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GSA abstract: Storage Dynamics Revealed by Water Isotopes Provide Insight into Water Quality Function of Stormwater Green Infrastructure

Later this month, Caytie, Garrett, and I will be representing the Watershed Hydrology Lab at the Geological Society of America Annual Meeting in Seattle, Washington. I will be presenting the following talk on Wednesday at 10:15 in WSCC Room 612.

Storage Dynamics Revealed by Water Isotopes Provide Insight into Water Quality Function of Stormwater Green Infrastructure

Jefferson, A., Sugano, L., Buzulencia, H., Avellaneda, P., and Kinsman-Costello, L.

Increasingly popular, stormwater green infrastructure is touted as improving water quality, through filtration and retention that allows plant uptake and biogeochemical processing to occur. Many data sets reveal large inter-storm variability of water quality in green infrastructure effluent, suggesting that internal dynamics that control water transit time may play an important role in the water quality functioning of green infrastructure. We hypothesized that collecting data on water stable isotopes, in addition to solute chemistry, would provide insight into transit times and would help explain variability in water quality flowing out of three forms of green infrastructure. Water isotopes, chemistry, and fluxes were measured from bulk precipitation, inflow, outflow, and surface water storage for a green roof, bioretention cell, and wetland at a site in northeastern Ohio.

On the green roof, outflow isotopes were variable within storms, but flow-weighted averages were similar to bulk precipitation for each event, suggesting transit times of minutes to hours. First flush behavior for solutes was exhibited for some storms and some solutes, but much of the inter-event variability in solute export could be explained by precipitation amount and antecedent dry period of each storm. In the bioretention cell, inter-event storage and release of old water is sometimes observed in the outflow isotopes. Outflow nitrogen concentrations were generally lower when old water was discharged, suggesting that denitrification is occurring within the bioretention cell. However, antecedent dry period also appears to influence nitrogen concentrations, suggesting some discharge of new water even during moderately-sized storms. Isotopic hydrograph separation was possible for some storms in the wetland, and in these cases, solute concentrations in the outflow can be explained by mixing of new water with previously ponded water. Where solute concentrations can’t be explained by mixing, biogeochemical processing may be happening during the storm period.

This work builds on work I presented earlier this year at the HydroEco 2017 (June) and the GSA regional meeting (March).

The 2016 Kent State Water and Land Symposium

A major focus for the Watershed Hydrology lab this fall has been preparing for the Kent State University Water and Land Symposium. Anne Jefferson was the symposium co-chair (with lots of help from Biology’s Chris Blackwood), and all of the lab members were involved in some way. Pedro, Laura, Hayley, and Cody presented posters. Caytie and Garrett helped with set up and were on tweeting duty. The symposium had about 400 attendees from universities, agencies, cities, non-profits, and the general public from throughout northeast Ohio. If you missed the event live or on twitter, here’s how it went down.

 

This year’s symposium occurred on October 5-6, 2016, and featured the theme of “Sustainability and Resilience on the Land-Water Continuum.”

Surface runoff from a closed landfill and the effects on wetland suspended sediment and water quality

Watershed Hydrology lab undergraduate Cody Unferdorfer will be representing the lab at this year’s Geological Society of America meeting in Denver in September. The work that he will be presenting will build on preliminary work that won the Kent State University Undergraduate Research Symposium Geology/Geography division in April, and Cody will have more and better data and analyses to show of at GSA.

Update: Cody will be giving a poster in the session on Undergraduate Research Projects in Hydrogeology on Sunday.

Surface runoff from a closed landfill and the effects on wetland suspended sediment and water quality

Cody Unferdorfer (1), Anne Jefferson (1), Lauren Kinsman-Costello (2), Hayley Buzulencia (1), Laura Sugano (1)
1. Department of Geology, Kent State University
2. Department of Biological Sciences, Kent State University

Abstract
During rainstorms, many wetlands receive surface runoff carrying sediment and dissolved materials. Some of the sediment and solutes remain within the wetland, where they impact aquatic organisms and nutrient cycling. With time, excess sediment can fill in a water body and destroy the aquatic ecosystem, or excess nutrients can lead to eutrophication. Closed landfills have compacted surfaces that can generate large amounts of surface runoff, and the goal of this project is to examine the effects of a closed landfill’s runoff on a wetland.

The study site is a constructed wetland in Parma, Ohio. Water samples were collected during storms beginning in July 2015. We monitored five locations at the wetland: inflow from the landfill; inflow from two green infrastructure treatment trains; inflow from a stream seep, and outflow. Water samples were analyzed for suspended sediment concentration, water stable isotopes, and dissolved forms of nitrogen and phosphorus. Discharge was measured at the outflow.

Based on a preliminary analysis of four storms, of the inflows; the landfill contributes the most suspended sediment with an average of 400 mg/L. There is no correlation between TSS and discharge at the outflow. Instead a first flush effect was observed, where TSS concentrations decreased with time. The landfill inflow is close to the wetland outflow, which could allow for suspended sediment to bypass most interaction with the wetland’s interior. However, comparing rain and wetland outflow stable isotopes shows that water residence time often exceeds a single storm, suggesting that there are opportunities for biogeochemical processing of nutrient inputs within the wetland.

Runoff from the landfill (right) enters the wetland (left) near the wetland's outlet structure. What impact does this muddy water have on the wetland itself? Photo by a Watershed Hydrology lab member, August 7, 2015.

Runoff from the landfill (right) enters the wetland (left) near the wetland’s outlet structure. What impact does this muddy water have on the wetland itself? Photo by a Watershed Hydrology lab member, August 7, 2015.