The Oceans 223
PO 4 3– (μmol l–1)
NO
μmol l
–1)
50
0.0 1.0 3.0 4.0
10
20
2.0
40
30
0
Fig. 6.21Global relationship between dissolved nitrate and phosphate in seawater based on
US Geochemical Ocean Sections (GEOSECS) programme data.
us that all elements are potentially toxic, making terms like nutri-
entimpossible to apply in an absolute sense.
6.5.5 Scavenged behaviour
Elements that are highly particle-reactive, characterized by large
z/rratios (see Section 5.2), often have vertical profiles with surface
maxima and decreasing concentrations with depth; aluminium (Al)
