In-situ Calibration of Underwater Membrane Inlet Mass Spectrometer for Simple Dissolved Gases
The Underwater Mass Spectrometer (UMS) provides unprecedented resolution and measurement detail for volatile compounds, including dissolved gases. However, interpretation of the measurements requires attention to several instrumental and environmental effects. We have developed a new calibration method to measure and correct for the influence of hydrostatic pressure, instrument internal temperature, electronic noise, sample temperature, water vapor, and external water temperature changes. We use an in-situ calibration method that samples continuously from a dissolved gas standard; the UMS and in-situ calibration were twice deployed on a submersible tow vehicle to capture profiles throughout the euphotic zone. The primary atmospheric gases - N 2, O2, Ar and CO2 - were measured while sampling from the calibration system to examine how independent variables (pressure, internal temperature, electronic noise baseline, sample temperature, water vapor pressure, and in-situ water temperature) cause variability in the UMS readings. Principal Component Analysis was used to evaluate sources of variability and generalized additive models were used to correct the UMS output. These models successfully correct UMS readings to calibrate for ambient sampling within 1% error. In-situ calibration allows for continuous, high fidelity measurements and better tracing of dissolved gases in the ocean.^
"In-situ Calibration of Underwater Membrane Inlet Mass Spectrometer for Simple Dissolved Gases"
Dissertations and Master's Theses (Campus Access).