Aircraft measurements of dimethyl sulfide (DMS) using a whole air samplingtechnique

We present a technique for the measurement of dimethyl sulfide (DMS) from a irborne and ground-based platforms, using whole air sampling followed by ga s chromatography with mass spectrometer and flame ionization detection. DMS measurements that were obtained during the 1999 NASA Pacific Exploratory M ission-Tropics B showed excellent agreement with independent in-flight DMS measurements, over a wide range of concentrations. The intercomparison supp orts two key results from this study, first that DMS can be accurately quan tified based on ethane and propane per-carbon-response-factors (PCRFs), and second that DMS is stable in water-doped electropolished stainless steel c anisters for at least several weeks. In addition, our sampling frequency an d duration are flexible and allow detail in the vertical structure of DMS t o be well captured. Sampling times as fast as 8 s were achieved and these d ata are suitable for DMS flux calculations using the mixed-layer gradient t echnique. Correlations between DMS and other marine tracers can also be rea dily investigated by this whole air sampling technique, because DMS is anal yzed together with more than 50 simultaneously sampled hydrocarbons, haloca rbons, and alkyl nitrates. The detection limit of the DMS measurements is 1 part per trillion by volume (pptv), and we conservatively estimate the acc uracy to be +/- 20% or 3 pptv, whichever is larger. The measurement precisi on (1 sigma ) is 2-4% at high mixing ratios (> 25 pptv), and 1 pptv or 15%, whichever is larger, at low mixing ratios (< 10 pptv).