120 R. T. Prentki et al. 



Prudhoe Bay lakes had a summer average of 4.4 ^g P liter ', and 

 Schindler et al. (1974) report an average of 2 /ug P liter ' for total 

 dissolved P (mostly DUP) in Char Lake. The PP concentrations in arctic 

 lakes appear to vary much more than the other phosphorus parameters, 

 being most obviously influenced by mechanical and thermokarst erosion 

 and suspension of particulates. Excluding samples containing organic soil 

 or sediment taken near the shore during storms, Ikroavik concentrations 

 ranged from 1.9 ^g P liter "^ to 57.5 Mg P liter"' in the summers of 1970 

 and of 1971, with a mean of 17.3 ^lg P liter"' (34 analyses). The Prudhoe 

 Bay lakes, on the other hand, averaged only 7 ^g P liter ' and ranged 

 from 1 .6 to 15 ^g P liter '(15 analyses), while Char Lake (Schindler et al. 

 1 974) ranged from I to 5 Mg P liter " ' . 



Alaskan coastal plain lakes and ponds differ in their predominant 

 forms of phosphorus. Thus, PP predominates in lakes and DUP in ponds. 

 Hutchinson (1957) states that most uncontaminated lake districts have 

 surface waters containing 10 to 30 ^g P liter ', with 10% of this being 

 phosphate (DRP). Of the arctic waters discussed above, only trough ponds 

 and Char Lake fall outside these limits. 



Sediment 



Sediment studies concentrated on interstitial water analyses, 

 chemical characterization of sediment phosphorus, and total phosphorus 

 determinations. 



Interstitial water was squeezed by N2 gas pressure from sediment 

 cores within 1 hour of collection. Dissolved reactive phosphorus was 

 determined as in the water column; however, turbidity blanks were 

 necessary due to precipitation of organics from solution upon addition of 

 the reagent. 



Sediment total phosphorus was determined by the single solution 

 phosphomolybdate technique of John (1970) on diluted perchloric or 

 perchloric-nitric acid digests of sediments (Sommers and Nelson 1972, 

 Jackson 1958). 



Fractionation of inorganic phosphorus in the sediments was 

 accomplished using the Williams et al. (1971a) modification of the Chang 

 and Jackson (1957) extraction scheme with some additional modifications 

 described in Prentki (1976). Phosphate concentrations in the Chang and 

 Jackson extractions were determined colorimetrically using John's 

 reagents. Internal standards and turbidity blanks were run on all samples 

 and boric acid was added to reduce fluoride interference in the NH4F 

 extracts. Citrate dithionate (reductant soluble) extracts required digestion 

 with persulfate to eliminate interference. Careful adjustment of sample 

 concentration and pH were also required in order to prevent precipitation 

 of the large amounts of iron present. Corrections for phosphorus activated 

 but reabsorbed during the NH4F extraction were attempted using the 



