It should be noted that the amount of nitrate at Station 126 

 was higher than at stations near the other rivers, in spite of a much 

 smaller amount of albuminoid ammonia. Nitrite also was somewhat more 

 abundant than at such stations, other than Station 250. This tends to 

 confirm the suggested explanation for the low nitrite and nitrate in 

 the presence of an abundance of free and albuminoid ammonia observed at 

 stations near Portage, Maumee, and Raisin Rivers, It was sug^.ested 

 that the large amount of phytoplankton at these stations resulted in 

 almost complete withdrawal of nitrite and nitrate as soon as these com- 

 pounds were formed from ammonia. Reference to Table 62 shows that 

 phytoplankton was rare at Station 126 in 1930; it was only l/26 as 

 abundant as at Stations 2$2 and 25U. Consequently there was slight 

 demand upon the nitrite and nitrate, and these compounds could accumu- 

 late in the water. 



In order to gain sone idea of the effect of sewage entering 

 Detroit River, a special series of samples was taken on September 23, 

 as shown in Table hi. The first sample was taken in Lake St, Clair near 

 its outlet, and progressing doimstreara, others were taken in mid-stream 

 at Belle Isle, Ambassador Bridge, and Fighting Island. Finally samples 

 were taken at Stations 219 and 126, If sewage has a marked influence 

 on the content of chloride and nitrogen of the river we should expect 

 such a serie-: of samples to show it. 



The nitrogen determinations, in general, do not show a con- 

 sistent increase in the down-river samples over those up-river. Free 

 ammonia vjas lowest in Lake St. Clair and highest at Station 126, but 

 it decreased rather than increased in the river itself. Albuminoid 

 ammonia was higher in Lake St. Clair than at Station 126, Nitrite was 

 the same at all stations above Station 126, and increased only slightly 

 at the latter. Nitrate vjas about the same at all stations. The data 

 in this single series of samples, are not consistent with the idea that 

 sewage pollution in Detroit River has a pronounced influence on the con- 

 centration of nitrogen compounds in the water. 



Further evidence on this point may be gained by examination of 

 some results on the water of Detroit River near its source in 1901 

 (Detroit Board of Hej^lth, 1902, page 61i) . The mean values (in parts per 

 million) for July, August, and September of that year were as follows: 

 free ammonia, 0,011; albuminoid ammonia, 0,093; nitrite, none; nitrate, 

 0,12. Comparison of these figures with the means for the same period 

 of 1930 at Stations 219, 126, and 13U (Table U6) shows that the latter 

 are somewhat higher, with two minor exceptions. However, the differences 

 are not great, and they hardly can be regarded as definite evidence of 



132 



