Road Salt Accumulation and Wash-out in Stormwater Detention Basins: Patterns and Implications for Biogeochemical Cycling

Monday, 15 December 2014
Lauren E McPhillips and Michael Todd Walter, Cornell University, Ithaca, NY, United States
There is increasing evidence that salt application to roads and parking lots in winter is driving a rise in chloride concentrations in streams in the northeastern United States. Our research focuses specifically on salt dynamics in stormwater detention basins, which receive runoff directly from parking lots and detain it before it reaches the stream. The four study basins are located on the Cornell University campus in Ithaca, NY USA. Between summer 2012 and 2014, soil electrical conductivity was continuously monitored inside and outside the basins using Decagon 5TE sensors and dataloggers. In two basins which drain stormwater quickly, conductivity levels changed minimally over the year. However, in the other two basins which drain much slower and often are saturated, conductivity increased through the winter, peaking at 8-10 mS/cm, and then took several months to decrease to baseline levels; thus the basins served as a source of salt to outflowing water even into the summer. This annual variation in soil salinity has implications for plant and microbial communities living in these basins. Research by colleagues has indicated that changing salinity can alter microbial communities and impact biogeochemical processes that play a role in water quality remediation. Thus we are also investigating the impact of salinity on denitrification rates in these basins. All of this information will help us understand what role stormwater detention basins are playing in controlling fluxes of road salt in watersheds, as well as how changing salinity influences the ecosystem services provided by these basins.