Actinide partitioning to an acidic, sandy lake sediment

Abstract

Knowledge of the partitioning of actinides to sediments in natural systems is essential for modeling their environmental fate. Using two different sequential extraction methods, we have studied the partitioning of U and Pu to an acidic, sandy lake sediment that was contaminated due to nuclear production activities. We find that both methods yield similar partitioning information, and that much of the U is associated with insoluble phases, whereas the majority of the Pu is extracted with oxidizable phases, defined to be predominantly organic matter. Our study suggests that U in this ecosystem is of natural origin. Although Pu and Fe in this system are known to cycle from the sediments to the water column during periods of anoxia, only a low percentage of Pu is extracted from the phases that are reducible, which are operationally defined as amorphous Fe oxides. Although this sediment is low in organic matter, our results suggest that natural organics dominate the partitioning of Pu in this system.

Use of Apatite for Chemical Stabilization of Subsurface Contaminants

“…Other major soil constituents were also noted to partition predominantly to the "Residual" fraction for both Series 57 composite soil samples: Fe (> 92%), Al (> 94%) and Mn (> 84 %). Loyland et al (2000) similarly note that partitioning of Fe and Al from sandy lake sediment indicates that they are predominantly refractory.…”

“…Although calcium is not a contaminant of concern, it is of interest to observe how calcium in the soil responds to the extraction procedures. Calcium frequently partitions to relatively "mobile" sites or sediment phases (Loyland et al, 2000). However, a high proportion of total Ca in the native soil used for testing (sample 02-0608) is present as the relatively refractory compound dolomite, CaMg(CO 3 ) 2 .…”

“…The sequence of extractions originally recommended by Tessler et al (1979), substantially equivalent to the modified recommendations of Phillips and Chapple (1995), appears to be the best documented and most frequently used protocol for estimating the partitioning of trace toxic metals in soil. (Recently, a somewhat modified sequential extraction scheme has been proposed to help elucidate the partitioning of actinides to contaminated soils and sediments; see Schultz et al, 1998;Loyland et al, 2000;Kurosaki et al, 2002). In this investigation, we have generally adapted the protocols recommended by Phillips and Chapple (1995).…”

Effect of gleysation on remobilization of radionuclides in waterlogged soils

“…Presently, available data on the potential mobility of technogenic radionuclides in soils and sediments are obtained mostly by the sequential extraction methods [4,5].…”

In-Situ Chemical Stabilization of Metals and Radionuclides Through Enhanced Anaerobic Reductive Precipitation

“…The results of these sequential extractions (or "fractionation") often allow a comparison of how tenaciously different metal contaminants partition to different soil and sediment compositions. The partitioning of contaminants to different geochemical fractions is related to the contaminant speciation (or chemical form), as well as other physiochemical factors (Loyland et al, 2000). Metals deemed least mobile in soil have a relatively small proportion of the total associated with the most readily accessible (or "exchangeable") fraction whilst having the greatest proportion associated with the most refractory (or "residual") fraction.…”