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USING AUTOMATIC SAMPLERS

USING AUTOMATIC SAMPLERS. Heather Bragg Oregon Water Science Center USGS Sediment Data Collection Techniques March 25, 2014. AUTOMATIC SAMPLERS. An automatic sampler is a device that …

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USING AUTOMATIC SAMPLERS

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  1. USING AUTOMATIC SAMPLERS Heather Bragg Oregon Water Science Center USGS Sediment Data Collection Techniques March 25, 2014

  2. AUTOMATIC SAMPLERS • An automatic sampler is a device that … • collects a volume of water/sediment mixture on its own from a point in a stream, lake, reservoir, well, or storm drain and … • places it in a container for later physical, chemical, or biological analyses.

  3. OUTLINE • Advantages & Disadvantages • Types of samplers • Pumps and other equipment features • Site selection • Sampler installation & maintenance • Sampler programming • Sample collection and field information

  4. ADVANTAGES • Can be pre-set to collect samples on a time, stage, discharge, volume, rainfall, and/or in-stream surrogate basis • Can collect samples over a runoff event

  5. ADVANTAGES (cont.) • Low labor costs for sample collection • May have the capability to be reprogrammed remotely • Samplers can be packaged in portable units that can be easily moved from site to site

  6. DISADVANTAGES • Collects a point sample • Has a limited number of samples that can be collected before it must be serviced • Requires power to operate • Most pumps have a limit of about 28 feet of lift • Sometimes has high installation costs, especially if multiple sites are required

  7. DISADVANTAGES (cont.) • Cannot collect samples for analysis of certain parameters • Requires maintenance of site and equipment • Possible cross contamination if not set up properly • Generally does not collect a sample isokinetically • Has limits on the concentration that can be accurately sampled, especially when sand concentrations are high

  8. TYPES of AUTOMATIC SAMPLERS • Passive • Set in place and collect one sample • Must be serviced after each sample before another sample can be collected • Stage must go down before sampler can be accessed

  9. PASSIVE SAMPLERS U-59 Single-Stage Type “C” Sampler

  10. Modified Single-Stage Sampler (Gray and Fisk, 1992)

  11. PASSIVESAMPLERS Recommendations for installation • Location • Near measuring section • Well-mixed section, in flow • Potential for debris blockages is minimized • Potential for removal is minimal • Influence of bedforms will be minimized • Bridge piers, abutments, and outcrops often used to anchor passive samplers • Multiple positions • Typically installed at several elevations

  12. TYPES of AUTOMATIC SAMPLERS • Passive • Pumping

  13. PUMPING SAMPLERS PS-69 Pumping Sampler

  14. PUMPING SAMPLERS Manning Pumping Sampler 36” Parshall Flume at several-acre basin in the northwest corner of a low-level nuclear waste burial facility in northwestern Illinois, Early 1980’s

  15. PUMPING SAMPLERS ISCO Automatic Pumping Sampler* *Use of firm, brand, or trade names does not constitute endorsement by the USGS

  16. PUMPING SAMPLERS Isco 6712 Fish trap facility White Salmon River, WA

  17. PUMPING SAMPLERS Isco 6712 Fish trap facility White Salmon River, WA

  18. PERISTALTIC PUMPS • Advantages • Liquid does not come in contact with pump • Easily Cleaned • Reversible • Disadvantages • Low lift capability • Creates a vacuum to lift • In-line velocity decreases as head increases

  19. SITE SELECTION • Safety hazards • Ability to collect cross-sectional samples at all stages of flow • Ability to determine surface water discharge for all flows • Representativeness of the cross section • Turbulence and flow paths

  20. SITE SELECTION • Protection from vandalism • Permission to install equipment and collect samples • Power availability • Height of lift and length of intake lines • Installation of intakes for the collection of representative samples and survival at high flows • Cost and difficulty in operation of the site, including temperature variations

  21. INSTALLATION • Minimize static head (max is <28 ft) • Minimize intake tube length, no dips • Part of the vertical sampled with USGS samplers • Where mean SSC is expected • Avoid dunes and bed contamination • Submerged at all times • Avoid bank effects • Place in zone of high velocity and turbulence

  22. INTAKE ORIENTATION Five orientations for automatic sampler orifices: • Pointed into flow • Perpendicular to flow • Pointing upward • Pointing downward • Pointing downstream

  23. SAMPLE COLLECTION • Discrete (Sequential) • individual sample is placed in a single bottle. • multiple bottles can be used for one sample by using the duplexing or multiplexing options. • Discrete samples can be analyzed separately or manually composited. • Composite • Several samples placed in single bottle • Must collect equal amounts of sample each time • Produces flow weighted mean concentration

  24. DISCRETE SAMPLING One sample per bottle Sample 3 Sample 2 Sample 4 Sample 5 Sample 1 SAMPLE COLLECTION

  25. Multiple bottles per sample Sample 2 Sample 1 SAMPLE COLLECTION

  26. SAMPLE COLLECTION • When a sample is triggered, the sample line is first purged, rinsed with native water, and then the sample is deposited in the sampler container. • Alternately, the sampler can be equipped with a valve system (located past the peristaltic pump head) to flush the line rather than purge and rinse.

  27. SAMPLER PROGRAMMING • Time-paced mode • Uniform • Non-uniform • Flow-paced mode • Parameter-controlled mode • Stage • Turbidity • Triggering of collection can be controlled by sampler or station’s data logger

  28. SITE VISIT • Manually cycle the sampler to collect a sample • Collect QC samples to evaluate the relation between pumped and cross-sectional samples • Download sampling report • Check sampler to ensure it has been operating correctly • Remove samples • Clean samplers and tubing • Replace used bottles with empty ones • Recheck sampling volume • Reprogram sampler

  29. FIELD FORM • Station Name - Record the full station name on all notes sheets • Station Number - Record full station number • Date - The date the sampler was serviced • Time - Record the time the sampler was stopped and when it was restarted • Stage - Gage heights, outside and inside readings

  30. FIELD FORM (Cont.) • Sampler - Record the make and model of the automatic sampler • Number of samples collected - From the sample record, record the number of samples that the record says were collected • Number of bottles - Record the number of bottles that have actual samples in them, compared with the number of samples from the above step. • If collected sequentially, the number should match. • If collected using the composite mode, compare the number of bottles that should have sample in them with the number of bottles that actually have sample in them.

  31. FIELD FORM (Cont.) • Condition of sampler - Record the general condition of the sampler, for example, if it appears to be collecting the proper volume, the battery voltage, the condition of the intake upon arrival at the site. • Maintenance - Record any maintenance that may have been done on the sampler or intake, including clearing debris from the intake. Record any changes that may have accrued as a result of this maintenance, such as change in volume pumped after cleaning of the intake.

  32. BOTTLE LABELS • Station Name - Record the full station name • Station Number - Record the station number • Date - Record the date the sample was collected, not the date of servicing of the sampler • Time - Record the time the sample was collected, not the time of servicing of the sampler • Stage - Record the gage height at the time the sample was collected, if available • Type - Record “pumped sample” • Bottle Number -Position of bottle in sampler • Initials - Put your initials on the bottle to denote that you were the one retrieving the samples and recording the information on the bottles.

  33. FIELD FORM - Example

  34. SUMMARY • Automatic samplers collect POINT samples and are rarely representative of the cross-sectional, depth-integrated suspended-sediment concentration • The resulting suspended-sediment concentration must be corrected

  35. REFERENCES • Guidelines and Standard Procedures for the Use of Automatic Samplers for the Collection of Surface-Water and Sediment Data, by G. Douglas Glysson (Currently in for approval by supervisor) (STATUS UPDATE?) • Lewis, Jack, and Rand Eads. 2009. Implementation guide for turbidity threshold sampling: principles, procedures, and analysis. Gen. Tech. Rep. PSW-GTR-212. Arcata, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station.

  36. Questions?

  37. DISTRIBUTION of SEDIMENT Sampler intake Sampled concentration = 930 mg/L Mean cross-section concentration = 929 mg/L

  38. DISTRIBUTION of SEDIMENT Sampler intake Sampled concentration = 800 mg/L Mean cross-section concentration = 1360 mg/L

  39. BOX COEFFICIENT • A mean flow-weighted x-sectional constituent concentration divided by a mean concentration at a point or vertical. Mean Concentration x-section mg/L ----------------------------------------- Mean Concentration pumped mg/L

  40. BOX COEFFICIENT- Example EWI 1 @ 12:31 Pumped sample = 392 mg/L X-section conc: 415 mg/L Box Coefficient = 415/392 = 1.06 EWI 2 @ 15:16 Pumped sample = 140 mg/L X-section conc: 173 mg/L Box Coefficient = 173/140 = 1.24

  41. BOX COEFFICIENT- Example

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