Proof-of‐Concept : Automated high‐frequency measurements of PCO₂ and TCO₂ and real‐time monitoring of the saturation state of calcium carbonate
The rapid increase in atmospheric carbon dioxide (CO₂) over the last 250 years has led to the absorption of approximately 550 billion tons of anthropogenic CO₂ by the global ocean. This oceanic uptake of CO₂ has resulted in decreasing pH and alterations to carbonate chemistry, threatening many ecolo...
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| Other Authors: | , , , |
| Format: | Other/Unknown Material |
| Language: | English unknown |
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Oregon State University
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| Online Access: | https://ir.library.oregonstate.edu/concern/graduate_projects/br86b7957 |
| Summary: | The rapid increase in atmospheric carbon dioxide (CO₂) over the last 250 years has led to the absorption of approximately 550 billion tons of anthropogenic CO₂ by the global ocean. This oceanic uptake of CO₂ has resulted in decreasing pH and alterations to carbonate chemistry, threatening many ecologically and economically important marine species. The majority of biological production takes place on highly dynamic coastal margins, which require instrumentation capable of high-frequency measurements. In practice, measurements of sufficient resolution often do not include all required analytical parameters necessary to constrain the carbonate chemistry in order to investigate biogeochemical processes relevant to ocean acidification. This report provides a proof-of-concept for the development of an instrument designed to make autonomous measurements of the partial pressure of CO₂ (PCO₂) and total CO₂ (TCO₂) in a continuous sample stream at high frequency, based on combination of two existing measurement techniques. The objective is to provide measurements sufficient to constrain the carbonate chemistry in ocean waters while capturing the variability seen over short timescales in estuaries and on coastal margins. By constraining the carbonate chemistry and performing real time calculations of the saturation state of calcium carbonate and other carbonate parameters, this instrument can be utilized as a monitoring tool for fisheries in need of high resolution time series carbonate data. In our combined system, PCO₂ is determined by measuring the infrared absorbance due to CO₂ in the re-circulated gaseous headspace of a shower-type equilibrator. For TCO₂ analysis, a low-flowing seawater sample stream is acidified and passed through a microporous membrane contactor. The evolved CO₂ diffuses into a high-flowing CO₂-free strip-gas stream and is measured by infrared absorbance in the same manner as the PCO₂ method. The results of laboratory testing indicated the instrument is able to resolve TCO₂ changes with 0.5% ... |
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