Literature Cited Ahmend, S., Evans, H. J., Biochem. Biophys. Res. Cornmun. 1, 271 (1959). Bigeleisen, J., J. Chem. Phys. 17, 675-78 (1949). Bremner, J. M., “Methods of Soil Analysis,” Black, C. A., Evans, D. D., White, J. L., Ensminger, L. E., Clark, F. E., Eds., Agronomy No. 9, Part 2, Amer. SOC.Agron., Madison, Wis., 1965, pp. 1236-86. Burk, D., Lineweaver, H., Horner, K., J . Bacteriol. 27, 325-40 (1934). Chena. H. H.. Bremner. J. M.. Edwards. A. P.. Science 146. 1 5 G and 75’(1964). ’ Delwiche, C. C., Johnson, C. M., Reisenauer, H. M., Plant Phvsiol. 36. 73-78 (1961). Dole, M., Lane, G. A., Rudd, D. P., Zaukelies, D. A., Geochim. Cosmochim. Acta 6, 65-78 (1954). Gaebler, 0. H., Choitz, H. C., Vitti, T. G., Vukmirovich, R., Can. J. Biochem. Physiol. 41, 1089-97 (1962). Hoering, T. C., Science 122, 1233 and 34 (1955).
Hoering, T. C., Ford, H. T., J. Amer. Chem. SOC.82, 376-78 (1959). Junk, G. A., Svec, H. J., “Nitrogen Isotope Abundance Measurements,” U.S. Atomic Energy Commission, Office of Technical Information, ISC-1138, 1958. Nier, A. O., Phys. Rev. 77, 789 (1950). Reisenauer, H. M., Nature 186, 375 and 76 (1960). Scalan, R. S.. Ph.D. thesis, University of Arkansas,. Fayetteville; Ark., ‘1959. Smith. P. V.. Jr.. Hudson. B. E.. Science 113. 557 (1951). Spedding, F.’H.,’Powell, J: E., Svec, H. J., J. Amer. Chem: Soc. 77, 6125-32 (1955). Tong, J. Y . ,Yankwich, P. E., J . Phys. Chem. 61,540-43 (1957). White, W. C., Yagoda, H., Science 111, 307-9 (1950). Wellman, R. P., Cook, F. D., Krouse, H. R., Science 161, 269 and 70 (1968). Wlotzka, F., Geochim. Cosmochim. Acta 24, 106-54 (1561).
Received for review January 5 , 1970. Accepted June 15, 1970.
Characterization of Bottom Sediments: Cation Exchange Capacity and Exchangeable Cation Status Stephen J. Toth and Arthur N. Ott Department of Soils and Crops, College of Agriculture and Environmental Sciences, Rutgers University, New Brunswick N.J. 08903
rn Two parameters, cation exchange capacity (CEC) and exchangeable cation status (ECS), were used to characterize bottom sediments collected from rivers, bays, and freshwater impoundments. It was necessary to investigate the effect of drying on CEC and exchangeable Fe and M n to arrive at satisfactory modifications of soil techniques used for these parameters. Wide variations were obtained in CEC and ECS values for the sediments. CEC and ECS values may be utilized for determining saltwater intrusions and pollution effects.
T
wo parameters that have been used to characterize soils are the cation exchange capacity (CEC), and exchangeable cation status (ECS). The cation exchange capacity is the ability of an exchanger, expressed in terms of me. per 100 g., to retain a specific cation at a certain pH value and salt concentration. The exchangeable cation status, also expressed in terms of me. per 100 g., refers to the amount of Na, K , Ca, Mg, and H held by the soil complex. The CEC values are used for estimating the total storage capacity of soils for a specific cation, and the ECS values are used for estimating the fertility levels of soils (Jackson, 1958). Values for these parameters are obtained by a variety of techniques (Bower and Truog, 1940; Chapman and Kelley, 1930; Jackson, 1958; Kelley, 1948). The factors that influence the magnitude of the CEC include: clay content, type of clay mineral, and organic matter content (Jackson, 1958; Kelley, 1948). Other factors include the p H of the displacing solution, the nature of the displacing cation, and the soil-to-solution ratio (Kelley, 1948). The purposes of the present study were to determine what modifications of existing soil methods were required for determining CEC and ECS values of bottom sediments and to present data on sediments from some rivers, bays, and freshwater impoundments.
Methods Sample Preservation and Preparation. Bottom sediments collected either as core or grab samples require special handling to ensure minimal chemical changes. Grab samples must be transferred immediately to plastic bags and tightly sealed. Core samples will normally contain a water layer on the surface which must be retained by immediate sealing of the top and bottom of the core. Both types of samples must be frozen as quickly as possible after collection and stored. The frozen samples must be thawed rapidly prior to sample preparation. Some chemical changes occur on the outer surfaces of the samples, as indicated by an oxidized layer of Fe. This layer must be removed before the sample is mixed. Since stratification of both organic and inorganic materials commonly occurs, the sample must be mixed thoroughly until all signs of stratification disappear. If necessary, distilled water can be added until a thick paste forms. The paste should be passed through a stainless steel screen (opening 2 mm. in diameter) to remove coarse particles, wood, and shellfish fragments. Cation Exchange Capacity (CEC). Fifteen-gram samples of organic sediments or 25 g. of sandy sediments are rapidly weighed into a 250-ml. beaker, in duplicate, and immediately covered with 100 ml. of N neutral NH40Ac solution (Schollenberger and Simons, 1945). At this time, additional samples are prepared for moisture determinations. After standing for 30 min., the solution plus the sample is transferred to a funnel fitted with a 12.5-cm. Whatman no, 40 filter paper. The sample is leached with small amounts of NHaOAc solution until 500 ml. of leachate are collected or until the pH of the solution, after passing through the sediment, is pH 7.0. The leachate obtained is used for the determination of exchangeable Fe, Mn, Zn, Cu, and Ni. The sediment remaining in the funnel, after leaching with N H 4 0 A c solution, is now washed five times with 25-ml. portions of 80% ethyl alcohol to remove excess NH,OAc. These Volume 4, Number 11, November 1970 935
_ _ _ _ _ ~ ~ ~ ~~
~
Table I. Effect of Drying on CEC Values of Bottom Sediments
5.24 0.94 2.78 3.20 4.16
Inorganic residuZ (%) 13.7 4.2 7.1 6.6 11.5
25.0 20.8 36.5 39.0 9.0
1.56 5.50 10.56 8.74 7.50
15.2 21.7 17.3’ 17.9 6.2
30.6 40.0 27.8
29.0 35.0 25.2
7.10 7.68 7.36
8.8 10.0 10.2
100.0 85.5 97.1
85.8 72.3 80.4
80.6 62.8 60.8
12,85 22.07 23.83
16.4 23.3 25.8
47.3
37.5
31 . O
CEC (me./100 g.)”
Sediment source Hudson River
Sample A B C D E
Wet
...
Air-dried 22.6 5.4 16.7 19.3 24.5
Oven-dried 17.8 5.0 12.8 17.0 20.0
Delaware River
A B C D E
31.3 24.7 43.4 41.3 9.7
29.2 22.5 40.0 40.3 9.5
Chesapeake Bay
A B C
33.5 42.9 31.7
Barnegat Bay
A B C
Mean a
... ...
...
...
Organic matter
(%I
15.7c
Oven-dried basis (105” C.). H202 treatment. Mean only of samples on which CEC values were determined in the wet state.
washings, are discarded, and the sediment is leached with a 10% NaCl solution until 500 ml. of leachate are collected. The leachate contains the adsorbed NH, ions previously retained by the sediment. Standard procedures are now used to determine the N H 4 content of the leachate. The CEC values are reported in terms of me. per 100 g. of oven-dried sample. Exchangeable Cation Status (ECS). Duplicate 10-g. samples of wet sediment are weighed and treated as follows: Freshwater sediments are transferred to a funnel fitted with a 12.5-cm. Whatman no. 40 filter paper and leached with NH40Ac. Two successive 250-ml. samples of leachate are collected and labeled 1 and 2. Brackish and saltwater sediments are transferred to a funnel fitted with a 12.5-cm. Whatman no. 40 filter paper and leached with distilled water until free of chlorides. The washings are discarded, and the sample is leached with NHIOAc and two successive 250-ml. samples of the leachates are collected and labeled 1 and 2 (Jackson, 1958). The Na, K, Ca, and Mg contents of leachate 1 and the Ca and Mg contents of leachate 2 are estimated by atomic absorption techniques using standards prepared in N neutral NH~OAC. Exchangeable Na, K, and exchangeable Ca and Mg plus Ca and Mg soluble from solid phase C a C 0 3 and (or) CaC03. M g C 0 3 are contained in leachate 1. Exchangeable Ca and Mg are estimated by subtracting the Ca and Mg content of leachate 2 from the Ca and Mg contents of leachate 1. (This method assumes that the carbonates continue to dissolve at the same rate throughout the preparation of leachates 1 and 2.) Exchangeable Fe, Mn, Zn, Cu, and Ni are then determined. The N H 4 0 A c leachates collected from the sediments in the determination of CEC values are transferred to beakers, the flasks are rinsed with 10 ml. of 10% acetic acid, and the wash936 Environmental Science & Technology
ings are added to the beakers. The leachates are evaporated to dryness on a steam bath to remove NH40Ac. The residue in the beaker is digested with a mixture of 10 ml. of concentrated H N 0 3 and 3 ml. of concentrated HCIOl until dense fumes of HC10, are produced. The samples are cooled, diluted with hot water, and filtered. The volume of the filtrate is reduced by evaporation to less than 25 ml.; the sample is transferred to a 25-ml. flask and made to volume. The Fe, Mn, Zn, Cu, and Ni contents are estimated by atomic absorption techniques and expressed as me. per 100 g. of oven-dried sample. The organic matter contents reported for the sediments represent the easily oxidizable fraction (Walkley and Black, 1934). Sediments containing high concentrations of C1 must be leached with distilled water and dried prior to estimating the organic matter content by this procedure. The CEC values of the inorganic fraction of the sediments were obtained by removing the organic fraction with H202 (Jackson, 1958) and then using the N H 4 0 A c method. The pH values of the sediments were determined on 1:5 sediment to distilled water ratios employing a glass electrode Beckman pH meter. Results and Discussion Bottom sediments are not simply a wet sample of soil since the conditions under which they are formed are different. Bottom sediments are normally subjected to reducing conditions except at the zone of contact with the aqueous phase whereas soils are usually formed under aerobic conditions. Further, sediments contain higher amounts of organic matter than soils and are also not subject to the leaching processes as are soils. Because of these differences, sediment samples require different methods of handling to obtain a representative subsample. Effect of Drying on CEC Values. Because of the differences
between sediments and soils, the effects of sample preparation and treatment on CEC values were investigated. The simplest procedure would be to air or oven-dry the samples before analysis. Indications that drying tends to alter the CEC had been obtained in earlier studies (McCrone, 1966). To determine the magnitude of this effect, three moisture levels were established in a series of samples. These were: wet samples after thawing, wet samples that were air-dried, and wet samples that were oven-dried at 105" C. to constant weight. The CEC values of these samples are reported in Table I. The data in Table I indicate that drying markedly reduces CEC values. These losses were expected, however, since during drying and subsequent rewetting with N H 4 0 A c solution, the organic matter exhibits a hysteresis effect (Mattson, 1936). Apparently, some exchange sites become unavailable for NH4 ion retention. The magnitude of this effect cannot be predicted, however, since reduction in CEC depends upon the nature of the organic matter. If plant or animal residues are not decomposed, the reduction in CEC will be small (Muller, 1932). On the other hand, well decomposed organic matter will exhibit large reductions in CEC. Another factor responsible for reductions in CEC values during the drying process is the presence of relatively high amounts of ferrous and manganous ions. These cations are rapidly oxidized in air to ferric and manganic ions and tend to precipitate as insoluble oxides, thereby blocking exchange sites. The magnitude of this effect is difficult to determine (Desilva, 1964). The loss in CEC values during drying is not directly related to the organic matter content of the sediments (Table I). This is indicated by a decrease of only 0.7 me. by oven-drying Sample E containing 7.50% organic matter, whereas Sample C with an organic matter content of 7 . 3 6 z lost 6.5 me. of CEC during the drying process. The mean loss in CEC values by air-drying was 9.8 me., and by oven-drying, 16.3 me. per 100 g. The data in Table I also emphasize the role of organic matter in the total CEC values. The mean CEC value of all samples examined in the wet state was 57.3 me., and that of the inorganic residues after the removal of organic matter was 15.7 me. per 100 g. This corresponds to a loss of 41.6 me. per 100 g., or represents a loss of 79 of the total CEC value. Effect of Drying on Exchangeable Iron and Manganese Contents. Relatively large amounts of ferrous and manganous ions are found in the N H 4 0 A c leachates collected from the C E C procedure. The presence of ferrous iron is indicated by the blue color reaction with K3Fe(CN)6and by the formation of Fe(OH)3 in the leachate upon exposure t o air. To determine the effect of drying on exchangeable F e and M n contents of sediments, a series of wet and oven-dried samples were leached with N H 4 0 A c solution, and the Fe and M n contents of the leachates were estimated. These data are presented in Table 11. The data indicate that drying the bottom sediments reduces exchangeable F e and Mn contents from very high to almost trace levels. Because of the behavior of F e and M n in sediments during the drying process, accurate measurement of these metals can only be made on either freshly collected or fresh frozen and thawed samples. Some oxidation of Fe occurs on the outer surface of the frozen samples, and it is suggested that about ' / 4 in. of the outer layer of these samples be removed prior to mixing the samples. Cation Exchange Capacity and Exchangeable Cation Status of Some Bottom Sediments. During the past five years, several thousand bottom sediments collected from the Hudson and Delaware Rivers, Chesapeake and Barnegat Bays, and from freshwater impoundments of New Jersey and Pennsyl-
vania have been examined for CEC and ECS values. Typical data are presented in Table 111.Omission of some values in the table is due to modification of the techniques and sample preparation methods over the development period. Examination of data in Table I11 indicates that CEC values of bottom sediments from rivers and bays are considerably higher than those of soils, which range from 1 to 15 me. per 100 g. in New Jersey. The highest CEC values recorded in Table I11 are from samples collected from deep holes in Barnegat Bay which contained very high amounts of organic matter. The CEC values of sediments collected from freshwater impoundments vary more than those collected from rivers or bays. This is probably related to the age of the impoundment and the degree of organic matter accumulation. The ECS values, especially exchangeable Na, K, Ca, and Mg, reflect the influence of waters with which the sediments are in contact, plus the presence of shellfish fragments. Brackish water sediments, such as those from the lower reaches of the Hudson and Delaware Rivers, are relatively low in Na, even though the sediments are subjected to saltwater intrusions. The explanation for the low Na values appears related to the ease of displacement of the Na ions by divalent Ca and (or) Mg ions, which exist either in the exchange complex or are present in saltwater. In sediments collected from saltwater, however, the concentrations of Na ions are suficiently high to replace Ca and Mg so that the exchange complex becomes almost completely saturated with Na ions. This behavior is demonstrated by the data presented for the Chesapeake Bay samples. A relatively high exchangeable Na value might be expected for samples collected from Barnegat Bay since it is subjected to tidal action. However, in the areas sampled, exchangeable Na is present in the exchange complex in only moderate amounts. This may be due to the influence of freshwaters which reach the areas sampled. The exchangeable Na content of freshwater sediments are low in comparison to brackish and saltwater sediments. The exchangeable K values of brackish and saltwater sediments are high when compared to that of soils which usually contain from 0.1 to 0.5 me. per 100 g. Freshwater sediments,
z
Table 11. Effect of Drying Bottom Sediments on Exchangeable Fe and Mn Contents. (me./100 g., oven-dried) Wet sample Oven-dried ____ _____ Fe Mn Fe Mn Sediment source Delaware River A 1 . 4 0 0 . 6 0 0.01 0 . 2 0 B 9.42 0 . 3 0 0.05 0.20 C 6.40 0.50 0.02 0.05 Chesapeake Bay
A B C
0.60 1.16 0.17
0.51 0.60 0.62
0.07 0.15 0.01
0.06 0.06 0.02
Barnegat Bay
A B C
12.47 11.59 2.97
0.16 0.10 0.10
0.13 0.15 0.20
0.01 0.00 0.01
New Jersey ponds
A B C D E
2.8 6.9 1.6 5.5 6.1
0.90 2.00 3.60 5.10 1.60
0.12 0.08 0.02 0.04 0.11
0.40 0.40 0.43 0.41 0.31
a
Calculated as divalent ions.
Volume 4, Number 11, November 1970 937
Table Ill. CEC and ECS Values of Some Bottom Sediments (me./100 g.)
Sediment source Sample Hudson River A B C D E F
CEC 24.7 34.0 34.0 25.8 25.8 31.8
Fe 1.0 0.3 0.6 0.4 0.3 0.4
Mn 1.3 1.7 1.0 1.2 1.6 1.9
Exchangeable cations Na K Ca Mg 2.4 0.4 3.9 2.4 3.7 0.6 9.1 5.9 5 . 3 0 . 6 6.4 5.0 3 . 0 0 . 5 6.2 4.1 2.1 0.3 7.5 3.5 2.0 0.3 6.4 2.7
Ha
Hb
H"
Hb
PH
15.6 14.7 17.3 11.9 12.4 20.4
13.3 12.7 12.7 10.7 10.5 18.1
63.1 43.2 50.6 46.1 48.0 64.1
53.8 37.3 37.3 41.4 40.6 56.9
N.D: N.D. N.D. N.D. N.D. N.D.
Delaware River
A B C D E F
31.3 24.7 43.4 20.8 33.8 24.5
1.4 9.4 2.9 8.1 4.2 8.0
0.6 0.3 0.2 0.5 0.2 0.5
1.50.7 0.55.4 0.9 0.6 0.30.3 0.20.4 0.20.5
5.0 5.4 4.7 4.5 3.8 5.1
6.3 3.5 4.7 2.1 2.0 2.7
17.8 15.0 32.5 13.6 26.9 15.8
15.8 5.3 29.4 0.0 22.5 7.3
56.8 60.5 74.9 65.3 79.5 64.5
50.4 21.4 70.0 0.0 66.5 29.8
7.1 6.3 6.5 6.4 6.4 6.5
Freshwater impoundmentsNew Jersey
A B C D E
30.4 36.0 7.1 8.1 6.8
0.7 1.2 0.4 1.7 0.6
0.3 1.0 0.2 0.7 0.5
0.40.5 0.4 0.5 0.30.2 0.20.1 0.20.1
4.4 3.4 1.0 1.6 3.9
6.6 6.5 0.8 1.1 0.5
18.5 25.2 4.8 5.1 2.1
12.9 23.0 4.2 2.7 1.0
60.8 70.0 67.6 63.0 30.8
42.4 63.9 60.0 33.3 14.7
6.0 6.5 5.6
Freshwater impoundmentsPennsylvania
A B C D E
21.5 43.0 46.2 28.4 33.0
12.2 5.0 5.5 4.0 15.8
9.7 2.7 5.1 7.1 2.5
0.1 0.4 0.4 0.6 0.2
0.3 0.3 0.3 0.4 0.3
4.1 7.3 4.0 4.3 5.3
1.1 1.0 1.5 1.3 2.8
15.9 34.0 40.0 21.8 25.4
0.0 26.3 29.4 10.7 6.1
73.8 80.0 86.5 76.7 73.9
0.0 61.1 63.6 37.6 18.4
5.2 5.4 5.8 5.8 4.3
Chesapeake Bay
A B C D E
42.0 35.9 40.6 42.9 33.5
N.D. N.D. N.D. N.D. N.D.
0.7 0.5 0.9 0.6 0.8
0.9 0.8 0.7 0.8 0.8
1.3 1.2 1.7 1.3 1.8
5.5
1.4 2.9 6.8 2.9 3.7
...
...
3.3 8.3 17.7 6.9 26.5
, . .
5.0 5.0 5.0 5.2
... ...
7.4 7.2 7.5 7.3 7.4
A B C
100.0 85.5 97.1
12.4 11.6 3.0
0.2 0.1 0.1
56.2 24.6 48.5
69.8 40.0 53.0
56.2 30.0 50.3
6.0 6.4 6.0
Barnegat Bay
CEC = (Na
+ K + Ca + Mg). * CEC = (Fe +
32.9 26.0 26.4 32.9 zl.0
7 . 6 2 . 7 5 . 6 1 5 . 3 69.8 1 0 . 8 2 . 7 10.7 25.0 36.3 1 3 . 0 2 . 7 10.7 1 9 . 1 51.6 Mn + Na 4-K + Ca + Mg). Not determined.
however, seem to contain about the same amount of exchangeable K as do soils. The exchangeable Ca contents of brackish water sediments are extremely variable and seem to be related to the amounts of shellfish fragments present in the sample. Exchangeable Ca contents of saltwater sediments were low even when shellfish fragments were present in the samples. This probably is due to the high N a content of seawater which results in Ca release from the exchange complex by N a ions. The exchangeable Ca contents of freshwater sediments are, however, related to the nature of the soils comprising the bottoms. The exchangeable Mg values are also extremely variable in bottom sediments. In brackish water sediments, the exchangeable Mg values are generally lower than those of Ca, whereas in saltwater sediments the reverse is true. This is especially true of sediments collected in Chesapeake Bay, and also in samples from Barnegat Bay, even though the latter samples are not completely saline, The high exchangeable Mg present in these samples may be related to the Mg content of seawater. Freshwater sediments contain exchangeable Mg in amounts which seem to be related to the soils in the watershed area. 938 Environmental Science & Technology
Unsaturation
... , . . , . .
... ...
5.5
6.9
The ferrous and manganous ions present in sediments must be considered as exchangeable since they are displaced during the leaching cycle with NH40Ac. The data presented in Table 111 are incomplete with respect to the distribution of these ions in the various types of sediments. This is because exchangeable Fe was not determined in the Chesapeake Bay samples. However, the data indicate that both Fe and Mn occur in relatively high amounts in the exchangeable form in some sediments. The Fe values listed in Table 111 range from 0.3 to 15.8 me., and the Mn values from 0.1 to 8.7 me. per 100 g. The exchangeable H ion values presented in Table I11 were estimated by summing the values of the exchangeable cations and subtracting the total from the CEC value (Jackson, 1958). An error may be introduced if the determinations of exchangeable Ca and Mg are incorrect. However, the direct determination of H ions in the NH40Ac leachate collected from the CEC method is impossible. This is because the leachate contains large amounts of dispersed organic matter plus ferrous and manganous ions. It is for this reason that the difference method for obtaining exchangeable H values has been used. The unsaturation values of the sediments have been
Table IV. Exchangeable Zn, Cu, and Ni Contents of Some Bottom Sedimentse (me./lOO g.) Sediment source
Sample
Zn
Organic matter
cu
Ni
(%I
F
0.025 0.021 0,083 0.090 0.112 0.381
0.010 0,010 0.010 0.010 0.020 0.030
0.003 0,001 0.001 0.007 0,010 0.230
1.56 4.63 10.56 7.02 11.26 11.28
Barnegat Bay
A B C
0.001 0.000 0.000
0.012 0.018 0.009
0.006 0.018 0.012
12.80 22,oo 23.75
Freshwater impoundmentsPennsylvania
A B C D E F
0.012 0.012 0.008 0.013 0.012 0,009
0.012 0.015 0.010 0.011 0.013 0.010
N.D.b N.D. N.D. N.D. N.D. N.D.
7.38 6.36 1.65 6.36 4.41 2.25
Delaware River
A B C D
E
Calculated as divalent ions. * Not determined.
calculated in two ways to show the effect of exchangeable Fe and Mn on this parameter. Without considering these two ions, the unsaturation values appear to be too high; but by including them, the values appear to be correct. The data in Table 111 also indicate that the exchangeable H ion contents of sediments are high and do not seem to be related to pH values. Exchangeable Cu, Zn, and Ni Contents of Bottom Sediments. During the analysis of N H 4 0 A c leachates collected during the CEC estimation, the Cu, Zn, and Ni contents were also determined. The values found were relatively high when compared with values from soils. Therefore, the Cu, Zn, and Ni contents were determined on a series of bottom sediments to note the variations in the concentrations of these metals. These data are presented in Table IV. The exchangeable Zn contents found ranged from 0.00 me. in the Barnegat Bay sediments to 0.38me. in a sample obtained from the Delaware River. The ranges of exchangeable Cu noted in the samples were from 0.01to 0.03me., and with Ni the ranges were from 0.001 to 0.23 me. per 100 g. Samples that contained large amounts of organic matter, or exchangeable H ions, contained large amounts of these metals in the exchangeable form. The order of abundance of these metals in bottom sediments was Zn > C u > Ni. This order is identical to the occurrence of the metals in surface waters of New Jersey (Toth, 1968).
Summary Studies were conducted to determine if soil methods used for CEC and ECS could be applied to bottom sediments, The most important findings were: The CEC and ECS values of bottom sediments need to be determined on fresh or frozen and thawed samples since drying reduces CEC and exchangeable Fe and Mn contents. Exchangeable H ions cannot be determined in NHIOAc extracts of bottom sediments due to the presence of large amounts of dispersed organic matter and exchangeable Fe and Mn. The best method for determining exchangeable H in bottom
sediments appears to be the summation method. Extremely wide variations are found in CEC and ECS values of bottom sediments. The organic matter content of bottom sediments is responsible for about 80 of the CEC. CEC and ECS values may be utilized in determining saltwater intrusions and pollution effects.
x
Literature Cited Bower, C. A., Truog, E., Ind. Eng. Chem., A n d . Ed. 12, 411-
413 (1940). Chapman, H. D., Kelley, W. P., Soil Sci. 30, 291-306 (1930). DeSilva, J., Toth, S. J.. SoilSci. 97, 63-73 (1964). Jackson, M. L.,“Soil Chemical Analysis,” Prentice-Hall, Englewood, N. J., 1958. Kelley, W. P., “Cation Exchange in Soils,” Reinhold Co., New York, 1948. Mattson, S., Soil Sci. 31, 57-79, (1936). McCrone, A. W., Geog. Rea. 56, 175-189, (1966). Muller, J. F., Soil Sci. 35, 229-237, (1932). Schollenberger, C. J., Simons, R. H., Soil Sci. 59, 13-24,
(1 945). Toth, S. J., J . Amer. Water Works Ass. 60,455-459, (1968). Walkley, A., Black, I. A.,Sail Sci. 37,29-38,(1934).
Receiced for reciew May 5, 1969. Accepted June 30, 1970.
CORRECTION
ACCUMULATIONS O F LEAD I N SOILS FOR REGIONS O F HIGH A N D LOW MOTOR VEHICLE TRAFFIC DENSITY In this article by A. L. Page and T. J. Ganje [ENVIRON.SCI. TECHNOL. 4, 140 (1970)], the following corrections should be noted in the Literature Cited section: Add: Mitchell, R . L., Reith, J. W. S., J . Sci. Food Agr.
17,437-40(1966). Swain, D . J., Mitchell, R. L., J . Soil Sci. 11, 34768 (1960). Change: Tsaihwa, J. C., to read Chow, Tsaihwa J.
Delete:
Volume 4, Number 11, November 1970 939
