2019 REUs presented at the CERF Conference in Mobile, AL
Factors responsible for the development of iron flocculate in streams with and without regenerative stormwater conveyance (RSC) structures
ASLO Aquatic Sciences Meeting, Granada, Spain
One ecological engineering design to reduce stormwater runoff and pollutants is called a Regenerative Stormwater Conveyance (RSC). RSCs are implemented in degraded headwater streams using sand, woodchips, cobble, and ironstone boulders to create stepped pool conveyance structures. Concern has been raised that RSCs exhibit excessive accumulations of flocculate mats created by iron-(Fe)-oxidizing bacteria. Iron sources and mat formation factors are poorly understood, as well as how RSCs affect habitat and water chemistry. Leaching was done on substrates used in RSC construction with and without added dissolved organic carbon (DOC) to identify Fe sources and factors driving its release. Riparian and hyporheic ground- and surface-water chemistry, and physical parameters, from 6 RSCs and 3 reference streams in urban catchments of the Coastal Plain and Piedmont physiographic provinces of Maryland were compared. A longitudinal transect of one RSC was done to evaluate density changes of Fe-oxidizing bacterial mats and the solute composition of water in pools/riffles of the structure. This study suggests that both ironstone and riparian soils contribute to Fe bacterial mat formation, a process accelerated by the presence of DOC.