PAH and PCB distribution in sediment fractions and sorptive phases

Contaminant distribution is integral to environmental evaluations of contaminated sediment on every level. The technical and economic feasibility of treatment or beneficial use is a function of the accessibility or separability of the contaminants within the sediment. The magnitude of release to the environment during dredging and disposal is dependent upon the partitioning behavior of the contaminants. Yet, little attention has been paid to contaminant distribution in the fine sediment fractions. Further, conventional distribution coefficients provide little information regarding the relative contaminant loading of each of the sorptive phases. Bioavailability of contaminants in oil and grease, soot and organic carbon, components of sediment total organic carbon (TOC), may be vastly different. Physical properties are also different and determine fate during treatment. This study focused on the relative distribution of PAHs and PCBs in size and density fractions of three sediments, which were physically separated for direct measurement of contaminants in the fractions and correlation to sorptive phase distribution. Oil and grease, soot, (non-black carbon) organic carbon and mineral clay were measured in sediment fractions. Correlations between contaminant mass and the sorptive phases were established for a linear model using statistical analysis. From this model phase specific contaminant concentrations were obtained and contaminant reduction potential evaluated. Contaminant concentrations were typically highest in oil and grease, soot, organic carbon, and clay, in that order. Black carbon and organic phases appear to be most important to PAH sorption. Clay appears to play a greater role in sorption of PCBs, although it was not significant for all sediments, and the influence of fine-grained organics on clay fraction sorption could not be distinguished without statistical analysis. Phase specific distribution coefficients were calculated based on predicted contaminant concentrations in the sorptive phases. Typically oil and grease and soot coefficients were larger than organic carbon coefficients. The magnitude of the soot coefficients was generally higher for PAHs than for PCBs. Predicted coefficients showed little dependence on log Kow, suggesting that in the natural environment, sorption of PAHs and PCBs is governed more by sorbent availability and steric effects, than by contaminant hydrophobicity

Mass Balance, Beneficial Use Products, and Cost Comparisons of Four Sediment Treatment

Approved for public release; distribution is unlimited. Prepared for U.S. Army Corps of Engineers and U.S. Environmental Protection AgencyERDC/EL TR-11-1 ii Abstract: The concept of contaminated sediment treatment producing a useful product has emerged in recent years, motivated by the cost of sediment disposal and by recognition of sediment as a resource rather than a waste. Contaminated sediment presents unique challenges for treatment, however, due to the character and complexity of the matrix, and the logistics and economics involved in coupling the process with a dredging operation. The objectives of this document are to capture the technical status of several promising treatment technologies of this type, to describe the process efficiency in terms of mass balance, to understand pre-treatment and posttreatment processing requirements, and to estimate full scale implementation costs at a scale compatible with a dredging operation