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J_ Soil Sample Headspace Screening Protocol <br /> Paragon field-screens soils for total organic vapors JOV) using a field-portable photoionization <br /> detector (PID) equipped with a 10.6 eV bulb. We program the PID with the isobutylene response <br /> factor(0.6), then calibrate it using a 100 parts per million (ppm) isobutylene gas standard to yield <br /> "total ionizable organic vapors" in ppmv (parts-per-million by volume), as benzene. We re- <br /> calibrate the PID in this way every 10-25 analyses thereafter. We operate and maintain the PID <br /> according to the manufacturer's specifications. <br /> Upon sample collection, Paragon partially fills either glass sampling jars (8 ounce or greater) or <br /> dedicated disposable Ziplock® plastic-freezer bags between one-half to one third with soil. We <br /> then seal the jars with aluminum foil or zip up plastic bags, taking care to ensure the threads <br /> cover the jar or the zipper of the plastic bag is free of soil. We shake the sample vigorously for 15 <br /> seconds, allowing the headspace to develop for at least one minute, then shake the sample <br /> vigorously for 15 seconds again. <br /> Paragon then inserts the PID probe through the aluminum foil (jar method) or into a small <br /> opening in the bag's seal (bag method) to a point approximately one-half of the headspace depth, <br /> taking care to avoid water droplets or soil particles. When ambient air temperatures are below <br /> approximately 10°C (45T), we conduct headspace development inside a heated vehicle or <br /> building. We record the highest PID response following probe insertion as the specific headspace <br /> concentration for that individual soil sample. <br />