population; in tMs respect River Raisin is second; Portage River third; 

 and Detroit River fourth. Over considerable areas in and near the rivers 

 the bottom was covered by organic debris, which would have a marked effect 

 on the chemistry of the water immediately in contact with it. The following 

 summary applies only to the water cne meter or more abo^e the bottom. 



Parts of the lake in which there was definite evidence of pollution, as 

 indicated by high albuminoid ammonia, were characterized by low nitrite and 

 nitrate as compared with parts of the lake in which the evidence of pollution 

 was less definite or lacking. This is believed to have resulted from the 

 utilization of nitrite and nitrate by plankton algae, for there was a direct 

 relationship between the abundance of phj't/oplankton and the intensity of 

 pollution. 



Chemical results obtained in Portage River at Port Clinton, and in the 

 lake near the mouth of the river indicate light pollution. The only definite 

 evidence of pollution was in the content of albuminoid ammonia, which was 

 somewhat higher than in the Island Section. In most of the sanples the dis- 

 solved oxygen content was in excess of 90 per cent of saturation, and in no 

 sample was it less than 77 per cent of saturation. Correspondingly satisfac- 

 tory results were obtained for free carbon dioxide and pH. It may be con- 

 cluded that pollution in Portage River has had no harmful chemical effect on 

 the water of Western Lake Erie. 



Maumee River near its mouth was heavily polluted as indicated by high 

 free and albuminoid ammonia (O.618 and 0.708 part per million), and by low 

 dissolved oxygen (not exceeding Ii9 per cent of saturation"^ . Immediately out- 

 side the mouth of the river free and albuminoid ammonia were consistently 

 high, and there was definite evidence of the effect of the river water at a 

 distance of 8.5 miles from the mouth. The oxygen content immediately outside 

 the mouth was sometimes low and sometimes high (range: 12 to 112 per cent of 

 saturation), but there were no marked withdrawals of oxygen at a distance of 

 2.25 miles or more from the mouth of the river. In Maumee Bay the harmful 

 chemical effect of the river water appeared to be restricted to a small area 

 near the mouth of the river. 



River Raisin at its mouth was definitely polluted as shown by the 

 hi{»h albuminoid ammonia (mean, 0.1^33 part per million), and by low oxygen 

 content. In one case there was total exhaustion of oxygen. The effect of 

 pollution was evident in the analyses for albuminoid ammonia in the lake at a 

 distance of at least two miles fix^m the mouth of the river, but no marked 

 withdrawals of oxygen definitely referable to pollution were noted at a dis- 

 tance greater than one-half mile, and only then in water recently discharged 

 from the river. Thus, the harmful effect of pollution apparently was restric- 

 ted to a very small area near the mouth of the river. 



There was no definite chemical evidence of pollution in the lake near 

 the mouth of Detroit River, nor in the river near its mouth. In most respects 

 the chemical results were similar to those obtained in the Island Section. On 



