ments investigated demonstrate the extremes of the principal effects involved. The experimental work described here relates specifically to the Upper Chalk, which is an almost pure carbonate lithology; problems would arise is extrapolating results to other lithologies, especially those with a higher clay mineral content. Studies on different rock types are the subject of further research and a detailed treatment is beyond the scope of this paper; however, it is likely that more severe fractionations could occur as the clay mineral fraction increased. All three methods of pore water extraction-squeezing, elutriation, and centrifugation-apparently are subject to some form of fractionation. Effects induced by squeezing are reviewed by Rieke and Chilingarian ( 2 4 ) ,and the problems involved by elutriation are fully discussed by Devine et al. (8). From this survey of the centrifugation technique it is concluded that, although absolute accuracy for some elements may be as low as &lo%,precision can be very good as long as a consistent procedure is adopted. The centrifuge offers a convenient, flexible, and relatively rapid and direct method of interstitial water extraction in which contamination can be readily controlled. I t is stressed, however, that information about sample lithology, physical properties of the host rock, details of the centrifuge method used, together with the water yields should always be quoted along with chemical results, and where possible, control experiments carried out which can characterize any fractionation effects for the rock type being studied. Acknowledgments
(5) Sayles, F. L., Manheim, F. T., Geochim. Cosmochim. Acta, 39, 102-28 (1975). (6) Manger, G. E., Wertman, W. T., U.S. Geol. Suru. Prof. Pap. 575-C, 192-4 (1967). (7) Schmidt, G. W., Bull. A m . Assoc. Pet. Geol., 57, 321-37 (1972). (8) Devine, S. B., Ferrel, R. E., Billings, G. K. Chem. Geol., 12, 219-28 (1973). (9) . . W e n d . R. W.. Griffin. G. F., Proc. Soil. Sci. SOC.Am.. 35. 661-4 71971). (10) Hassler, G. L., Brunner, E., Trans. Am. Inst. Min. Metall. Eng., 160,114-23 (1945). (11) McCullough, J . J., Albaugh, F. W., Jones, P. M., API Drill Prod. Prac., 180-8 (1944). (12) Slobod, R. L., Chambers, A., Prehn, W. L., Trans. A m . Inst. Min. Metall. Eng., 192,127-34 (1951). (13) Marx, J. W., ibid., 207,88-91 (1956). (14) Johnson, A. I. Prill, R. C., Morris, D. A,, U.S. Geol. Suru. Water Supply Pap. 1662-A, 60 pp (1963). (15) Jones, B. F., Vanderburgh, A. S., Truesdell, A. M., Rettig, S. L., Chem. Geol., 4,253-62 (1969). (16) Sholkovitz, E., Geochim. Cosmochim. Acta., 37, 2043-73 (1973). (17) Richards, L. A. Weaver, L. R., J . Agri. Res., 69, 215-35 (1944). (18) Washburn, E. W.,Proc. N u t . Acad. Sci., 7,115-16 (1921). (19) Lovelock, P. E. R. “Aquifer properties of the Permo-Triassic sandstones of the United Kingdom”, Unpubl. PhD Thesis, Univ. of London, 1972. (20) Manheim, F. T., Bischoff, J. L., Chem. Geol., 4,63-82 (1969). (21) Presley, B. J., Kaplan, I. R., in “Initial reports of the Deep Sea Drilling Project, Vol. IV”, R. G. Bader, Ed., pp 415-30. US. Govt. Print. Off., Washington, D.C., 1970. (22) Lovelock. P . E. R.. Price. M.. Tate. T. K.. J . Inst. Water Eng., 29,157-74 (1975). (23) Bischoff, J. L.. Greer, R. E., Luistro, A. 0.. Science, 167, 1245-6 (1970). (24) Rieke, H. H., Chilingarian, G. V., “Compaction of argillaceous sediments”. “Develooments in Sedimentolow”., 16.. 424 .ww. _ Elsevier, Amsterdam, 1’974. (25) Kharaka. Y. K.. Berry. ” . F. A. F.. Geochim. Cosmochim. Acta., 37,2577-2603 (1973). (26) Giddings, D. R., “An experimental method for the determination of pH and the analysis of bicarbonate when a limited sample volume is available”, Unpub. Rep. Inst. Geol. Sci., WD/ST/ 74/19,1974. (27) Giddings, D. R., “A method for chloride analysis of waters when a limited sample volume is available”, ibid., WD/ST/74/2, 1974. (28) Perkin Elmer Corp., “Analytical methods for atomic absorption spectrophotometry”, 1973. (29) Fritz, J. S., Yamumura, S. S., Anal. Chem., 27, 1461-4 (1955). Ross, J. W., ibid., 40, 1169-71 (1968). (30) Frant, M. S., (31) Cawse, P. A,, Pierson, D. K., “An analytical study of trace elements in the atmospheric environment”, U.K. Atomic Energy Authority Rep. R7134,34 pp, H.M.S.O., London, 1972. (32) Edmunds, W. M., Giddings, D. R., Morgan-Jones, M., A t . Absorp. Neusl., 12,45-9 (1973). Y“
We thank M. Bird of the Hydrogeological Department for carrying out determinations of pore size distribution, and P. E. R. Lovelock for work on an earlier draft of this manuscript. This paper has been improved by discussions with several of our colleagues in particular M. Price and M. Morgan-Jones. This paper is published with the approval of the Director, Institute of Geological Sciences. Literature Cited (1) Edmunds, W. M., Lovelock, P. E. R., Gray, D. A,, J . Hydrol., 19, 21-31 (1973). (2) Manheim, F. T., U.S. Geol. Suru. Prof. Pap. 550-C, 256-61 (1966). (3) Presley, B. J., Brooks, R. R., Kappel, H. M., J . Marine Res., 25,3555 (1967). (4) Reeburgh, W. S., Limnol. Oceanogr., 12,163-5 (1967).
Receiced for reuielc: January 14, 1974. Accepted January 12,1976.
Correction Authors Paul Barton and Terdthai Vatanatham regret an omission in the presentation of Equation 10 (page 263) in their paper, “Kinetics of Limestone Neutralization of Acid Waters” [Enuiron. Sci. Technol., 10, 262-6 (197611. The equation should read:
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