Filter Sampler

Electronic versions of the instruction manuals for the filter sampler and the sampling head are here and here

Filter Baking

• The PSI group usually bakes their filters in the lab, and then ships/brings them to the field site.

• Filter Baking Procedure (from Peter Zotter at PSI): A whole pack of filters (~30) is put in a quartz petri dish and put in the oven (8h at 800°C) and on the next morning after the filters have cooled down, they are wrapped in aluminum foil. So the whole procedure takes about 24h (8h prebaking and a long time cooling down) even though the only workstep which takes some time for me is wrapping the filters in foil (~30min up to 1h). Barend van Drooge suggests putting the filters in foil before baking, so the foil is cleaned as well and handling of filters is minimized.

Blanks

• Field and lab blanks must be made. PSI recommends 2 lab blanks be taken just after pre-baking and 2 more lab blanks be taken after all the preparation steps (i.e., prebaking -> wrapping in foil and storing the filters in the freezer -> defrosting and unpacking if you stored the pre-baked filters in the freezer before using them -> putting the filter in the filter holder -> remove filter from filter holder again and then put it in the freezer). There is no need to create lab blanks after the campaign.

• For field blanks, the more the better. Taking a blank every three days is recommended, or two times a week if one wants to conserve filters and time.

PM1 Sampling Head

• The VOLUMETRIC (i.e., "real") flow rate must be 30 m3/hr for the size cut to be accurate. NOTE: At high elevations (Boulder), the sampler can achieve this flow without difficulty (moving less mass for given volume of air), but at sea level the pump/motor can barely achieve this flow rate.

Other Info

• There are 15 filter holders, but not all need to be in the filter sampler when collecting. Thus, one can remove a few holders so that they can be pre-loaded with filters. This practice should minimize downtime when changing filters, and hopefully promote filter cleanliness.
• There is a large rotameter that can be used to verify the flow out of the sampler. The flow read off the rotameter must be corrected for temperature and pressure (see the bottom of this webpage for a good summary of correction equation: http://www.skcinc.com/prod/320-100.asp)

BEACHON

• Sampling Times and Limits of Detection:

1. Chris Geron (U.S. E.P.A) measured OC levels are 0.5-2 ugC m-3 for 48-hr samples (July & August 2008)

2. Barend L. van Drooge (Molecular Tracers Analysis) needs approximately 100m3 sample. Doing the math, that means 13 1/3 hours sampling time, if we divide filters into quarters.

3. Andre Prevot (14C analysis) needs 12 hrs sampling time (Patrick Hayes has a spreadsheet from Peter Zotter with calculations). This is figured with 0.5 ug/m3 concentrations, and two (16.3 mm diameter) punches taken from a filter. The 14C analysis will require 1/2 a filter given the area of the punches (2 punches for TC, 2 for OC, and 2 for Sunsent ECOC, plus extra material as a precaution).

CONCLUSION: Sampling time should be a minimum of 12 hours, or 24 hours if one wants to be very cautious. That would correspond to 64 filter samples taken for BEACHON (32 days/12hours).

• Tentative Filter Sampler Schedule:

See spreadsheet here: https://spreadsheets.google.com/spreadsheet/ccc?key=0AlKzqypIvZJtdDFILUFtMG9hY0M1WVZYb1ZrV3NWWHc&hl=en_US&authkey=CNGlwpQK

Jul 15th: 24 hr filter collection (1 d, 1 filter)

Jul 16th - 25th: 12 hr diurnal average, 24 hr total collection time per filter (10 d, 10 filters, 2 day oversampling)

Jul 26th - Aug 2th: 6 hr diurnal average, 12 hr total collection time per filter (8 d, 16 filters, 2 day oversampling)

Aug 3rd - Aug. 9th: 24 hr filter collection (7 d, 7 filters)

Aug. 10th - Aug 15th: 12 hr filter collection (6 d, 12 filters)

Therefore, 46 filter samples will be collected. Also, 4 lab blanks and 10 field blanks will be collected. In total, blanks and samples will be 60 filters.