Coastal Flooding Redistributes Water Dispersible Colloids Impacting Dissolved Oxygen Dynamics
Authors
Kenton Rod1* (kenton.rod@pnnl.gov), Kennedy Doro2, Kaizad Patel1, Kenneth Kemner3, Stephanie Wilson4, Pat Megonigal4, Theresa O’Meara5, Vanessa Bailey1
Institutions
1Pacific Northwest National Laboratory, Richland, WA; 2University of Toledo, Toledo, OH; 3Argonne National Laboratory, Lemont, IL; 4Smithsonian Environmental Research Center, Edgewater, MD; 5Oak Ridge National Laboratory, Oak Ridge, TN
URLs
Abstract
Coastal soils are increasingly impacted by hydrologic intensification in the form of rising ocean waters and floods from storm surges and precipitation. Alternating salt and freshwater has the potential to disperse mineral and organic colloids, which can lead to disintegration of soil structure and clogging of pore spaces and can reduce important functions like infiltration and gas exchange. Additionally, colloids are important to carbon and nutrient cycling, potentially influencing biological oxygen demand. To investigate the oxygen dynamics in repeatedly flooded soils, the team conducted a series of laboratory-based flood simulations on intact soil cores from an A and B horizon collected from the toe slope of an upland forest at the Smithsonian Environmental Research Center, Maryland, U.S. The team subjected the cores to 24 hours of saturation with saltwater from the Rhode River estuary followed by 24 hours of saturation with freshwater, with a 24-hour draining event in between flood events. Significant changes were found in pore size distribution, significant redistribution of colloids, and the A horizon became sodic after three saltwater floods. During draining, oxygen diffusion into soil was reduced for saltwater flooded soils, likely due to clogging of smaller pores. The team also found that oxygen consumed varied between soil horizons relative to water dispersible suspension fraction and that of the bulk soil. Researchers concluded that a relatively small number of saltwater flooding events can induce a measurable change in soil physical properties, impacting the biogeochemical dynamics of the soils.