Sustainability Videos & Lecture Series

Elisabeth Larson: I’m a grad student in the School of Life Sciences and my advisor is Nancy Grimm, and I’m also in the interdisciplinary–sorry, Integrative Graduate Education and Research Training or IGERT program in urban ecology through GIOS, and so I’ve gotten a lot of funding from them. A significant portion of the funding for this project is actually from a National Science Foundation dissertation improvement grant that I got as well.

Nancy Grimm: One of the major components of the LTER is to understand how materials move through the environment, so things like nitrogen, phosphorus, carbon, other of those major elements as well as metals and organic pollutants and that sort of thing, and so we’re interested in that. In this arid environment, what we actually find is that materials move mostly either through the air or when there are storms. Elisabeth Larson: I’ve been doing research on storm water retention basins which are a really common feature in the Valley for handling storm water runoff and preventing flooding. One of the things I’m particularly interested in is nutrient cycling, especially processing of nitrogen. We know that storm water tends to have really high concentrations of various forms of nitrogen in it and those can be–sort of act like as a fertilizer or sometimes be considered pollutants. It’s important and interesting to me to figure out what happens to those.

Nancy Grimm: It will be a really exciting experiment. The results I think are gonna tell us a lot about what happens when storms occur.

Elisabeth Larson: What we’re doing is we’re taking water. We’ve got a permit from the city to tap a fire hydrant. The fire hydrant has a meter on it so that we know how much water we’re gonna add. We’re basically simulating a five year storm. We calculated the contributing area to this basin, so basically this basin is draining this whole parking lot right here. All the water that would fall eventually makes its way into this basin.

We know how much water to add to simulate that size storm. What we’re doing is we’re using an isotope of nitrogen, N15. We’re adding that to the system so that we can trace the processes that are happening, so the transformations of nitrogen from one form to another. That’s really exciting and cool too because not many people work with isotopes of N15. It makes things a little bit more complicated analytically, but it’s pretty exciting.

The setup that we have is we have the fire hydrant and a backflow preventer attached to that and then a hose that comes off of that. The pressure coming out of the hose is too high to put directly onto the soil, plus we wanna separate the water into two input flows ‘cause this basin has basically two main inputs to it. What we’ve done is we’ve directed the hose into a pool, a little, well, not a little, but a kiddie pool, three feet high, ten feet in diameter, that slows down the water. Then we have two submersible pumps with other hoses coming up out of that that go to the two inputs to the site. That’s the way we’re gonna deliver the water to the system.

At three places we collected soil and temperature. Then we also collected carbon dioxide flux coming–recorded carbon dioxide flux coming up out of the soil.

Nancy Grimm: We’re really trying to figure out what some–first of all, understand what happens to those materials and, second, we understand what some better practices might be in designing things like retention basins or neighborhood flow paths, where the water goes and things like that in order to determine how you can reduce the impact of those materials that are going into these kinds of basins.

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The above transcript provided by Landmark Associates.