15 m
-
v
HOC1 Predominates
any assumptions about activity coefficients or liquid junction potentials as would be necessary if the thermodynamic ionization constant were used. Our results should prove useful in interpreting biotoxicity data obtained in estuarine waters and in modeling the kinetics of chlorine degradation in estuarine and marine waters.
Predominates
h
.-c
. I -
._
b -
IO
Acknowledgment We are indebted to Frank Herr for advice and assistance during this work.
-
6
Literature Cited 5 =in
-Typical pH Values -
J
Surface Waters
0
I
1 0
PH Figure 2. Fields of predominance of HOC1 and 0CI;based on Equa-
tion 9 Hatched area represents field of typical estuarine pH values
result suggests that some ion pairing is occurring between OC1- and cations in seawater. For comparison, the recent work of Pytkowicz and Hawley (19) indicates that a = 0.81 for HCO, and = 0.51 for F - in seawater. Ion pairing probably affects the diffusivity of OC1- and consequently its toxicity to organisms, but the degree of association is so small that if this effect is observable, it will appear only a t chlorinities approaching that of seawater.
Summary At constant temperature, the apparent ionization constant of hypochlorous acid decreases with increasing chlorinity, the amount of this shift being large enough to suggest that the hypochlorite ion is partly associated with cations in seawater. In most normal marine and estuarine waters the OC1- ion will predominate over HOCl and over OC1- ion pairs. Our data permit the relative concentrations of HOCl and OC1; to be calculated in marine waters in terms of the readily measurable parameters pH, T , and chlorinity. In such calculations it ii: unnecessary to make
(1) Brungs, W. A., J . Water Pollut. Control Fed., 45, 2180-93 (1973). (2) Zillich, J. A., ibid., 44,212-20 (1972). (3) Fair, G. M., Morris, J. C., Chang, S. L., Weil, I., Burdeu, R. P., Air Water Works Assoc. J., 40,1051-61 (1948). (4) Morris, J. C., in “Principles and Applications of Water Chemistry”, S. D. Faust and J. V. Hunter, Eds., pp 23-53, Wiley Rr Sons, 1967. (5) Farkas, L., Lewin, M., Block R., J . Am. Chem. SOC.,71, 198891 (1949). (6) Hawley, J. E., Pytkowicz, R. M., Marine Chem., 1, 245-50 (1973). (7) Klotz, I. M., “Chemical Thermodynamics”, 2d ed., p 427, W. A. Benjamin, 1964. (8) Bates, R. G., “Determination of pH”, Wiley & Sons, 1973. (9) Robinson. R. A,. Stokes. R. H.. “Electrolvte Solutions”. Butterworths, 1968. (10) Mason. C. M.. Culvern. J. B.. J . Am. Chem. SOC.. 71. 2387-92 ( 1949). (11) Prideaux, E. B. R., J . Chem. SOC., 1944, DD 606-11. (12) Finkelstein, N. P., Verdier, E. T., Tra& Faraday SOC., 53, 1618-25 (1957). (13) Kester, D. R., Pytkowicz, R. M., Limnol. Oceanogr., 14, 68892 (1969). (14) Edmond. J. M.. Gieskes, J. M. T. M., Geochim. Cosmochim. Acta 34,1261-91 (1970). (15) Goldhaber, M. B., Kaplan, I. R., Marine Chem., 3, 83-104 (1975). (16) Robinson, R. A,, Wood, R. H., J . Solution Chem., 1, 481-88 (1972). (17) de Valera, V., Trans. Faraday SOC., 49, 1338-51 (1953). (18) Morris, J. C., J . Phys. Chem., 70,3798-3805 (1966). (19) Pytkowicz, R. M., Hawley,. E., Limnol. Oceanogr., 19,223-33 (1974).
Received for review J u n e 24, 1975. Accepted December 22, 1975. National Science Foundation Grant GA-40118 and the Uniuersity of Maryland Computer Center supported this work.
NOTES
Some Relationships Between Exchangeable Copper and Lead and Particulate Matter in a Sample of Hudson River Water E. J. Catanzaro Lamont-Doherty Geological Observatory of Columbia University, Palisades, N.Y. 10964 In any natural water system, copper and lead occur in solution, on the surface of particles, and inside particles. Most analyses of trace metals in natural waters are concerned with quantities in solution (i.e., 2 p in size. The measured metal contents of the
unfiltered aliquots increased with time; with the copper apparently reaching equilibrium after about 20 days, and the lead never reaching equilibrium during the 30-day time period of the tests. The lead results for the unfiltered aliquots are much more variable than the copper results, suggesting the presence of relatively large (>8 p ) lead-rich particles in the water, possibly originating from atmospheric fallout of aerosols derived from auto exhausts of leaded gasolines.
tained 1 ml (500-ml bottles) or 2 ml (1-1. bottles) of ultraand 4 pg of an enriched 206Pbspike and 20 pg pure "03 of an enriched 65Cu spike. Five aliquots were unfiltered, and duplicate aliquots were filtered through Whatman No. 41 (20-25 p ) , No. 40 ( 8 p ) , and No. 42 (2 p ) filter paper. The pH of the original sample was -6.5; that of the acidified aliquots was -1.5.
(1 1.) was acidified with 2 ml of HN03 and spiked with 10 pg of 65Cu; no *06Pb spike was added because this aliquot was used to determine the isotopic composition of the lead in the sample. The aliquot was analyzed 12 days after spiking. The result (7.75 ppb) agrees well with those of the last two unfiltered aliquots (7.63 and 7.73 ppb). For aliquots analyzed after 20 days, duplicate analyses show good precision. Statistical analysis of these and some previous duplicate analyses (2) yield a standard deviation (a) of 1.8% per analysis and a 95% confidence limit ( t u ) of 4.3% for a single analysis (based on seven degrees of freedom).
Analytical Technique The analytical technique has been previously described ( I , 2). In brief, an electrolytic cell is formed by suspending two 50-mil platinum wires in the sample and impressing a 1.9-V potential across the wires. Metallic copper plates out on the cathode and PbOz on the anode. The cell is run overnight at a current of -20 mA. The copper is stripped from the cathode by dipping it in l/2 ml of a 50% H N 0 3 solution, and the PbOz is stripped from the anode by dipping it in 1hml of a 99:l 2% HN03:35% H202 solution. The entire chemical procedure was performed in a positively pressurized, filtered air, double-doored clean lab. All reagents were ultrapurified and only FEP Teflon containers were used (except for the 6Y2-galpolyethylene collecting bottle). Total procedure blanks were on the order of 0.02 and 0.01 pg for copper and lead, respectively. Isotopic ratios were measured on a single-focusing, 12-in. radius of curvature mass spectrometer with expanded-scale recorder. Copper analyses were made on a single-filament platinum ribbon source at a temperature of -1100 "C; lead analyses were made on a single-filament rhenium ribbon source at a temperature of -1300 "C. Results The analytical results are listed in Table I. For copper, the average values for each group of aliquots are (ppb):
61
1
0
10
1
20
I
30
Number of days between spiking and electroplating
Figure 1. Variations of measured copper and lead with time (unfil-
Unfiltered = 7.26 (7.69, see text) < 2 5 p = 3.88 30 p in size are not uncommon close to highways ( 4 ) . In summary, it is rather difficult to propose concrete conclusions on the basis of the small amount of data presented here, but the results do support the tentative conclusions reached in the discussion and certainly suggest that differential analysis of the components of river water will prove fruitful for the study of trace metal cycles.
-
Literature Cited (1) Catanzaro, E. J., J . Water Pollut. Control Fed., 47,203 (1975).
(2) Catanzaro, E. J., Proc. Second A n n . Enuiron. Biogeochem. Symp., Hamilton, Ont., Canada, 1975. (3) Hall, S . K., Enuiron. Sei. Technol., 6, 31 (1972). (4) Huntzicker, J. J., Friedlander, S. K., Davidson, C. I., ibid., 9, 448 (1975). Rwpiiied for reuieu September 5 , 1975, Accepted January 15, 1976. This uork u a s partial13 supported by Environmental Protection Agency Grant R803113.
