Project Title: Phosphate-Based Heavy Metal Stabilization Technologies for Contaminated Sediments and Dredge Material
Principal Investigator(s): Taylor Eighmy, Bradley Crannell, Les Butler, Frank Cartledge, Earl Emery.

Accomplishments
Scheduled Tasks:

1. Completion of x-ray photoelectron spectroscopy and scanning electron microscopy analysis.
2. Completion of geochemical modeling of batch treated sediments.
3. Analysis of diffusion tubes located at UNH including the completion of x-ray powder diffraction analysis of sediment barrier interfaces.
4. Completion of analysis at Louisiana State University including XANES, XAFES, and diffusion profiles.
5. Creation of the final project report.

1. Scanning electron microscopy (SEM) of the diffusion samples has been completed. Elemental quantification of the material before and after exposure to diffusing heavy metals was also completed.
2. Geochemical modeling of the batch treated sediments has been initiated, but not completed. A new version of MINTEQ call "Visual MINTEQ 1.05" was released on 8/5/01. All modeling will be checked using this newer version of the program.
3. Analysis of the diffusion tubes, which were located at UNH, has been completed. This includes the determination of metal profiles, along with mathematical modeling to determine the effective diffusion coefficients. SEM and XRD analysis of the interfaces of these tubes has also been completed.
4. The diffusion profile analysis at the CAMD facility was completed. However, the XAFES/XANES work was not completed.
5. The creation of the final project report is well underway. The rough draft is currently completed for the diffusion half of the work, and a finished report will be available before the scheduled deadline of October 31, 2001.

Difficulties Encountered
The difficulties encountered in this section of the research were largely due to equipment failure, both of the x-ray photoelectron spectroscopy instrument at UNH, and the entire CAMD facility at LSU. The CAMD facility was anticipated to be shutdown for 6 to 8 weeks during this reporting period for recalibration and realignment of the ring. However, the realignment took much longer than expected, and the ring was shut down for several months from March 1, 2001 to August 7, 2001. Prior to this ring shutdown, the specific beamline on which the XAFES/XANES work that was to take place was under construction. The current beam is giving an unsteady energy source, and will not be corrected until September 1, 2001.

Anticipated Success in Meeting Project Objectives in Scheduled Project Period
It is anticipated that the project objectives will be met during the period between August 15, and October 31, 2001. The reason for this is that the CAMD facility is back online, and final signal calibration is taking place. The XAFES/XANES data should be available by September 15, 2001. Likewise, the XPS machine will be repaired before the end of August, and work on the final report is well underway.

Preliminary Results
A sampling of the preliminary data regarding the SEM work is shown in Figures 1-3. Elemental quantification of the material before and after exposure to diffusing heavy metals was also completed. Figure 1 represents a low magnification scan of the Newtown creek sediments that were spiked with heavy metals prior to diffusion. Figure 2 is a higher magnification image, of the same sediment that shows the presence of diatoms, while Figure 3 shows the reactive phosphate barrier from Florida in low magnification. The hole in the center of the sand grains on the left side of this image was often observed in the samples. At higher magnification of the phosphate barrier the phosphate sand grains are shown to be a relatively porous agglomeration of smaller particles.

Figure 4 shows the X-ray diffraction pattern for a Florida phosphate reactive barrier after diffusion of Cd, Cr, and Cu through the material. Table 1 indicates the major and minor minerals found in the barrier materials after diffusion. There is preliminary evidence that metal phosphate apatite minerals are forming in the interface, especially in the case of cadmium where Cd5(PO4)3OH was observed.

Example diffusion profiles collected at the CAMD facility are shown in Figures 5 and 6. Diffusion coefficients were calculated using four separate methods. Each calculation method has a certain set of assumptions that allow them to describe the system with varying degrees of accuracy. We shall be comparing the error function methods of calculating effective diffusion coefficients. Table 2 summarizes the effective diffusion coefficients for each of the diffusion column types collected both at LSU and UNH. Preliminary analysis of this data suggests that despite some of the reactive barriers having a larger grain size (less tortuosity), diffusion of some metals occurred more slowly through these materials. This implies that the reactive barrier is functioning, by actively inhibiting the migration of these metals. This is further supported by the diffusion of a non-reactive tracer (bromine) through the materials at a faster rate.

The creation of the final project report is well underway. The rough draft is currently completed for the diffusion half of the work, and a finished report will be available before the scheduled deadline of October 31, 2001.

Tasks and activities for next reporting period

Tasks for the next reporting period

1. The analysis of the remaining samples using XPS.
2. The completion of the XAFES/XANES work at LSU.
3. The generation of the final report.

Work plan to accomplish tasks
The XPS analysis will involve several days work using the instrument and will be completed by the end of August.

The CAMD facility is currently back on-line, and the beamline is functional. Therefore the work will completed by September 15, 2001. A Ph.D. student, Ming Yin, is currently working full time on this project, and will complete the task when the beam line becomes available.

The due date for the final report is October 31, 2001. A rough draft for the first half of this report has been completed. Therefore, it is anticipated that the report will be finished well before this time.

Concerns or difficulties
The concern associated with these tasks is primarily the calibration of the CAMD synchrotron ring. I have met with Joseph Hormes the CAMD facility director and Roland Tittsworth the researcher in charge of recalibrating the ring. Both have assured us that our project has the top-priority at the facility, but acknowledge that it has taken much longer than expected to realign the ring, and produce a steady beam of light.

The XPS machine has been repaired, and will require several days of pumping to have the vacuum restored before full operation is possible.

Expenditures
Expenditures to date have been within budget. Some analytical costs were incurred during this reporting period as well as purchases of new computer software for modeling diffusion. A significant restructuring of finances during this period from RLI expenditures has allowed for the purchase of some automatic titration units, which will greatly speed, simplify, and improve future research on this technology.