80 



R. T. Prentki et al. 



TABLE 4-3 Chemical Composition of Sediments, in Ponds B, C and D, 

 15 September 1970 



Sample 



Ca 



Mg 



Fe 



Mn 



Cu 



Zn 



mg(g dry wt)- 



Water 

 Icontent 

 (% dry wt) 



PondB 



0-lcm, oxidized 

 1 l-4cm, reduced 



6-1 0cm, reduced 

 12-1 6cm, reduced 



PondC 

 0-lcm, oxidized 

 l-4cm, reduced 

 7-1 0cm, reduced 



12-1 5cm, reduced 



P mgCgdry wt) 



-1 



Fe mg(g dry wt) 



% Organic 



21 



20 



17 



23 



18 



13 



6 



4 



4 



24 

 16 

 12 

 17 

 15 

 9 



70 



60 



37 



22 



2 



2 



2 



2 



10 



67 

 42 

 65 

 42 

 32 

 60 



the silicomolybdate method. Conductivity was measured in 1970 on an 

 impedance bridge at 25°C. Bicarbonate anion was calculated from 

 alkalinity and chloride estimated by difference from the sum of strong 

 cations minus bicarbonate. 



The ponds are dilute salt solutions with chloride the major anion and 

 sodium the major cation (Figure 4-3). Concentrations of chloride, sodium, 

 bicarbonate, magnesium, and calcium all parallel conductivity and the 

 concentrations of these ions are controlled by abiotic factors. Thus, during 

 freeze-up, ions are excluded from ice and become concentrated in the 

 remaining water. For example, Kalff (1965) found that alkalinity in 



