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Office of Water Mercury workshop- sampling.ppt Mercury Collection and Analysis in Ambient and Effluent Waters using EPA Method 1631 Overview of Sampling.

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Presentation on theme: "Office of Water Mercury workshop- sampling.ppt Mercury Collection and Analysis in Ambient and Effluent Waters using EPA Method 1631 Overview of Sampling."— Presentation transcript:

1 Office of Water Mercury workshop- sampling.ppt Mercury Collection and Analysis in Ambient and Effluent Waters using EPA Method 1631 Overview of Sampling and Analysis William Telliard U.S. EPA Office of Science and Technology

2 Office of Water Mercury workshop- sampling.ppt Contamination Control Philosophy u Ensure any object or substance that contacts the samples is nonmetallic and free from any material that may contain metals of concern u Mercury must be eliminated or reduced to a level that will not compromise the measurement l Sample bottles l Sampling equipment l Reagents l Laboratory environment l Laboratory glassware and equipment

3 Office of Water Mercury workshop- sampling.ppt Equipment Cleaning u Preclean l All equipment and containers must be non-metallic l Clean all sampling equipment and containers using detergent, mineral acids, and reagent water as described in Method 1669 u Verify cleanliness l Generate acceptable equipment blanks l Demonstrates equipment and containers are free from contamination u Storage l Fill cleaned sample containers with 0.1% (v/v) ultrapure HCl and individually double-bag l Bag or wrap all sampling equipment for storage and shipment

4 Office of Water Mercury workshop- sampling.ppt Sample Collection Using Method 1669 “Clean Hands/Dirty Hands” u A two-person sampling team is required l One person is designated “Clean Hands” and performs all operations involving direct contact with the sample and bottles l The other person is designated “Dirty Hands” and is responsible for operation of machinery and activities not involving direct contact with the sample l Sampling personnel must wear clean, non-talc gloves, and may need to wear other clothing, such as disposable coveralls or nylon windsuits, caps, and shoulder-length glove liners, to prevent sample contamination

5 Office of Water Mercury workshop- sampling.ppt Sample Collection Using Method 1669 The presence of potential sources of contamination is of extreme importance in site selection u To minimize contamination— l Collect samples facing upstream and upwind l Avoid collecting samples during precipitation events – During a 9 POTW Great Lakes study, the Hg field blank collected on the only rainy day had a Hg concentration 3 times higher than any other field blank in the study – Collect samples as far as possible from metal supports, bridges, wires, and heavily traveled roads

6 Office of Water Mercury workshop- sampling.ppt Sample Collection Using Method 1669 (cont.) u Method includes procedures for collection of samples for determination of total recoverable metals and dissolved metals u Sample Filtration l For dissolved metals, samples are filtered through a 0.45-um capsule filter at the field site l A continuous-flow sampling system with an in-line filter can simplify sample collection and filtration u Sample Preservation l Conducted in the field or in the laboratory l Field preservation must be performed in a glove bag or a designated clean area

7 Office of Water Mercury workshop- sampling.ppt Quality Assurance/Quality Control u Equipment Blanks l Bottle blanks l Sampler Check Blanks u Field Blanks l Must be collected to assess the likelihood of contamination in the samples. l Field blanks are collected before samples u Field Duplicates l Collected to assess precision of the sampling and analytical processes

8 Office of Water Mercury workshop- sampling.ppt Blanks and Definitions u Equipment Blank l 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 l 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 u 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 equipment system, and analyzing the sample

9 Office of Water Mercury workshop- sampling.ppt Summary Rigorous sample handling procedures are necessary to ensure samples are not contaminated u Stringent QC is necessary to ensure the validity of the analytical results u Not all of the procedures described in Method 1669 may be necessary for effluent sampling l Level of protection required depends on sampling environment, monitoring levels of interest, and metals of interest l The low levels of Hg (<36 ng/L) found in a 9 POTW Great Lakes Study suggests these clean techniques may be required for some metals

10 Office of Water Mercury workshop- sampling.ppt Laboratory Analysis using Method 1631 u For determination of mercury in filtered and unfiltered water by oxidation, purge and trap, desorption, and cold-vapor atomic fluorescence spectrometry (CVAFS) u Method detection limit is 0.2 ng/L and the range is ng/L u The ease of contamination samples cannot be overemphasized l Method includes suggestions for improvements in facilities and analytical techniques that minimize contamination and maximize the ability of the laboratory to make reliable trace metals determinations u Performance-based u Accompanied by Method 1669

11 Office of Water Mercury workshop- sampling.ppt Laboratory Analysis using Method 1631 (cont.) u A mL sample is collected directly into a specially cleaned, pretested, fluoropolymer bottle using appropriate sample handling techniques u For dissolved mercury, the sample is filtered through a 0.45 uM capsule filter u The sample is preserved by adding 5mL/L of pretested HCl or 5 mL/L BrCl solution. u BrCl solution is added to oxidize all Hg compounds to Hg(II) u The sample is pre-reduced with NH 2 OH-HCl to destroy the free halogens

12 Office of Water Mercury workshop- sampling.ppt Laboratory Analysis using Method 1631 (cont.) u The sample is then reduced with SnCl to convert Hg(II) to volatile Hg(0). u The Hg(0) is separated from solution by purging with nitrogen onto a gold-coated sand trap u The trapped Hg is thermally desorbed from the gold trap into an inert gas stream that carries the released Hg(0) into the cell of a CVAFS for detection u Quality is assured through calibration and testing of the oxidation, purging, and detection systems.

13 Office of Water Mercury workshop- sampling.ppt Figure 1. Cold Vapor Atomic Fluorescence Spectrometer (CVAFS) System (Method 1631)

14 Office of Water Mercury workshop- sampling.ppt Figure 2. Automated Mercury Fluorescence System (Method 245.7)

15 Office of Water Mercury workshop- sampling.ppt Clean Spaces Guidance u Draft guidance on the establishment of trace metal clean rooms in existing facilities was completed in April 1995, with minor revisions in January The guidance includes: u A general design of a trace metals clean laboratory; l Delineation of the hierarchy of cleanliness needed within the laboratory, including change rooms; l Description of HEPA-filtered air and clean water supplies, which are essential in a trace metals laboratory; and l Detailed descriptions of materials and modifications used to construct a trace metals clean room in an existing laboratory.

16 Office of Water Mercury workshop- sampling.ppt Clean Spaces Guidance (cont.) u Basic requirements l metal free work surfaces and hoods l positive pressure with HEPA-filtered air l clean water u Achieved with commercially available materials u Installed into existing facilities l Paint the walls with metal-free paint (epoxy- or latex-based) to which has been added a small amount of sulfur powder to react with mercury that could diffuse out of the underlying surfaces l All metal fixtures and appliances should be replaced with non-metal counterparts

17 Office of Water Mercury workshop- sampling.ppt Analysis Tips u Clean all work surfaces in which samples will be processed u Reagent water should be monitored for Hg u Samples known to contain high levels of mercury (greater than 100 ng/L) should be diluted prior to bringing them into the clean room or area u Sample processing and analysis should occur as far as possible from sources of airborne contamination u Effluent from the CVAFS should pass through either a column of activated charcoal or a trap containing gold or sulfur to amalgamate or react mercury vapors


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