Paull, C.K., Matsumoto, R., Wallace, P.J., and Dillon, W.P. (Eds.), 2000
Proceedings of the Ocean Drilling Program, Scientific Results, Vol. 164
41. DATA REPORT: EFFECTS OF DRYING METHODS AND TEMPERATURES ON WATER CONTENT
AND POROSITY OF SEDIMENT FROM THE BLAKE RIDGE1
W.J. Winters2
This study was primarily conducted to determine if a 105°C drying
temperature had overestimated the shipboard water content and porosity values of sediment from Holes 991A, 995A, and 996E during Leg
164. Water contents were determined at sea by drying metal beakers
filled with sediment in a convection oven at 105°C for 24 to 36 hr
(Paull, Matsumoto, Wallace, et al., 1996). Those data, in conjunction
with the measurement of mass and volume of the dried sediment, were
used to calculate downhole porosity (volume of voids/total sample
volume) profiles. The porosity values, in turn, were used in a number
of other studies. For example, they set boundaries on the amount of
gas hydrate that was present in Pressurized Coring System (PCS) samples (Dickens et al., Chap. 11, this volume). This re-examination of
shipboard porosity was undertaken after it was suggested by some investigators that a potential existed for a gross overestimation of water
content caused by the oven-drying process. The data presented here,
determined from samples dried at different temperatures, can also be
used in a comparison with more direct measurements of porosity by
other methods (e.g., mercury injection).
The effect of drying temperature on water content has been examined previously for a number of soils (Lambe, 1951), but not for modern deep-sea marine sediment. Brown and Ransom (1996) proposed
that drying smectite-containing sediment at a high temperature can
drive off interlayer water and thereby significantly overestimate water content and porosity. This is increasingly important for deeper
sub-bottom sediments where bound water can comprise a majority of
the sample’s moisture content.
METHODS
A 3-cm-thick, whole-round subsample was trimmed from each
10-cm whole-round section initially obtained at sea for consolidation
testing. The consolidation sample had been completely sealed in wax
and was stored at a temperature of ~4°C. The 3-cm subsample was
quartered and used for the following analyses: (1) air drying at 23°C,
and then oven drying in 10°C increments from 30° to 120°C; (2) oven
drying at 60°C for mineralogy and grain-size analyses; (3) freeze drying; and (4) microwave oven drying. This report focuses on the incrementally dried water content results because the technique used to
obtain them was the most similar to the shipboard procedure. Each
drying temperature increment lasted at least 24 hr.
Grain-size analyses, for estimating hydraulic equivalents, were
performed using methods presented in Poppe (1988a). The coarse
fraction was determined by use of a settling tube or sieves, and a
Coulter Counter measured the amount of fine fraction present.
Sample mineralogy was determined by X-ray diffraction (XRD)
methods (Poppe, 1988b). Unoriented aggregate mounts were used to
estimate the relative mineralogic composition using external stanPaull, C.K., Matsumoto, R., Wallace, P.J., and Dillon, W.P. (Eds.), 2000. Proc.
ODP, Sci. Results, 164: College Station, TX (Ocean Drilling Program).
2
U.S. Geological Survey, 384 Woods Hole Rd., Woods Hole, MA 02543, U.S.A.
[email protected]
1
dards, whereas oriented clay mineral mounts were created by a technique described by Pollastro (1982). Clay estimates were made using
Biscaye’s (1965) method.
RESULTS
Water content values obtained from incremental oven drying to
60°C compare favorably with those obtained from drying at a constant temperature of 60°C (Fig. 1). This suggests that incremental
drying produces results that are similar to those obtained from typical
constant temperature drying techniques. Approximately 80% of the
water content and porosity values calculated during this study are
similar to at-sea determined values (Figs. 2, 3) indicating that most
samples did not lose water during storage. The progressive increase
in drying temperature continually reduced the amount of water left in
the sample, thereby increasing the calculated water content and resultant porosity values. However, each increase in temperature produced a relatively small change in water content. The average poros90
80
70
Water content (%) oven dried at 60°C
INTRODUCTION
60
50
40
30
20
10
0
0.00
10.00
20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00
Water content (%) incrementally dried to 60°C
Figure 1. Water contents determined at a constant 60°C drying temperature
vs. incrementally dried samples.
431
DATA REPORT
A
B
0.00
0.00
WC (dry) (%) Ship
WC (dry) (%) 23°C
100.00
WC (dry) (%) 60°C
10.00
WC (dry) (%) Ship
WC (dry) (%) 120°C
WC (dry) (%) 23°C
200.00
WC (dry) (%) 60°C
WC (dry) (%) 120°C
20.00
Depth (mbsf)
300.00
400.00
30.00
500.00
40.00
600.00
50.00
700.00
800.00
60.00
0
20
40
60
80
Water content (dry) (%)
100
120
0
20
40
60
80
100
Water content (dry) (%)
120
140
160
995A
991A
C
0.00
10.00
WC (dry) (%) Ship
WC (dry) (%) 23°C
20.00
WC (dry) (%) 60°C
Depth (mbsf)
WC (dry) (%) 120°C
30.00
40.00
50.00
60.00
20
30
40
50
60
70
80
Water content (dry) (%)
996E
90
100
110
Figure 2. A. Water content vs. depth for Hole 991A. Shipboard drying was performed at a constant temperature of 105°C. Air drying was at 23°C, whereas other
drying temperatures were reached in 10°C increments. B. Water content vs. depth for Hole 995A. Shipboard drying was performed at a constant temperature of
105°C. Air drying was at 23°C, whereas other drying temperatures were reached in 10°C increments. C. Water content vs. depth for Hole 996E. Shipboard drying was performed at a constant temperature of 105°C. Air drying was at 23°C, whereas other drying temperatures were reached in 10°C increments.
432
DATA REPORT
A
B
0.00
0.00
Porosity (%) Ship
Porosity (%) Ship
Porosity (%) 23°C
Porosity (%) 23°C
100.00
Porosity (%) 60°C
Porosity (%) 60°C
10.00
Porosity (%) 120°C
Porosity (%) 120°C
200.00
20.00
Depth (mbsf)
300.00
400.00
30.00
500.00
40.00
600.00
50.00
700.00
800.00
60.00
50
55
60
65
Porosity (%)
991A
70
75
30
80
35
40
45
50
55
60
Porosity (%)
995A
65
70
75
80
C
0.00
10.00
Depth (mbsf)
20.00
30.00
Porosity (%) Ship
Porosity (%) 23°C
Porosity (%) 60°C
Porosity (%) 120°C
40.00
50.00
60.00
40
45
50
55
60
Porosity (%)
65
70
75
996E
Figure 3. A. Porosity vs. depth for Hole 991A. Results were obtained by air drying samples at 23°C or in 10°C increments. B. Porosity vs. depth for Hole 995A.
Results were obtained by air drying samples at 23°C or in 10°C increments. C. Porosity vs. depth for Hole 996E. Results were obtained by air drying samples at
23°C or in 10°C increments.
433
DATA REPORT
ity increase with temperature change from air drying at 23°C to oven
drying at 10°C increments to 120°C ranged from 0.95 to 3.31 points
(1.7% to 7.1%) (Table 1; Figs. 2, 3).
All sediment samples graded as clayey silt according to the shorebased technique (Table 1), whereas semiquantitative shipboard analysis typically described the sediment as nannofossil-rich silty clay or
predominantly clay sized. The relatively small amount of smectite
(8% to 17% of total sample mass; Table 1) occurring in only four of
the samples (Hole 995A) may explain why small changes in porosities were observed with large temperature changes. However, the
magnitude of porosity change is not directly related to the amount of
smectite present. The northern Barbados accretionary wedge sediments studied by Brown and Ransom (1996) possessed considerably
more smectite than the samples collected from the Blake Ridge on
this Ocean Drilling Program (ODP) leg.
SUMMARY
Oven drying of sediment samples at 105°C at sea during Leg 164
produced water content and porosity results that are comparable to
other methods of drying and do reflect actual in situ conditions in undisturbed cores despite the clay-rich composition of the sediment.
Therefore, the original shipboard index values are valid for use in gas
hydrate and other models. Because smectite was present in relatively
small amounts in Hole 995A sediment, and perhaps at other locations, the drying temperature had little effect on the calculation of porosity and other index properties. However, future ODP legs may
want to address the drying temperature issue during an early stage of
the cruise.
Valentine and Judy Commeau for providing helpful reviews. The author also wishes to thank the captain and crew of the JOIDES Resolution and to thank ODP for providing the sediment samples upon
which this study was based.
REFERENCES
Biscaye, P.E., 1965. Mineralogy and sedimentation of recent deep-sea clays
in the Atlantic Ocean and adjacent seas and oceans. Geol. Soc. Am. Bull.,
76:803–832.
Brown, K.M., and Ransom, B., 1996. Porosity corrections for smectite-rich
sediments: impact on studies of compaction, fluid generation, and tectonic history. Geology, 24:43–84.
Lambe, T.W., 1951. Soil Testing for Engineers: New York (Wiley).
Paull, C.K., Matsumoto, R., Wallace, P.J., et al., 1996. Proc. ODP, Init.
Repts., 164: College Station, TX (Ocean Drilling Program).
Pollastro, R.M., 1982. A recommended procedure for the preparation of oriented clay-mineral specimens for X-ray diffraction analysis: modification to Drever’s filter-membrane peel technique. Open-File Rep.—U.S.
Geol. Surv., 82–71.
Poppe, L., 1988a. Texture. In Booth, J.S. (Ed.), Sediment Monitoring at
Deep-Ocean Low-Level Radioactive Waste Disposal Sites: Methods
Manual. EPA Rep. 520/1-88-002:18–41.
————, 1988b. X-ray diffraction mineralogy. In Booth, J.S. (Ed.), Sediment Monitoring at Deep-Ocean Low-Level Radioactive Waste Disposal
Sites: Methods Manual. EPA Rep. 520/1-88-002:42–50.
ACKNOWLEDGMENTS
The author is grateful to Larry Poppe and Alex Robinson for performing the XRD and grain-size analyses, respectively; and to Page
Date of initial receipt: 15 April 1998
Date of acceptance: 25 September 1998
Ms 164SR-240
Table 1. Calculated water content and porosities of samples in this study at different incremental drying temperatures, grain sizes, and smectite quantity.
Sample
description
(cm)
434
Depth
(mbsf)
Water content,
dry 23°C
(%)
Water content,
dry 60°C
(%)
Water content,
dry 120°C
(%)
Porosity,
23°C
(%)
Porosity,
60°C
(%)
Porosity,
120°C
(%)
Sand
(%)
Silt
(%)
Clay
(%)
164-991A1H-4, 130
2H-4, 136
3H-4, 130
4H-4, 70
5H-4, 60
6H-5, 100
5.80
14.96
24.40
33.30
42.70
54.10
70.73
63.96
52.05
65.94
59.18
53.16
73.06
66.46
54.50
70.16
62.95
57.88
74.26
67.68
55.59
71.80
64.81
59.57
65.20
62.89
57.96
63.59
61.05
58.48
65.93
63.78
59.08
65.02
62.52
60.53
66.30
64.19
59.56
65.54
63.19
61.21
2.6
2.0
5.8
2.4
1.0
4.0
65.8
56.6
65.5
67.1
66.8
70.5
31.7
41.4
28.7
30.5
32.5
25.5
164-995A2H-1, 139
7H-1, 37
19H-2, 140
31X-1, 110
42X-2, 70
57X-2, 130
66X-4, 125
80X-1, 75
3.09
49.57
148.48
253.40
350.80
467.00
546.11
666.85
66.54
83.48
57.44
48.09
40.02
33.11
45.76
34.85
68.71
86.99
61.60
51.68
43.78
36.60
49.64
38.56
69.56
88.32
62.77
52.67
44.77
37.80
50.83
39.45
63.80
68.86
60.35
56.02
51.46
46.73
54.80
48.00
64.54
69.74
62.01
57.79
53.70
49.23
56.80
50.53
64.82
70.06
62.45
58.25
54.25
50.04
57.39
51.10
5.6
1.5
0.3
0.4
0.2
0.4
1.4
0.2
55.2
51.2
61.1
56.6
53.6
55.8
49.7
52.3
39.2
47.2
38.6
43.0
46.2
43.8
49.0
47.5
164-996E2H-1, 125
2H-5, 107
4H-6, 43
5H-6, 62
6X-5, 140
7H-7, 60
5.35
11.17
29.63
38.72
49.41
58.53
65.93
43.97
63.57
63.33
67.14
50.23
68.52
45.10
65.81
65.78
69.66
52.50
69.68
45.68
66.75
66.67
70.64
53.37
63.59
53.81
62.74
62.65
64.01
57.10
64.48
54.44
63.55
63.54
64.86
58.17
64.86
54.76
63.88
63.85
65.17
58.57
8.0
6.1
4.5
5.3
5.3
6.8
57.6
56.1
67.9
51.9
68.6
62.5
34.4
37.8
27.7
42.9
26.1
30.7
Smectite
(%)
8
8
10
17