10 INJURY BY SMELTER WASTES. 



EXPERIMENTAL INVESTIGATIONS RELATING TO THE ACTION 

 OF SULPHUR DIOXID ON VEGETATION. 



ORGANS OF THE PLANT THROUGH WHICH INJURY TAKES PLACE. 



In carrying' on an investigation of this kind it was first necessar}' 

 to ascertain whether or not sulphur dioxid was injurious to plant life, 

 how small a (|uantity was injurious, and through what organs of the 

 plant such injury took place. Light is thrown on this subject by the 

 work of foreign chemists. 



Freytag'* sho\Yed that sulphur dioxid and trioxid do not injure 

 the plant through the roots. His experiment consisted in watering 

 wheat, oats, and peas with large amounts of dilute sidphurous acid 

 in one case and sulphuric acid in another. The plants neither wilted 

 nor reduced their yield. Von Schroeder and Schmitz-Dumont '' 

 made an investigation on pines, firs, lindens, and Norway maples in 

 1896, in which they treated (1) the aerial parts of the plants with 

 sulphur dioxid, (2) the aerial parts of the plant and the earth with 

 sulphur dioxid, and (3) the earth in which the plant was growing 

 with dilute sulphurous acid. They also showed that the injury to 

 vegetation by sulphur dioxid is not through the roots, but through 

 the medium of the leaves, and that even extremely minute quantities 

 of sulphur dioxid are injurious. 



AVieler in his work entitled '' Untersuchungen iiber die Einwir- 

 kung schwefliger Saure auf die Pflanzen," which has been published 

 since the Avork at Redding was done, also gives numerous experi- 

 ments to shoAv that minute amounts of sulphur dioxid injure plants 

 through the leaves, but he also states that in the course of time the 

 sulphur dioxid and trioxid present in smelter smoke injuriously 

 affect the soil and so indirectly injure the plant through the roots. 

 He is further of the opinion that soils subjected to the action of 

 sulphur dioxid suffer from a reduction in the lower forms of animal 

 and plant life which are so necessary to the series of natural changes 

 taking place in normal soils. He is also of the opinion that such 

 soils suffer a loss in bases, which eventually causes them to become 

 acid, as not enough bases are present to form humates with the humic 

 acid. In proof of the latter point, he has taken soil samples from 

 the vicinity of several smelters and found that all of them contained 

 free humic acid. 



Wieler's conception of this additional injurious action of sulphur 

 dioxid on the soil has been published so recently that the writer has 

 not been able to investigate the subject sufficiently to express a defi- 



o Mitt. d. konigl. landw. Akad^, Poppelsdorf, 1S69. 

 ^Thar, forstl. Jahrb., 1896, 46: 1. 



