From Galena-Park-Monitoring-Report-FINAL.pdf

B. Monitoring Equipment and Analysis (Page 13 of the PDF)

Particulate matter samples were gathered using two MiniVol11 Tactical Air Samplers (TAS).12 Our partners Global Community Monitor have much experience using MiniVols. They are manufactured by Airmetrics, a Eugene, OR based company providing innovative air sampling equipment. Although the MiniVol is not a reference method sampler, its manufacturer states that “the MiniVol™ TAS gives results that closely approximate data from Federal Reference Method samplers.”13

The MiniVol uses a system that includes a pump, impactors, and a mechanical filter. Each MiniVol is calibrated by Airmetrics before it is sold. The calibration ensures that the pump draws 5.0 liters of ambient air per minute. The monitor is equipped with a flow meter that allows operators to check the flow rate before and after each use. With a flow-rate of 5 liters per minute (approximately the same as that of the human lungs), each MiniVol collected 7.2 cubic meters of air during a 24-hour sample.

The MiniVol can be configured using a variety of impactors to sample particulate matter in the ranges of 10 microns (PM-10), 2.5 microns (PM2.5), and total suspended particles (TSP). For this project. Air Alliance Houston collected only PM2.5 samples for 24-hour periods. Samples are collected in a 47 millimeter (mm) mechanical filter. Filters were purchased and prepared for use by CHESTER LabNet (CLN), a Tigard, OR based specialty laboratory that focuses on inorganic air quality analysis. Samples were collected using CLN’s procedures for proper handling, storage, and shipment of filters. Samples were returned to CLN for analysis.14

Two types of filters were used: Teflon and quartz. Samples taken with Teflon filters were analyzed using two analytical protocols. A gravimetric analysis yields a total PM2.5 mass. CLN weighs each filter after conditioning at a constant temperature and relative humidity prior to shipment using a balance accurate to one microgram. After sampling, the filter is reconditioned and then CLN reweighs the filter to determine the total weight of material present. Dividing this weight by the total volume of air sampled (7.2 m3 for a 24-hour sample) gives an average concentration of PM2.5 in the ambient air during the 24-hour sample collection. Teflon filters were also analyzed using an x-ray fluorescence (XRF) analysis that determined concentrations of forty different elements.

Quartz filters were used to sample for elemental and organic carbon. Quartz filters must be refrigerated before and after use, and during shipping, in order to limit volatilization of collected material. Quartz filters were analyzed using the National Institute for Occupational Safety and Health (NIOSH) Method 5040 for diesel particulates as elemental carbon. Method 5040 determines total carbon as organic carbon and elemental carbon. Elemental carbon was then used to calculate the concentration of diesel particulates.

C. Monitoring Protocol and Quality Control (Page 14 of the PDF)

All participants in the study handling the MiniVols were trained in their use by Denny Larson of Global Community Monitor. Two monitors were deployed side-by-side throughout the project. Each monitor includes an on-board programmable timer. Timers are programmed to sample for twenty-four hours and independently verified. Monitors are powered by on-board battery packs. Battery packs are exchanged after each run for freshly charged batteries. Monitors were placed in secure locations on the roofs of one or two story buildings. Each monitor was positioned according to manufacturer specifications and GCM training to avoid nearby objects or conditions that could impact sample collection and accuracy. Monitor flow rates were checked before and after each sample collection. Programmable timers were also checked to ensure samples were collected for twenty-four hours. Procedures were documented on field data sheets required by CLN. A detailed protocol checklist developed and used by Air Alliance Houston throughout the project is included as Appendix D.

1. Duplicate Samples

Typically, one monitor used a Teflon filter and the other a quartz filter. However, on five occasions, the same filter type was placed in each monitor in order to perform a duplicate sample analysis. Three duplicates were performed using Teflon filters; two with quartz filters. Results of duplicate samples are reported as the average of the two samples.

A regression analysis of the three Teflon duplicates is included in the independent analysis of this project performed by Laura Campos, a graduate student with the Rice University Department of Statistics.15 Two of those duplicates showed good precision. A third showed poor precision, with a relative error of 91%. Possible causes for this error were discussed, but no conclusions were reached. Mark Chernaik, Ph.D., Science for Citizens, offered this explanation:

First, the two samples collected at 2000 Clinton Drive (City Hall) on 22-23 January 2013 were co-located. However, the PM2.5 levels are not comparable, differing by almost 100% (19 versus 36.2 ug/m3. Interestingly, the XRF levels of these two collated samples are comparable (for example, iron levels of 0.157 versus 0.161 ug/m3). Since the XRF levels are comparable, my best guess is that some error with the gravimetry analysis may have produced the anomalous result.16

The two duplicate samples performed on quartz filters were not included in Ms. Campos’ regression analysis. Those duplicates were found to have relative errors of 4% and -31%, respectively.

2. Field Blanks

Several field blanks were also included in the project. Each field blank was transported to the monitoring site, removed from its package, placed in the monitor while it was turned off, immediately removed from the monitor, returned to its package, and placed in the closed casing of the monitor during its 24-hour run. Three field blanks were included using this procedure: one quartz and two Teflon. The results of their analysis are below:

Table 1: Field Blanks

Lab ID	Start Date	Total PM2.5 (μg)	Total Organic Carbon (μg)	Total Elemental Carbon (μg)	Total Carbon (μg)
13-U164	1/20/2013		4.309 ± 1.668	0.0000 ± 1.390	4.309 ± 3.058
12-T3958	5/21/2013	130 ± 10
12-T4053	8/7/2013	8 ± 10

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11 MiniVol is a trademark of Airmetrics. 12 Initially, the project included sampling with a DustTrakII aerosol meter. Early difficulties with the DustTrakII led to its data being discarded. It has since been repaired and recalibrated and will be included in future studies. 13 See http://www.airmetrics.com/products/minivol/index.html. 14 Full data reports, field data sheets, and chain of custody forms for this project are available upon request.