Chemistry 79 



the chironomid larvae and oligochaetes which stay mostly in the top 4 cm I 

 of the sediment (see Chapter 7). 



The percent organic content continues to decrease in the top 20 cm 

 but the pattern below this depth varies from pond to pond (Table 4-3). In 

 Pond C, for example, the mean values for the 0-10, 10-20, 20-30, 30-40, 

 and 40-50 cm sections were 70%, 60%, 37%, 23%, and 3%, respectively. 

 Below 40 cm the sediment consists of sand and ice layers. In contrast, for 

 Pond D the mean values for 10 cm sections were 67%, 42%, 66%, 42%, 33% 

 and 58%. In this pond the sand is mixed with ice and peat layers. 



MAJOR IONS 



Water Chemistry 



Dissolved sodium, magnesium, calcium, potassium, iron, and silica 

 were sampled weekly in several ponds during the summers of 1970 and 

 1971 . Cations were determined by atomic absorption and reactive silica by 



TABLE 4-2 Depth Profile of Organic Carbon, Percent Organic Content, 

 Interstitial CO 2, and Leachable Dissolved Organic Carbon in 

 the Sediment of Pond A, 16 August 1973 



A sediment core 9 1cm diameter X 1cm was stirred once a day in 100 ml distilled water 

 for six days at 25-28 ° C. The water was filtered through Reeve Angel 984 ultra filter 

 before analysis. 



