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We investigated biogeochemistry along a 12-m hyporheic mesocosm that allowed for controlled testing of seasonal and spatial water quality changes along a flowpath with fixed geometry and constant flow rate. Water quality profiles of oxygen, carbon, and nitrogen were measured at 1-m intervals along the mesocosm over multiple seasons. dissolved oxygen (DO) and temperature profiles were monitored on 18 dates between May 2019 through August 2020. Grab samples to monitor profiles of carbon, nitrogen, and various other solutes along the mesocosm were collected in December 2019 and August 2020 to provide more comprehensive biogeochemical analyses at time points when the dissolved oxygen (DO) and temperature profiles were at or near the maximum seasonal differences. Mesocosm monitoring ceased abruptly due to the Holiday Farm Fire, which burned from September through October 2020, cutting off personnel access and electrical power to the mesocosm facility.
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Solute dynamics in the hyporheic zone of a headwater stream in Watershed 1 at the Andrews Experimental Forest, 2016-2018
This project examined the interactions between stream water and subsurface sediment to quantify how these interactions influenced organic C respiration and dissolved inorganic C (DIC) production in the hyporheic zone of a high-gradient headwater mountain stream draining a forested catchment at the H. J. Andrews Experimental Forest, Oregon, USA. The study used six 2-m long hyporheic mesocosms which were packed with streambed sediment in the spring of 2016. The mesocosms are located at the Watershed 1 (WS1) stream gage and stream water from WS1 has been pumped through the mesocosms continuously since they were first packed through the end of (and beyond) this study in autumn of 2018. The mesocosms were designed around 1-m long 20-cm diameter aluminum pipe segments with sample ports located each meter along the flowpath through each mesocosm – thus sampling at the inlet, at 1 m, and at the outlet which represents the full 2-m long flow path. Sampling was conducted on seven dates between Oct 23 2016 and Aug 27 2018. On two of these dates, only background samples were collected. On the remaining 5 dates, sampling was designed around continuous-injection tracer experiments using both a conservative tracer (salt) and a reactive tracer (various dissolved organic substrates). For background sampling events, samples were generally only collected once. The tracer experiments involved 4 discreet sampling times: 1. pre-injection (under background conditions); 2. early plateau; 3. late plateau, and 4. post-injection (and in one injection experiment, a 5th sample at late-post-injection time). For each round of samples, the mesocosm water temperature, pH, EC, and DO were measured with sensors in a small flow-through cell. Then water samples were collected for laboratory analysis for both DOC and DIC. The median travel time of water through each pipe segment of the 2-m mesocosms was also calculated from the conservative tracer break-through curves.
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- Award ID(s):
- 2025755
- PAR ID:
- 10647967
- Publisher / Repository:
- Environmental Data Initiative
- Date Published:
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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