Research

Our group focuses on understanding the linkages between biogeochemical cycles and global change in riverine environments. The mechanisms driving carbon and nitrogen release from rivers and floodplains are strongly interlinked and feedback between biogeochemical, hydrological and ecological processes. In this regard, a current project—Watershed SFA—is focused on quantifying the impact of early snowmelt, reduced snowpack and other changes in the hydrologic cycle on nutrient release, promoting microbial metabolism and shrub encroachment. 

In the past, we have successfully developed a reactive transport model for the Rifle site, situated on the floodplain of the Colorado River, with the overarching goal of understanding the impacts of temperature and precipitation changes on carbon and nitrogen export. See Arora et al. (2016a), Yabusaki et al. (2017) and Dwivedi et al. (2018) 

Our group is working towards an enhanced weathering LDRD funded under the LBL-wide carbon negative initiative. Here, the goal is to  establish an integrated experimental-modeling-de-risking approach to provide optimization strategies to farmers, land managers and other relevant stakeholders to quickly identify conditions, implementation procedures and other land and crop management practices that promote long-term C sequestration and other co-benefits through enhanced weathering and mineralization. Learn more about the Carbon Removal and Mineralization Program here.

Hot spots and hot moments of biogeochemical processes have been defined as having a small spatial and short temporal size but large contribution to biogeochemical cycling. Our group has been actively involved with developing wavelet-based techniques and applying reactive transport models to identify the occurrence of and causes for hot spots and hot moments of biogeochemical activity. We have been successful in applying these data and modeling techniques to characterize geochemical hot phenomenon at a municipal landfill site, a floodplain site and in arctic soils. See Arora et al. (2013, 2016a, 2016b, 2019a) and a review of these approaches in Arora et al. (2022).

Quantifying biogeochemical cycles in natural environments necessitates understanding the complex interactions between hydrological and geochemical processes, and specifically how these interactions are shaped by subsurface heterogeneity across scales. Heterogeneity in the form of macropores and fractures provides preferential flow paths and impacts contaminant transport. Biogeochemical processes are also strongly affected by such heterogeneities. Our work suggests that lithological layering or interface (e.g. plume fringe, wetland-aquifer boundary, etc.) increases biogeochemical activity around that interface. Our work further indicates that using appropriate representation in models is critical to capturing these processes in the porous media. See Arora et al. (2011, 2012, 2015, 2017). A review of approaches for characterizing and monitoring the heterogeneous vadose zone, as well as incorporating this heterogeneity in models is provided in Arora et al. (2019b).

Water resource allocation decisions and management have become increasingly complex, given the need to adapt to climate change, land-use change due to population and economic growth, and occurrence of extreme or hazardous natural or environmental events. To address the critical problems related to water resource planning and management, new versatile approaches and simulation tools are desperately required that would facilitate a holistic understanding of the distribution of water resources and assessing surface water and groundwater vulnerability at the watershed scale. In this regard, our efforts have focused on developing new surrogate models for water balance, identifying minimum parameters for groundwater recharge and designing pollution prevention/intervention strategies. See Arora et al. (2020), Mueller et al. (2020) and Sahu et al. (2020).