Development and testing of a novel sulfur dioxide sonde

Abstract. A novel technique has been developed to measure sulfur dioxide (SO2) using a modification of the existing electrochemical concentration cell (ECC) ozonesonde technology. The current sonde-based method SO2 (i.e., dual-sonde approach) involves launching two ozonesondes together, with one sondes having filter remove at inlet. profile is determined by taking difference between measurements from instruments. works well in typical tropospheric conditions when [O3]>[SO2] but saturates [SO2]>[O3] and large uncertainties upper troposphere lower stratosphere that would limit its effectiveness measuring an explosive volcanic eruption. Due these limitations, several modifications were made create single-sonde system directly sonde). These included (1) positively biased ECC current, (2) addition O3 removal filter, (3) sample dryer. sonde measures as reduction current. There was strong correlation (r2>0.94) Thermo 43c analyzer during controlled laboratory tests pre-flight tests. Varying humidity levels affected sonde's sensitivity (avg =84.6±31.7 ppbv µA−1, 1σ RSD =37 %) initial field tests, which resolved adding dryer upstream pump This significantly reduced variability increased =47±5.8 =12 %). Field near Kīlauea volcano (before 2018 eruption Lower East Rift Zone), Costa Rica's Turrialba volcano, anthropogenic plumes Athabasca oil sands region Alberta, Canada. single-SO2-sonde effective, inexpensive instrument for both ground-based vertical profiles natural sources eruptions) over wide range concentrations.