Selective Analytical Partitioning Of Sediments To Evaluate Potential Mobility Of Chemical Constituents During Dredging And Disposal Operations

Selective Analytical Partitioning of Sediments to Evaluate Potential Mobility of Chemical Constituents During Dredging and Disposal Operations

Disposal of dredged material at sea

Selective Analytical Partitioning of Sediments to Evaluate Potential Mobility of Chemical Constituents During Dredging and Disposal Operations

When sediments are agitated by dredging and subsequent resuspension in water by discharge operations, there is a possibility that large amounts of some chemicals in the sediment could be released into the water column. To better understand the short- and long-term release effects of sediment resuspension on water quality, a functionally derived sediment selective extraction procedure was developed. This procedure explores the association of trace metals and other elements or compounds within sediments and their distribution among sediment phases of various stability and mobility. The effect of these sediment fractions or extractable phases upon water quality as indicated by the standard elutriate test and the relation of elutriate concentrations to these fractions was thoroughly investigated. The sediment chemical partitions studied in the selective extraction procedure were those dissolved or in solution in sediment interstitial water; sorbed on sediment mineral and organic material (exchangeable); occluded, co-precipitated, or bound within iron and manganese oxide and hydroxide partitions; bound in organic matter as complexes and compounds precipitated as sulfide salts; and occurring as an extremely stable residual partition in mineral crystalline lattice. Results of the sediment partitioning fractionation scheme showed that these operationally or functionally defined phases in a sediment could be isolated with good elemental mass balance and precision among the phases.