Mercury Collection and Analysis in Ambient and Effluent Waters using EPA Method 1631 QA, QC, and Data Verification

1. Mercury Collection and Analysis in Ambient and Effluent Waters using EPA Method 1631QA, QC, and Data Verification Judy Schofield DynCorp, Science and Engineering Group Office of Water SCC-99-004.ppt

2. Clean Techniques Review • General requirements • Clean sampling and storage procedures • Clean sample handling procedures in field and lab • Use of clean bench or a clean room • Comprehensive QA/QC program • Analysis of blanks, blanks, and more blanks • Level of cleanliness needed may vary, depending on metal, target concentration, and sampling location

3. Blanks and Definitions Review • Equipment Blank • Bottle Blank - generated by filling a sample bottle with reagent water acidified to pH < 2, allowing the bottle to stand for 24 hours, and analyzing the water • Sampler Check Blank - generated at the lab by processing reagent water through the sampling equipment using the same procedures that will be used in the field, and collecting and analyzing the water • Field Blank - generated by filling a large carboy with reagent water in the laboratory, transporting the container to the field, processing the reagent water through the entire sampling system, and analyzing the sample

4. Blanks and Definitions (cont.) • Reagent Blank • Determines Hg concentration in solutions of reagents • Generated by adding all analytical reagents to previously purged reagent water in the bubbler

5. Blanks and Definitions (cont.) • Analytical Batch • A set of samples oxidized with the same batch of reagents, and analyzed during the same 12-hour shift. • A batch may be from 1 to as many as 20 samples.

6. Method Detection Limit Establishes ability to detect Hg

7. Test Spike Amount Minimum Criteria Frequency Initial Precision and Recovery (IPR) 5 ng/L Initial demonstration 4 replicates Average percent recovery = 79 - 121 Relative standard deviation £ 21% Initial Precision and Recovery Establishes laboratory ability to generate acceptable precision and recovery with the method

8. Reagent Blanks Determine level of contamination in all solutions of reagents Test Spike Amount Minimum Criteria Frequency Reagent Blanks NA Each new batch of reagents, and in triplicate each month £ 25 pg

9. Equipment Blanks Demonstrate the sample bottles are free from contamination Test Spike Amount Minimum Criteria Frequency Bottle Blanks NA 1 per cleaning batch < 0.5 ng/L or £ one- fifth Hg in associated sample(s), whichever is greater

10. Equipment Blanks (cont.) Demonstrate the sampling equipment is free from contamination Test Spike Amount Minimum Criteria Frequency Sampler Check Blank NA 1 following each cleaning batch < 0.5 ng/L or £ one- fifth Hg in associated sample(s), whichever is greater

11. Field Blanks Demonstrate acceptable levels of contamination associated with sample collection, handling, and transport Test Spike Amount Minimum Criteria Frequency Field Blanks NA 10% from same site at same time < 0.5 ng/L or £ one- fifth Hg in associated sample(s), whichever is greater

12. Ongoing Precision and Recovery Demonstrate lab operations are in control (e.g., acceptable precision and recovery) within each analytical batch Test Spike Amount Minimum Criteria Frequency Ongoing Precision and Recovery (OPR) 5 ng/L Prior to and after analysis of each analytical batch Percent recovery = 77 - 123

13. Matrix Spike/Matrix Spike Duplicate Demonstrates the precision and accuracy of the method and the sample matrix Test Spike Amount Minimum Criteria Frequency Matrix Spike/ Matrix Spike Duplicate (MS/MSD) Compliance limit or 1-5x background, whichever is greater 10% from a givensampling site or discharge Percent recovery = 71 - 125 Relative Percent Difference £ 24

14. Blank Results • Provide information about extent and nature of contamination • Can be used to identify areas in need of future corrective action • If desired, lab blank (e.g., reagent blank) contamination can be corrected through reanalysis • Field and equipment blank contamination cannot • Effect of blank contamination on data quality depends on extent of contamination, type of blank, and level of interest

15. Initial Precision and Recovery Results • If desired, IPR failures can be corrected by reanalysis • IPR series must be analyzed on the same instrument/detector system as field samples • Failure to meet recovery criteria suggests lab may not be capable of producing accurate results with the method and its equipment/procedures • Failure to meet standard deviation criterion suggests that the lab may not be capable of producing precise results with the method, its equipment, and its procedures

16. Ongoing Precision and Recovery Results • If desired, OPR failures can be corrected by reanalysis • In general, low OPR recoveries suggest a negative bias and high recoveries suggest a positive bias in field samples • If OPRs were not analyzed at the required frequency, IPR, other OPR, and MS/MSD data may be used to assess data quality

17. Matrix Spike/Matrix Spike Duplicate Results • If MS/MSD results fail to meet performance criteria but all other QC results are acceptable, method may not be appropriate for sample matrix • Low spike recoveries suggest suppression from matrix • High spike recoveries suggest enhancement from matrix • Highly divergent recoveries indicate poor precision of the method with the matrix, and indicate that results for samples may be less precise than normal

18. Multiple QC Failures • Examine QC in terms of type (e.g. laboratory, field or matrix QC) and direction • Laboratory QC failures suggest that the analytical process may be responsible for field and/or matrix QC failures • Multiple failures biased in the same direction can allow statements to be made about data quality with increased certainty • Multiple failures with widely divergent impacts suggests data are too unreliable for many uses

19. Corrective Actions • Should be taken as soon as is practical • Examine trends (blanks, OPR, and MS/MSD control charts) • Examine corrective actions taken by the lab and discuss (with lab and facility) additional measures that should be taken in the future • Implement method improvements based on systematic trends identified within and across laboratories

20. Why Bother? • Town of Falmouth, Maine conducted a study in 1998 • Historical Methods (Method 245.1) • < 220 ppt • Method 1631 • 62.9 ppt • Method 1631 with Method 1669 • 15.3 ppt

21. Sampling Tips • Do not use sample containers that have not been demonstrated to be clean • Either do not sample when it’s raining or prevent rainwater from falling into the sampling container • Face upstream and upwind • Avoid all sources of potential contamination including improperly cleaned equipment atmospheric inputs, and human contact • Do not breathe into the sample bottle if you have mercury amalgam fillings in your teeth

22. Sampling Tips (cont.) • Do not sample under or near a bridge or other metal structure. Metals can slough off of the structure and contaminate the sample. • Do not sample when the wind could blow metal, debris, or dust particles into the sample bottle • In general, the more blank samples that are collected and analyzed, the better the assessment of whether or not contamination has occurred. Method 1669 includes the minimum requirements for field and equipment blanks when collecting samples for mercury analysis at water quality criteria levels.