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Microplastics from the 1950s found in London lake sediments

March 1, 2019
Hampstead Pond No.1 in North London.

Hampstead Pond No.1 in North London. Image: Paul Robertson | Flickr Creative Commons

Microplastics dating back to the 1950s have been found in a sediment core taken from the lake bed of Hampstead Pond No.1 in London, UK. Plastic pollution is frequently featured in the news as a contemporary, oceanic environmental problem. However, a new open-access study by Dr. Simon Turner from University College London and colleagues provides evidence of long-term plastic accumulation in urban freshwater environments.

Hampstead Pond No.1 is one of thirty ponds on Hampstead Heath in North London, dug in the 17th and 18th centuries as reservoirs. Other ponds on the Heath are open to outdoor swimmers, anglers and model boating enthusiasts. However, despite their location in a cherished area of urban green space, the new study demonstrates that the ponds have been receiving plastic pollution for more than 60 years.

Plastic in UK lakes: a growing issue of concern

The impetus for the study, published in the Journal of Paleolimnology, arose from previous research carried out between 2008-2012 on other UK lakes. Dr. Turner explains, “At Edgbaston Lake, Birmingham we observed a lot of litter in the reed-filled margins but less in the deep water – and like some of the beach clean ups, some of the plastic waste, including crisp packets, drinks bottles, especially noticeable by their packaging design and best-before dates, had clearly been hanging around for a considerable period of time.

“What we realised was the amount and type of litter accumulating in lakes, especially plastic waste, had not really been assessed, especially when compared to marine habitats and simple questions like ‘how long has plastic been accumulating in lakes’ and ‘has plastic litter in lakes changed over time’ remained largely unanswered.”

In 2015, Rebecca Vaughan – at the time a UCL undergraduate – carried out a study of Edgbaston Lake to quantify just how much plastic waste was present in the lake sediment. Dr. Turner then built on this study to explore whether it was possible to identify microplastics (less than 5mm in diameter) in a dated lake sediment core. He and his research team chose an archived sediment core from Hampstead Pond No. 1, as it was accurately dated, large in volume, and surrounded by urban spaces which could provide sources of plastic pollutants.

As there is no long-term monitoring of plastic waste, such historical cores can provide a picture of plastic pollution through time. Plastics generally degrade very slowly –  a process which has been estimated to take hundreds of years – and so are likely to have built up in sediments in many freshwater environments. However, historical lake sediment cores had not been analysed for plastic pollutants prior to this study.

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Selected microplastic particles and fibres found in HAMP1 sediment core from Hampstead Pond No.1. Image: Turner et al (2019)

Microplastics in Hampstead Pond No.1

Dr. Turner and colleagues found a range of microplastic fibres and fragments in the Hampstead Pond No.1 sediment core. The fibres – of varying colours – are likely to be derived from the breakdown of synthetic textiles, and released into the lake from wastewater and sewage (although these inputs are relatively low in the pond), or via clothing, textiles, swimwear or fishing line. Microplastic fragments in the core were all orange foam polystyrene particles, ranging from 0.2–2mm in size.

Whilst there are some fibres in the core which may date from the late 19th and early 20th centuries, the majority of the microplastics found in the study date from the 1950s onwards. The accumulation rate of microplastics in the lake sediment was at its highest in the decade before 2009, when the core was taken.

Dr. Turner explains, “Like other contaminants released into aquatic systems, the composition and abundance of microplastics looks to have varied over time, as a result of changing industrial and domestic sources. We only have really started to quantify the inputs, transport and burial processes of microplastics in lakes, but this paper and others similar, are a step in understanding the global movement and accumulation of plastic waste in aquatic systems.”

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Reflections from neighbouring houses on Hampstead Pond No.1 after dark. Image: Chris Guy | Flickr Creative Commons

Microplastics and freshwater conservation

Microplastics can be ingested by freshwater organisms, as this recent paper by Dr. Fred Windsor and colleagues shows, potentially leaching harmful contaminants and additives into their bodies, or altering their physiology. As a result, understanding the transmission of microplastics through freshwater food webs – and their subsequent burial in sediments or transport elsewhere – is a key topic for research.

Dr. Turner says, “To get low density microplastic waste into benthic sediments we have to have a mechanism for accumulation and sinking – be it biofouling or ingestion and burial with organisms. Considering how resilient to degradation plastics were designed to be, my thoughts are that once in a lake, microplastics probably go through quite a few organisms before ultimate burial.”

Microplastic research in freshwaters is a growing area of scientific interest, and this paper contributes significantly to the field by showing that historical patterns of plastic pollution can be found in lake bed sediment cores. Clearly, plastic pollution is a key – if under-communicated – topic for freshwater conservation and policy. As Dr. Turner puts it, “Plastic waste in the environment – it’s not all about the oceans.”

Read the journal article

Turner, S., Horton, A.A., Rose, N.L. et al. (2019) “A temporal sediment record of microplastics in an urban lake, London, UK”, J Paleolimnol. https://doi.org/10.1007/s10933-019-00071-7

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