Feedback Loops and Abiotic Determinants of Biomass Growth and its Impact on Chromium Reduction in the Hyporheic Zone
Authors
Marc Berghouse1,2*, Rishi Parashar1 (rishi@dri.edu)
Institutions
1Desert Research Institute, Reno, NV; 2University of Nevada, Reno, NV
Abstract
Within the hyporheic zone, a complex interplay of abiotic processes dictates the growth conditions of biomass. Factors like soil heterogeneity, stream conditions, temperature fluctuations, and nutrient availability all converge to shape this environment. Given the hyporheic zone’s potential to bioremediate contaminants through biotic and abiotic reduction, decoding these growth determinants has broader ecological significance. In this study, the team presents a numerical exploration of how varied initial conditions influence biomass growth and its impact on modeling of chromium reduction through Monod kinetics. The modeling approach simulates a two-dimensional cross-section of the hyporheic zone, integrating surface water-groundwater interactions through river stage changes. To effectively capture bioclogging dynamics and soil respiration, researchers enhanced the reactive transport model, PFLOTRAN, to account for biomass decay influenced by fluid velocity and the dependency of biomass growth on temperature. The diverse simulation conditions, augmented by sensitivity analyses for pivotal abiotic factors, offer holistic insights into microbial growth dynamics and chromium reduction through PCA and correlation heatmaps. Comprehensive comparisons of mean values over time, and spatial variability distributions of key parameters, serve as the foundation of the analysis. In addition to investigation of correlated features in our simulations, researchers also present a deep-learning-based upscaling model. The team tested 5x and 10x upscaling and showed that the method offers accuracy and considerable speed up compared to Monte-Carlo simulations. The team investigated the nuanced relationships between abiotic elements and bacterial proliferation and highlight how these relationships impact chromium reduction in the hyporheic zone. Through this multifaceted study, the team offers a fresh perspective on the modeling of reactive transport in the hyporheic zone.