Plastics in karst groundwater systems

This project is focussed on the fate and impact of plastic pollution in karst groundwater systems. Plastic contamination is pervasive and a serious global issue, contaminating even remote locations such as deep underground water stores. However, there has been almost no research undertaken on the occurrence and fate of plastics in groundwater systems which are key drinking water supplies around the world. Some of the most important groundwater stores are found in karstic terrains, often characterised by the presence of cave networks, sink holes and rapid subsurface transport of pollutants. Around 14% of the earths land surface is covered by karst terrains and 25% of the global population completely or partially dependent on drinking water from karst systems. Chalk is an example of a karst system which in Europe we rely on heavily for drinking water - yet there is no published research on microplastic pollution in UK karst. This project will assess micro (1-1000 micron) and nano-plastic (<1 micron) contamination across a range of European karst systems (from karstfied systems with lower vulnerability to the most highly vulnerable karst). Through sampling springs and other outflow points the project will elucidate relationships between the degree of karstification and the nature of microplastic pollution, including the amount and type of plastics, their size ranges and shape characteristics. The project will include extensive fieldwork across the UK, and in Croatia/Slovenia to collect representative samples across the full spectrum of different types of karst.

Research questions include: (1)Do MPs in karst systems pose a threat to drinking water and groundwater dependant ecosystems? (2) Does the nature of the karst system (i.e. degree and type of karstification) control the abundance and type of MPs found in groundwater? (3) How are MPs in karst affected by the environmental setting (e.g. landuse or specific sources of MPs) and what are the key sources of MPs in karst groundwater systems? (4) Does the nature of the karst system control the physical characteristics of MPs, type, size and shape?


A significant aspect of this project will be the development and use of novel sampling and analytical protocols that can be a beacon for future regulatory monitoring - which is at an early stage for groundwater pollution. This will also be the first study to try and assess near nano-plastics (NNP) in groundwater (i.e. 1-20 microns range), a critical topic to understand, given the degradation of MP to smaller sizes, enhanced transport and potential bioavailability of smaller particles, and the fact that many aquifers are able to filter out larger plastic litter via matrix/pore flow. To address these challenges, the project will apply validated analytical methods to isolate and detect microplastics in groundwater samples, which is currently a barrier precluding proper comparison of data from different studies. A range of analytical methods will be used and compared to characterise MP and NNP contamination in groundwater. Fourier Transform Infra-Red (FTIR), and Laser Direct Infra-Red (LDIR) techniques will be used to characterise microplastic numbers, polymers and size distribution. To explore the feasibility of detection of near nanoplastics, a combination of flow cytometry and nano-tracking analysis (NTA) coupled with selective staining of plastics could be a promising first step into this challenging analytical space that will be explored within the project.