A Portable and Autonomous Mass Spectrometric System for On-Site Environmental Gas Analysis

Abstract

1We developed a portable mass spectrometric system ("miniRuedi") for quantificaton of 2 the partial pressures of He, Ne (in dry gas), Ar, Kr, N 2 , O 2 , CO 2 and CH 4 in gaseous and 3 aqueous matrices in environmental systems with an analytical uncertainty of 1-3 %. The 4 miniRuedi does not require any purification or other preparation of the sampled gases and 5 therefore allows maintenance-free and autonomous operation. The apparatus is most suit-6 able for on-site gas analysis during field work and at remote locations due to its small size 7 (60 cm × 40 cm × 14 cm), low weight (13 kg), and low power consumption (50 W). The gases 8 are continuously sampled and transferred through a capillary pressure reduction system into 9 a vacuum chamber, where they are analysed using a quadrupole mass spectrometer with a 10 time resolution of 1 min. The low gas consumption rate (< 0.1 ml/min) minimises interfer-11 ence with the natural mass balance of gases in environmental systems, and allows the unbi-12 ased quantification of dissolved-gas concentrations in water by gas/water equilibration using 13 membrane contractors (gas-equilibrium membrane-inlet mass spectrometry, GE-MIMS). The 14 performance of the miniRuedi is demonstrated in laboratory and field tests, and its utility is 15 illustrated in field applications related to soil-gas formation, lake/atmosphere gas exchange, 16 and seafloor gas emanations.

Advances in understanding river‐groundwater interactions

“…Brennwald et al [] developed a new system for on‐site environmental gas analysis (Figure ). They developed a portable (i.e., it can be easily carried by two people) and autonomous mass spectrometric system (“miniRuedi”) for quantification of the partial pressures of He, Ne (in dry gas), Ar, Kr, N 2 , O 2 , CO 2 , and CH 4 in gaseous and aqueous matrices in environmental systems.…”

“…Figure and figure caption obtained directly from Brennwald et al []. (top) Schematic overview and (bottom) photo of the miniRuedi mass‐spectrometer system (see also Table 1): 6‐port inlet selector valve (S), capillary (C), inlet valve (V), quadrupole mass spectrometer (QMS), turbomolecular pump (TP), and diaphragm pump (DP).…”

81Kr dating – A tool for finding and studying paleogroundwater

“…The combination of 81 Kr and 4 He may become a very useful tool for paleogroundwater research. Since 4 He is considerably easier to measure, it can be used in a screening campaign to identify samples potentially containing very old ground water [22]. Once suitable sampling locations are chosen based on the 4 He data, a second more strategically planned campaign for 81 Kr sampling can be undertaken.…”

Continuous in situ measurement of dissolved methane in Lake Kivu using a membrane inlet laser spectrometer

“…In the last 3 decades, natural sources contributed ∼ 35-50 % of the total global methane emissions, and fresh water constituted one of the largest fluxes after natural wetland and together with geological sources (including seafloor). This highlights the importance and urgency of obtaining a better inventory of the sources of CH 4 reducing the uncertainties of the contributions of aquatic systems (lakes, rivers, estuaries, coastal seas and open ocean) (Ciais et al, 2013). Fast-response instruments for in situ dissolved gas measurements and dynamic profiling can provide the data for a better understanding of the processes of production, transport and transformation.…”