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 The following laboratory procedures describe methods for obtaining initial
contaminant fluxes from exposed sediment. The procedure involves sampling
air that has been passed over the sediment surface. Sediment is prepared and
loaded into a chamber, herein referred to as a "flux" chamber, which is sealed,
and air is then passed over the sediment for a prescribed period. The exit air is
passed through contaminant-specific adsorbent-filled air sampling tubes that can
be analyzed for volatile COC.
F.2.1 Apparatus
The following items are required:
b. Air supply of sufficient purity not to interfere with emissions data and
with a means to control a constant flow rate.
c. Laboratory air or compressed air from a cylinder may be used for
pushing air over the sediment surface.
d. A vacuum pump can also be used to pull air over the sediment surface.
e. Flow meter used to determine air flow through the chamber with the
ability to handle air flows of greater than 1 L/min.
Contaminant-specific air sampling tubes.1
f.
g. Tygon tubing used to attach traps, supply air, and flow meter.
F.2.2 Flux chamber
Flux measurements are conducted using a chamber detailed in Figure F-1.
The chamber is constructed of two pieces of anodized aluminum, which are
sealed together with an o-ring and threaded fasteners to ensure an airtight seal.
The bottom portion of the chamber is designed to hold a 10-cm depth of
sediment with a surface area of 375 cm2. The upper portion is grooved to
provide an air space above the sediment for air flow and is designed with
channels to distribute air flow uniformly across the sediment surface. A glass
window can be inserted in the top portion of the chamber to allow for visual
monitoring of the sediment surface.
1
Supelco Inc., PA, supplies a wide variety of prepacked air sampling tubes. Table F-1
gives a list of commonly analyzed volatile compounds and appropriate sampling tube.
F2
Appendix F Laboratory Evaluation of Volatile Emissions and Volatile Dispersion Modeling
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