Technical Approach

Resuspension events will be characterized in three sediment integrity states: (1) bedded sediments (with associated physicochemical vertical gradients and effects); (2) resuspended sediments through time (0.25 to 4 hours); and (3) redeposition to a bedded sediment state. The dissolved and particulate phases for each of the three sediment integrity states will be characterized physically and chemically. These analyses will focus on particle sizes and associated binding phases (residual to extractable fractions) of key bioavailability factors that will include mineral type, surface area, particulate and dissolved organic matter, acid volatile sulfides and simultaneously extracted metals, and iron and manganese oxides and oxyhydroxides. The data will be used to test and validate existing chemical speciation models (WHAM 6, Visual Minteq, WHAMEQL) for metal partitioning. WHAMEQL will be extended to include both equilibrium speciation and kinetics using the TICKET modeling framework. TICKET will then be interfaced with sediment transport model PTM and TICKETPTM validated in small to large mesocosms. Simultaneous with the physical and chemical characterizations of the three sediment integrity states, exposures will be linked to short-term effects (mortality, feeding, embryo development, bioluminescence) on benthic macroinvertebrates, fish, and tissue uptake. Invertebrate and fish tissue uptake will be compared to the passive samplers. This comprehensive assessment will provide a validated model that predicts whether environmentally significant levels of metals are released into the overlying water column during resuspension events and whether subsequent newly deposited sediments are more or less toxic.