river water appeared to be restricted to a small area near the mouth of the 

 river. The water of Maumee River was more heavily polluted that that of any 

 other tributary studied. 



River Raisin Section 

 Oxygen, carbon dioxide, and hydrogen-ion concentration 



One regular station (Station 117) in this section was visited in all 

 thj'ee years. Station 117 is two miles out from the ncuth of River Eaisin, 

 where the depth is about 6 meters. Saiiples were taken on l5 dates, but not 

 always at both surface and bottom because the temperature was usually nearly 

 uniform. The data art given in Table 35. 



The surface water was ^^enerally well supplied with oxygen, although 

 on three occasions in 1929 it was below 90 per cent saturation. Judging by 

 thp temperature data, the water at this point is frequently mixed from top to 

 bottom so that chemical conditions are usually almost uniform. However, on 

 two occasions (July 2, 1928, and June 20, 1929) there was temporary stagna- 

 tion of the lower water, resulting in considerable withdrawal of oxygen. It 

 seems probable that at night, especially during a period of cloudy weather, 

 the oxygen content of the water would become very low. Accordingly a sample 

 was taken at 3:00 A.M. on July 27, 1929, following three days characterized 

 by cloudy weather. The oxygen was lower at that time than in most of the 

 other samples, all of which were taken in the daytime, but the withdrawal 

 was much less than might be expected under the circumstances. Data on free 

 carbon dioxide and pH are lacking for June 20, 1929 but presumably that was 

 the time of maximum free carbon dioxide and lowest pH. With minor exceptions 

 there was a carbon dioxide deficit or only a slight excess, and the pH was 

 8.0 or above. The range of methyl orange alkalinity was about the eame as 

 recorded for stations in the Island Section. On the basis of the data pre- 

 sented, the chemistry of the w ater at this station may be regarded as satis- 

 factory. The evidence for pollution is negative, for the few cases in which 

 the oxygen content was low may have resulted from natural causes. 



In 1930 the investigation was extended to include River Raisin at its 

 mouth and parts of the lake near the river, to determine to vjhat extent, if 

 any, the lake is affected by vjater from the river. The last mile of the 

 principal outlet of River Raisin has been canalized, and the canal walls pro- 

 ject a quarter of mile from the lake shore. Monroe Light is at the end of 

 the north wall. The river current is usually very weak and reverses period- 

 ically. Station 200 v/as established in the ship canal at the level of Monroe 

 Light. Other stations were established north, south, and east of Station 200, 

 as indicated in Table 36. The depth at these stations ranges from 3 to 6 

 meters and samples were always taken at £ point about one meter above bottom. 



Ill 



