SUMMARY OF THE REMEDIATION TECHNOLOGIES DEVELOPMENT FORUM

IINERT SOIL-METALS ACTION TEAM

CONFERENCE CALL

January 19, 1999

3:00 p.m.–4:00 p.m.

On Tuesday, January 19, 1999, the following members of the IINERT Soil-Metals Action Team met in a conference call:

Bill Berti, DuPont Life Sciences (Co-Chair)
Harry Compton, U.S. Environmental Protection Agency (EPA)
Andrew Green, International Lead Zinc Research Organization (ILZRO)
David Mosby, Missouri Department of Natural Resources (DNR)
Gary Pierzynski, Kansas State University
Also present was Christine Hartnett of Eastern Research Group, Inc. (ERG).

PLANS FOR FUTURE MEETINGS

Bill Berti noted that Action Team members have expressed interest in having two face-to-face meetings during the first half of 1999. He said the meetings would cover the following topics:

• Human health issues. Berti asked whether participants wanted to meet in Kansas City, Missouri, to discuss the Joplin site and human health issues. Conference call participants agreed this would be a good location and suggested having the meeting in March 1999.
• Ecological endpoints. Berti asked whether conference call participants would be interested in meeting in Idaho or British Columbia to discuss ecological endpoints. He noted that the Bunker Hill site (in Kellogg, Idaho) and the Trail site (in British Columbia) have been suggested as potential host sites for the meeting. He said interesting ecologically based projects are ongoing at both sites. Conference call participants noted that these sites are within driving distance of each other. One conference call participant recommended visiting both sites during the Action Team meeting. Berti said that a Trail site representative, Bill Duncan, recommended visiting in June. Berti said he would gather more information about field trip opportunities at these two sites.

Berti said he would like to confirm the locations and dates of both meetings by mid-February 1999.

EVALUATING SOIL FUNCTION

Harry Compton noted that biosolid demonstrations are ongoing at the Bunker Hill and Leadville sites. At the latter, Compton noted, treatment plots have been established along 7 acres of alluvial mine deposits in the upper Arkansas River. Compton said that he and Mark Sprenger believe it is important to assess soil function at these demonstration sites. They will do so, he explained, by comparing pre-treatment and post-treatment soil function data. Compton noted that pre-treatment data results have already been obtained and that post- treatment samples will be collected in the spring. Ideally, he said, summary reports will be released in fall 1999.

Compton noted that he and Sprenger drafted a list of tests that may be useful in accessing soil function. Berti said that he received a draft and has made some changes and additions. During these initial stages of list compilation, Berti said, it is wise to include as many tests as possible so that none are accidentally overlooked. Because the list is currently 13 pages long, Berti divided the tests into three tiers and subdivided the tiers into several sections. For example, he said, Tier I is separated into Section 1–Soil Tests for Agronomic Characterization (e.g., soil pH and specific gravity); Section 2–Soil Metal Extraction tests (e.g., acid digestion and water extract tests); Section 3–Other Soil Tests; and Section 4–Mineralogic Studies. Berti said that Compton and Sprenger provided information about how to perform tests or where to send samples for analysis. Berti said he has not yet had a chance to add this information for tests that he added to the list. Berti agreed to send the latest version of the list to conference call participants.

David Mosby and Andrew Green mentioned two other groups that are currently assessing soil function. Mosby said that the potentially responsible parties (PRPs) at a site in Jasper County are writing a report on soil function. Mosby said he expects to receive a copy of the report in the near future. He said that the PRPs conducted earthworm studies and other soil function studies. Their motivation, Mosby explained, stems from the fact that soil function was identified as a major risk driver during an ecological risk assessment. Green said that he has been working with a European group on a zinc risk assessment that is using soil microbial toxicity endpoints, including: c-mineralization (respiration), N-mineralization (nitrification and ammonification), and enzymatic activities (e.g., amylase, cellulase, phosphatase, protease, urease). Green said the main drivers for the risk assessment of microbial activity were nitrification and respiration.

UPDATE ON ACTIVITIES AT THE JOPLIN, MISSOURI, SITE

Conference call participants discussed the following issues related to the Joplin site:

• During the October 7 Joplin Site Committee meeting, Mosby said, Action Team members compiled a table that summarizes bioavailability data. Mosby said he is working with researchers from the University of Missouri to resolve questions that were raised about some of the swine dosing study values. He expects to have resolution on this issue by the end of the month. He noted that additional swine dosing studies were recently completed on samples collected in October 1998. He said he expects to receive preliminary data from these studies in the near future. Mosby said that he will analyze the bioavailability data and release a draft report in March 1999. He expects the report to be finalized no later than June 1999.
  
• Berti noted that Dean Hesterberg plans to conduct X-ray absorption spectroscopic (XAS) analyses on some of Joplin’s soil samples. Berti said that Hesterberg plans to use the Brookhaven synchrotron to perform the work. According to Berti, Hesterberg hopes to document changes in lead species across the different soil treatments. Mosby asked whether XAS analysis is considered more accurate than the EDX method. Gary Pierzynski said it is unclear how well the XAS analysis will work. Using this approach, he explained, investigators receive information about the average signal of all the particles in a beam. It may be difficult, therefore, to use this information to gain a clear picture. Berti agreed that it is still unclear how useful XAS will be in this application. He noted that it is a relatively new technology and has not often been applied to environmental samples. Berti said that Hesterberg plans to conduct his analysis in late April 1999. (See Attachment A for additional information on using XAS to speciate lead in soils.)
  
• Berti said that Sally Brown gave him samples that were collected from Joplin in September 1997. He said he plans to contact John Drexler to ask if he will perform in vitro analyses on the September 1997 samples and four additional samples. The latter, Berti noted, were accidentally missed during the May 1998 sampling event.

NEXT CONFERENCE CALL

The next conference call is scheduled for February 16, 1999, between 3:00 p.m. and 4:00 p.m. EST.

MISCELLANEOUS

Mosby recently learned that a city in Vermont is using orthophosphates to address lead contamination in groundwater. He first became aware of that practice when a person sent a letter to DNR with some questions about it. According to the letter, Mosby said, the approach is commonly used and involves maintaining a phosphate level of 1.5 milligrams per liter. Mosby asked conference call participants whether they were familiar with this practice; no one had ever heard of it. Green wondered whether using such an approach would cause algal blooms.

Attachment A: Notes From Dean Hesterberg

Note: Dr. Hesterberg could not attend the conference call, but he did provide the following information as an attachment.

Because XAS yields information on the average LOCAL molecular bonding environment for the entire sample probed by the X-ray beam, it is very difficult to be able to give, for example, a full speciation for a soil. The problem is that soils are composed of 61% oxygen (the dominant ligand bonded to the multitude of different cations) on a mole fraction basis. So, the first shell information derived from EXAFS analysis will essentially always be metal-oxygen bonding (except in the case of metal-sulfide bonding when metal sulfides are present). Thus, knowing that the metal is bonded with oxygen tells you nothing about speciation (unless in comparison with sulfides). So, you need to understand what the higher shell information means, and the higher-shell signals are weaker and have more variability, making it difficult. As the capabilities of synchrotron facilities and detectors improve, then better quality data will make the higher shell spectral information more accessible. Another advantage of XAS spectroscopy is that it is applicable in some soils to metal concentrations < 100 mg/kg.

If a soil contains predominantly (e.g., >80%) of a given species, and a representative standard for that species has unique spectral features compared with all other possible species, then you can say with a high degree of certainty that this species is dominant in the soil. One cannot get that kind of information from EDX (Energy Dispersive X-rays) alone, as EDX only tells you the collection of elements at a given point in the sample with no information on how these elements are bonded together. Another advantage of XAS over EDX is that field moist samples are more easily measured, with minimal sample pretreatments. Ideally, both techniques (and others) would be used to complement each other in determining metal species in soils.

As a specific example: the purpose of amending a Pb-contaminated soil with hydroxyapatite is to form chloropyromorphite, a highly insoluble form of Pb. If 95% of the soil Pb is converted to chloropyromorphite, then the XAS spectrum should be nearly identical to that of a chloropyromorphite standard - having characteristics such as a longer first-shell Pb-O bond and evidence of higher shell Pb-P or Pb-Pb interactions (these are even unique for chloropyromorphite compared with hydroxypyromorphite). Some limited experiments that we did analyzing physical mixtures of pyromorphite and Pb-carbonate (cerrusite) showed that some of the distinguishing characteristics of spectra disappear when even 25% of another lead species is present. But, we have not explored in detail what (if any) spectral features ARE changing systematically along this series. In my opinion, if the technique cannot assess these physical mixtures appropriately, then it would be difficult to assess such a combination of phases in a soil sample.

However, on the positive side, there are still options: - X-ray spectroscopy of Pb lead at different edges, multi-component fitting of the original EXAFS (chi) spectra, and using spatially-resolved EXAFS/XANES spectroscopy. Facilities such as the Advanced Photon Source (APS) in Argonne, IL are designed to do such studies quite efficiently.

In Dr. Hesterberg's opinion, another positive aspect of XAS spectroscopy should be its applicability for looking for CHANGES in the Pb speciation in a treated soil sample, whereas doing a fundamental species characterization for a given soil sample is difficult. In both cases, it would help immensely to know many other soil characteristics that are indicative of possible chemical species of metals that are likely to occur in the soil.