323
The Carbonate System
divalent metals form very strong complexes with organic ligands in seawater. It is not clear
at the present time how this speciation will be affected by low pH. The only study that I am
aware of at present is the formation of Cu 2+ complexes with natural organic ligands in seawater (Louis et al., 2009). These workers characterized the acid–base properties of the ligand
(Figure 7.77). They found that the concentration of the ligand decreased when the pH range
decreased from 8.0 to 7.0. As one might expect, a lower pH will decrease the formation of
organic complexes of Cu 2+ . It is hoped that over the next 10 yr more studies will be made on
the effect of pH on the speciation of divalent metals with organic ligands in seawater.
2010
2005
2000
Year
pCO
2 , µatm
1995
1990
300
320
340
360
380
400
420
Mauna Loa Atm pCO 2
Surface Waters pCO 2
Figure 7.64
The increases in pCO 2 in the atmosphere and water at the Hawaii Ocean Time Series station.
Year
1990
1995
2000
2005
2010
pH
8.04
8.06
8.08
8.10
8.12
8.14
Slope = –1.8 × 10
–3 /y
Figure 7.65
The decrease in pH in surface water at the Hawaii Ocean Time Series station.