ABSTRACT CTS-9422962 It is proposed to experimentally investigate supermicron particle aggregation and sedimentation in relatively idealized conditions, in order to better understand the basic physical processes and provide a data base for modeling. The specific objectives are to conduct flow visualization in a laboratory system, analyze and model the fundamental parameters controlling gravity induced aggregation, and characterize retarded coagulation and subsequent aggregate morphology in quiescent environmental systems. The proposed quiescent reactor apparatus allows for real time observation of gravity-driven aggregation dynamics, with simultaneous measurements of particle/aggregate size, velocity and shape. The effects of shear flow, Brownian diffusion, sedimentation, aqueous chemistry, and particle surface characteristics on aggregation will be investigated. The experimental results will be introduced in a model applicable to natural and engineered systems. The project will improve basic understanding of gravity-driven aggregation and sedimentation occurring in natural surface- and ground water environments, including chemical cycling, particulate dynamics, and contaminant redemption. ***
