2005 Annual Report 4d.Progress report. This report serves to document research conducted under a Specific Cooperative Agreement between ARS and Ohio State University. Additional details of research can be found in the report for the parent research project 6408-12130-012-00D, Process, Control, and Prediction of Erosion and Runoff on Upland Areas in Agricultural Watersheds. This project seeks to determine the effect of geochemical factors on sediment quality. Nine sediment cores were collected using vibracore technology to represent the Yalobusha River arm, the Skuna River arm, and the main pool of Grenada Lake. These cores were analyzed for various physical, chemical and mineralogical properties that could be useful for evaluating the stratigraphy and environmental impact of Grenada Lake sediments. The results indicated that the pH of sediment waters ranged between 5.5 and 6.5 with no consistent trends with depth. The concentrations of dissolved Ca, Mg, and Si tended to decrease with depth; whereas, Na distributions were relatively constant. Arsenic was the most significant trace element in all pore waters with concentrations ranging from 40 to 150 parts per billion in the most recent sediments. Concentrations generally decreased with depth, suggesting a man-induced source. Particle size determinations revealed greater clay and smaller sand contents in the most recent sediments. Clay mineralogical analyses indicated that smectite was more abundant in the post- construction sediments than in those comprising the basin floor in the main pool and Skuna arm of the reservoir. In contrast, smectite distributions in sediments form the Yalobusha arm were much more uniform with depth. This distribution of smectite within the reservoir suggests that it may be a good indicator of sediment provenance. Data analysis is continuing.