Filter Sampler

This page is a work in progress...

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.

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:

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 nine field blanks will be collected. In total, blanks and samples will be 51 filters.