ations of the wetland by dredging, draining, or cov-
previously been detected in the sediment. White
ering. However, some sediments may undergo WP
phosphorus was detectable in the water column
overlying contaminated sediment. In general the
decontamination naturally in areas that are sea-
WP concentration in water was over 1000 times
sonally subaerially exposed and where sufficient
less than the concentration in the sediment. Dis-
drying of the sediment occurs. The persistence
turbance of the underlying contaminated sedi-
and attenuation of millimeter-size white phos-
ment increased the concentration of WP in the
phorus particles was studied by laboratory and
water column.
field experiments.
AEHA collected water samples from 22 sites in
In laboratory experiments where WP particles
ponds, distributaries, and the Eagle River. White
were incubated under constant moisture contents
phosphorus was detected in the water column at
(degree of saturation = 0.45, 0.64, 0.82, 1, or >1)
and temperatures (4, 15, or 20C), WP particles
six sites where the sediments were also highly
contaminated. The WP concentration ranged
were persistent at moisture contents at or above
from 0.013 to 0.069 g/L in unfiltered samples
saturation. Laboratory-constructed WP particles
water. White phosphorus was not detectable in
incubated well below saturation (saturation level
water overlying uncontaminated sediments.
= 0.45 or 0.64) were lost rapidly (24 hours) at
20C, within 30 days at 15C, and persisted over
Walsh, M.E. (1994) White phosphorus in plants at
the time interval tested (approximately 60 days)
at 4C. For samples incubated slightly below sat-
Eagle River Flats. In Interagency expanded site
investigation: Evaluation of white phosphorus con-
uration (saturation level = 0.82), results were vari-
tamination and potential treatability at Eagle River
able, with significant loss in some samples and no
Flats, Alaska (C.H. Racine and D. Cate, Ed.).
change in other samples.
CRREL Contract Report to U.S. Army Garrison,
In field experiments on ERF, WP particles were
Alaska, Directorate of Public Works, FY93 Final
incubated at 5 cm depth in salt marsh sediments
Report, p. 263265.
at 10 monitoring sites ranging from permanently
Plant samples were collected from sites in Area
flooded ponds to intermittently flooded ponds to
C where WP was previously detected in the sedi-
unflooded mudflat and levee sites. WP particles
ment. Samples of Zannichellia palustris, Carex
were persistent in the permanently flooded area,
Lyngbyaei, Scripus paludosus, Hippurus tetraphylla,
but there was loss of WP in areas with unsaturat-
Potamogeton pectinatus, and Triglochin maritima
ed exposed sediments. Unsaturated conditions
were minced in isooctane and the extract ana-
were detected down to 30 cm at monitoring sites
lyzed by gas chromatography. WP was detectable
on the river levee and mudflat and two intermit-
in the roots of Carex Lyngbyaei (2.27 g/g) and
tent pond sites, indicating that loss of WP is possi-
Zannichellia palustris (0.16 g/g), both of which
ble at depth. However, at depth, loss is likely to
were growing at sites with WP sediment concen-
be slower owing to consolidation, lower tempera-
trations exceeding 2000 g/g. While it is unlikely
tures, and longer periods of saturation.
that plant materials (seeds and leaves) represent a
Resampling of an intermittent pond and WP-
major food chain pathway of exposure to WP for
contaminated sites, identified and sampled in
herbivores, the sorption of WP to organic plant
previous years, also showed loss of WP after the
detritus (dead plant pieces in the sediments) may
area was subaerially exposed in 1994.
provide a pathway to invertebrate detritivores.
Based on the above results, initial remediation
efforts involving active manipulation of the site
Walsh, M.E., and C.M. Collins (1995) Investiga-
should be restricted to contaminated permanent-
tions of natural size reduction of white phospho-
ly ponded areas. At intermittent pond sites where
rus particles in Eagle River Flats sediment. In
Interagency expanded site investigation: Evaluation of
be monitored for continued loss of WP.
white phosphorus contamination and potential treata-
bility at Eagle River Flats, Alaska (C.H. Racine and
Walsh, M.E., C.M. Collins, and R.N. Bailey
D. Cate, Ed.). CRREL Contract Report to U.S.
(1996) Enhancement of intrinsic remediation of
Army, Alaska, Directorate of Public Works, FY94
WP particles by sediment warming in intermit-
Final Report, p. 471528.
tent ponded areas of Eagle River Flats. In Inter-
Remediation of sediments at Eagle River Flats,
agency expanded site investigation: Evaluation of
a salt marsh contaminated with solid particles of
white phosphorus contamination and potential treata-
white phosphorus (WP), may require severe alter-
bility at Eagle River Flats, Alaska (C.H. Racine and
68
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