Agriculture Reference
In-Depth Information
(a)
(b)
H 2 CO 3 *
HCO 3
CO 3 2
H 4 SiO 4
H 3 SiO 4
H 2 SiO 4 2
H 2 CO 3
(c)
(d)
NH 4 +
H 2 PO 4
HPO 4 2
NH 3
PO 4 2
H 3 PO 4
(e)
(f)
CH 3 COO
HS
H 2 S
CH 3 COOH
S 2
456789 0 1
456789 0 1
pH
Figure 3.1 Distribution of dissolved acid-base species at constant total concentration in
solution (after Morel and Herring, 1993). Reproduced by permission of Wiley, New York
solution pH and ionic strength. Complexation of metals with ligands can result
in the total concentration of the metal being far greater than the concentration of
the free ion. This topic is covered in detail by Morel and Herring (1993), Stumm
and Morgan (1996) and, for chelation by humic substances, by Tipping (2002).
A complex is a species in which a metal atom or ion is attached by coordinate
bonds to one or more ligand ions or uncharged molecules. The complex may
itself be positive, negative or uncharged. In forming a coordinate bond the ligand
donates a pair of electrons to the metal. In so doing the ligand is acting as a
Search WWH ::




Custom Search