14 



INJURY BY SMELTER WASTES. 



in the open, made dnring 1907 since Bnlletin 80 was published, give 

 the following results: 



Table 1.— Effect of fumigating trees growing in the open icith varying strengths 

 of suljihar dioxid, as shoivn hy the sulphur trioxid determined in the foliage. 



[Calculated to dry basis.] 



It will at once be seen from the foregoing table that all of the 

 plants growing in the open wdiich were treated with sulphur dioxid 

 contained more sulphur trioxid in their leaves than the control plants, 

 and that the percentage of sulphur trioxid in the ash of fumigated 

 plants is higher than it is in those not fumigated. These results 

 at once suggest a method for determining wdiether trees around a 

 smelter were killed by the fumes or died from other causes. 



FIELD INVESTIGATIONS OF THE ACTION OF SULPHUR DIOXID 

 FUMES ON VEGETATION. 



A CALIFORNIA SMELTER AND CERTAIN FOREIGN SMELTERS. 



The next step in the investigation w^as to determine whether the 

 dead and badly injured trees around the smelting works near Ked- 

 ding, Cal., usually contained more sulphur trioxid than trees of 

 the same species which stood close by in the same soil, but w^ere not 

 killed. Of 25 pairs of trees examined in various directions from the 

 smelter 80 per cent contained more sulphur trioxid in the leaves 

 of the injured trees than in the leaves of the uninjured ones, while 

 20 per cent showed the reverse. It was further show^n that in 80 

 per cent of the cases the injured trees contained a larger percentage 

 of sulphur trioxid in the ash of the leaves than did the uninjured 

 trees.'^ 



U. S. Dept. Agr., Bureau of Chemistry, Bui. 89. 



