On the transport mechanisms, ecological interactions and fate of microplastics in aquatic environments

Mendrik, Freija

Abstract

Microplastics are now persistent throughout aquatic systems globally and can cause a range of ecological damage. The transport of microplastics is influenced by the polymer type, in addition to physical, biological, and chemical gradients plastic particles move through as they are transported across freshwater to marine environments. The combined influence of these mechanisms on microplastic fate is largely unquantified, which prevents identification of accumulation zones and the related development of effective mitigation measures. This research applies a multidisciplinary approach that combines innovative experiments and physical modelling with detailed fieldwork to quantify the main factors influencing microplastic transport and fate. Using a suite of novel settling experiments, biofouling is shown to be a principal factor affecting microplastic deposition through changes in specific density. Yet settling regimes differ depending on polymer and shape as well as ambient sediment and salinity concentrations. To understand particle distribution further, abundances and fluxes of microplastics within a large river system are coupled with hydrological data to explore how microplastics are transported through the vertical water column , finding that most are dispersed below the water surface, yet concentration is dependent on seasonal discharge. Finally, the role of complex coastal ecosystems as a sink for microplastics is investigated in a hydraulic flume under a range of flow conditions. It is shown, for the first time, that microplastic trapping efficiency could be high for both sparse and dense coral canopies due to a reduction in streamwise velocities causing settling on, within, and behind coral structures. It is concluded that although sediment laws can provide a basic understanding of microplastic transport, a new generation of microplastic transport regimes is needed. The findings from the thesis enhance our knowledge of the complex mechanisms that govern microplastic transport and fate in aquatic environments and this new understanding is contextualised in terms of their broad ecological implications.

Citation

Mendrik, F. (2022). On the transport mechanisms, ecological interactions and fate of microplastics in aquatic environments. (Thesis). University of Hull. Retrieved from https://hull-repository.worktribe.com/output/4224632

• Thesis Type: Thesis
• Deposit Date: Jan 12, 2023
• Publicly Available Date: Feb 24, 2023
• Keywords: Geography; Environmental science
• Public URL: https://hull-repository.worktribe.com/output/4224632
• Additional Information: Energy and Environment Institute
• Award Date: Jun 1, 2022