. Fishing nets, made up of synthetic plastic materials, are a major source of marine pollutants and act as a vector for transporting other toxic chemical pollutants. Approximately 10% of total marine plastic pollutants come from commercial fishing nets, and each year up to 1 million tons of fishing gear are discarded into the marine ecosystem. It can be estimated that by 2050 the amount will be doubled, adding 15-20 million metric tons of discarded lost fishing gears into ocean. The gradual and increased deposition of plastic pollutants in aquatic habitat also affects the whole food chain. Recently, microbial degradation of marine plastics has focussed the eyes of researchers and a lot of investigations on potential microbial degraders are under process. Microorganisms have developed the ability to grow under plastic stress condition and adapt to alter metabolic pathways by which they can directly feed upon marine plastic pollutants as sole carbon source. The present review compiles information on marine plastic pollution from discarded and abandoned fishing nets, their effect on aquatic ecosystems, marine animals and food chain and discusses microbial remediation strategies to control this pollution, especially and their implications in the marine ecosystems.