Characterization of Highway Stormwater Runoff from Various Land-Use in Tennessee

Abstract

This study aimed to characterize highway stormwater runoff in Tennessee, and to understand possible sources of ammonia and nitrates in the runoff across three sites with varying land-use. Influences from atmospheric deposition were determined using statistical correlations and possible sources were tracked using dual stable isotopic (δ18O and δ15N) analysis. The contribution of vegetation as a source or sink was analyzed by preventing mowing of the sites for a duration of one year, after which mowing continued as scheduled. Statistical significance testing was also performed to determine significant differences in stormwater characteristics between seasons and land-use. Preliminary results show that stormwater quality from highways is more complex than previously hypothesized. A significant difference in chlorides and ammonia was observed during winter months, which could be contributed to the use of road salts, and decaying vegetation releasing stored nutrients, respectively. From dual stable isotopic analysis, atmospheric deposition was observed as a source of nitrate at all study sites; however soil and fertilizers were also identified as a source, especially for areas with adjoining agricultural practices. Further analysis is being conducted to determine their relative contributions to nitrogen pollution. These results, along with comprehensive characterization of Tennessee’s highway runoff will be presented.