The chemistry of natural waters - Geochemistry: An Introduction - page 161

Table 7.1 Water-column properties in the Pacific at 26 ◦ N and 160 ◦ E

Depth Temp. Salt O 2 PO 4 SiO 3 NO 3

( ◦ C) (ml l − 1 ) ( μ mol l − 1 ) ( μ mol l − 1 ) ( μ mol l − 1 ) (m) (psu)

0 25.62 35.05 4.84 0.16 4.8 0.1

10 25.49 35.07 4.81 0.11 4.4 0.2

20 25.30 35.07 4.82 0.11 4.3 0.2

30 24.92 35.08 4.90 0.12 4.1 0.2

50 23.70 35.10 5.01 0.10 4.3 0.2

75 22.03 35.07 5.06 0.11 4.8 0.4

100 20.55 35.01 5.00 0.15 5.4 0.8

125 19.31 34.94 4.86 0.16 4.7 1.3

151 18.35 34.89 4.79 0.24 5.4 2.1

201 17.04 34.79 4.73 0.36 7.8 4.0

252 16.15 34.71 4.74 0.42 8.2 6.7

302 15.38 34.64 4.66 0.47 10.3 7.0

403 13.15 34.46 4.46 0.78 16.1 13.1

504 10.59 34.25 4.26 1.29 27.6 18.8

605 7.97 34.12 3.31 1.89 44.1 26.1

706 6.07 34.13 2.35 2.38 65.3 33.8

807 4.95 34.18 1.55 2.81 87.8 38.8

908 4.26 34.25 1.28 2.91 107.6 41.5

1009 3.86 34.34 1.03 3.06 118.6 42.4

1111 3.44 34.40 1.05 3.06 126.1 42.9

1212 3.16 34.46 1.09 3.06 131.7 42.5

1313 2.96 34.49 1.23 3.05 139.1 42.3

1415 2.76 34.51 1.43 2.97 141.7 42.5

1516 2.60 34.53 1.57 3.03 146.4 41.8

1770 2.23 34.58 1.90 2.87 151.4 41.5

2024 2.00 34.62 2.21 2.89 157.1 38.9

2533 1.72 34.65 2.65 2.74 157.7 37.9

3043 1.58 34.67 2.90 2.67 155.4 37.3

3554 1.51 34.68 3.31 2.61 155.6 36.4

4067 1.47 34.69 3.50 2.57 152.5 35.7

4580 1.47 34.69 3.78 2.56 148.2 35.0

5095 1.46 34.70 3.83 2.51 142.9 35.3

5610 1.52 34.69 3.99 2.48 138.6 35.4

16. Discuss the properties of the water column in the Pacific at 26 ◦ N and 160 ◦ E
( Table 7.1 ) by plotting temperature, salt, O 2 , and the nutrients vs. depth. Identify the
thermocline, the oxygen minimum. What is the halocline? Compare the profile of the
soft (N, P) and hard (Si) nutrients.
17. Silicon and erbium (Er) concentrations have been analyzed in samples taken at dif-
ferent depths of the water column at a South Atlantic station ( Table 7.2 ). Plot Si vs.