Environmental Engineering Reference
In-Depth Information
Table 22.4
Degradability of some NSO-HET under different redox conditions
Electron acceptor
NO
3
-
SO
4
2-
Substance
O
2
Fe(III)
CO
2
Acridinone
?
?
?
?
?
Benzofuran
+
-
+
+
-
+
c
+
c
+
c
+
c
+
c
Benzothiophene
Carbazole
+
+
+
+
?
Quinoline
+
+
+
+
+
Quinolinone
+
+
+
+
+
Dibenzofuran
+
+
+/-
+
?
Dimethylbenzofuran
+
-
-
?
?
Dimethylquinoline
+
-
-
-
?
2-Hydroxybiphenyl
+
?
?
+
+
Isoquinoline
+
+
-
+
+
Isoquinolinone
+
-
+
+
+
Methylbenzofuran
+
+
-
?
?
Methylbenzothiophene
+
?
?
?
?
Methylquinoline
+
+/
−
+/
−
+/
−
+/
−
Methylquinolinone
+
−
+/
−
+/
−
?
Methyldibenzofuran
?
?
?
?
?
Methylisoquinoline
?
?
?
?
?
Phenanthridinon
?
?
?
?
?
Xanthenon
?
?
?
?
?
+ transformation proven; - transformation not proven; +/
transformation not always or
not for all isomers proven; ? no data available;
c
transformation only co-metabolic proven
−
microbial activities (Eschenbach et al.
1998
). In this case the PAHs are not
mineralized but transformed to polar metabolites. These products may form stable
bonding to natural organic matter such as humic substances. This so-called humi-
fication was first investigated for aerobic PAH degradation and was recently also
proven for anaerobic conditions using
14
C-labled PAH and NSO-HET contaminants
(Berghoff et al.
2007
).
The mobility of organic contaminants in the subsurface is influenced mainly
by sorption processes on natural organic matter. PAHs are hydrophobic substances
and, therefore, adsorb much stronger than e.g. monoaromatic contaminants. This is
indicated by the high octanol-water partition coefficient
k
ow
(see Table
22.2
). As a
consequence, the high molecular PAHs (e.g. Benzo[a]pyrene) are found only in the
source zone and usually not in the plume. Due to the fact that sorption is reversible
later mobilisation might be possible.
22.5.4 Summary
Tar oils are multi-component mixtures. Without total source removal the emission
of contaminants out of the NAPL phase will go on for a long time. The mobility
as well as the degradability of the constituents differs in a wide range (e.g. BTEX
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