J. J. Griffith 



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Table VII. Analyses of Soils affected by River Water where Land is 

 more or less protected by embankments. 



B. = Badly affected. S. = Slightly affected. 



Further Deduction.s from Tables V, VI and VII. 



(a) Lead occurs in practically all affected soils. Zinc also is present 

 in most of them. Copper and arsenic were not detected in any of the 

 soils dealt with, except in samples from a few small strips of land close 

 to the leats and refuse heaps of a few mines which were found to contain 

 small quantities of copper. 



(6) There is usually much more of the toxic metals in the soil than 

 in the subsoil. But in some cases the subsoil contains more than the 

 soil. Sample 21, Table VII, is an instance of contaminated land where 

 lead and zinc are present in the subsoil but not in the soil. 



(c) There had been no undesirable increase of fine silt in any of the 

 samples examined. 



To sum up, a consideration of the figures given in Tables V, VI and 

 VII suggests that admixture with mine refuse may possibly lower soil 

 fertility in the following ways: 



1. By the toxic action of lead and zinc — Tables V, VI and VII. 



2. By unfavourably affecting the mechanical composition — Table VI. 



3. By lowering the percentage of plant food in the soil. 



(a) Decrease of potash — Table VI. 



(6) Decrease of nitrogen — Tables V, VI and VII. 



