• Microplastics in freshwater systems –

presence, origins and ecological effects

Alice Horton

Centre for Ecology and Hydrology, UK

• Microplastics – what are they?

Plastic fragments/pellets/fibres/films <5mm

Sources:

- Primary: polyethylene/polypropylene ‘microbeads’ from

personal care products and cosmetics, industrial pellets

- Secondary: Breakdown of large litter, shedding of

nylon/polyester fibres (laundry)

• Microplastics - why study them?

• Microplastics are everywhere!

• Rivers and land recognised as sources but

little studied

• Sewage treatment works do not capture

these small particles

• Can be ingested by organisms

• Act as vectors for transport of persistent

organic pollutants (POPs)

• Storm drain input

• Effluent input (‘grey water’)

• Combined Sewage Overflows (raw sewage)

• Land runoff

• Drainage ditches (agricultural)

• LitterPhoto: James Miller

• Inputs to rivers in the UK

Microplastics in wastewater and sewage sludge

Removal efficiency of microplastics following wastewater treatment processes:

• 99% (Magnusson and Norén 2014)• 98% (Murphy et al, 2016)• 95% (Talvitie et al, 2017)• 97% (Mintenig et al, 2017)

However due to large volumes processed, one large STW could still release approx.

900,000 – 800,000,000 MPs per day!

Environmental transport of microplastics

Horton et al (2017). Science of the Total Environment

• Microplastics in the Thames river basin, UK – a study

• 4 sites chosen: 2 dirty (> 25% effluent on

average) and 2 clean (< 4% effluent on

average)

• 4 replicate sediment samples

• Size fractions 1-2mm and 2-4mm

• Sorted visually and by density separation

to ensure all particles were encountered.

Flotation and filtration system for extracting microplastics from sediment, Alice HortonFloated sediment Floated plastic particles

Horton et al (2017). Marine Pollution Bulletin

• Microplastics: sample sorting and analysis

Increasing effluent load

Horton et al (2016). Marine Pollution Bulletin

• Microplastics – Raman spectroscopy

- Polypropylene- Unknown particle

- Copper phthalocyanine- Unknown particle

• Microplastics – exposure

Depending on the environment and organisms, exposure will occur

in different ways.

Numerous variables influence organisms’ exposure, including:

- Proximity to source

- Habitat

- Behaviour

- Feeding habits

In addition to polymer characteristics including:

- Polymer type

- Particle size

- Biofouling

Effects fall into 2 main categories:

Physical damage & chemical damage

These can occur in combination.

• Our approach to fish sampling:

• The UK National Fish Tissue Archive

In 2007, CEH and the UK Environment Agency (EA) began to build an archive of fish tissue samples from a selection of English rivers.

• EA monitor fish stocks annually • normally: throw all back• now: give us 10 roach (10 cm+) from

selected sitesSize, weight and gender recorded Frozen on site (liquid N2)

Vacuum packed and stored at -80°C

Fish dissected and gut removed

Gut contents analysed for microplastics

Slide adapted from an original by Monika Juergens

• Common roach in the Thames - fish gut analysis

Location Distance downstream

Cricklade 36.047

Castle Eaton 42.619

Sandford-Abingdon 105.915

Caversham-Sonning 161.511

Temple-Marlow 186.949

Shepperton-Sunbury 234.155

Sunbury-Molesey 238.729

• Roach gut analysis - results

Polymers identified as:Polyethylene

PolypropylenePolyester

Microplastics are ingested!

Average plastics in gut vs distance from source

Differences in ingestion based on:1. Gender2. Size of fish

• Ingestion of microplastics and chemical bioaccumulation

• Freshwater midge larvae – Chironomus sancticaroli• 1% by mass nylon, 13-18 µm• PBDEs: 47, 99, 100, 153

• Etc… see Elma’s presentation

Horton et al., SETAC Europe 2016

• Microplastics in terrestrial environments• No known studies quantifying microplastics in

the terrestrial environment

• Plastic litter breaks down in the environment

• Microplastics (beads and fibres) enter terrestrial environment via sewage sludge application to land

• High potential for retention

Photo: Alice Horton Photo: Alex Walton

• Difficulties in microplastics research

• Definition of ‘microplastics’ – very broad!• What is a plastic? A ‘pure’ polymer? Any composite containing plastic?

• Different polymers, sizes, shapes, ages will behave differently and have different effects.

• Environment will determine ecological interactions

• Comparability between studies: different methods• Sampling• Particle extraction • Minimum and maximum size counted• Particle identification

• Many studies rely on visual identification – very subjective

• Environmental studies are time-consuming!

Thank you

Acknowledgements: Alex Walton, Elma Lahive, Dave Spurgeon, Claus Svendsen, Richard Williams, Monika Juergens,

Angela Palacio, Lindsay Newbold, Rodrigo G. Disner, Mário A. Navarro-Silva.

I have credited photos where possible, apologies where credit was not available and has not been given.

References• Horton, A. A., Walton, A., Spurgeon, D. J., Lahive, E., & Svendsen, C. (2017). Microplastics in freshwater and terrestrial environments: Evaluating

the current understanding to identify the knowledge gaps and future research priorities. Science of The Total Environment (in press).

• Horton, A. A., Svendsen, C., Williams, R. J., Spurgeon, D. J., & Lahive, E. (2017). Large microplastic particles in sediments of tributaries of the River Thames, UK - Abundance, sources and methods for effective quantification. Marine Pollution Bulletin, 114(1), 218-226.

• Horton A. A., Palacio-Cortes A. M., Lahive E., Newbold L., Pereira M. G., Disner R. G., Navarro-Silva M. A., Grassi M. T., Spurgeon D. J. Ingestion of microplastics by the chironomid Chironomus sancticaroli and effects on the microbiome in the presence of PBDEs. In: SETAC Europe 26th Annual Meeting, Nantes, France, 22-26 May 2016

• Magnusson, K., Norén, F. (2014). Screening of microplastic particles in and down-stream a wastewater treatment plant. IVL Swedish Environmental Research Institute, C 55.

• Mintenig, S.M., Int-Veen, I., Loder, M.G., Primpke, S., Gerdts, G. (2017). Identification of microplastic in effluents of waste water treatment plants using focal plane array-based micro-Fourier-transform infrared imaging. Water Research 108, 365-372.

• Murphy, F., Ewins, C., Carbonnier, F., Quinn, B. (2016). Wastewater Treatment Works (WwTW) as a Source of Microplastics in the Aquatic Environment. Environmental Science & Technology 50, 5800-5808.

• Talvitie, J., Mikola, A., Setala, O., Heinonen, M., Koistinen, A. (2017). How well is microlitter purified from wastewater? - A detailed study on the stepwise removal of microlitter in a tertiary level wastewater treatment plant. Water Research 109, 164-172.

Additional reading:

• Boucher, J., Friot, D., 2017. Primary Microplastics in the Oceans: a Global Evaluation of Sources. IUCN, Gland, Switzerland.

• Carr, S.A., Liu, J., Tesoro, A.G., 2016. Transport and fate of microplastic particles in wastewater treatment plants. Water Res. 91, 174–182.

• Ziajahromi, S., Neale, P.A., Leusch, F.D., 2016. Wastewater treatment plant effluent as a source of microplastics: review of the fate, chemical interactions and potential risks to aquatic organisms. Water Sci. Technol. 74, 2253–2269.