Low impact developments are one of the main tools to improve stormwater quality. Stormwater control measures (SCMs) have been developed to help address the growing urban stormwater problem. Stormwater basins such as detention and retention basins are used to address these concerns. These basins commonly include some soil-based media to promote water filtration and storage. Furthermore, they improve water quality through sedimentation, filtration, and biological transformation. The nitrogen cycling genes in the soil of basins and the changes through the season is an important factor affecting the efficiency of the basin in removing the nutrients, which is our main focus in this study. In this study, we study one detention basin on the Edwards Aquifer's recharge zone, the primary water source for San Antonio. We studied the nitrogen cycle in the basin based on the nitrogen species concertation in the stormwater samples and comparing them to the genes responsible for nitrogen cycling in soil samples. Inflow and outflow stormwater samples are collected for each rain event using automated samplers. Soil samples are collected within the basin in the summer and winter. After extracting DNA from the soil samples, the abundance of different nitrogen cycling genes will be measured by qPCR. Nitrite and ammonia are completely removed from the stormwater. However, we saw the nitrate concentration is increasing in the outlet in most cases. Studying different types of functional genes present in the basin and their abundance across the basin and various depths would help better understand the removal of the nutrients in these basins. Collecting soil samples from different depths and locations of the basin will help us distinguish functional genes responsible for removing or adding the nitrogen species to the water.
Basin picture taken on November 2020
Acknowledgment.
The city of San Antonio funded this project.
