A versatile optode system for oxygen, carbon dioxide, and pH measurements in seawater with integrated battery and logger

Abstract

Herein, we present a small and versatile optode system with integrated battery and logger for monitoring of O2, pH, and pCO2 in seawater. Three sensing materials designed for seawater measurements are optimized with respect to dynamic measurement range and long‐term stability. The spectral properties of the sensing materials were tailored to be compatible with a commercially available laboratory oxygen logger that was fitted into a pressure housing. Interchangeable sensor caps with appropriate “sensing chemistry” are conveniently attached to the end of the optical fiber. This approach allows using the same instrument for multiple analytes, which offers great flexibility and minimizes hardware costs. Applications of the new optode system were demonstrated by recording depth profiles for the three parameters during a research cruise in the Baltic Sea and by measuring surface water transects of pH. The optode was furthermore used to monitor the concentration of dissolved oxygen in a seagrass meadow in the Limfjord, Denmark, and sensor packages consisting of pO2, pH, and pCO2 were deployed in the harbors of Kiel, Germany, and Southampton, England, for 6 d. The measurements revealed that the system can resolve typical patterns in seawater chemistry related to spatial heterogeneities as well as temporal changes caused by biological and tidal activity.

Optical Sensing and Imaging of pH Values: Spectroscopies, Materials, and Applications

“…Whereas stability of the chromophore can be adequate for relatively short-term usage (e.g., in disposable sensors), it may not be the case if the sensor has to maintain high accuracy during many months without possibility of recalibration (like on Argo floats in oceanography). For instance, BF 2 chelated chromophores (BODIPYs and aza-BODIPYs) may exhibit slow decomposition in aqueous media, the drift being temperature-dependent 537 and probably pH dependent. Photostability is a critical parameter if high light intensities are involved (e.g., in microscopy or in fiber-optic microsensors).…”

Review of Dissolved Oxygen Detection Technology: From Laboratory Analysis to Online Intelligent Detection

“…An intelligent dissolved oxygen sensor can perform analog and digital signal processing on the collected dissolved oxygen signals, realize intelligent transmission, and achieve a “plug and play” effect. At the same time, through the combination of software and hardware, the intelligent dissolved oxygen sensor can compensate for and correct the detection results in real time [21]. In short, the intelligent dissolved oxygen sensor has the ability of real-time signal acquisition and intelligent data processing, which can meet the requirements of the long-term in situ measurement of the dissolved oxygen content, and effectively overcome the problems of the traditional detection technology [22].…”

Air–water gas exchange in lakes and reservoirs measured from a moving platform by underwater eddy covariance

“…where J air-water is the exchange rate, or vertical flux, of the gas (positive upward), C water is the gas bulk concentration below the film on the water-side, C air is the concentration above the film on the air-side, and k is the gas exchange coefficient, often also referred to as the "gas transfer velocity" or "piston velocity." For most gases, C water and C air are straightforward to measure continuously in situ with modern autonomous sensors (Koopmans and Berg 2015;Fritzsche et al 2017;Staudinger et al 2018) or calculate from known relationships, whereas the complexity of gas exchange and its many controlling variables are contained entirely in k (Macintyre et al 1995;McKenna and McGillis 2004;Cole et al 2010). Estimating k from Eq.…”

“…Despite the complexity of processes that control air–water gas exchange, the widely used expression for its magnitude is simple and assumes conceptually that gas is transported by molecular diffusion across intact boundary layers, or thin films, on each side of the interface (Whitman 1923; Liss and Slater 1974): where J air–water is the exchange rate, or vertical flux, of the gas (positive upward), C water is the gas bulk concentration below the film on the water‐side, C air is the concentration above the film on the air‐side, and k is the gas exchange coefficient, often also referred to as the “gas transfer velocity” or “piston velocity.” For most gases, C water and C air are straightforward to measure continuously in situ with modern autonomous sensors (Koopmans and Berg 2015; Fritzsche et al 2017; Staudinger et al 2018) or calculate from known relationships, whereas the complexity of gas exchange and its many controlling variables are contained entirely in k (Macintyre et al 1995; McKenna and McGillis 2004; Cole et al 2010).…”