The biogeochemical reactivity of dissolved gas and vapor species in the abiotic compartments of our planet are monitored using gas analysers at one or more stages of their biogeochemical cycle. These methods can be used to determine the presence and concentration of contaminants in surface water and to estimate the physical parameters of groundwater recharge based on their dissolved species content. Tracing gas concentrations in this manner enables analysts to approximate the hydrologic turnover of water and the residence time of surface water in natural environments.
Analysts have performed high-frequency in-situ measurements on a variety of dissolved species from subsoils, and samples taken from rivers and lakes. These long-term measurements have provided quantifiable information for conclusions relating to evapotranspiration in natural ecosystems.
Using precise gas analyser probes, it is possible to determine:
- The physical parameters of water recharge based on the concentration of noble gases such as neon (Ne), argon (Ar), helium (He), xenon (Xe), and krypton (Kr) over time;
- The biogeochemical reactivity and flow physics of water based on the presence of oxygen (O2), methane (CH4), hydrogen (H2), nitrous oxide (N2O), and dinitrogen (N2);
- The hydrologic cycles of natural ecosystems based on helium-4 (4He) dating.
This article will explore the use of Hiden Analytical gas analysers for identifying dissolved gaseous compounds from in-situ samples.
Gas Analysers for Hydrogeology
Membrane Inlet Mass Spectrometry (MIMS) is a gas analysis system designed for quantitative assessment of dissolved gas species in hydrological samples. It features a sensitive inlet probe with a permeable membrane that allows dissolved gas molecules to diffuse into the vapour phase of the instrument for molar mass observation via the gas analyser’s precise ion source.
This equipment was optimised for the aforementioned hydrogeological studies with an improved extraction membrane capable of withstanding rugged field use for in-situ measurement of ground- and surface water. Analysts could accurately determine the presence and concentration of distinct gases to sub-parts per billion levels based on their unique mass signatures, with exceptional measurement stability over measuring periods ranging from a few days to a month.
The potential applications of these conclusions have been explored in a range of seminars, with potential benefits for gas and heat tracing between boreholes and gas profiling for drilling applications. Contaminant analysis and environmental studies also stand to benefit from the robust potential of MIMS in-situ measurement capabilities.
MIMS Gas Analysers from Hiden Analytical
At Hiden Analytical, we provide leading-edge analytical equipment for a range of industrial and academic applications. Our versatile catalogue of gas analysers is suitable for hydrological studies in a range of ecosystems, from oceanic to groundwater compartments.
The HPR-40 DSA MIMS system is optimised for real-time analysis of dissolved gaseous species with a mass detection range up to 200 amu with options for higher mass ranges, depending upon application requirements. It features interchangeable inlet probes for variable measurements of soil cores, estuary and river analysis, groundwater studies, and more.