THE DISTRIBUTION OF HYDROGEN IONS IN THE SEA 



INTRODUCTION 



It has long been known that sea water has a slightly 

 alkaline reaction, that is, the concentration of the hydroxl 

 ions slightly exceeds that of the hydrogen ions. The 

 hydrogen-ion concentration, and hence the hydroxl-ion 

 concentration, since the product of the two is a constant, 

 varies in sea water within relatively narrow limits and 

 is regulated by the so-called buffer mechanism or buffer 

 system. This system has been investigated by Buch, 

 Harvey, Wattenberg, and Gripenberg (1932), by Buch 

 (1933), and by Moberg, Greenberg, Revelle and Allen 

 (1934), and it has been shown that the main factors in- 

 volved are the salts of weak acids, chiefly carbonates 

 and bicarbonates, free and hydrated carbon dioxide, the 

 total salt content, and the temperature. The variations 

 in the hydrogen-ion concentration encountered in the sea 

 are owing chiefly to variations in the total carbon diox- 

 ide content, that is, the carbon dioxide existing as free 

 CO2 or in carbonate or bicarbonate ions. The hydrogen- 

 ion concentration is therefore an approximate measure 

 of the total carbon dioxide in sea water. 



The quantity of carbon dioxide is altered by biologi- 

 cal activity, being consumed by plants and liberated by 

 animal respiration and decomposition of organic material. 



For that reason a correlation between the hydrogen-ion 

 concentration and the abundance of plants or animals 

 may be expected. It is also probable that the hydrogen- 

 ion concentration per se may affect the physiological 

 processes of organisms in the sea. Many geochemical 

 processes that take place in the sea are influenced by 

 the hydrogen-ion concentration. Of these a well-known 

 example is the precipitation or solution of calcium car- 

 bonate. 



An excellent account of investigations of the hydrogen- 

 ion concentration in sea water undertaken prior to 1933 

 has been published by Wattenberg (1933) and consequent- 

 ly this subject will not be discussed in the present re- 

 port. Wattenberg also discusses the different factors 

 responsible for variations in the hydrogen-ion concen- 

 tration in the sea. 



As previously stated (p. 3) the data here presented 

 are not corrected for temperature and consequently 

 they are comparable with most of the previously pub- 

 lished data except those of Wattenberg. The data are 

 shown in the station graphs (figs. 14-92), in the pH sec- 

 tions I to XVI, and also in table 2 (I-B, pp. 16-55, 56- 

 115, and 183-257). 



CARNEGIE SECTIONS 



Section I. stations 24 to 13: more or less north and 

 south from Grand Banks of Newfoundland to latitude 8° 

 north between longitudes 35° and 50° west. --At the sur- 

 face the pH values ranged from slightly above 8.1 at the 

 northern, to more than 8.3 at the southern stations. At 

 some of the stations, mostly in the central part of this 

 section, high pH values extended to considerable depths, 

 the line representing pH=8.0 being found at depths below 

 700 meters, whereas at some stations near the two ends 

 of the section it was as near to the surface as 100 me- 

 ters or less. Except at the last-mentioned stations the 

 change in pH with depth is small. Only at a few stations 

 toward the south is there a marked minimum and at the 

 central stations it is entirely lacking. 



At station 19 the pH is uniform below 1000 meters 

 and at station 18 it continues to decrease to 3000 meters. 

 In the northern part of the section pH = 7.9 represents 

 the minimum at 600 meters. In the southern part the 

 minimum occurs in the Antarctic Intermediate Current, 

 the value at station 22 being pH = 7.7. The pH of the deep 

 water throughout the section is approximately 7.9. 



Section II. stations 34 to 25: approximately east and 

 west in the tropical North Atlantic along the parallel of 

 about 12° north from Panama to longitude 37° west.-- 

 The pH of the surface water is above 8.3 throughout, ex- 

 cept at stations 31 to 33 in the Caribbean. The transi- 

 tion zone extends to 500 meters in the western part of ^ 

 the section but toward the east it gradually shifts to- 

 ward the surface until at station 25 it is confined to the 

 upper 200 meters. A minimum in pH occurs between 

 500 and 1000 meters, with values between 7.7 and 7.8. 



The deep water has a pH somewhat over 7.8 in the west- 

 ern part and over 7.9 in the eastern part of the section. 



Section HI. stations 60 to 72 and 40 to 37: in the 

 southeastern Pacific, beginning at approximately lati- 

 tude 40° south, longitude 100° west, extending north- 

 northeast to the coast of Peru at latitude 17° 30' south, 

 thence northward to the Central American Bight. --At 

 the surface there is a general decrease in pH from the 

 tropics to the higher latitudes. At stations 37 and 38 the 

 pH is above 8.3, and at stations 39 and 40 it is between 

 8.2 and 8.3. From stations 72 to 62 it is between 8.1 and 

 8.2 except at stations 70 and 63, where it is below 8.1. 

 At the two southernmost stations the values are also be- 

 tween 8.0 and 8.1. 



Below the surface there is a more rapid change in 

 pH than at the Atlantic stations, the change being more 

 rapid in the northern part of the section from stations 

 37 to 68. Here the line representing pH = 7.7 fluctuates 

 between a depth of about 50 and 350 meters, whereas at 

 most stations south of station 61 it is found at depths be- 

 low 1000 meters. At stations 69 and 70 the lines curve 

 toward the surface which gives evidence of upwelling. A 

 minimum pH value occurs at all the stations at depths 

 ranging down to 1000 meters in the northern part and 

 down to nearly 1600 meters in the southern part of the 

 section. The minimum pH values at nearly all the sta- 

 tions are between 7.6 and 7.7. In the deeper water the 

 pH is slightly more than 7.7. 



Stations 35 and 36: in the Central American Bight, 

 east of the north end of Section III. --The pH concentra- 

 tion at these stations is similar to that in the northern 



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