Field Notes

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Gilbert Tract: 2024-08-16 07:00:00 (DOY 229)
Author: Daphne Szutu
Others: Kuno, Carlos, Amelia, Charlie, Hannah

Summary: 3rd day of chamber campaign for CH4 and N2O fluxes, regular data download, installed new EXO3s in channel with ADCP, downloaded channel miniDOT, cleared weeds near ADCP

2024-08-16
Gilbert Tract

Kuno, Carlos, Amelia, Charlie, Hannah, and I arrived around 7:00 PST (8:00 PDT) for the chamber campaign. Amelia is a new postdoc in Jill Banfield’s lab. Charlie is an undergrad student in Rob Rhew’s lab, and Hannah is an undergrad student at Harvard and will be doing her senior thesis with Jackie Matthes. It was mild and sunny with a breeze picking up through the morning. Vector control was driving back and forth on the Burroughs parcel, towing an ATV.

Today is the third day of chamber campaign. These measurements during the growing season will be compared with the measurements from the chamber campaign in December 2023 during the senescent season. The chamber campaign consists of taking CH4 and N2O fluxes at open water locations around the wetland. We have two CH4 analyzers and one N2O analyzer for this campaign. We are trying to get spatially diverse samples, with both channel and edge locations. At each location, we are also measuring water parameters (pH, DO, conductivity, temperature, water depth) and recording the GPS location. At randomly chosen sampling sites, we are also collecting a soil sample ~10cm deep for Kuno to analyze for genetic information (max 20 soil samples per day).

Kuno, Carlos, and Amelia were team A. Charlie and Hannah were team B. Each team took chamber fluxes at about 15 locations each (with a combination of dark and clear chambers), recorded water parameters, measured the water depth, and recorded the GPS location. For this campaign we borrowed two water quality probes from Patty’s department that measured pH, DO (as RDO), conductivity, and temperature. Team A measured both CH4 and N2O fluxes (analyzers carried in backpacks), and Team B measured only CH4 fluxes (analyzer floated in large orange tub). I got Charlie and Hannah started with sampling—Hannah was a pro since this is her third day on the campaign. In one of our sampling points underneath the cattail canopy, we saw a few crayfish hanging out just under the water surface.

I started with regular tower servicing around 9:30 PST. I downloaded met, cam, and USB GHG data. Since I had waders on already, I checked the Campbell conductivity sensor attached to the fence post and confirmed that its orifice was clear. I downloaded data from the Song Meter Micro, changed its desiccant, and connected via Bluetooth to confirm that its battery was still good (100%).

I cleaned flux and rad sensors. I scratched the lower 7700 mirror while cleaning off bird poop in the middle. There might have been grit in the bird poop or in the rag. Next time I would soak the bird poop in some alcohol to make it a bit softer before wiping it away. The scratches are in the middle of the mirror and it doesn’t seem like the RSSI was affected. The wash reservoir was full. I also cleaned some bird poop out of the rain bucket.

The staff gauge read 31cm at 9:32 PST.

I measured the surface water conductivity off of the boardwalk. This was after sampling started so the surface water had been disturbed more than usual.

Sample, temperature-compensated conductivity, temperature
Surface, 446 uS, 23.3 C

The 7500 read: 412ppm CO2, 727mol/m3 H2O, 24.5C, 101.4kPa, 100SS – 102 after cleaning
The 7700 read: 2.12ppm CH4, 45RSSI – 79 after cleaning

Dennis arrived around 10:00 PST (11:00 PDT) to observe the chamber campaign. Charlie and Hannah showed him some of the soil samples they had taken. There’s a clear change in texture from the squishy peat in the top 2-3cm to the hard clay in the bottom 8-10cm.

Dennis and I went to the channel around 10:25 PST (11:25 PDT) to install our new EXO on the ADCP mount. We had originally planned to bolt the EXO mount on the side of the ADCP mount, but then realized the EXO would block the z-direction of the ADCP. Dennis suggested mounting it behind the ADCP. The ADCP mounting plate is attached to an adjustable, sliding bracket that lets you adjust the angle of the mounting plate. I drilled two new holes in the EXO mount and attached it to the bottom of the sliding bracket with stainless steel hardware. It’s about 10cm from the bottom of the guard to the ADCP mounting plate. The EXO is mounted horizontally, although it won't be quite level. I thought that might be too close to the plate, but Dennis said it’s fine because we’re not measuring velocity or turbulence, just scalars, and we can assume the water is mixed well enough near the sensors. I also moved the channel miniDOT from behind the ADCP plate to above the EXO.

The EXO is installed with the black plastic sensor guard, but not the cap. At Hill Slough, the cap encouraged a fish to take up residence, so we didn’t install a cap here either. The EXOs are all calibrated without the sensor guard cap.

Sensors installed:
sn 23H107001 EXO3s
sn 24F102410 Turbidity
sn 22C100780 fDOM
sn 24F100050 Conductivity/Temperature
sn 24G102326 pH/ORP
sn 24F104086 wiper

The EXO3s model does not have an internal battery compartment and needs external power. It is wired to CR6 sn 2115 and powered with the ADCP solar/battery system. The CR6 measures every 5 minutes and saves 30 minute averages. The real-time data from the CR6 looked reasonable, although the last two columns (salinity in PSU and wiper voltage) were NAN. Probably need to adjust the EXO’s internal settings. These data columns aren’t too important because salinity is redundant with conductivity (which is getting saved), and wiper voltage is a diagnostic to check that the central wiper is working.

Future improvements:
- The CR6 needs another short mounting screw
- Replace 2-terminal screw terminal with 4-terminal screw terminal for power
- Connect to the EXO to confirm data columns (need to connect via bluetooth)

I downloaded the channel miniDOT and swapped its desiccant. I downloaded the ADCP data, reset its clock, and double-checked that I restarted logging. The ADCP was complaining that too many internal files was slowing it down. I left a mothball in the enclosure for the ants. Dennis raked weeds from near the ADCP and wiped off all the algae that had accumulated on the sensor.

Dennis and I went back to the tower around 12:00 PST (13:00 PDT) for lunch. Kuno, Carlos, and Amelia were done with their samples and eating lunch (in the sun—why??). Dennis left after lunch. Kuno and I went to go check in on Charlie and Hannah, who were were finishing up sample 15, so Kuno told them that was enough.

We packed up and headed home at 13:30 PST (14:30 PDT).

7 photos found

20240816GT_7700Scratches.jpg ( 2024-08-16 10:52:27 ) Full size: 1440x1920
I scratched the lower 7700 mirror while cleaning off bird poop in the middle. RSSI seems fine.

20240816GT_CanopySample.jpg ( 2024-08-16 10:03:43 ) Full size: 1440x1920
Charlie carefully placing the soil chamber down underneath the cattail canopy. We saw 3+ crayfish hanging out just under the water near the chamber.

20240816GT_ChamberCampaign.jpg ( 2024-08-16 10:43:54 ) Full size: 1440x1920
Charlie and Hannah sampling CH4 fluxes on open water

20240816GT_DennisHannahCharlie.jpg ( 2024-08-16 10:54:18 ) Full size: 1920x1440
Hannah showing Dennis one of the soil samples collected during the chamber campaign

20240816GT_ExoEnclosure.jpg ( 2024-08-16 13:02:05 ) Full size: 1440x1920
ADCP enclosure after adding the CR6

20240816GT_HannahCharlie.jpg ( 2024-08-16 09:23:47 ) Full size: 1920x1440
Hannah and Charlie taking sample B1 at Gilbert Tract during the last day of the chamber campaign. They are recording open water CH4 fluxes.

20240816GT_NewExoMount.jpg ( 2024-08-16 12:11:11 ) Full size: 1440x1920
The EXO3s and miniDOT for the Gilbert Tract channel are installed behind the ADCP plate