Chemistry 97 



Some of the DIC is present as dissolved CO 2; this quantity will be 

 frozen out of the ice and moved downwards as the sediment freezes. In one 

 experiment, about 40% of the DIC was purged from the interstitial water 

 within seconds, indicating that most of it was present as CO2. 



In the tundra soils, there is a large-scale release of CO2 in the early 

 fall and again in the spring thaw (Coyne and Kelley 1971). This is 

 presumably caused by freezeout of CO 2 followed by movement of the gas 

 upwards through soil cracks or along roots and stems. This would not 

 happen in the ponds because there are few plants or cracks. 



OXYGEN 



Water Column 



The concentration of oxygen was not measured routinely. Analyses 

 were made of transects of Ponds C and E on 23 July 1970, one week after 

 the oil spill on E, and on Pond B and experimental subponds on 23 August 

 1972. The azide modification of the Winkler method was used in 1970 

 (American Public Health Assoc. 1960) and a Yellow Springs Instrument 

 probe in 1972. 



Measurements in the middle of Ponds B and C gave mid-day 

 concentrations of 10.6 and 11.4 mg O2 liter"' or 97% and 88% of 

 saturation. In Pond C, the concentration decreased towards the shallow 

 sides of the pond and the minimum value of 3.5 mg (31% of saturation) 

 was reached in 2 cm of water within the Carex bed. This low concentration 

 is partially a result of the reduced water circulation and partially a result 

 of high sediment respiration in an area with only a small amount of oxygen 

 in the water column above. Evidence for the importance of sediment 

 respiration comes from an average (n = 2) of 91% of oxygen saturation in 

 two subponds with sediment bottoms and an average of 109% in two 

 similar ponds with plastic bottoms. This is an indication that there is a net 

 production of oxygen in the water column and a net utilization in the 

 benthic community. 



Most surface waters of the world, whether fresh or salt, are near 

 saturation with respect to oxygen. The major exceptions appear to be 

 those supersaturated waters with high photosynthesis-to-respiration ratios 

 and undersaturated waters such as freshly upwelled oceanic waters and 

 highly colored lakes (Hutchinson 1957). The oxygen concentrations in 

 arctic tundra ponds are in agreement with the generalization that highly 

 colored waters are oxygen-deficient. Thus, Kalff (1965) found that the 

 oxygen concentration in his Barrow ponds ranged from 60% to 118% of 

 saturation, but normally fell below 100%. Reed (1962) found that ponds 

 along the Colville River area usually ranged between 60% and 70% of 



