Potential Color Change Dynamics of Beneficial Use Sediments

Berkowitz, J.F.; VanZomeren, C.M., and Priestas, A.M., 2018. Potential color change dynamics of beneficial use sediments. Sediment color is important in determining aesthetic and habitat suitability for beach nourishment projects; however, sediment derived from dredging operations must meet locally established color compatibility requirements (i.e. cannot be too dark). Often, potential sediment sources are close to meeting specified thresholds, and previous observations suggest that sediments may lighten over time following beach nourishment. This work seeks to characterize the degree of color change potential based on the removal of constituents affecting sediment color. Thus, a sequential chemical treatment was developed to examine color changes associated with the removal of carbonates, organic matter, and iron oxide coatings from sediments collected from eight U.S. Army Corps of Engineers dredging operations. The results show that Munsell values increased by an average of 1.0 unit (became lighter in color) upon removal of these secondary constituents. In addition, five of the eight sediments examined surpassed established color thresholds (Munsell value ≥ 5) from their pretreated state. This procedure is meant to serve as a proxy for removal of these constituents by natural processes. Study findings suggest that sediments with initially unacceptable color, and high capacity for color change, may increase potential use of limited sediment resources. Future work will further relate color shifts to sediment composition, sediment mixing, and solar bleaching to predict sediment color changes under real-world scenarios.