sites and mudflat sites were similar to those ob-
level then fluctuated over the remaining time
served in the laboratory for the samples incubated
monitored, with the lowest water depth (3 cm) re-
at degree of saturation of 0.82 at 15 or 20C. The
corded on August 18.
mass of P4 for at least one replicate was reduced by
Residual white phosphorus. On August 2223, five
samples were removed from each site to examine
several orders of magnitude. According to a
the physical appearance of P4 particles. When par-
KruskalWallis test (a nonparametric equivalent of
ticles were found, they appeared to be unchanged
one-way ANOVA), the length of time in which un-
(i.e. they were lustrous in appearance). In the in-
saturated conditions existed had a significant ef-
termittent ponded sites, significant surface crack-
fect on the residual mass of white phosphorus
ing of the drying sediment was observed. For all
found at each site (p = 0.0027) (Table 12). For those
samples that were located within or adjacent to
sites where unsaturated conditions were detected
cracks, the P4 particle was not found. In one sam-
(sites 210), the length of time sediments were un-
ple, a spherical void space with a diameter of 1.8
saturated and sediment temperatures were greater
than or equal to 20C at 5 cm deep also had a sig-
mm (the original diameter of the P4 particle) was
observed.
nificant effect but less so (p = 0.0234) (Table 12).
The mass of P4 in each of the five replicate sam-
ples remaining at each site on August 30 was nor-
Resampling of field-contaminated sites
malized to the initial mass and plotted vs. site (Fig.
Method
31). There was no change in the mass of P4 parti-
In August 1992 we examined the variability in
cles removed from the permanently flooded site
(site 1). The results for the intermittent ponded
site in the intermittent pond of Area C (Racine et
5.0
4.9
4.8
4.7
20
30
10
20
30
10
20
30
June
July
August
Figure 30. Average (24-hour) pond surface elevation at site 1.
1
10
10 0
1
10
2
10
10 3
4
10
5
10
6
Site 1
2
3
4
5
7
8
9
10
Figure 31. Residual P4 found in five replicate samples normalized to initial mass from each site.
Site 1 is permanently flooded, sites 25 are intermittently flooded, sites 68 are on the mudflat,
and sites 910 are on the river levee.
29
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