EAGLE RIVER FLATS FY 00
48
first inserted into a plug of saturated sedi-
tures at 5-cm depth were 21.7 ,18.3, 21.1, and
18.6C for 1997, 1998, 1999, and 2000, respec-
ment, then the plug of sediment was placed
in a nylon stocking, which was placed within
tively. The maximum hourly average sedi-
ment temperature (24.4C) occurred on 24
the top 5 cm of saturated sediment at each
monitoring station. We recovered the plugs
June 2000 at 1800 hours.
from each station on 1721 August 2000 to
Data from our piezometer data station
determine if the total white phosphorus mass
show the relationship between groundwater
had decreased. We also recovered plugs that
elevation and tension in the surface sedi-
were planted in June 1999. To determine if the
m e n t s . When groundwater elevations
white phosphorus particles had changed, the
dropped to 50 cm below the sediment surface,
sediment samples containing particles were
tension rises above 5 cbars, the estimated air
placed into isooctane to extract white phos-
entry point (Hemond and Chen 1990) for sedi-
phorus residue prior to analysis by gas chro-
ment in this part of ERF (M.E. Walsh et al.
matography.
1995b). The groundwater elevation dropped
below the bottom of the piezometer well (1.04-
m depth) on 6 June (Fig. III-2-10) and did not
rise into the well again until 2 July following
RESULTS AND DISCUSSION
a flooding tide.
The results of monitoring are discussed by
We recovered the remains of white phos-
location within ERF. White phosphorus con-
phorus particles we planted in 1999 and 2000.
centrations for all composite and discrete
In each year we planted five 5.6-mg particles
samples are listed in Appendix Tables III-2-
for a total mass of 28 mg and we recovered a
A1 and III-2-A2.
total mass of 0.099 and 12.1 mg from the 1999
and 2000 particles, respectively, so removal by
Area C (Pond 183, 146, and 164)
sublimation/oxidation was 99.6% (for two
Sediment temperature and moisture con-
seasons) and 56% (for the 2000 season) (Table
ditions were monitored at four sites within
III-2-5).
Area C (Fig. III-2-3, Table III-2-4). Previous
In 1997 we collected composite samples
work has shown that to promote sublima-
from five grids in Area C and found the high-
tion/oxidation of white phosphorus particles,
est concentrations in the sample (C 100 m)
sediments must first be desaturated. Then
taken from the west side of Pond 183. In 1998,
sublimation/oxidation will occur, and the rate
1999, and 2000 we again collected replicate
at which it occurs increases exponentially
composite samples from this grid. White
with increased temperature. Moisture sensors
phosphorus is still detectable within this grid,
at the C 100 m and C piezometer sites (Fig.
but the concentration has declined from 0.07
g/g in June 1997 to 0.00055 g/g in August
III-2-8, III-2-9) showed that the sediments
desaturated (increased in resistance and ten-
2000 (Table III-2-6).
sion above baseline) around 27 May 2000 and
We installed a datalogger and resampled
remained unsaturated until a flooding tide on
Pond 146, adjacent to Canoe Point in Area C,
2 July 2000. For the rest of the summer, there
in an area that was dredged in 1996 but still
were brief periods where the sediments
had high white phosphorus concentrations in
started to desaturate, but frequent rain con-
1999 (Fig. III-2-4). Sediments started to dry at
s t a n t l y rewetted them, and the pond
the end of May 2000 but were wetted by a
reflooded in August. Sediment temperatures
flooding tide on 3 June (Fig. III-2-9). Sediments
were lower than those observed in 19971999
were unsaturated again by 10 June and re-
at the C 100 m station. During the time that
mained unsaturated until rain on 29 June, fol-
sediments were unsaturated, mean tempera-
lowed by the July flooding tides. During the
tures at 5-cm depth were 17.5, 15.8, 16.8, and
time that the sediments were unsaturated, the
14.6C for 1997, 1998, 1999, and 2000, respec-
average temperature was 14.9C. The maxi-
mum hourly temperature was 25.0C on 24
tively. Maximum 24-hour average tempera-
Previous Page
