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