EGU24-8953, updated on 08 Mar 2024
https://doi.org/10.5194/egusphere-egu24-8953
EGU General Assembly 2024
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.

Subsurface transport of microplastics in riverine sediment: Impacts of different rain events and particle density

Jaswant Singh1,2, Reza Dehbandi2, Neeraj Chauhan2,3, Uwe Schneidewind2, Lee Haverson2, Brijesh K Yadav1, and Stefan Krause2,4
Jaswant Singh et al.
  • 1Department of Hydrology, Indian Institute of Technology, Roorkee, Uttarakhand, India
  • 2School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, United Kingdom
  • 3Department of Chemistry & Centre of Advanced Studies in Chemistry, Panjab University, Chandigarh, India
  • 4Univ Lyon, Université Lyon 1 Claude Bernard, ENTPE, CNRS, UMR 5023 LEHNA, 3 Rue M. Audin, 69518 Vaulx-en-Velin Cedex, France

Microplastics (MPs) have emerged as a growing concern, posing potential risks to both marine and terrestrial environments. While surface soils are recognised as a primary sink for these particles, the vertical mobility of MPs in the subsurface remains uncertain due to a lack of comprehensive scientific data. Here, we conducted column experiments to study the transport behaviour of MPs through and retention in subsurface sediment. Two types of pre-stained MPs (median size 50.4 µm) with densities greater than (polystyrene) and smaller than (polyethylene) water were added to the top of large (110 cm) wet-packed fine gravel columns - the most common gravel found in the subsurface zone of the riverine environment. The concentration of deposited MPs was 50,000 particles per kilogram of sediment, derived from an extensive literature survey of polluted sites. Various scenarios, including continuous rain, wet-dry cycles, and dry conditions (characterised by a single rain event followed by a subsequent drying period), were implemented to simulate diverse rain events. 20 mL of water samples were systematically collected at specified intervals from different ports of the column at depths of 30, 50 and 70 cm. Additionally, continuous effluent collection took place at the bottom port (90 cm), which was connected to a pump that maintained a controlled flux at around 4.6 mL/min. At the end of the experiment, gravel samples were methodically collected from discrete sediment layers within the columns (0–5 cm (top of the source layer), 5–10 cm (source layer), 10–30 cm, 30–50 cm, 50–70 cm, 70–90 cm) to quantify the MP mass retained in the column. Results showed that the smallest PS-MPs with a continuous flow system exhibit the highest potential for transport due to higher density and less hydrophobicity compared to PE. With increasing rain events, MPs in the source sediment layer decreased, while MPs concentrations in deeper column layers increased significantly. Furthermore, an intriguing observation indicates that as these MPs undergo more wet-dry cycles, their penetration depth substantially increases. The results indicate that sediment may not only act as a sink for MPs but also as a possible entry point to subsurface receptors such as subterranean fauna and aquifers. This research underscores the intricate dynamics of MPs in sediment and raises awareness regarding the potential environmental consequences.

 

Keywords: Microplastics, Transport, Raining events, Density, Hydrophobicity

 

How to cite: Singh, J., Dehbandi, R., Chauhan, N., Schneidewind, U., Haverson, L., Yadav, B. K., and Krause, S.: Subsurface transport of microplastics in riverine sediment: Impacts of different rain events and particle density, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8953, https://doi.org/10.5194/egusphere-egu24-8953, 2024.