Analysis-on-a-roll platforms towards automated and high frequency in-situ sensing of natural geochemical fluxes

Iurkov, Aleksei

Abstract

In the context of the rapidly intensifying crisis of climate change, the intricate dynamics of Earth's ecosystems have assumed a paramount significance. The carbon cycle plays a significant role in the dynamics of the earth’s ecosystem, and anthropogenic emissions of CO2 into the atmosphere have a significant effect on it. It is the geological part of the carbon cycle that is the least studied because measuring the content of carbonates in groundwater is a difficult task and consequently there is little data on high-frequency changes in the concentration of carbonates over a long period of time. Unlike traditional laboratory analyses, on-site measurements involve collecting data directly in the natural habitat of a water body, which allows information to be received in real time and taking into account a specific context (temperature, humidity, weather etc.). This approach not only reduces the risk of contamination of samples during transportation, but also allows capture of dynamic changes occurring over a short period of time, which otherwise could be missed due to sporadic sampling.
This thesis presents the design and development of an innovative device capable of overcoming the obstacles that have prevented comprehensive measurements of the chemical composition of water in-situ, especially with regard to the content of carbonates. Previous attempts at in-situ chemical measurement with devices based on microfluidic lab-on-a-chip technology have proved difficult due to issues such as the lack of reliability of the complex fluidic system and the need to use bulky and possibly short-lived liquid regents. The system developed in this work is based on another type of microfluidic sensors known as Paper Analytical Devices (PADs), which are more suited to use in challenging locations. These have been previously applied to environmental monitoring but typically via manual sampling using single devices. This thesis describes a development of fully automated in-situ measurement system using a continuous roll of PADs (LOAR – Lab on a Roll). This provides a platform with a potential for wide applicability in water chemistry analysis, but this work focus use of carbonate PADs based on colorimetry detection. Two approaches to detection are investigated: one based on embedded system digital cameras and the other one using low-cost spectral sensors. These approaches are compared via modelling and experimental evaluation. The camera-based approach is shown to be more efficient and offers greater flexibility through use of machine learning to assist the measurement process. The accuracy of water chemistry measurement is potentially impacted by sampling errors (e.g. aliasing and jitter) and this is discussed and possible mitigations considered. The thesis also describes the design (mechanical, electronic and software) of an in-situ LOAR prototype and an its evaluation which demonstrates its feasibility. The experience gained leads to detailed recommendations for development of future versions.

Citation

Iurkov, A. Analysis-on-a-roll platforms towards automated and high frequency in-situ sensing of natural geochemical fluxes. (Thesis). University of Hull. https://hull-repository.worktribe.com/output/4702966

• Thesis Type: Thesis
• Deposit Date: Jun 4, 2024
• Publicly Available Date: Jun 12, 2024
• Keywords: Engineering
• Public URL: https://hull-repository.worktribe.com/output/4702966
• Award Date: May 21, 2024