LOW-COST MONITORING OF CO<sub>2</sub> CONCENTRATIONS AND FLUXES WITHIN THE CRITICAL ZONE: INSIGHTS FROM THE SPRINGFIELD PLATEAU AQUIFER, NORTHWEST ARKANSAS

Blackstock, Joshua M.; Covington, M. D.; Williams, Sarah G. W.; Myre, Joseph M.; Rodríguez, J. E; Hays, Phillip D.; Cooper, Max P.; Perne, Matija

doi:10.1130/abs/2018sc-310271

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“…Thus, the LC-GEMS is a valid and promising technique for obtaining representative trends as well as preliminary data from field sites. The median percent difference between the LC-GEMS and C-sense reading on April 28th was 19.9% (grey squares), similar to the agreement previously found among other gas extraction systems [101]. The median percent difference between the LC-GEMS and C-sense reading on April 19th and 20th was 21.3% (black circles).…”

Section: Interpretation Of Field Measurement Resultssupporting

confidence: 85%

“…As discussed in Section 2.6.4, the percent difference between the LC-GEMS and reference C-sense is on a similar order of magnitude compared to other current gas extraction techniques [29,101] for certain temperature changes. Future improvements can be made to the calibration protocol for the LC-GEMS to achieve good measurement agreement for temperatures outside the range of 15-20 ∘ C used to calibrate in this study.…”

Section: Discussionmentioning

confidence: 82%

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Field-Portable dissolved gas sensing and perspectives in aqueous microplastic detection

Blevins¹

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Global temperature rise and increased atmospheric carbon dioxide (CO2) levels have affected the health of the world’s ocean and water ecosystems, impacting the balances of natural carbon cycling and causing ocean acidification. Additionally, as global temperatures rise, thawing permafrost has stimulated increased release of methane (CH4), a gas with a shorter lifetime in the atmosphere but with even more heat trapping ability than CO2. In situ analysis of dissolved gas content in surface waters is currently performed with large, expensive instruments, such as spectrometers, which are coupled with gas equilibration systems, which extract dissolved gas from water and feed it to the sensor. Accurate, low cost, and portable sensors are needed to measure the dissolved CH4 and CO2 concentration in water systems to quantify their release and understand their relationship to the global carbon budget. At the same time, while greenhouse gases are well established threats to water ecosystems, the ubiquity and potential consequences of microplastics in aqueous environments are just beginning to be recognized by the environmental research community. Microplastics (MPs) are small particles of polymer debris, commonly defined as being between 1 μm and 1000 μm. Despite the pervasiveness of MPs, our ability to characterize MPs in the environment is limited by the lack of technologies for rapidly and accurately identifying and quantifying MPs. This thesis is concerned with the engineering challenges prompted by the need for high quality and quantity environmental data to better study and the impact, cycling, and prevalence of these pollutants in aqueous environments. Three distinct investigations are presented here. First, the design of the Low-Cost Gas Extraction and Measurement System (LC-GEMS) for dissolved CO2 is presented. At just under $600 dollar to build, the LC-GEMS is an ultra-portable, toolbox-sized instrument for dissolved gas sensing in near-surface waters. The LCGEMS was characterized in the lab and demonstrated linear relationships with dissolved CO2 as well as temperature. Lab calibrations and subsequent field testing in the Little Sippewissett Marsh, in Falmouth, Massachusetts showed that the LCGEMS captures both diurnal and minute-time scale trends in dissolved CO2. Second, this thesis presents the novel design of three simple and low-cost planar nanophotonic and plasmonic structures as optical transducers for measuring dissolved CH4. Through simulations, the sensitivity of the structures are evaluated and found to exhibit superior performance in the reflectance intensity readout mode to that of the standard surface-plasmon-polariton-mode Spreeta sensor. A practical, small, and low-cost implementation of this chip with a simple intensity-based measurement scheme is proposed. This design is novel in the space of dissolved gas monitoring because it shows potential to measure directly in the water phase while being robust and low-cost to implement. Finally, this thesis presents a literature review and perspective to motivate the development of field-deployable microplastic sensing techniques. A framework for field-deployable microplastic sensing is presented and seeks to inform the MP community of the potential in both traditional MP analysis techniques and unconventional methods for creating rapid and automated MP sensors. The field-deployabilty framework addresses a full scope of practical/technological trade-offs to be considered for portable MP detection.

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Section: Interpretation Of Field Measurement Resultssupporting

confidence: 85%

Section: Discussionmentioning

confidence: 82%

Field-Portable dissolved gas sensing and perspectives in aqueous microplastic detection

Blevins¹

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LOW-COST MONITORING OF CO₂ CONCENTRATIONS AND FLUXES WITHIN THE CRITICAL ZONE: INSIGHTS FROM THE SPRINGFIELD PLATEAU AQUIFER, NORTHWEST ARKANSAS

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Field-Portable dissolved gas sensing and perspectives in aqueous microplastic detection

Field-Portable dissolved gas sensing and perspectives in aqueous microplastic detection

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LOW-COST MONITORING OF CO2 CONCENTRATIONS AND FLUXES WITHIN THE CRITICAL ZONE: INSIGHTS FROM THE SPRINGFIELD PLATEAU AQUIFER, NORTHWEST ARKANSAS

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Field-Portable dissolved gas sensing and perspectives in aqueous microplastic detection

Field-Portable dissolved gas sensing and perspectives in aqueous microplastic detection

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LOW-COST MONITORING OF CO₂ CONCENTRATIONS AND FLUXES WITHIN THE CRITICAL ZONE: INSIGHTS FROM THE SPRINGFIELD PLATEAU AQUIFER, NORTHWEST ARKANSAS