Chemistry 107 



movement of water through the soil into the ponds. Accordingly, we have 

 decided that this input is not important. 



The final input to be considered is from the meltwater that enters the 

 pond in mid-June. As discussed in Chapter 3, the ponds retain some of the 

 meltwater, as they normally are below capacity at the beginning of the 

 melt season. This retained water amounted to an average of 5.8 cm (the 

 difference between the fall low water level at the end of 1970 and the spring 

 peak in 1971). The measured nitrogen quantities were as follows: ice in the 

 ponds contained 33 /ug DON liter' '; snowmelt water contained 37 ^g DIN 

 liter '; and runoff water, after contact with the soil, contained 16 Mg DIN 

 and 339 Mg DON liter ' on 10 to 15 June 1973. Since the water flushed out 

 of the ponds had about the same concentrations of nitrogen as the water 

 entering the ponds, the DIN and DON added from the meltwater was only 

 1.7 mg and 39 mg m ' yr' respectively. 



The loss of nitrogen in the runoff (10 to 27 June 1972) was 1.53 mg 

 DIN and 37.9 mg DON m "^ The average flow-weighted concentration of 

 DIN was 14.4 ^g and of DON was 357 Mg liter ', which agree with the 

 initial pond concentrations in Figure 4-12. 



A budget of measured and estimated influxes and losses from Pond B 

 shows that most of the DIN comes in from rainfall and most of the DON 

 from spring runoff (Table 4- 1 2). From these data, it would appear that the 

 pond accumulated nitrogen each year but the 61 mg total N m ~ ' estimate 

 is very small when compared with the 219,000 mg N m ' in the top 10 cm 

 of sediment. Char Lake, the only arctic lake studied in detail, accumulated 

 87 mg N m "^ (de March 1978) while temperate lakes may accumulate 400 

 to 1300 mg N m "' (Likens and Loucks 1978.) 



Uptake of Inorganic Nitrogen 



Ammonia and nitrate uptake rates were measured with the methods 

 of Dugdale and Dugdale (1965). In this technique, '''N labeled nitrate and 

 ammonia were added to samples, the particulate material recovered on a 



TABLE 4- 1 2 Nitrogen Budget for Pond B 



