Underwater cryotrap‐membrane inlet system (CT‐MIS) for improved in situ analysis of gases

Abstract

Membrane inlet sensor techniques allow online, real‐time and in situ analyses of gases during the investigation of aquatic environments. Of specific interest for research and applied objectives are quantifications of gases like methane, higher hydrocarbons, carbon dioxide, nitrogen, volatile organic compounds, and pollutants. For these objectives, membrane inlet systems are coupled to optical or solid state sensors as well as mass spectrometers. Besides the gases of interest, large quantities of water vapor are passing through the membrane and are thus introduced into the sensor system. This downgrades the detection limit, affects the ionization efficiency of mass spectrometers, or could cause the condensation of water within infrared sensors. In this study, we describe a novel robust, low‐power cryotrap coupled to a membrane inlet system (CT‐MIS), which is suitable to be used in harsh environments, including underwater applications. The entire system is of small size and weight, is operated at −85°C, and requires an energy consumption of less than 10 Watt. By using the cryotrap, we are able to reduce water vapor in the analytical line by more than 98%. The detection limits for major and trace gases are considerably improved this way. For the trace gas methane (CH4), the detection limit was lowered from 100 to 16 nmol/L, which allows the measurement of methane in surface and bottom waters of coastal areas and lakes. In case of membrane failure, the CT‐MIS acts as a security system by shock‐freezing the water, thus blocking the capillary connection to the analyzer unit.

Ecological succession leads to chemosynthesis in mats colonizing wood in sea water

“…Deep-sea mats have, however, been studied in other chemosynthetic ecosystems such as mud volcanos , cold seeps Gentz and Schlüter, 2012) or hydrothermal vents (Taylor et al, 1999;Alain et al, 2004). These studies highlighted the key role played in sulfidic habitats by Epsilonproteobacteria (Campbell et al, 2006) during the establishment of deep-sea chemosynthetic ecosystems.…”

Submarine groundwater discharge to the Baltic coastal zone: Impacts on the meiofaunal community

“…In situ measurements of the methane flux from the sediment into the water column were performed with an underwater mass spectrometer (Bell et al, 2007(Bell et al, , 2011Gentz and Schlüter, 2012;Schlüter and Gentz, 2008;Short et al, 2001Short et al, , 2006Wenner et al, 2004). Fluxes were calculated on the basis of changes in gas concentrations within the chamber over time.…”

A Review of the Emerging Field of Underwater Mass Spectrometry

“…The same group later developed a Sterling pump-based cryotrap membrane inlet system, the CT-MIS (Gentz and Schlüter, 2012). Cryotraps applied in laboratories had successfully lessened interferences due to a high amount of water vapor entering the sensor system, and considerably improved the detection limits for e.g., VOCs, CH 4 , and DMS (Desmarais, 1978;Mendes et al, 1996;Damm et al, 2008).…”

“…UMS has already been put to practical use. For example, these systems have been placed on mobile platforms to produce two-and three-dimensional underwater maps of chemical distributions (e.g., Wenner et al, 2004;Camilli et al, 2010;Gentz and Schlüter, 2012). Other UMS systems have been developed to target understudied areas of ocean chemistry, such as in situ isotope ratios (Camilli and Duryea, 2009) and porewater composition (Bell et al, 2012).…”