0.020 









 Ql 



(/) 



E 



0.016 



0.012 



c 

 o 



TO 

 0) 



o 



c 



o 



.O 



0.008 — 



0.004 



0.000 



As Pb 



B 



Ni 



Cd 



Se 



Cr Zn 



Cu 



