Model of a Standard Operating Procedure (SOP) for manual gravimetric PM measurements with a Low Volume Sampler

Transcription

1 Model of a Standard Operating Procedure (SOP) for manual gravimetric PM measurements with a Low Volume Sampler How to use this specimen SOP This model SOP aims at giving support to network operators in setting-up or updating a SOP for gravimetric PM measurements. It gives example text for the necessary points which need to be addressed in a SOP. However, it can only serve as an extended template because a SOP needs to describe the actual circumstances of a network (site locations, exact type of an analyzer, organization and planning of the maintenance procedures etc.). Thus, these items have to be formulated for each monitoring network individually and in a specific way. In particular where concrete figures (e.g. for uncertainties, diameter of connection lines etc.) are given in the example text, these have to be verified and adapted individually for each measurement network. The model SOP exemplifies measurements with a Low Volume Sampler. However it can easily be adapted for measurements with a High Volume Sampler. Example text is written in normal style, explanations and directions for needed specific input in italic style. SOP version Give date and number of the current version of the SOP. Responsible person Name of the author of the SOP. Implementation of this SOP version Date of the setting into force of the current version of the SOP and signature of the authorized person. Measurement principle Particulate matter (PM) is collected on a filter during 24 hours at a controlled flow rate by means of a vacuum pump. The mass of the PM collected is determined from the mass difference of the filter before and after sampling. The concentration of the PM in air is calculated from this mass and the volume of air sampled. The methodology described is in conformity with European Standards EN 14907: 2005 (for PM2.5) and EN 12341: 1998 (for PM10). AirMonTech Specimen SOP PM-Gravimetry 1/8

2 Users of the SOP Specify here the group of people who will have to work according to the SOP. Equipment and Materials In the Lab: - Microbalance, resolution 10 μg; reference weights 100 mg and 1000mg - Static discharger - Temperature/relative humidity sensors - Conditioned weighing room and cabinets for filter conditioning - Filter holders - Transport boxes for filters - Filters: 47 mm diameter, for low volume sampling (LVS) - Tweezers, labels, Petri dishes 50 mm diameter In the field: - High Volume Sampler with sampling head - Flow calibrator - Portable temperature/relative humidity sensor - Filter cartridges - Silicone grease and cleaning material General remarks: The procedures described are in conformity with the relevant clauses of EN and EN and the manufacturer s recommendations. Laboratory procedure General The weighing room conditions should be verified before each weighing session by plotting and archiving the Temp/RH graph for the last three days. All manipulations of filters shall be performed using tweezers. The tweezers should be cleaned after each weighing session. Filters shall never be touched by hand. AirMonTech Specimen SOP PM-Gravimetry 2/8

3 Personnel to enter the laboratory should wear the appropriate clothing. Checking of new batches of filters Visually inspect new packages of filters before use. Remove 4 filters from the package to serve as reference filters, to replace reference filters from the previous batch. Put 2 of these in Petri dishes labeled as REF1 and REF2; these filters are conditioned together with blank and loaded filters, and are used to check the weighing procedure. Put the 2 others in Petri dishes labeled SPA1 and SPA2; these filters are conditioned together with blank and loaded filters, and may be used as spares. Conditioning is performed in the cabinets with Petri dishes uncovered. Checks before each weighing session Weigh the reference mass piece and record its mass (Microbalance Check). The recorded mass shall not differ by more than 20 μg from the reference mass. Else, the deviation shall be eliminated before proceeding. Weigh the weighing room blank filters. The masses shall not deviate by more than 40 μg (LVS) or 500 μg (HVS) from those obtained at the previous session. Else, the deviation shall be eliminated before proceeding. Check current Temp/RH conditions of weighing room. Record all findings. Labeling of samples Petri dishes for blank and sample filters are labeled. (Describe here a labeling system allowing for clear identification of PM fraction, station, date etc.) Conditioning and weighing of unloaded filters Place undamaged filters in Petri dishes and place these in the conditioning cabinet. Condition the filters for a period of 48 hours (at 19 C to 21 C and 45 % RH to 50 % RH). Remove the filter from its Petri dish, discharge if necessary in accordance with the instructions of the manufacturer of the discharger, weigh and record its mass in units of milligrams. Place the filter back in its Petri dish. Place the label on the Petri dish. Repeat the procedure after the second conditioning period. The masses recorded shall not differ by more than 40 μg. Else, the cause of the deviation shall be investigated and solved before proceeding. In case of a deviation for a single filter: replace by one of the spares. In case of deviations for more than one filter: recondition and reweigh. If the problem persists, the complete batch of filters shall be discarded and replaced. Consult the supplier. Take the average mass of the two weighings as the mass of the unloaded filter: m(u). Mark the label on the Petri dish to indicate that the filter is ready for use in the field. Unloaded filters may be kept for a period of maximum 1 month after weighing before use in the field (total storage time in weighing room and sampler before sampling). In most cases the results of the first weighing differ only slightly from the average of the first and second weighing. As a consequence, the second weighing may be waived if the additionally resulting uncertainty was calculated and included in the uncertainty budget of the method. However, it is up to individual laboratory to AirMonTech Specimen SOP PM-Gravimetry 3/8

4 demonstrate that this situation is appropriate to its own situation. It is also possible to define a procedure where only a subset of filters is reconditioned and reweighed. Some filter types do not reach a stable mass reading within the prescribed conditioning period, but need a preconditioning procedure at high relative humidity. Preparation of filter holders Clean the filter holders if necessary; check if the O-rings are still in good shape, else replace. Place the filters in the appropriate holders. Holders are marked with a number (0 to 14). The blank filter has to be placed in the holder numbered 0 and the rest filters in ascending order. Place the filters in the transport boxes. Each station must have dedicated transport boxes. Cover/close the boxes for transportation to the monitoring stations. At minimum one filter shall not be sampled but shall remain in the cassette to serve as a field blank. Handling, conditioning and weighing of loaded filters Filter holders/cartridges shall be placed in the weighing room immediately after receipt. The period between receipt and conditioning shall not be more than 7 days. Remove the filters from the filter holders and place them in the appropriate petri dishes (corresponding code). All filters shall be visually checked prior to use for defects such as holes or loose material, and discarded if defects are found. Place the Petri dishes in the conditioning cabinet. Condition the filters for a period of 48 hours. Remove the filter from its Petri dish, discharge if necessary in accordance with the instructions of the manufacturer of the discharger, weigh and record its mass in units of milligrams. Place the filter back in its Petri dish. After the first weighing the filters shall be reconditioned for another hours and reweighed. Repeat the weighing after the second conditioning period. The masses recorded shall not differ by more than 60 μg (or more than 40 μg for field blanks). Else, the cause of the deviation shall be investigated and solved before proceeding. In case of a deviation for a single filter: proceed. In case of deviations for more than one filter: recondition and reweigh. Note the deviations in the spreadsheet. Take the average mass of the two weighings as the mass of the loaded filter: m(l). Mark the label on the Petri dish to indicate that the loaded filter has been weighed. See also comments above for weighing of unloaded filters. Calculation of PM mass concentration The PM mass concentration C in units of micrograms per cubic meter is calculated as C = m(l) m(u) V amb where m(l) is the mass of the loaded, m(u) of the unloaded filter in micrograms per cubic meter and V amb the volume of air sampled expressed at the average ambient temperature and pressure during sampling, in cubic meters. AirMonTech Specimen SOP PM-Gravimetry 4/8

5 Field procedure Cleaning and greasing the impactor plate Grease the clean plate with a thick layer of silicone grease, making sure that the ventilation holes remain open. Release the sampling head and clean the inlet. Change impactor plates and close the sampling head. Clean the used impactor plate and place it in the transport case. Checking the flow rate The sampler flow rate is checked every 3 months by measuring the flow rate with a calibrated flow meter. If the flow rate differs by more than 2% from the set value, the flow controller shall be adjusted as described in the instrument manual. Routine maintenance Perform the scheduled maintenance as required by the maintenance schedule. All performed maintenance steps have to be documented in the LOG-book together with date, time and name of the operator. Here the different maintenance activities should be described. They may comprise e.g.: Flow controls, leak tests, cleaning processes, filter and scrubber replacements, check of sensors and status signals. A full list of required maintenance procedures and schedules can always be found in the instrument manual. Make sure that at least the tests described in EN (or even better in the new EN 12341) are performed. Documentation and forms In the appendix examples of a checklist for general controls in the stations (Appendix 1) and for the documentation of the maintenance of the sampler (Appendix 2) are given. All completed forms are stored in the LOG book together with the following information: name of the operator date, time and location model and serial number of analyser and calibrator gas cylinder serial number and cylinder concentration (observe the cylinder expiry date on the cylinder certificate). AirMonTech Specimen SOP PM-Gravimetry 5/8

6 References EN (2005). Ambient air quality - Standard gravimetric measurement method for the determination of the PM2,5 mass fraction of suspended particulate matter. EN (1998). Ambient air quality Determination of the PM10 fraction of suspended particulate matter Reference method and field test procedure to demonstrate reference equivalence of measurement methods. The above two standards are under revision. The new EN (Ambient air - Standard gravimetric measurement method for the determination of the PM10 or PM2,5 mass concentration of suspended particulate matter) will combine EN 12341:1998 and EN 14907:2005 and supersede these standards. The draft of the new EN is currently in enquiry and will presumably enter into force in Revision History In this paragraph the history of revisions of the SOP is documented. It is sufficient to list here the revision dates together with keywords of the revised items. However, all old versions have to be stored at a secure place defined here. Acknowledgement Valuable input was provided by the Air Quality Section of the Department of Labour Inspection of Cyprus and by the Swiss National Monitoring Network NABEL. AirMonTech Specimen SOP PM-Gravimetry 6/8

7 Appendix 1: Example of a checklist for general controls in the stations: General checks Site: Zurich fulfilled barometric pressure mbar pump of main sampling line working... air conditioning working... water from zero air compressor drained.. pressure at zero air compressor > 4 bar.. temperature in pump compartiment around 20 C... inlet filters changed (only NOx and CO ). still sufficient filters in stock..... VOC-GC: water in H2-generator filled... cylinder pressures recorded. SO2 cylinder.. NO cylinder. CO cylinder. CH4 cylinder... synthetic air bar 114 bar 133 bar 138 bar 18 bar Final control All MKAL: Mode = Automatic, Stat = Measure. Easycomp: maintenance switched off.... PC: backup made, HandyDrive removed from adaptor data acquisition started... climatisation working Remarks: Site possibly influenced by nearby construction work from 3-6 October 2011 AirMonTech Specimen SOP PM-Gravimetry 7/8

8 Appendix 2: Example of a maintenance protocol HIVOL PM10 Station: ZUE Date: Work: 1440 min Pause: 0 min Filter Nr Start date: at 00:00 hours (winter time) fulfilled Filter Nr Start date: at 00:00 hours (winter time) Last filter number corresponding to number in sampling list? Correct order of filter numbers checked? Correct flow setting checked at rotameter? (513 l/min) Greased impactor plate in sampling PM10 head no action turned replaced 1 Remarks concerning special events: Comments with filter numbers and dates Failure (Filter ): filter changer blocked Filter : Sampling time only 955 minutes General remarks: AirMonTech Specimen SOP PM-Gravimetry 8/8