adaptable to field work involving 

 sampling swift streams, frcm bridges, 

 or lakes from small boats. A portable 

 resistance theimometer is suitable for 

 lakes and deep, slow moving streams as 

 it readily gives temperature with depth. 

 When the stream is swift, it is possi- 

 ble to get a reliable water temperature 

 by leaving the samples in the stream for 

 a sufficient period to cool or warm to 

 the river temperature- The samples can 

 then be quickly brought to the surface 

 and a hand theimometer immersed in the 

 center of the water in the samples. 



Dissolved oxygen : These samples must be 

 collected with a sampler that permits 

 collection without agitation or expo- 

 sure to air. They must be dosed, imme- 

 diately following collection, with 

 reagents for iodine liberation. Samples 

 so dosed can be stored out of the sun- 

 light for later titration in the labora- 

 tory. If not dosed immediately, organic 

 decomposition will alter the dissolved 

 oxygen content or, if the sample waims, 

 the oxygen solubility is lessened £uid 



when the sample stopper is removed, 

 oxygen will escape. 



Carbon dioxIJ e: This must be detennined at 

 the time of collection as organic deccan- 

 position in the sample increases the 

 carbon dioxide content. 



pH, alkalinity and hardness : These should 

 be detennined when the sample is col- 

 lected, or at least within 12 hours 

 unless the sample can be refrigerated. 

 Production of carbon dioxide by biologi- 

 cal deccanposition will lower the pH and 

 alkalinity of the sample on standing. 



To investigate the effect of delayed 

 analyses, samjiles of Snake River water 

 were tested on collection and the re- 

 mainder then returned to the laboratory 

 for periodic determinations on pH, total 

 aLLkalinity, carbonate alkalinity and 

 total hardness. Figure 10 is an average 

 plot of these deteminations over a 

 period of 62 days. During these 62 days, 

 the samples remained on the laboratory 

 shelf in a quiescent state. In the first 



120 9 



O O O 



TOTAL HARDNESS 



PH- 



20 



SEPTEMBER 



OCTOBER 



10 20 



NOVEMBER 



SNAKE RIVER 



EFFECT OF SAMPLE STORAGE ON 

 pH, ALKALINITY, AND HARDNESS. 



SAMPLE COLLECTED SEPT 14, 1955 



FIG. 10 



30 



