1. ZINC CYCLE Zn2+ and chelates Available at pH < 7.7 Industrial
discharge
Rainfall
Plant and animal residue,
microbial pool
Animal accumulation
Plant uptake
SOIL CLAYS:
Muscovite
Illite
Chlorite
Montmorillonite
Kaolinite
Adsorption
Highly soluble compounds:
Hydroxydes:
Zn(OH)amorph +2H+, ZnO(zincite) + 2H+;
Carbonates: ZnCO3 (smithonite)+ 2H+;
Silicates: Zn2 SiO4(willemite)+4H+;
Soil-Zn and Zn-Fe Oxides:
Soil-Zn+ 2H+, ZnFe2O4(Franklinite)+8H+;
Chlorides: ZnCl2;
Sulphates: ZnSO4(zincosite),
ZnO*2ZnSO4 + 2H+, Zn(OH)2*ZnSO4 + 2H+.
Low Soluble compounds:
Phosphates: Zn(PO4)2*4H2(hopetite)+ 4H+.
Complexation
AIR
Fertilizers
Pesticides
Minerals:
Spharelite,
Zincite, etc.
Precipitation
Hydrolysis Species:
ZnOH+H+ (soluble at pH>7.7)
Zn(OH)2 + 2H+ (soluble at pH>9.11)
+nH2O
Chloride complexes:
ZnCl, ZnCl2, ZnCl3, ZnCl4 (small amount)
+nCl
Other complexes:
ZnH2PO4 (low soluble)
ZnHPO4 +H+ (soluble at pH>7.7)
ZnNO3 (small amount)
Zn(NO3 ) 2 (small amount)
ZnSO4 (soluble at pH>7.7)
+H2PO4
or nNO3
Zn2+ and chelates
Available at pH < 7.7
Soil Organic Matter
Surface
water
ZINC CYCLE
Human uptake