title: Membrane inlet mass spectrometer for the quasi-continuous   on-site analysis of dissolved gases in groundwater.
abstract: We developed a stand-alone system based on a membrane inlet mass spectrometer (MIMS) for measuring dissolved gas concentrations in groundwater under field conditions. The system permits the concentrations of dissolved gases (He, Ar, Kr, N(2), and O(2)) in groundwater to be determined quasi-continuously (every 12 min) with a precision of better than 4% for He and Kr, and with a precision of 1% for Ar, N(2), and O(2) in air-saturated water. The detection limits are below 3 × 10(-9) cm(3)(STP)(g) for the noble gases and below 400 × 10(-9)cm(3)(STP)(g) for N(2) and O(2). The results of a first deployment of the system in the field indicate that changes in the concentration of Ar that result from diel fluctuations of 3°C in the river water temperature were still able to be resolved in groundwater, although the corresponding temperature signal almost vanished.
authors: Department of Water Resources and Drinking Water, Eawag, Swiss Federal Institute of Aquatic Science and Technology, Dübendorf, Switzerland. lars.maechler@eawag.ch
authors: Lars
authors: L
authors: Mächler
authors: Matthias S
authors: MS
authors: Brennwald
authors: Rolf
authors: R
authors: Kipfer
mesh_terms: D005740:Gases / Q000032:analysis*; D060587:Groundwater / Q000737:chemistry*; D013058:Mass Spectrometry / Q000379:methods*; D008567:Membranes, Artificial; D015203:Reproducibility of Results; D012995:Solubility
chemical_list: D005740:Gases; D008567:Membranes, Artificial