Chemistry 117 



TABLE 4-16 Phosphorus Concentrations in Barrow Ponds, Monthly 

 A verages for 1970 and 1971* 



1970 



1 97 1 



Pond 



June 



July 



August 



June 



July 



August 



Dissolved reactive phosphorus 

 B 1.9 2.3 



1.9 



2.2 



2.3 



2.9 



Dissolved unreactive phosphorus 

 B 6.6 7.0 



C 5.5 10.4 



10.4 

 13.2 



2.3 



1.4 



0.6 



12.2 



15.5 



14.4 



1.8 



1.5 



1.4 



10.5 



13.9 



11.2 



2.0 



1.1 



1.6 



9.2 



12.8 



11.5 



*Data are expressed as jUg P liter- 

 water contact time associated with a shallow snow pack and resulting 

 slower flow rates. Such a flow dependence was observed in 1972 for runoff 

 at weir 1 (see Figure 3-2 for location) where DUP concentrations increased 

 from 8.3 Ag P liter ^ ' at no flow to 24.0 ng P liter ' at 80 m ' hr ' 



DUP is the predominant phosphorus form in the ponds, averaging 

 12.2 Mg P liter"' or 56% of the water column phosphorus (excluding 

 zooplankton phosphorus) in the three control ponds listed in Table 4-16. 

 Diel oscillations in concentrations range between 4 and 5 ^g P liter"' and 

 appear to be related inversely to temperature. Approximately 70% of DUP 

 is probably refractory; it is resistant to both naturally occurring 

 phosphatases (Prentki 1976) and photo-oxidation by sunlight (Barsdate 

 and Prentki personal communication). The other 30% of this phosphorus 

 is in the form of XP and colloidal P; these forms can be rapidly autolyzed 

 and enzymatically hydrolyzed to phosphate (Prentki 1 976). 



Particulate phosphorus (PP), another important fraction of the total 

 phosphorus, showed no discernible pattern of monthly average or seasonal 

 concentration (Figure 4-16, Table 4-16). The grand average of 10. 1 ^Lg PP 

 liter ' for the three ponds is assumed to be the sum of phytoplankton, 

 sestonic bacteria, and detrital phosphorus. However, it may overestimate 



