Road salt reduces plant cover in bioretention systems within road rights-of-way

Abstract

Bioretention systems for managing urban runoff rely on healthy plants to reduce runoff and nutrient pollution via evapotranspiration and uptake. However, loss of plant cover is common and, in cold climates, potentially caused by the application of road salt. To investigate the impact of road salt on bioretention systems, we measured salt concentrations in the media and plant tissues and assessed plant cover at 19 sites in Toronto, Canada, in the field. Winter road salt was identified as the primary driver of plant cover loss: low-tolerance species accumulated excessive sodium and chloride, resulting in chlorotic and necrotic damage even under moderate salinity (median electrical conductivity..