Environmental Engineering Reference
In-Depth Information
Sediment
(Organic Carbon)
Microbial
Degradation
Slow
CO
2
Pore Water
Rapid
K
oc, rapid
Bioconcentration
Factor
Deposit-Feeder (Lipid)
Figure 2.3
The recalcitrant compound pore water pool is probably the most biolog-
ically available. Kraaij's (2002) conceptual model (modified above) equates recalci-
trant compound in pore water to the rapidly desorbing fraction of recalcitrant
compounds from sediment organic matter. Part of the pore water recalcitrant com-
pounds can be taken up into benthic macrofaunal lipid. However, neither Kraaij's
conceptual model nor most of those currently proposed take into consideration the
ability of sedimentary bacterial communities to mineralize recalcitrant compounds.
The factors that determine this partitioning of the pore water recalcitrant compounds'
pool between macrofaunal lipid and microbial mineralization are not well under-
stood.
aluminum smelter potlines. Aluminum smelter-derived PAH in sediments
from Sunndalsfjord, Norway (Naes and Oug, 1998 and Naes et al., 1999) were
present at lower levels (15 mg/kg) than Kitmat sediment but were likewise
not biologically available because they were associated with soot particles.
Song et al. (2002) showed that black carbon constituted between 18 and 41%
of the total organic carbon of soil and sediment samples collected from Guang-
zhou, China. The percentage of soot in any particular series of sediment sam-
ples can be highly variable due to variability in air and water currents, which
deposit them in aquatic systems, and sediment particle segregation, resuspen-
sion, redistribution, and transport by episodic water currents.
2.5 Effects of diagenesis and weathering on recalcitrant
compound geosorbents
In addition to the
sources of sediment organic matter (e.g., vascular plants,
algae), diagenesis and weathering affect sediment quality characteristics
that are correlated to rates of recalcitrant compounds' sorption and desorp-
tion (Luthy et al., 1997). Some diagenetically aged organic matter (e.g., coal
and shale) exhibits a high degree of condensation, is reduced in the relative
amount of oxygen-containing functional groups (reflected in H/O and O/
C atomic ratios), and contains more aromatic carbon rings (measure by
ultraviolet (UV) and infrared (IR) absorbance). This reduced organic matter
