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Presented at the NABS Annual meeting, Anchorage, Alaska, 2006
in Hyporheic Processes
Particle retention in benthic biofilms
L. Marx, K.E. Searcy, S. Arnon, and A.I. Packman.Department of Civil and Environmental Engineering, Northwestern University, Evanston, Illinois, 60201
A variety of particles, including pathogens and particulate organic carbon, can be removed from the water column through entrapment in biofilms that form on submerged aquatic surfaces. The objective of this research is to determine the processes that regulate the capture of micron-sized particles in benthic biofilms. A small recirculating flume was used to mimic natural conditions typical of wetlands and slow-flowing rivers. After three months of biofilm growth, fluorescent latex micro-beads of 1 and 5 μm diameter were injected into the system, and their deposition was monitored for several days. At an overlying velocity of 5 cm/s, 90% of all injected particles were removed from the water column after 72 hours. At a velocity of 0.9 cm/s, similar results were found for 5 μm particles, but only 40% of 1 μm particles were removed after 96 hours. Following each experiment, biofilm and sediment samples were obtained in order to measure particle retention in each of these reservoirs. Higher concentrations of particles were observed in the biofilms than in the sediments. These results suggest that benthic biofilms, overlying flow conditions, and particle size all play significant roles in regulating the removal of fine organic particles from surface waters.
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