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Microplastics in the environment: an emerging threat to agro-ecosystems?

  • Full or part time

    Dr Paul Kay
  • Application Deadline
    Monday, January 06, 2020
  • Competition Funded PhD Project (European/UK Students Only)
    Competition Funded PhD Project (European/UK Students Only)

Project Description

Microplastics (plastics < 5mm) are emerging contaminants of concern and are increasingly being detected in our natural environment, in rivers, lakes, soils and sediments. Terrestrial systems have received far less scientific attention than their aquatic counterparts, even though microplastic pollution has been suggested to be 4-23 fold larger than in the ocean (Horton et al., 2017). The use of organic soil amendments, such as sludge application, can inadvertently introduce microplastics. Following their addition, microplastic fibres are persistent in the environment, with detections reported in agricultural fields up to 15 years after sludge was incorporated into the soil (Zubris and Richards, 2005). It has been estimated that microplastics now comprise between 0.5-2 % by volume in agricultural soil systems.

Soils are essential components of terrestrial ecosystems. Microplastic contamination has been shown to disturb vital relationships between soil and water, as well as having consequences for soil structure and microbial function (de Souza Machado et al., 2018). Common microplastic types (polyacrylic fibers, polyamide beads, polyester fibers, and polyethylene fragments) at environmentally relevant incorporation volumes were observed to affect soil bulk density, water holding capacity, hydraulic conductivity, soil aggregation, and microbial activity. It remains largely unknown what effects on soil function such as this have on wider ecosystem functioning.

This project addresses the risk that microplastics place on agro-ecosystems by evaluating impacts of microplastics on a wider suite of soil physico-chemical measurements. Controlled laboratory and field scale experiments at the University of Leeds farm will also investigate the subsequent impact on crop growth and development. The potential for microplastics to significantly alter soil properties and influence plant growth and development raises a number of concerns pertaining to sustainable agriculture and urgently warrants further investigation given the increasing use of sludges in agriculture, as a means of meeting fertiliser demand whilst disposing of a wastewater by-product.

Aim and objectives
The overall aim of this project is to better understand the fate and effects of microplastics in agro-ecosystems. This will be achieved using a combination of an experimental approach in the laboratory and field trials utilising facilities available at the University of Leeds farm. The specific objectives are to:
1. Characterise inputs of microplastics into agricultural soils environment
2. Undertake controlled experiments to study the environmental fate of microplastics (field and laboratory experiments)
3. Investigate the impact of microplastic pollution on crop growth and development using controlled field trials.

Funding Notes

NERC DTP funding at University of Leeds

See:View Website


de Souza Machado, A.A., Lau, C.W., Till, J., Kloas, W., Lehmann, A., Becker, R., Rillig, M.C., 2018. Impacts of Microplastics on the Soil Biophysical Environment. Environ. Sci. Technol. 52, 9656–9665.
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. Sci. Total Environ. 586, 127–141.
Zubris, K.A. V., Richards, B.K., 2005. Synthetic fibers as an indicator of land application of sludge. Environ. Pollut. 138, 201–211.

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