Table 12. Results of KruskalWallis test to determine if a) the
length of time sediments were unsaturated at 5 cm deep or b) the
length of time unsaturated and temperature greater than or
equal to 20C had an effect on residual WP found at each site.
Number of days
Number of days
unsaturated and
T > 20C
unsaturated
Site
Mean rank
Site
Mean rank
0
1
44.8
0
10
21.5
16
2
35.8
39
9
1
28
3
28.6
44
2
6
34
4
20
88
3
34.2
40
5
26.4
150
4
27.8
42
6
21.5
169
5
20
48
7
32.4
209
8
26.4
63
8
24.4
217
7
23.6
87
9
6
258
6
32.4
89
10
15.1
H = 25.2; p = 0.0027.
H = 17.7; p = 0.0234.
limit) were found in the intermittent ponded
al. 1993). Samples were taken at 1-m intervals out
area. This pattern of contamination indicates that
to 5 m along eight axes around the center point
white phosphorus may be persistent only in the
(Site 883) (Fig. 16). P4 particles were isolated and
permanently flooded areas. However, one site in
measured from the sample collected at the center
the intermittent pond of Area C (Site 883) was
point (Racine et al. 1993). During 1993, Anchor-
found in 1992 to have very high concentrations of
age experienced an unusually warm and dry
white phosphorus (>200 g/g) (Fig. 16). From
summer, and this area was above the water level
tide table data for 1990 to 1994 (Fig. 32) and the
through June and July 1993. We revisited this site
assumption that the flats flooded every time the
on August 19,1994, and repeated the close-inter-
predicted high tide for Anchorage was greater
val sampling to determine if the pattern and level
than 31 ft, this site was mostly likely exposed to
of contamination had changed.
air each summer except for 1991 when the flats
In addition, samples were collected from the
flooded each month. The longest period of expo-
crater (Miller's Hole) (Fig. 16) produced by the
sure was in 1993, when Anchorage also experi-
detonation of an 81-mm P4 smoke round in May
enced an unusually warm, dry summer. Given
1992. Samples were taken from the rim and cen-
an elevation of 4.77 m and the drying data ob-
ter of the crater. Details of the procedures used to
tained along the transect described above, the
collect the samples are given in Appendix B.
moisture content of the surface sediments proba-
Results
bly decreased below saturation during the sum-
Sampling for white phosphorus contamina-
mer of 1993. The water depth was approximately
tion by various agencies continued at Eagle River
8 cm when the site was sampled in August 1992,
Flats in 1994 (Racine and Cate 1995). Any white
and the site was subaerially exposed when sam-
phosphorus detected by these field sampling ef-
pled in August 1994 (Fig. 33).
forts has persisted in ERF since at least February
When sampled in 1992 and 1994, sediment
1990, when training with white phosphorus mu-
was taken at 1-m intervals in a radial pattern
nitions was suspended at Eagle River Flats.
(Fig. 34). Samples taken in 1994 showed that the
White phosphorus continues to be detected at
moisture content ranged from 40 to 46% on a dry
high concentrations in the permanent ponds of
weight basis. The patterns of contamination for
Area C. In contrast, intermittent ponded areas
August 1992 and August 1994 (Fig. 34) show that
and mudflats tend to have low concentrations or
there is a reduction in the number of samples in
undetectable levels of white phosphorus. For ex-
the highest-concentration group (>10 g/g),
ample, the transect described above passed
from four to one (Fig. 35). There is also an in-
through a heavily cratered area (1025% crater
crease in the number of samples in the lowest-
cover), yet no white phosphorus was detected in
concentration group (<0.001 g/g), from 15 to 25.
the mudflat and river levee samples, and trace
The results were compared using a sign test for
amounts (near or below the certified reporting
paired observations. If the differences between
30
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