How do HVO scientists measure volcanic gas emissions?
USGS Hawaiian Volcano Observatory geochemists use both remote and direct sampling techniques to measure compositions and emission rates of gas from Kīlauea Volcano. Because of the technical challenges posed by Kīlauea ‘s unique eruptive style, gas emissions are measured “campaign style,” that is, scientists must go to the field to collect the data. To determine the rate at which sulfur dioxide (SO2) is emitted, HVO scientists measure the amount of ultraviolet (UV) radiation energy absorbed by the volcanic gas plume as sunlight passes through it. They do this by attaching a mini-UV spectrometer—called “Flyspec” because of its small size—to a field vehicle and driving the upward-facing instrument beneath the plume. Using data collected in this way, scientists can then compute the SO2 emission rate, typically reported in units of metric tonnes per day (one tonne equals 2,200 pounds). During periods of elevated SO2 emissions, HVO strives to measure emission rates daily. Flyspec measurement
