Roche receives multiple awards to pursue research on river sediments

There are 18 major river basins in the lower 48 contiguous United States, comprising more than 250,000 rivers, primarily dominated by the Pacific Northwest, Great, Colorado, and Mississippi River basins.

These veins of the country, the American river systems, do far more than just convey water across the land. They provide important services to humankind, yet numerous challenges from agricultural runoff, climate change, and other human activities are creating significant negative impacts.

In the last year, Assistant Professor Kevin Roche in the Department of Civil Engineering secured more than $600,000 in funding to advance the mechanistic understanding of how rivers generate and attenuate several of these societally-relevant chemicals.

Expanding Microzones Research

Building on his previous funding into Idaho riverbed pollution from the Environmental Molecular Sciences Laboratory, a Department of Energy facility, Roche's collaborative research grant from the National Science Foundation aims to enhance the understanding of nitrous oxide emissions from river systems and their impact on greenhouse gases.

In his earlier DOE-funded work, using advanced laboratory techniques, his team developed new experimental reactors to monitor the complex interactions of bacterial growth, fluid flow, and oxygen availability within river sediments. Roche's newest grant allows his team to use these reactors, together with additional experimental and modeling tools, to quantify how these interactions influence emissions from river sediments.

"We're excited to build on some of the great work other Boise State researchers have done and help unravel this paradox," Roche said. "Many scientists believe that bacterial communities are so good at using oxygen that they create small regions of anoxia that are ripe for nitrous oxide generation."

With a more comprehensive look at the dynamics between river and groundwater systems, Roche believes the team's experiments and simulations will help provide a multidisciplinary understanding of how these regions change over time and connect observations to larger scale experiments.

Local River Impact

Roche's second NSF grant will use Boise River sediments to better understand how pharmaceuticals and personal care products (PPCP) move and degrade within river systems. These chemicals can adversely impact aquatic organisms at very low concentrations, but most are still not regulated.

"Cities in water-stressed climates will have to increasingly rely on treated water to meet demand," Roche said. "So, it's crucial for the public to understand how to properly dispose of PPCPs, as well as for scientists and engineers to understand how we can better design these compounds so they break more readily into benign products."

Roche said that oftentimes when bacteria break these compounds down, they generate byproducts that can be just as toxic as the original compound. "It is crucial that we have predictive tools that account for the fact that these compounds are being generated diffusely throughout the river network."

Roche and his team in the Hydrologic Interfaces and Processes Laboratory will leverage advanced measurement capability at the Biomolecular Research Institute to monitor PPCPs and their degradation byproducts within controlled laboratory experiments. By combining these lab results with mathematical models, the team expects to better predict how, when, and where PPCP concentrations exceed levels that are concerning for aquatic organisms or human health.

The team expects the insights gained will help other researchers better understand how byproducts degradation can persist and the toxic effects in river systems, improving strategies to help mitigate these impacts and protect aquatic ecosystems.

"It is expensive and difficult to measure these compounds in environmental waters, meaning we can't monitor everything everywhere at all times," Roche said. "This is where modeling comes in. I think the models we're developing will be useful for cities and regulatory agencies to identify where and when they should be investing in these monitoring efforts."

Engaging Future Environmental Stewards

In addition to advancing scientific knowledge, Roche's NSF grants include a commitment to educational outreach. The research team plans to leverage existing outreach programs at Boise State to mentor K-12 students and engage the community through STEM programs.

The team has partnered with the Intermountain Bird Observatory to expand their educational program at the Diane Moore Nature Center, which encompasses a recently restored side channel of the Boise River. This initiative aims to increase public awareness of the connections between groundwater quality and river health.

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