Sediments and sediment-derived soils in Illinois: pedological and agronomic assessment.

Dredging sediments from water bodies in Illinois is done to preserve reservoir capacity, maintain navigation and recreation channels, and restore habitats, but the fate of the sediments is an issue. In anticipation of a major sediment dredging operation in Lake Peoria in the Illinois River, a retrospective study of sediment placement operations was performed. Sediments previously dredged from reservoirs and placed in retaining ponds were sampled along with adjacent upland soils which served as references. Sediments from the Illinois River above Peoria were sampled from islands, river bottom, and adjacent floodplain. Dredged sediment retention ponds initially support wetland vegetation. After dewatering, the physical properties of sediments tend to become similar to upland soils and the retention basins are then able to support conventional agriculture. Sediment organic matter content was similar to local reference surface soils, and soil pH of the sediments was neutral or above. Sediment textures are dominated by silts and clays, with the Lake Peoria samples being most clayey. Calcium was the dominant cation in all the samples, and micronutrients measured were in adequate supply for plant growth. However, because the Illinois River watershed includes industrial inputs, river sediments contained elevated levels of some metals, but they were generally below levels of regulatory concern. Results indicated that properly handled dredge sediments could make high quality agricultural soils. In addition, sediment placement on poor soils could improve their productivity.