Flow-through integrating cavity absorption meter: experimental results

Musser, Joseph A.; Fry, Edward S.; Gray, Deric

doi:10.1364/ao.48.003596

Cited by 15 publications

(5 citation statements)

References 11 publications

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“…Integrating cavity absorption meters (ICAMs) are designed to collect scattered light inside an integrating cavity filled with the water sample (Gray et al 2006; Musser et al 2009; Fry 2018). ICAMs can be used to measure absorption either by discrete samples or in flow‐through set‐ups.…”

Section: Symbol Meaning Unitsmentioning

confidence: 99%

Hyperspectral optical absorption closure experiment in complex coastal waters

Kostakis

Twardowski

Roesler

et al. 2021

Limnology & Ocean Methods

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Accurate measurements of absorption data are required for the development and validation of inversion algorithms for upcoming hyperspectral ocean color imaging sensors, such as the NASA Phytoplankton, Aerosol, Cloud, and ocean Ecosystem mission. This study aims to provide uncertainty estimates associated with leading approaches to measure hyperspectral absorption coefficients in complex coastal waters. Absorption spectra were collected at 12 different stations, all located in the Indian River Lagoon, Florida, USA, between 09 January 2017 and 13 January 2017. Measurements included spectral absorption coefficients in the visible range (400-700 nm) associated with dissolved, a CDOM , total particulate, a p , and total nonwater, a nw , fractions, and were made both in situ and from discrete samples. Discrete sample approaches included dual-beam spectrophotometer, liquid waveguide capillary cell, point-source integrating cavity absorption meter (PSICAM) for dissolved matter absorption samples, and quantitative filter technique ICAM measurements and the dual-beam spectrophotometer with center-mounted integrating sphere filter pad technique, while the Turner Designs ICAM, and WET Labs AC-s, and AC-9 instruments were used to determine absorption coefficients in situ. The Gershun approach, determining absorption from measurement of the irradiance quartet with respect to depth was also assessed in situ. Measurement uncertainties and relative accuracies were quantified for each of these approaches. Results showed generally strong agreements between different discrete sample methods, with average percent absolute error %δ abs < 7% for a CDOM and < 9% for a p . In situ approaches showed higher variability and reduced accuracy. For a nw , %δ abs deviation relative to PSICAM data was on average 12% to 20%. Results help identify remaining technological gaps and need for improvements in the different absorption measurement approaches.Light absorption is a fundamental property of natural waters influencing the propagation of the underwater light field (Mobley 1994;Zaneveld et al. 2005;Wo zniak and Dera 2007). Absorption acts as a spectral filter for incident and scattered solar irradiance (e.g., Jerlov 1976;Morel and Prieur 1977;Lewis et al. 1990). Light absorption is commonly quantified as spectral absorption coefficient a(λ) (m À1 ), where λ is the wavelength in vacuum. The accurate quantification of this coefficient and its variability are important for understanding many physical and biological processes in the upper ocean, which are driven by or depend on solar radiation, for example, various photochemical reactions, heating of water column, availability of energy for photosynthesis, or availability of light for animal vision that is important even at mesopelagic depths. Absorption coefficients can provide information on the nature and concentration of various nonwater constituents dissolved and suspended within water (e.g., Twardowski et al. 2005;Wo zniak and Dera 2007;Twardowski et al. 2018a), such as phytoplankton pigments...

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Section: Symbol Meaning Unitsmentioning

confidence: 99%

Hyperspectral optical absorption closure experiment in complex coastal waters

Kostakis

Twardowski

Roesler

et al. 2021

Limnology & Ocean Methods

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“…Furthermore, the multiple light reflections on the cavity wall lead to a long optical path length within the instrument and therefore enhance its sensitivity. Recently, this kind of device have been adapted also for in situ measurements [10], [14], [24], [34], but tests of such instruments under long-term field conditions are still scarce. Furthermore, a complete automation of these systems would also be desirable to improve their value for marine research.…”

Section: Introductionmentioning

confidence: 99%

In Situ Observations of Biological and Environmental Parameters by Means of Optics—Development of Next-Generation Ocean Sensors With Special Focus on an Integrating Cavity Approach

Wollschläger

Voß

Petersen

2016

IEEE J. Oceanic Eng.

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To meet the requirements of increasing environmental awareness in aquatic ecosystems, optical techniques offer a fast and reliable opportunity for a wide range of applications providing high-resolution measurements. In this respect, important parameters which have to be addressed include phytoplankton biomass and taxonomic composition, total suspended matter, dissolved organic matter, as well as hazardous substances, e.g., polycyclic aromatic hydrocarbons (PAHs). Requiring comparable low effort, optical methods are a convenient and noninvasive way to derive information on the optical active substances in different water bodies. Various approaches and devices are available, either aiming on the determination of the water's inherent optical properties or on measuring the fluorescence properties of different constituents. This contribution presents the objectives and measurement principles of two new optical sensor developments in this respect. A special focus lies on an integrating cavity approach for hyperspectral absorption measurement. This approach overcomes two common problems in classical absorption measurement of seawater: 1) usually low concentration of absorbing material in the water negatively affecting accurate measurements of untreated samples; and 2) errors introduced by light scattering of particles requiring empirical corrections to obtain good accuracy. To combine these advantages with the possibilities of automated, long-term high-frequency measurements, an integrating cavity was adapted for flow-through operation. First field results obtained by the resulting Hyperspectral Absorption Sensor (HyAbS) in the North Sea and off the Norwegian coast are evaluated and compared with discrete measurements. The second development is a matrix-fluorescence sensor with flexible wavelength configuration for the detection and characterization of dissolved substances, such as fluorescent dissolved organic matter (FDOM) and PAHs. Here, the measurement principle of the sensor and first field results from a related, laboratory-based method will be presented as a preliminary work necessary for the development of the final in situ sensor. Furthermore, future plans for both instruments as well as a possible combination will be discussed. In summary, both approaches have the potential to be multiparameter instruments for high-resolution measurements of environmental parameters.Index Terms-Fluorescent dissolved organic matter (FDOM), hyperspectral absorption, in situ measurements, matrix fluorescence, ocean observatories, sensor development.

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“…Integrating cavity spectroscopy is a highly sensitive technique for weak absorption measurements [1][2][3][4][5]. Most recently, it has been used to demonstrate enhanced detection of extremely low concentrations of biological waste products in water supplies [6].…”

Section: Introductionmentioning

confidence: 99%

Integrating cavity ring-down spectroscopy (ICRDS) and the direct measurement of absorption coefficients

Fry

Mason

2016

Phys. Scr.

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Absorption of light at various wavelengths (i.e. absorption spectroscopy) is a powerful tool for identifying the presence of chemical compounds or specific substances in a sample. Cavity ring down spectroscopy (CRDS) is a well-known technique for very high sensitivity absorption spectroscopy. Another technique, integrating cavity spectroscopy has the additional unique feature of providing accurate absorption data even in the presence of severe scattering. This paper describes a combination of these two techniques that has led to an extremely powerful and useful new technology—integrating CRDS.

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Flow-through integrating cavity absorption meter: experimental results

Cited by 15 publications

References 11 publications

Hyperspectral optical absorption closure experiment in complex coastal waters

Hyperspectral optical absorption closure experiment in complex coastal waters

In Situ Observations of Biological and Environmental Parameters by Means of Optics—Development of Next-Generation Ocean Sensors With Special Focus on an Integrating Cavity Approach

Integrating cavity ring-down spectroscopy (ICRDS) and the direct measurement of absorption coefficients

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