Biofilms Enhance the Adsorption of Toxic Contaminants on Plastic Microfibers under Environmentally Relevant Conditions.

Microplastics (MPs) exposed to the natural environment provide an ideal surface for biofilm formation, which potentially acts as a reactive phase facilitating the sorption of hazardous contaminants. Until now, changes in the contaminant sorption capacity of MPs due to biofilm formation have not been quantified. This is the first study that compared the capacity of naturally aged, biofilm-covered microplastic fibers (BMFs) to adsorb perfluorooctane sulfonate (PFOS) and lead (Pb) at environmentally relevant concentrations. Changes in the surface properties and morphology of aged microplastic fibers (MF) were studied by surface area analysis, infrared spectroscopy, and scanning electron microscopy. Results revealed that aged MFs exhibited higher surface areas because of biomass accumulation compared to virgin samples and followed the order polypropylene>polyethylene>nylon>polyester. The concentrations of adsorbed Pb and PFOS were 4-25% and 20-85% higher in aged MFs and varied among the polymer types. The increased contaminant adsorption was linked with the altered surface area and the hydrophobic/hydrophilic characteristics of the samples. Overall, the present study demonstrates that biofilms play a decisive role in contaminant-plastic interactions and significantly enhance the vector potential of MFs for toxic environmental contaminants. We anticipate that knowledge generated from this study will help refine the planetary risk assessment of MPs.

A disaster risk reduction framework for the new global instrument to end plastic pollution.

There are many benefits to be realized by applying a disaster risk reduction framework to the context of plastic pollution, especially in regards to operationalizing the precautionary principle that is inherent in many international treaties and conventions. We explore the implications of framing plastic pollution as a 'disaster' in light of the development of the new global instrument to end plastic pollution by aligning the objectives of the United Nations (UN) Sendai Framework for Disaster Risk Reduction 2015-2030 (SF) and the UN Sustainable Development Goals (SDGs); and thereby also complementing the many climate and non-climate mandates embedded within the UN Framework Convention on Climate Change (UNFCCC). It has been proposed that the UN global instrument to end plastic pollution could be based on the guidelines of the Paris Agreement (PA), driven by national action plans, potential to offset and mandatory reporting requirements. Adding a disaster risk reduction lens to this approach will strongly complement and enhance the environmental and human health outcomes aspired for the global and legally binding treaty to end plastic pollution. We provide an overview to reinforce the mutual benefits of cooperation and coordination, linking the SF, UNFCCC and SDGs to the future international instrument.

Fate and transformation of microplastics due to electrocoagulation treatment: Impacts of polymer type and shape.

The prevalence and adverse impacts of microplastics requires the identification of science-based abatement measures. Electrocoagulation treatment is a cost-effective oxidation process that removes numerous pollutants, including to some extent, microplastics. The performance of a custom-built electrocoagulation reactor was determined by calculating the removal efficiency. The effects of the oxidation process on polymer types (polyamide (PA), polyethylene (PE), polyethylene terephthalate (PET) and polypropylene (PP)) and shapes (fibres and fragments) were investigated in synthetic wastewater and laundry wastewater. The calculated removal efficiency suggested that electrocoagulation treatment was an effective technology for microplastics abatement. More fibres tended to be removed than fragments, viz. 92% fibres removed versus 88% fragments. The findings also demonstrated that specific polymers were preferentially removed, viz. PET > LDPE > PP > PA. Further analysis indicated that the electrocoagulation treatment affected microplastic polymers physically, viz. flaking and changed surface conditions, as well as chemically, viz. changes in vibrational energies of C-O-C stretching bonds, C=O stretching bonds, C-H stretching bonds and formation of reactive oxygen species (ROS). Our findings indicate that whilst seemingly effective, electrocoagulation treatment induces changes to microplastic polymers that could beneficially lead to degradation, and/or further fragmentation or breakdown and thereby potentially generating more bioavailable toxic nanoplastic byproducts.

Occurrence and distribution of microplastics in long-term biosolid-applied rehabilitation land: An overlooked pathway for microplastic entry into terrestrial ecosystems in Australia.

Wastewater treatment plants (WWTPs) efficiently eliminate over 98% of microplastics (MPs) from wastewater discharge, subsequently accumulating them in sludge. This sludge is frequently employed as fertilizer in agricultural practices or land rehabilitation. While there is significant research on biosolid application in agriculture, the discussion regarding its application in rehabilitating industrial zones and MPs contamination is limited. The current study investigates the abundance, distribution, and composition of MPs in rehabilitation land with long-term biosolid-application in Australia. Three minesite fields (designated 1-3), each with distinct biosolid application histories since 2011, 2012, and 2017, and a control field without any biosolid application history, were chosen for this study. The abundances of MPs in biosolid-applied fields 1-3 (6.04 ± 1.92 x 102 MP kg-1; 4.94 ± 0.73 x 102 MP kg-1; 2.48 ± 0.70 x 102 MP kg-1) were considerably higher compared to non-biosolid-applied field (0.70 ± 0.63 x 102 MP kg -1). This indicates that the application of biosolids significantly contributes to the presence of MPs in the soil. Moreover, the results suggest that with each successive application, the abundance of MPs increases. The abundance and size of MPs in both biosolid and non-biosolid soils decreased as the soil depth increased. Microbeads were dominant in soils where biosolids were applied (up to 61.9%), while fibres were dominant in non-biosolid soils (accounting for 85.7%). The distribution of plastic polymer types varied among fields and soil depths. Most MPs were microbeads of polyamide (PA), fragments of polyethylene (PE), foam of polystyrene (PS), and fibres of rayon. This research presents evidence that the extended utilization of biosolids results in elevated MP pollution in minesite rehabilitation land, highlighting a frequently overlooked origin of MP contamination in terrestrial settings. Additional evaluations needed to understand ecological risks of MPs in soil ecosystems affected by biosolid application.

Polymer prioritization framework: A novel multi-criteria framework for source mapping and characterizing the environmental risk of plastic polymers.

Plastics are an intrinsic part of modern life with many beneficial uses for society. Yet, there is increasing evidence that plastic and microplastic pollution poses a risk to the environment and human health. Microplastics are increasingly grouped as a complex mix of polymers with different physicochemical and toxicological properties. This study attempts to assess the hazardous properties of common polymer types through the development of an integrated multi-criteria framework. The framework establishes a systematic approach to identify plastic polymers of concern. A semi-quantitative method was devised using twenty-one criteria. We used a case study from Victoria, Australia, to evaluate the effectiveness of the framework to characterize the environmental risk of common polymer types. A wide range of data sources were interrogated to complete an in-depth analysis across the material life cycle. We found that three polymers had the highest risk of harm: polyvinyl chloride, polypropylene, and polystyrene; with dominant sectors being: building and construction, packaging, consumer and household, and automotive sectors; and greatest leakage of plastics at the end-of-life stages. Our findings illustrate the complexity of microplastics as an emerging contaminant, and its scalability supports decision-makers globally to identify and prioritize management strategies to address the risks posed by plastics. ENVIRONMENTAL IMPLICATION: The hazardous nature of mismanaged plastics is an international concern. The negative impacts on the environment and human health are increasingly coming to light. Consequently, resource constraints limits the ability to address all problems. Our work adopts a holistic approach to evaluate the risk of harm from microplastics across the entire life cycle to allow for targeted management measures. The hazard assessment of common polymer types developed using a multi-criteria framework, presents a systematic approach to prioritize polymers at any scale. This allows for the development of optimal investments and interventions to ensure that high-risk environmental problems are addressed first.

Estimation of the mass of microplastics ingested - A pivotal first step towards human health risk assessment.

The ubiquitous presence of microplastics in the food web has been established. However, the mass of microplastics exposure to humans is not defined, impeding the human health risk assessment. Our objectives were to extract the data from the available evidence on the number and mass of microplastics from various sources, to determine the uncertainties in the existing data, to set future research directions, and derive a global average rate of microplastic ingestion to assist in the development of human health risk assessments and effective management and policy options. To enable the comparison of microplastics exposure across a range of sources, data extraction and standardization was coupled with the adoption of conservative assumptions. Following the analysis of data from fifty-nine publications, an average mass for individual microplastics in the 0-1 mm size range was calculated. Subsequently, we estimated that globally on average, humans may ingest 0.1-5 g of microplastics weekly through various exposure pathways. This was the first attempt to transform microplastic counts into a mass value relevant to human toxicology. The determination of an ingestion rate is fundamental to assess the human health risks of microplastic ingestion. These findings will contribute to future human health risk assessment frameworks.