2024 Abstracts

Integrating Organic Matter Measurements into Watershed Hydro-Biogeochemical Models


Peishi Jiang1* (peishi.jiang@pnnl.gov), Zhi Li1, Katherine Muller1, Jianqiu Zheng1, Glenn Hammond1, Tasneem Ahmadullah1, Hyun-Seob Song2, Vanessa Garayburu-Caruso1, Matthew Kaufman1, Alan Roebuck1, Stephanie Fulton1, James Stegen1, Xingyuan Chen1, Tim Scheibe1


1Pacific Northwest National Laboratory, Richland, WA; 2University of Nebraska–Lincoln, NE



Watersheds play significant roles in modulating carbon and nitrogen cycling and removal of excess nutrients. The incorporation of molecular-level characteristics of organic matter (OM) from field measurements is expected to greatly improve the ability of watershed hydrobiogeochemical models to capture distinct water quality and quantity signatures under disturbance, thus facilitating iterative coupling with field measurements under model-experiment (ModEx) framework. However, the connections between OM measurements and biogeochemical reaction network from batch to watershed scales are missing. Researchers developed an integrated modeling approach that links site-scale OM chemistry measurements to watershed-scale modeling. At the site scale, a Python workflow was developed to connect OM chemistry informed by high-resolution Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) into an aerobic respiration simulator using the PFLOTRAN reaction sandbox. Moreover, to account for the role of non-oxygenic electron acceptors in regulating organic matter turnover and the fate of carbon, researchers expanded the aerobic respiration-based carbon speciation by incorporating both detailed OM chemistry and electron acceptors other than oxygen. At the watershed scale, researchers developed an integrated model that couples the formulated site-scale batch reaction in PFLOTRAN with a distributed flow and transport model ATS. Researchers have employed ATS to study the impact of wildfire disturbance on watershed hydrological response by implementing a new fire module to modify the soil properties in fire scars. Researchers demonstrated the usage of the watershed model to evaluate the downstream runoff to wildfires across multiple watersheds in Pacific Northwest, such as Naches River Watershed. To further study disturbance impacts on watershed biogeochemistry, future work will: (1) incorporate the generalized carbon speciation method into the Python workflow; (2) enable characterization of spatiotemporal variation of reaction networks in watershed models; and (3) leverage additional advances the team has contributed to, such as the omics-to-reactive-transport pipeline that explicitly links microbial genomics to PFLOTRAN.