Methods for rapid gas sampling with high horizontal spatial resolution in a manner suitable for subsequent constituent gas analysis
A gas sample storage chamber is used to continuously acquire a gas sample. After the sample has been acquired, the stored gas in the chamber can be analyzed. This analysis can provide a time history of the gas sample, since mixing and diffusion of the gas sample in the chamber can be made sufficiently negligible. The gas flow rate for analysis differs significantly from the acquisition flow rate.
1. A method of gas analysis, the method comprising:
providing a mobile platform;
providing a gas sample storage chamber disposed on the mobile platform and configured to have an acquisition mode where sample gas is acquired from at least two distinct locations as the mobile platform moves by continuously admitting ambient gas to the gas sample storage chamber at an acquisition flow rate;
performing analysis of the sample gas by flowing the sample gas from the gas sample storage chamber to a gas analysis instrument in an analysis mode and at an analysis flow rate, wherein the acquisition flow rate and the analysis flow rate differ by 40% or more of the acquisition flow rate;
wherein switching from the acquisition mode to the analysis mode is based on a trigger.
2. The method of claim 1 , wherein the analysis flow rate is slower than the acquisition flow rate.
3. The method of claim 2 , wherein the analysis flow rate is between 0.01 and 0.5 times the acquisition flow rate.
4. The method of claim 2 , wherein the gas analysis instrument is an isotope ratio instrument.
5. The method of claim 1 , wherein the analysis flow rate is faster than the acquisition flow rate.
6. The method of claim 5 , wherein the analysis flow rate is 2 or more times the acquisition flow rate.
7. The method of claim 5 , further comprising:
providing one or more auxiliary gas sample storage chambers disposed on the mobile platform and configured to have an acquisition mode where sample gas is acquired from at least two distinct locations as the mobile platform moves by continuously admitting ambient gas to the auxiliary gas sample storage chambers at an auxiliary acquisition flow rate;
performing analysis of the sample gas by flowing the sample gas from the auxiliary gas sample storage chambers to the gas analysis instrument at an auxiliary analysis flow rate, wherein the auxiliary acquisition flow rate and the auxiliary analysis flow rate differ by 40% or more of the auxiliary acquisition flow rate.
8. The method of claim 1 , wherein the trigger is provided by a real-time gas analysis instrument disposed on the mobile platform.
9. The method of claim 1 , wherein the trigger is provided by the gas analysis instrument, and wherein the gas analysis instrument is a real-time instrument disposed on the mobile platform.
10. The method of claim 1 , wherein the trigger is provided by an indicator selected from the group consisting of: physical landmarks, latitude and longitude data, wind speed, wind direction, atmospheric stability, time, and user input.
11. The method of claim 1 , wherein the gas sample storage chamber is configured as a tube having a length to diameter ratio of 100 or more.
12. The method of claim 1 , further comprising:
performing position vs. time measurements of the mobile platform; and
relating the position vs. time measurements of the mobile platform to gas measurements vs. time to provide gas measurements vs. position.
13. The method of claim 1 , wherein the analysis flow rate depends in part on a measured gas analysis signal obtained during the analysis mode from the gas analysis instrument.
14. The method of claim 1 , wherein ambient gas is admitted to the gas sample storage chamber at the acquisition flow rate under active control by a gas flow system.