Environmental Engineering Reference
In-Depth Information
100˚C. The volume of these extracts, usually about 45 ml, was reduced to
approximately 5 ml under a stream of dry nitrogen. The extracts were then
processed through a Supelclean LC-Si (Supleco) cleanup column. The extract
volumes were next reduced to 1.0 ml under dry nitrogen, and the extracts
were sealed in crimp-top amber vials. Some soil extracts contained so much
material that a final volume of 2 ml was used. For all POPILE soil samples,
two dilutions (1:50 and 1:200) of each sample were analyzed to keep the
measured PAH concentrations within the range of the standard curve. The
internal standard, P-terphenyl d14, was added to each sample vial to give a
final concentration of 50 ng/l.
All GC-MS analyses were performed on a Hewlett Packard 6890 gas
chromatograph with a 5973 mass selective (MS) detector or a flame ionization
detector (FID). The column used was a DB 5 (30 m long) column. The splitless
injector temperature was 275˚C. The column temperature was ramped from
80 to 280˚C at a rate of 8˚C per minute, followed by a rise to 300˚C at 4˚C
per minute and a plateau at 300˚C for 5 min. This gave a run time of about
37 min per sample. Standard curves were prepared by injecting a mixture
of 16 PAHs (Fisher Scientific PAH standards) at 10, 20, 40, 80, and 120 ng/
l. The mixture contained naphthalene, acenaphthalene, acenaphthene, fluo-
rene, phenanthrene, anthracene, fluoranthene, pyrene, benz(a)anthracene,
chrysene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene,
indeno(1,2,3-c,d)pyrene, dibenz(a,h)anthracene, and benzo(g,h,i)perylene.
Standard curves were checked for linearity over the range listed above.
7.3.6 Pilot studies: experimental design
Two pilot-scale studies on land-farming bioremediation of PAHs were con-
ducted concurrently. These studies are compared in Table 7.12. One study
placed the contaminated soil in simulated land treatment units (LTUs). The
objective of the first 6 months of the LTU study was to simulate land farming
of PAH-contaminated soil with and without cultivation (phase 1). These
LTUs were exposed to the natural variety of climate conditions and required
extensive maintenance to adjust soil moisture to suggested optimal
land-farming conditions. The following 24-month LTU study eliminated
maintenance and decreased the cultivation frequency. Although this study
required 24 months, it was not personnel intensive. The advantage gained
was the extensive degradation database and the comparison of natural atten-
uation to minimal land-farming treatments. The second pilot-scale project,
the trough study, used the same highly contaminated POPILE site soil as the
LTUs. The troughs were operated in the open, under cover, where they were
exposed to changes in temperature but did not receive direct sunlight or
precipitation. The trough study was designed to study changes in PAH
degradation patterns between bioaugmentation and biostimulation. The two
pilot-scale projects allowed comparison between six field treatment varia-
tions using the same soil. Table 7.12 also describes the amendments used for
biostimulation and bioaugmentation.
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