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Development of an Electrochemical Sensor for Quantification of Soil Phosphorus

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Title: Development of an Electrochemical Sensor for Quantification of Soil Phosphorus
Author: Zeitoun, Reem
Department: School of Environmental Sciences
Program: Environmental Sciences
Advisor: Biswas, Asim
Abstract: Unregulated applications of phosphorus (P) fertilizers to agricultural fields have led to P enrichment in agricultural watersheds and resulted in eutrophication and serious water quality issues with the health of North America’s Great Lakes. Better P measurement tools are required to characterize soil P variability within agriculture landscapes to identify areas for site-specific management of P fertilizers and targeted best management practices implementation. Traditional P tests are expensive and labor- and time-intensive. Electrochemical sensors have shown potential as low-cost, instant, accurate, and reliable measurement tools for various nutrients and chemical properties. In this thesis, electrochemical P sensors based on potentiometric and cyclic voltammetry approaches were developed for soil P tests in laboratories and infields. Experimental data on the response time, selectivity, repeatability, and sensitivity of the sensors were compiled. Potentiometric cobalt-based alloy sensor showed a unique selectivity towards multiple P species (H2PO4- and HPO42-) with a response time of ~9 min and a limit of detection of 0.51 mg.L-1 P, exhibiting a new reaction response towards phosphate ion. On the other hand, cyclic voltammetry scans using carbon screen-printed electrodes (SPEs) on phosphomolybdate complex P standard solutions and soil P extracts showed an instant response in detecting redox current peaks of the complex and achieved a lower limit of detection of 0.18 mg.L-1 P, The performance of the SPEs was optimized towards a higher sensitivity, lower limit of detection, and longer lifetime using mechanical polishing and was verified against well-established accredited soil P tests. A novel reagentless approach was developed and showed success towards using the cyclic voltammetry approach infield with zero chemicals involved by providing the extraction and reaction zones of P on a single piece of paper. The research showed that electrochemical soil P characterization can be useful for rapidly and accurately quantifying soil P to derive P maps from the sensors data needed for site-specific management strategies. The low cost, low mass, low volume, and robust nature of the electrochemical cyclic voltammetry approach offers a promising technology for future precision agricultural systems.
Date: 2021-12
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Embargoed Until: 2022-12-20

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