“There are processes at work everywhere and, in particular, in rivers and aquatic systems that alter the organic material,” she says. “For example, bacteria eat carbon. It’s a food source. So the molecule that started out looking like a piece of tree won’t look like a piece of tree after the bacteria have been eating it. It’s a different material.
“The sun also beats down on the reservoir,” she adds. “The sun’s energy is very powerful, and many organic molecules have chemical bonds that are sensitive to photons from the sun. Ultraviolet light will break down organic material. We hope to look at how much of the organic carbon is photochemically active, capable of being broken down by sunlight, and what effects sunlight has on the amount of carbon and types of molecules present.”
One hypothesis holds that “all the processes will make the carbon at the bottom of the river more resistant to degradation, that it can’t be broken down very easily and that all the carbon that makes it to the ocean is pretty tough stuff that nothing wants to eat,” she says. “It may start out pretty tasty to bacteria, but by the time it gets to the bottom, after being eaten up and beat up by sun, there’s not much good stuff left and it’s highly degraded and not very reactive.”
A second hypothesis suggests that “terrestrial material gets beat up and there’s not much left, but that the algae add their riverine carbon, and you end up getting a mixture of fresh and not-so-fresh carbon,” she adds, predicting she may have some preliminary answers within several months. “Right now we have students collecting samples from the lower part of the river,” she says.
Interestingly, little baseline knowledge exists as to the amount and condition of carbon in the river.
“It’s a simple question: how much and what kind of carbon gets to the bottom of the river? But there are all these interactions that you have to investigate in order to answer it,” she says.
Much of her studies in biogeochemistry focus on how geochemical, microbial and anthropogenic processes affect elemental cycles in modern and paleo-environments. “These studies require investigations of mechanisms that operate on time scales from days to millennia,” she says. “The main goal is to gain a better understanding of the interactions between the physical, chemical and biological processes that control the distributions of these climatically important elements and how they change through time.”
More specifically, as to her Colorado River research, she adds: “It’s fundamental we begin to study managed rivers, because that’s what we have.”