Thursday, April 17, 2014, 4:30PM - 5:30PM
ARC room 248
Global measurement of nitrous oxide and its stable isotopes using cavity ring-down spectroscopy
Nitrous oxide (N2O), a greenhouse gas ~300 times the 100 year global warming potential of CO2, is currently increasing at a rate of 0.77 ppbv yr-1 mainly due to increased microbial production from fertilized agricultural systems. Due to the complexity of microorganism processes within soil, the spatiotemporal effects of fertilizer on N2O production at a high resolution remain largely unconstrained. Advances in the use of intramolecular, or position-specific, stable isotope techniques (β position 15N14N16O versus α position 14N15N16O) can be a robust tool in order to determine the biological and physical controls over N2O emission. Picarro Instruments recently developed a wavelength-scanned cavity ring-down spectrometer coupled with a quantum cascade laser capable of the mid-infrared wavelength detection needed for N2O. This technique allows for streamlined simultaneous and continuous measurement of N2O concentration, δ15Nα-N2O, and δ15Nβ-N2O with measurement uncertainties of < 0.5 ppb and 1.5‰ for mole-fractions and isotopic delta values, respectively. A subset of sites from the NOAA Global Monitoring Division (GMD) Cooperative Sampling Network is being measured in order to describe the global distribution of N2O and its isotopes on a seasonal level. We expect to see a seasonal cycle in N2O isotopomers due to stratospheric mixing in the spring of each hemisphere and heightened ocean and soil microbial activity in the summer and fall of each hemisphere. I'll share my progress on methodology development and data management as well as current challenges.