To illustrate the effort required to maintain the O2 program, we will follow an individual sample flask as it travels from Scripps to a field station and returns for analysis. Flask # 143, which we will call Aerial, is shown here. Aerial is designed to sample uncontaminated air via a dual valve flow through system and contains a stir bar to enable mixing of the sampled air during analyses.
Aerial will be simultaneously sampled with one or two companion flasks to provide duplicate data for quality control. Prior to departing the O2 lab, we purge Aerial and the other flasks with unpolluted marine background air collected at Scripps.
We pack Aerial and her companions in shipping boxes with protective foam inserts and ship them to one of the 9 stations in our global network.
On this trip, Aerial is going to Cold Bay, Alaska, where some of the most rapid changes in the earth’s climate are already being felt. In the past she has been to Mauna Loa Volcano on the big island of Hawaii, as well as to the South Pole.
Sometimes we fill Aerial at the end of the Pier at Scripps. We also supply air samples to our partners at other research institutions around the globe.
At the scheduled sampling time, we assemble Aerial with her duplicate companions to an air line connected to an aspirated intake manifold. The valves are opened, and sample air is flushed through all the flasks.
After a minimum of 1 hour of flushing , we close the valves, capturing identical samples of air in Aerial and her companions. The flasks are then shipped back to Scripps.
Back in the O2 lab we install Aerial and two other flasks, not necessarily her companions during sampling, on the analysis line. We slowly add a calibration gas with a precisely determined O2 composition through the inlet valve, forcing the sample gas into the instrument(s). We repeatedly compare the instrument response for the sample to appropriate calibration gases to precisely determine the O2 concentration.