United States Environmental Protection Agency Environmental Monitoring Systems Laboratory P.O. Box 93478 Las Vegas NV 89193-3478 November 1990 OFFICE OF RESEARCH AND DEVELOPMENT -P1 ;i SUf ) TECHNOLOGY SUPPORT PROJECT &EPA Field-Portable X-Ray Fluorescence INTRODUCTION THE SURVEY Field-portable X-ray fluores- cence (FPXRF) is a site- screening procedure using a small, portable instrument (15-25 lbs, or 7-12 Kg) that addresses the need for a rapid turnaround, low-cost method for the in situ analy- sis of inorganic contaminants. Traditional Contract Labora- tory Program (CLP) methods of analysis may take 20 - 45 days per site to complete and ihe analysis would cost much more than FPXRF. FPXRF .¦;an measure inorganic dements when used with the proper radioisotope source snd the appropriate stan- dards. FPXRF is capable of simultaneous analysis of up to six analytes per model. More than one model can be applied to each spectrum obtained. This method is useful at various levels of analysis, with data quality dependent upon the exten- siveness of the survey, the type of standards used, and the reinforcement of data by other collaboratory methods. FPXRF can be used for periodic monitoring as remediation proceeds. The following table includes the elements that are on the EPA's Inorganic Target Analyte List, with asterisks designating the ones quantifi- able by FPXRF. The EMSL-LV has been requested to analyse six of these elements to date: arsenic, chromium, copper, iron, lead, and zinc. Though detection limits are highly matrix dependent and site specific, the detection limits for these elements have been in the 100 - 500 mg/Kg range. The instrument used at the EMSL-LV is an X-MET 880. TABLE 1 INORGANIC TARGET ANALYTE LIST Aluminum * Calcium Magnesium ' Silver * Antimony * Chromium Manganese Sodium * Arsenic * Cobalt * Mercury * Thallium * Barium * Copper * Nickel * Vanadium Beryllium * Iron * Potassium * Zinc * Cadmium * Lead * Selenium Cyanide * Indicates FPXRF quantifiable analytes. An FPXRF survey is a com- bined effort of field scientists and geostatisticians. Ideally, it is a pre-survey aerial photo- graphic evaluation of the site, a screening on-site to collect site-specific calibration stan- dards, an off-site calibration of the instrument, and a final on-site visit for data collection and quality control. Then geostatistical interpretation is done and a site screening re- port is published. Typically a field survey is re- quested by an EPA region. RPM's can contact local con- tractors with the equipment and expertise to do an FPXRF survey. When spe- cial help is needed, the RPM may contact the EMSL-LV for expert advice. The team that responds is equipped with an FPXRF instrument and all of the necessary supporting equipment to adequately as- sess the site. Using the cali- bration curve that has been generated from site-specific standards, the X-ray re- sponses of the routine samples are regressed against this curve and an ana- lytical result is generated. Geostatistics, an interpretive method which allows for the similarity between neighboring samples, is used to optimize the sampling design prior to the survey. After the sampling, geostatistics is used to ana- lyze the data and to produce concentration isopleth maps. :C22EX9.: ------- INSTRUMENTATION X-ray fluorescence is based on the fact that atoms fluoresce in a unique and characteristic way. By bombarding a sample with energy, the instrument causes an electronic instabil- ity. As the instability "relaxes" to a more stable energy level, X-ray fluorescence is emitted. The detector senses and counts this spectrum of radiation which is a "finger- print" of the specific analyte and, on this basis, identifies the atom. Quantitation is done against a calibration curve that was generated by the analysis of site-specific standards. X-ray fluorescence has been a standard laboratory method for years and the recent availability of portable instruments now allows this method to be taken into the field for use at hazardous waste sites. HOW A FIELD SURVEY IS CONDUCTED To effectively use FPXRF, the field scientist must ask a few questions. What is the objective of the survey? What data are needed? What is the most efficient sampling scheme? What are the data quality objectives? A complete FPXRF analysis is based on calibration of standards that are specific to the site. These standards are collected on the initial site-screening visit and are analyzed by a complete CLP procedure in order to cali- brate the FPXRF instrument. Numerous in situ measure- ments are made on the hazardous waste site. QA/ QC is integrated into the program. The resulting data are not only quantitative, but of known quality. COST ADVANTAGES AND LIMITATIONS The average cost of in situ FPXRF surveys, based on a limited number of surveys performed by the EMSL-LV team in 1989 has been between $25,000 and $35,000. This cost includes labor, transportation, an aerial photographic pre- survey, analysis of about 15 site-specific standards per analyte, the FPXRF survey of up to 150 measurements per day, and a final report. A typical survey in 1989 took about 3 days. The complete procedure from pre-survey through final report took about 4-6 weeks. Advantages Low cost Ease of operation - portable, moves to any site Rapid results - real time (once site-specific standards are available) Limitations Complex data interpretation - for geostatistical investigations Matrix variability type of soil influences results Less sensitive than a complete CLP analysis REFERENCE Raab, G. A., R. E. Enwall, W. H. Cole, III, M. L. Faber, and L. A. Eccles, July 1990, X-Ray Fluorescence Field Method for Screening of Inorganic Contaminants at Hazardous Waste Sites. In: Hazardous Waste Measurements, M. Simmons, Ed., Lewis Publishers, Chelsea, Ml. FOR FURTHER INFORMATION For technical information about FPXRF, contact: Mr. William H. Engelmann U.S. Environmental Protection Agency P.O. Box 93478, Las Vegas, NV 89193-3478 (702) 798-2664 FTS 545-2664 For Technology Support information, contact: Mr. Ken Brown, Manager Technology Support Center U.S. Environmental Protection Agency P.O. Box 93478, Las Vegas, NV 89193-3478 (702) 798-2270 FTS 545-2270 • FAX/FTS 545-2637 The Technology Support Center fact sheet series is developed and written by Clare L. Gerlach, Lockheed Engineering & Sciences Company, Las Vegas. ------- |