Rationale: Although local case studies provide evidence of freshwater microplastic (MP) contamination, a local approach limits the potential for generalisation and up-scaling of site-specific research. The absence of systematic freshwater microplastic surveys impedes our understanding of how their concentration, composition and properties vary globally.

Research question: This project aims to understand the distribution of MPs in rivers globally, and in particular how their physical (size, shape, density) and chemical properties (incl. additives such as Bisphenol A (BPA) and Nonylphenol (NP)) differ.  MP characteristic differences are expected in relation to catchment properties, prevalence of primary and secondary MP sources, and hydrodynamic and sediment conditions.

Objective: Develop a simple, robust, low-cost, standardised and well-documented approach for the first coordinated global MP river survey to advance site-specific knowledge towards generic and transferable system level understanding.

Methods: Utilising global partnerships, sediment and water samples are being collected from a range of rivers with a custom-made low-cost yet robust sampling kit. Sediment and water samples collected globally will be returned to the University of Birmingham whereby microplastic contamination will be quantified using various novel techniques such as Nile Red and Thermo-Gravimetric-InfraRed-Gas Chromatography/Mass Spectrometry (TG-IR-GC/MS). The comparison of low-tech (field applicable) and high-tech (laboratory-based) approaches will be utilised to benchmark the utility of the field approaches for routine monitoring. 

All data collected will be GPS tagged and dated, and the results will be compiled into an open-access and FAIR (Finable, Accessible, Interoperable and Re-suable) database hosted by UoB.

Partners involved with Work Package 1: Currently we have partners from French Guiana, Punta Arenas and Argentina – South America.

In Africa we have Nigeria, Sierra Leone, Zambia, Kenya and South Africa. Both Canada and the United States of America are represented, as well as Australia and New Zealand. In Southeast Asia we have partners from Indonesia, Malaysia, Thailand and Cambodia.

We also have 17 partners in the United Kingdom sampling rivers from Scotland, Wales and Great Britain. In Europe partners are located in Spain, Finland, Brussels and Greece.

We are always looking for more partners so if you are currently working on microplastics or already work in a freshwater system and can collect sediment and water samples. The 100 Plastic Rivers team will send you a sample kit and standardised protocol. The samples will then be sent back to UoB for further analyses. 

Rationale: Initial investigations indicate that streambed sediments can be hotspots of microplastic accumulation. However, current technological constraints critically limit the understanding of how microplastic properties affect their transport and accumulation and the release of additives such as BPA and NP from freshwater-sediment interfaces.

Research question: Which processes control the transport and accumulation of microplastics with different shapes, densities, composition and the release of BPA and NP at freshwater-sediment interfaces?

Objective: Analyse microplastic property-dependent transport, accumulation and BPA and NP release under variable hydrodynamic, geomorphological and sediment conditions.

Methods: Details will be added in due course following our analysis of the suitability and robustness of currently available methods.

Rationale: Global assessments of the risks of microplastic accumulation and potential contaminant leaching in freshwater systems require quantitative modelling tools. The current lack of suitable modelling tools for analysing microplastic transport mechanisms, their fate and biogeochemical alteration (e.g. biomolecule adsorption) hampers adequate assessment and management of environmental risks.

Research question: How can transport, accumulation, and BPA and NP release from microplastics be predicted under variable hydrodynamic, biogeochemical and sediment conditions?

Objective: Develop modelling tools for the prediction of microplastic transport and transformation for simulating reactive fluid and microplastic particle flow at freshwater-sediment interfaces including the quantification of BPA and NP release that can be adapted to further contaminants.

Methods: Once the database is available (from WP1 supplemented with data curated from the literature) various modelling approaches will be developed including Bayesian networks and Quantitative Structure Activity Relationships.

Rationale: A profound assessment of microplastic risks to freshwater food webs is currently hampered by the critical knowledge gaps of the drivers for microplastic entry, transfer and biomagnification within the food webs and enhanced toxicity due to Trojan horse effects, when microplastics carry xenobiotics such as BPA and NP directly into the organism.

Research question: What properties of microplastics drive the uptake in the aquatic food webs and does biomagnifying occur under realistic environmental conditions. Do microplastics increase the uptake of BPA and NP via Trojan horse effects and/or biomolecule-enhanced release?

Objective: Identify functional pathways and drivers for microplastic uptake and biomagnification. Quantify ecotoxicological impact through freshwater food webs as well as the potential for enhanced uptake through Trojan horse effects with BPA and NP leaching from ingested microplastics. Biomolecule driven enhanced release from microplastics as a result of attachment to natural organic matter or organism-secreted biomolecules will also be explored.

Methods: Selection of species for individual and food web experiments is currently underway. Lab-scale exposures will be performed with mixtures of microplastics varying in physical and bio-chemical traits to identity potential drivers for uptake and biomagnification. Novel methods for tagging different polymers will be implemented in the mesocosm experiments to aid the identification and propagation of different polymers. Laboratory- based experiments will be carried out to identify concentrations of selected microplastics and their additives, under standardised and realistic exposure conditions over acute and chronic timescales.  Microplastics will be tested virgin and following ageing under realistic exposure conditions, and extensive experience from the field of engineered nanomaterials fate and toxicity (nanotoxicity) will be leveraged. This community has already been working for > 5 years to revise the standard OECD test guidelines, developed initially for dissolved chemicals, to take account of the unique features arising from the large surface of particulate pollutants including microplastics.