THE EFFECT OF TYPE AND SIZE ON ORGANIC PARTICLE DEPOSITION VELOCITY.

D.J. Van Horn¹, L.J. Standley¹, J.D. Newbold¹, and M.L. Van Horn². ¹Stroud Water Research Center, 970 Spencer Rd, Avondale Pennsylvania 19311, ²University of Washington Social Development Research Group, 9725 3rd AVE NE Suite 401, Seattle WA 98115

Fine and very fine particulate organic matter (FPOM, 53-106 μm, and VFPOM, 15-52 μm) provide sources of energy for stream ecosystems, serve as vectors for pathogens, and transport absorbed contaminants. Their transport and fate is strongly influenced by deposition mechanisms. To investigate the influence of particle characteristics, we compared deposition velocities (V_dep) of FPOM and VFPOM fractions of six types of particles: stream seston, liquid manure, applied liquid manure containing topsoil, forest loam, highway runoff, and wastewater treatment plant effluent (WWTPE). V_dep was measured by injecting particles into 30-m long streamside flumes. Mean V_dep (mm/s) for FPOM ranged from 0.351 (forest loam) to 1.170 (highway runoff) and for VFPOM 0.263 (forest loam) and 0.625 (highway runoff) with significant effects of size, type, and size-type interaction. WWTPE FPOM particles deposited at a high rate despite high organic matter content and low quiescent water fall velocity (V_fall). Among the other types of particles V_dep and V_fall correlated at 0.88 for FPOM and 0.98 for VFPOM indicating that density influenced deposition. However the high V_dep for WWTPE suggests an influence of surface characteristic, perhaps related to its “sticky” fungal hyphae matrix composition.