Progress Report for the period 8/15/2000 through 1/31/2001

Project Title:

Phosphate-Based Heavy Metal Stabilization Technologies for Contaminated Sediments and Dredge Material

Principal Investigator(s):

Dr. Taylor Eighmy, University of New Hampshire
Bradley Crannell, University of New Hampshire
Dr. Les Butler, Louisiana State University
Dr. Frank Cartledge, Louisiana State University
Earl Emery, Louisiana State University

Advisory Board:

Mr. Dave Hartman, N.H. Office of State Planning
Dr. Tom Fredette, U.S. Army Corp of Engineers
Mr. Peter Kinner, Normandeau Associates Incorporated
Mr. Mark Lyons, Wheelabrator Technologies
Mr. Brian Smith, Great Bay NERR
(Note: replaced Peter Wellenberger, Great Bay NERR)
Dr. Chuck Nieder, Hudson River NERR
Dr. Mike De Luca, Mullica River NERR
Dr. Chris Deacutis, Narragansett Bay NERR

Work Accomplishments

Tasks Scheduled for this reporting period:

1. Bioassay analysis of the treated Providence harbor and clean sediment samples will be conducted.
2. The annual meeting of overseeing board will be held in November.
3. The x-ray powder diffraction analysis (XRPD) and x-ray photoelectron spectroscopy (XPS) analysis of main batch treatment study will be conducted.
4. There will be leaching studies of treated sediments to determine effectiveness of phosphate treatment in batch reactions.
5. The Center for Advanced Micromachine Design (CAMD) will finish setting up their new beamline and Louisiana State University will be collecting lead diffusion data.

Progress on tasks for this reporting period:

The bioassay analysis has been completed for both the Providence harbor and clean sediment samples by Envirosystems of Hampton, NH. It consisted of a 10-day amphipod test in which Ampelisca abdita, a tube dweller, was used. Results of the tests are shown in Table 1 and indicated two things, (i) the phosphate treatment is not toxic to amphipods as shown by the treated clean sediments, and (ii) that the treatment did not statistically increase survivorship in the treated contaminated sediments. The later result may be partially explained by the presence of many organic contaminants in the Providence harbor sediment. It would not be expected for the treatment to have a direct affect upon the toxicity of organic pollutants, but these pollutants may have affect amphipod survivorship.

Table 1: Amphipod survivorship during 10-day amphipod tests.






The annual meeting of the project advisory board was held on January 10^th, 2001. The meeting focused both on current research, and future proposals for continuation of research. Although the meeting was originally intended to be held in November of 2000, scheduling conflicts and the desire for direct input on new grant proposals required the delay. Minutes of the meeting will be made available through the project website at http://www.unh.edu/ciceet/phosphate .


The x-ray powder diffraction (XRPD) analysis of the main batch treatment study was completed and x-ray photoelectron spectroscopy (XPS) analysis of the treated sediments was initiated. XRPD analysis results are summarized in Table 2. Results indicated that many phosphate minerals formed in all three sediments as a result of the batch treatment. Both cadmium and lead were observed forming highly insoluble apatite structure metal phosphates. Zinc and copper were shown to form stable phosphate minerals, but these tended to be dominated by solid solutions, where the metals are substituted into a calcium apatite structure. Although these solid solutions are less stable than pure metal apatites, they are still considered highly insoluble. Their formation is consistent with previous stabilization research results by Crannell et al., 2000.

Table 2: Selected metal phases observed in Newtown Creek, Cocheco River, and Providence Harbor sediments.

Three leaching studies were conducted on the main batch treated sediments to determine effectiveness of phosphate treatment in batch reactions. The leaching procedures used included TCLP, pH-dependent leaching, and total availability leaching. The main conclusion from these experiments is that the treatment is highly effective at reducing the solubility of many heavy metals such as Pb, Cd, Cu, and Zn even under aggressive leaching conditions. Reductions in metal solubility were up to two orders of magnitude, as in the case of Pb during the pH-dependent leaching procedure. The treatment was less effective at reducing metal solubility in the Cocheco river sediment than in the Providence harbor sediment. This points to the need in future research for specifically formulating the treatment separately for each individual sediment, which is a common practice in industrial phosphate treatments of waste materials.

Results of the TCLP testing are presented in Table 3. The solubility of Ba, Cd, and Cr were reduced by the treatment. The solubility of Zn was slightly increased by the treatment. The changes in metal solubility for As, Pb, Hg, Se, Ag, and Cu were not able to be determined because of detection limits.

Table 3: TCLP Leaching of Newtown Creek Sediments


 

Results of the pH-dependent leaching tests are presented in Table 4. Treatment was most effective at reducing the solubility of metals in the Providence Harbor sediments. Pb, Cd, Zn, and Cu were the heavy metals best treated in this sediment. Phosphate solubility increased only slightly despite the large quantities of phosphates added to the system. This indicates the apatite minerals formed are highly stable even under aggressive leaching conditions.

Table 4: pH-dependent leaching of three batch treated sediments.

Total availability leaching is the most aggressive of the three leaching procedures. Results of the tests indicated that reductions in solubility ranged from Pb (0 to 38%), Zn (0 to 29%), Cu (-125 to 65%), and Cr (15 to 27%). Considerable differences existed in the treatment effects between the sediments; pointing to the need to make treatment formulations specifically for individual sediments and contaminants.

During the course of diffusion experiments it was realized that the synchrotron beam-line energy would not be sufficient to determine Pb or Cl concentrations in the diffusion columns at the monochromated x-ray beamline station within the Center for Advanced Micromachine Design (CAMD) facility. A solution was reached by negotiation with the CAMD facility to gain access to a newly built station that offered a higher-energy beam and more overall beam-time. The CAMD has finished setting up the new beamline, and Pb, Cr, Cu, and Br diffusion data has been collected. The new beamline became available around CAMD on October 2000. Diffusional data for day 400 of the experiments were successfully collected for 30 columns. Dehydration reactions in many of the other columns prevented their analysis. Analysis of these columns has begun and indicates that Florida phosphates inhibit lead diffusion significantly more than clean sediment barriers. Synthetic hydroxyapatite effectively reduced the diffusion zinc and copper.

Preliminary analysis of the diffusional data that was collected at UNH is shown in Figure 5. Results indicate that phosphate barriers inhibit lead diffusion through the columns over clean sediment barriers. Calculated rates for lead diffusion through barriers were comparable with those in published literature for clay materials ranging from 4.4e-10 m²/s to 2.54e-9 m²/s (Shackelford, et al., 1989).

Figure 1: Comparison of lead diffusion through clean sediments vs. a reactive barrier.


 

A presentation of the results to date for the batch treatment study was made on December 4, 2000 to the Conference on Dredge Material Management and a paper associated with this presentation will be published in the meeting proceedings. A presentation was also made of the methods and results to date for the LSU diffusion study on August 23, 2000 to the American Chemical Society National Meeting. References for these publications are listed below.

Tasks and activities for next reporting period

1. Completion of treatment effects analysis including x-ray photoelectron spectroscopy and scanning electron microscopy.
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, diffusion profiles, and 3D imaging selected tubes.
5. Creation of the final project report.

Expenditures

Expenditures to date have been within the range anticipated to date. Some analytical costs were incurred during this reporting period as well as purchases of new computer software for exchanging information between UNH and LSU. Expenditures are within anticipated costs.

Literature Cited