||HydroGeoLogic, Inc., Herndon, VA. ;Allison Geoscience Consultants, Inc., Flowery Branch, GA.;Environmental Protection Agency, Athens, GA. Ecosystems Research Div.
This report presents metal partition coefficients for the surface water pathway and for the source model used in the Multimedia, Multi-pathway, Multi-receptor Exposure and Risk Assessment (3MRA) technology under development by the U.S. Environmental Protection Agency. Partition coefficients values are presented for partitioning between soil and water; partitioning between the suspended sediment load and the water in streams, rivers, and lakes; partitioning between riverine or lacustrine sediment and its porewater; and partitioning between dissolved organic carbon (DOC) and the inorganic solution species in the water of streams, rivers, and lakes. Some partition coefficients are also presented to represent metal partitioning between the solid phase of waste and its associated leachate. Partition coefficients are presented for antimony (Sb), arsenic (As), barium (Ba), beryllium (Be), cadmium (Cd), chromium (Cr), cobalt (Co), copper (Cu), lead (Pb), molybdenum (Mo), mercury (Hg), methylated mercury (CH(sub 3)Hg), nickel (Ni), selenium (Se), silver (Ag), thallium (Tl), tin (Sn), vanadium (V), and zinc (Zn). A two-phase approach was used in developing the needed partition coefficients. In the first-phase, a literature survey was performed to determine the range and statistical distribution of values that have been observed in field studies. This included the collection of published partition coefficients for any of the metals in any of the environmental media of interest, or our estimation of partition coefficients from reported metal concentration data when feasible. In the second-phase effort, statistical methods, geochemical speciation modeling, and expert judgement were used to provide reasonable estimates of those partition coefficients not obtained from our literature search and data processing. The report concludes with a discussion of the many sources of uncertainty in the reported metal partition coefficients.