Field Notes

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Sherman Wetland: 2021-05-06 00:00:00 (DOY 126)
Author: Camilo Rey-Sanchez
Others: Robert, Julie, Patty

Summary: 2nd round of chamber measurements of CH4 flux in hotspot and open water; LGR calibration

Robert and I arrived at 9 AM. We met Julie at the main gate shortly after. It was a clear sunny day with a strong breeze, especially in the morning. We prepared the inflatable boat and took some measurements in the open water, around the area of the maximum contribution to the footprint.

I also collected some exploratory data on CH4 flux from leaves by combining the Li-6400 with the Li-7810. I just connected the sample tube to the output tube and then the exhaust from the cuvette to the input tube in the Li-7810. I was not sure this was going to work but it did. It is a closed system with a very small volume, which means the concentration of CO2 is depleted rapidly, so individual leaf measurements should not last more than 2 minutes. After this time the CO2 concentration can go down to 350 ppm. I had issues with the batteries I had brought (they were fully charged but apparently are not holding charge enough) so I was not able to collect that many leaves. I still need to analyze the data but it seems like there was only a small amount of CH4 coming out of leaves.

We then went to the hotspot around 1 PM, and sample multiple times around the boardwalk with the floating chamber. Then we went about 65 m south to sample an area that I thought to be outside of the hotspot but after entering this open water area it was clear by the bubbles and by the smell that this was also a high CH4 flux area. The data from the floating chamber seemed to confirm this.

We also run a short test to see if we can see CH4 emissions from the road, above where the gas pipeline should be. There was a very minute steady increase in CH4 concentration of about 1 ppb per second, which was surprising. I will need to process the data to get the precise magnitude of the flux, but this should transform to about 2 nmol m-2 s-1.

We left at 4:30 PM.

Patty Notes:
Patty arrived 12:30pm. Julie Robert and Camilo already here, working on chamber measurements in footprint.
I calibrated LGR with NOAA standard and changed the top inlet filter. Everything looked good.
Praxair at 1600 psi
CO2 = 426 ppm
D13 C = -17.6 per mil
D18O=-100 per mil
H2O =393ppm
gas temperature =44.5 C
gas pressure =119.76torr
laser response =12.60us
Laser adjust looks good= -1.875

NOAA tank is low 700psi-need to order new one

Ran praxair again one last time to make sure running properly at 1:28pm, everything looked good.

5 photos found

20210506SW_Li-6400-CH4.jpg ( 2021-05-06 11:48:05 ) Full size: 1440x1920
Exploratory plant CH4 fluxes by combining the Li-6400 with the Li-7810