The analytical methods employed for inorganic analyses in the environmental chemistry program at CEMRC are based, when applicable, on various standard procedures (EPA, 1983, Methods for Chemical Analysis of Water and Wastes, EPA/600/4-79-020; EPA, 1997, Test Methods for Evaluating Solid Waste, Physical/Chemical Methods, EPA/SW-846; American Public Health Association, 1981, Standard Methods for the Examination of Water and Wastewater, 20^th Edition). For some matrix/analyte combinations, appropriate external standard procedures do not exist, and for those cases, specialized procedures have been developed to meet the needs of the WIPP EM.

Instrumentation

A DIONEX 500 ion chromatography (IC) system was used to determine the concentrations of a suite of anions, including nitrate, nitrite, sulfate, chloride, fluoride and phosphate in water samples and aqueous extracts of aerosol samples, soils and sediments. Configured differently, the same instrumentation was used to determine the concentrations of several cations (calcium, magnesium, sodium, ammonium and potassium). The anion analyses were performed with the use of AS11 and AS14 anion exchange columns and AG11 and AG14 guard columns, with chemical suppression and conductivity detection. The cations were determined using a CG12A guard column and a CS12A analytical column, with the same type of chemical suppression and conductivity detection.

Elemental analyses employed an atomic absorption spectrometer (AAS) with a computer-controlled Perkin-Elmer 5100PC atomic absorption unit with Zeeman background correction. Samples are introduced into the AAS by aspiration through an air/acetylene flame, by vaporization in a heated graphite furnace, by flow-injection via a heated quartz cell, or through an unheated quartz cell (for Hg). Additional inorganic analyses were performed using a Perkin-Elmer Optima 3300 dual-view, inductively-coupled plasma atomic (or optical) emission spectrometer (ICP-ES). In February 1999, the Optima ICP-ES was replaced by a Perkin-Elmer Elan 6000 inductively-coupled plasma mass spectrometer (ICP-MS). The three instruments used for the elemental analyses are complementary; AAS is more sensitive than the ICP-ES and the ICP-MS for some elements, especially for the hydride elements (As, Se and Hg), but compared with the ICP-ES and the ICP-MS, the AAS has a narrower linear range, requires more operator effort for calibration and operation and has a much lower sample throughput. The ICP-MS is much more sensitive than the ICP-ES, lowering detection limits by ten to a hundred times for some analytes, and allowing analyses for substantially more elements, including the rare earths.

General Quality Control

Several analytes are readily determined by more than one of the four instruments used at CEMRC, which facilitates intra-laboratory comparisons as summarized below. Some of these internal QC comparisons are also summarized in the sections of this report that deal with specific media.

Independent quality assurance samples are obtained and analyzed to verify the performance of the instrumentation and the proficiency of the analyst. Both blind samples (obtained from an outside source, with true value not known at the time of analysis) and reference samples (obtained from an outside source or prepared internally, with true values known at the time of analysis) are used to perform this function. Regular quality control verifications and batch QC provide records of sample performance data. Copies of the analytical data and performance results are maintained in the environmental chemistry instrument laboratory. The laboratory also carried out several informal inter-laboratory comparisons, and has recently begun participation in performance testing under the National Voluntary Laboratory Accreditation Program (NVLAP); no NVLAP results had been received by the end of 1999.

Calibrations are verified with a standard obtained from a source different from that used in procuring the primary calibration standards. The calibration standards and the verification standards used at CEMRC are, where possible, traceable to NIST. A calibration blank is analyzed at the beginning of each workday when samples will be run, after every ten samples, and at the end of the day. To pass the calibration verification, blank results must be less than the minimum detectable level or + 3 SD of control limits. Analysis of a blank and a standard are performed at a frequency of 10% during analytical runs, and these are repeated at the close of each analytical run to verify continued calibration validity. Batch quality control samples are counted as samples in determining the 10% frequency, but the continuing check samples are not counted as samples in determining the 10% frequency.

Various types of field blanks, check solutions and laboratory fortified (spiked) samples are analyzed along with the samples as part of the QA/QC procedures. These vary somewhat among matrices and analyses as described in more detail below. In addition, when feasible, duplicate samples are processed to evaluate reproducibility and sample homogeneity. Control charts for each matrix have been established, and + 3 SD limits have been determined for future reference. Control charts are used to track the performance of the instrument and the sample preparation procedures. Similarly, spike recoveries are calculated, tracked and reported along with the analytical data.

Quality Control for Analyses by IC

For the IC analyses, QC samples are analyzed with each sample batch as an indicator of the reliability of the data produced. The types, frequencies of analysis and limits for these QC samples have been established in a set of standard operating procedures.

Method Detection Limits (MDL) were established for each analyte in each sample matrix according to EPA Method 300.0 (Determination of Inorganic Anions by Ion Chromatography) (Table K1). Fluoride was not determined in aerosol filters and soils due to co-eluting organic peaks, but method development is underway to correct this. QC samples included Laboratory Reagent Blanks (LRB), with one LRB prepared for each sample batch (normally a set of ten samples). LRB results below MDL are considered acceptable (Table K2). For aerosol filter analyses, some LRB results indicated reagent blank contamination, and this was subsequently identified and eliminated; the samples could not be reanalyzed because the filters are consumed in the analysis process. Laboratory Fortified Matrix (LFM) samples were also used for QC, with one LFM analysis per sample batch. Results from analyses of LFMs are used to calculate matrix spike recoveries, with recoveries of 70-130% considered acceptable. As prescribed by EPA Method 300.0, chloride and sulfate values in water samples and chloride and sulfate values in sediments were not reported because the concentration of the fortification was less than 25% of the background concentration (Table K3).

One duplicate analysis was performed for each sample batch. When feasible, duplicate aliquots of some field samples were analyzed. In cases where duplicate aliquots from the original sample were not feasible (such as aerosol filters), separate aliquots of the sample extract were analyzed. The relative percent difference (RPD) between the sample and the duplicate was calculated, with a difference of < 20% (or an absolute difference of + MDL for samples less than five times the MDL) considered acceptable (Table K4). Sulfate duplicates in water and sulfate and chloride in sediments were not within limits because the sample concentrations were beyond the instrument's calibration of 50 ppm for chloride and 100 ppm for sulfate. The duplicates were not analyzed at the diluted level.

A Laboratory Fortified Blank (LFB) was prepared and analyzed with each sample batch, using a spiked ultrapure water sample for aerosol filters and water samples, and certified reference materials (CRM) for soils and sediments. Recoveries of 85-115% were considered acceptable for aerosol filters and water samples, and the analyses of the LFBs produced values well within this range (Table K5). The CRM was "Anions in Soils" from Environmental Research Associates (ERA) in Arvada, Colorado and it was used as the reference material for both soils and sediments. Use of an end-over-end rotator was necessary to achieve the limits set by ERA for this CRM (Table K6). Because there is no existing standard reference method for extracting soils or sediments for anion analysis, the results obtained by different methods may not be directly comparable.

Low-volume aerosol filters were also analyzed by IC for five cations with overall acceptable results (Table K7). Acceptance limits for each QC parameter were the same as previously described.

Quality Control for Elemental Analyses by ICP-ES, ICP-MS and AAS

For elemental analyses, sets of quality control samples comparable to those previously described for the IC analyses were included with each sample batch. Detailed performance results for all QC measures are not presented here due to the number of elements that are determined by ICP-ES, ICP-MS and AAS. For all media (aerosol filters, water, soils and sediments), ICP-ES, ICP-MS and AAS values were reported relative to the method detection limit as determined by EPA protocols (Table K8 and Table K9). Digestion QC samples were analyzed at a frequency of 10% relative to samples. The digestion QC control parameters used for the evaluation of metals in aerosol filters included LRB filters and vendor-supplied certified reference filters. Due to sample volume limitations, duplicate and post digestion spike analyses could not be performed for the ICP-ES or ICP-MS analyses of the aerosol samples.

For water, soils and sediments, a practical quantitation limit (PQL) was also calculated to evaluate precision based on the analysis of duplicate samples. The PQL is obtained by multiplying the method detection limit (MDL) by five. The digestion quality control parameters used for the evaluation of metals in water, soils and sediments were based on EPA Contract Laboratory Program (1994, U.S. EPA Contract Laboratory Program National Functional Guidelines for Inorganic Data Review, EPA 540/R-94013) and SW846 methods (EPA, 1997, Test Methods for Evaluating Solid Waste, Physical/Chemical Methods, EPA/SW-846). No comparable control parameters presently exist for aerosol samples.

For aerosol samples, unused cellulose ester filters were used as LRB samples. LRB results above the MDL were subtracted from each associated batch of sample results, because the LRB results were greater than the MDL for many of the analytes studied. Analysis of reagent digests have shown the contamination to be inherent to the cellulose ester filters for some of these analytes (Ca, Cr, Cu, Mg, Ni and Pb), while others (Ce and Sm) are introduced in trace amounts by the reagents used for digestion. A cellulose ester CRM ("Trace Metals on Filter Media" from High Purity Standards in Charleston, South Carolina) was also used for QC of aerosol sample analysis. Mean recoveries for all analytes were within 15% of the manufacturer's established true values.

For FAS samples, unused Versapore® filters were used as LRB samples. LRB results above the MDL were subtracted from each associated batch of sample results, because the LRB results were greater than the MDL for several of the analytes studied. Analysis of reagent digests have shown the contamination to be inherent in the Versapore filters for several analytes (Cu, K, La, Mg, Na, Nd, Ni, Pb and Sm), while others (Dy, Gd) are introduced in trace amounts by the reagents during digestion. A cellulose ester CRM ("Trace Metals on Filter Media" from High Purity Standards in Charleston, South Carolina) was used for QC of the FAS samples. Mean recoveries for all analytes were within 15% of the manufacturer's established true values, with the exception of Cu. The filter fortified by High Purity Standards has a much lower Cu background than the Versapore filter and the Cu level contained in the Versapore filters is significant compared to the fortification level, producing a low bias in CRM recovery when blank subtraction is used.

Four standard QC measures were used in association with analyses of drinking water and surface water samples. Ultrapure water was used for LRB samples and average concentrations were less than the MDLs for all analytes except Tl, Th and Ca in drinking water samples and As, Cr, Ti, Ni, Sr, Ag, Sb, Ba, Th, U, Na and Ca in surface water samples. The amounts of Sr, Ba, U, Na and Ca in the samples were so much higher than in the reagent blanks that the contribution from the blank was negligible. The sample values for Tl and Th in drinking water may be biased 21% and 12% high, respectively, because blank subtraction was not performed. Likewise, surface water results for Cr, Ti, Ni, Sb and Th are biased 67%, 0.2%, 25%, 122% and 40% high. Surface water results for Ag were all less than the MDL. Samples were not blank corrected following the procedure prescribed by the EPA Contract Laboratory Program (1994, U.S. EPA Contract Laboratory Program National Functional Guidelines for Inorganic Data Review, EPA 540/R-94013). However, the sample values for As were corrected for the reagent blank recoveries to correct for the slight high bias (10%). A LFB was prepared by adding a known quantity of each analyte of interest to ultrapure water. All analytes for drinking water and surface water had recoveries within the 85-115% limits as specified by EPA methods.

LFM samples were also used for QC in analyses of water samples, with all recoveries within the 70%-130% acceptance window, with the exception of Sr (0%) in drinking water and in surface waters (0%). If the concentration of the fortification is less than 25% of the background concentration, the recovery of the LFM is usually not reported. In this case, the background concentration of Sr in drinking water was 1680%, and Sr in surface water was 455%, so the results were within acceptance limits. A duplicate digestion analysis of water samples was also performed to demonstrate reproducibility, but a slight modification of the EPA CLP program was used for acceptance determination. If the sample result was less than the PQL, a + PQL control limit was used. If the sample result was greater than the PQL, a +20% RPD control limit was used. All duplicate results were within these modified acceptance limits with the exception of Cr, Ag, Sb and Th in drinking water and Gd, Th, As and Se in surface water. In compliance with the EPA Contract Laboratory Program (1994, U.S. EPA Contract Laboratory Program National Functional Guidelines for Inorganic Data Review, EPA 540/R-94013), the results for these analytes should be considered estimates.

For soils and sediments, LRB samples of ultrapure water were compared to MDLs to determine if contamination was introduced during sample preparation. LRB results were within acceptance limits for soils with the exception of Be, Ni, Ag, Sb, Ce, Pr, Nd, Pr, Nd, Th and Ca, which were above the MDL. However, the sample measurements were at least ten times higher than the LRB results for Be, Ce, Pr, Nd, Th and Ca and therefore the contaminant effects on the measurements were considered negligible. Sample results were not corrected by blank subtractions, therefore results may be biased high for Ni, Ag and Sb. Sediment LRB results were less than the MDL with the exception of the following analytes: Be, Ni, Zn, Sr, Sb, La, Eu, Th, U and Ca. The elemental concentrations of all analytes, excluding Sb, in sediment samples were several orders of magnitude higher than LRB results, and therefore the contaminant effects on measurements in sediments are considered negligible. Sb results in sediments may be biased high because the results were not corrected for the laboratory reagent blank.

A CRM ("Priority Pollutant T/CLP Soil" from ERA) was obtained and prepared with the soil and sediment samples to demonstrate matrix-specific performance of digestion and analysis procedures. All analytes except Se were recovered within the supplier’s specified control limits for all digestions. The Se CRM results recovered slightly high for two of the soil batches. However, the Se concentrations in all samples associated with these batches with high CRM recoveries were at or below the MDL, therefore re-digestion for Se was not performed. Duplicate digestions were preformed for soil and sediment using a modification of the EPA CLP program for acceptance determination. If the sample result was less than the PQL, a + PQL control limit was used. If the sample result was greater than the PQL a +20% RPD control limit was used. For soils and sediments, the average RPD over the digestions performed was within acceptance limits for all analytes, except Hg, Se and Tl and the absolute difference on the duplicates was used to determine that these analytes were still within limits. A LFM also was prepared with an average recovery within 70%-130% windows for all analytes with the exception of Sb at 33%. Mn, Ba, Sb and Sr in sediments recovered at 0%, 0%, 37% and 774% , respectively. A low bias for Sb was expected due to the digestion procedure used, as noted in the CEMRC 1998 Report. For Mn, Ba and Sr in sediment, the concentration of the fortification was less than 25% of the background concentration (Mn 106%, Ba 103%, Sr 109%), so the results for these analytes were acceptable.

Conclusions and Future Improvements

In IC analyses, development is in progress to improve the resolution of fluoride and its separation from co-eluting organic species. As a result of this effort, quantification of acetate and formate should be possible for certain types of samples. Although CEMRC has already demonstrated low elemental MDLs, these could be improved for some analytes (including Sn, Zn, Na, Mg, Al, K, Ca, Ni, Pb, Mn and Fe) by reducing reagent blank contamination from the acids used to prepare standards and samples. In addition to the double distillation already in use, elimination of metal corrosion inside fume hoods is being undertaken to further reduce trace contamination. Another method is also being developed to prepare soils and sediments via closed vessel microwave digestion, which should also improve MDLs and increase sample throughput. As noted in the matrix-specific descriptions, blank-correction for results was inconsistently applied among media types. A blank-correction standard is under development for adoption in future analyses.

The CEMRC radioanalytical program conducted extensive method development throughout 1999, resulting in standard methodologies for determining background levels of alpha- and gamma-emitting radionuclides in soil, and for Pu in air filters. Methods were also developed for less sensitive measurements of alpha-emitting radionuclides in water and for gross alpha/beta and gamma measurements in aerosol samples from the WIPP exhaust airflow.

During 1999, the CEMRC radioanalytical program participated in two rounds of the National Institute of Standards and Technology Radiochemistry Intercomparison Program (NRIP). A Report of Traceability was received for measurements of two analytes in glass fiber filters and three analytes in water. The radioanalytical program also participated in the DOE Environmental Measurement Laboratory-Quality Assurance Program (EML-QAP), resulting in "acceptable" ratings for 45 individual determination of ten analytes in glass fiber filters, soil, vegetation and water samples (Table L1).

Other routine activities conducted for radioanalyses include (1) tracking and verification of analytical instrument performance, (2) use of ACS grade reagents, (3) use of ASTM Type II water for reagent preparations, (4) use of NIST traceable radionuclide solutions and (5) verification testing of radionuclide concentrations for tracers not purchased directly from NIST. In addition to analyte-surrogate isotopic tracers used in samples, ¹⁴⁸Gd is added to samples where no alpha emitters are expected (e.g. thorium blanks) to provide a monitor of detector performance.

Blanks are used to identify contamination or interference carried through the actinide analytical process. Table L2 summarizes the results of reagent blank analyses completed while processing WIPP EM soil, water and FAS samples during 1999, which constituted approximately 10% of the sample load. Batches of samples where Pu or Am blanks were greater than MDC were reanalyzed. The results indicate that Pu and Am contamination (most likely from sample cross contamination) is detected, but infrequently, and the practice of analyzing blanks at least 10% of the time should be continued to monitor for contamination. Contamination of natur