192
Crustacea and Molluscs
a situation can result from long biological half-lives of metals in the organisms (half
lives of the order of a year or more), or from uniform levels of the metals in the
seawater, or a combination of the two.
Lead. The high lead concentrations in seawaters adjacent to urban areas result from
the combustion of lead alkyls as anti-knock agents in gasolines [565]. Both direct
atmospheric input and sewage, storm, and river runoff contribute to the anthropogenic lead burden of surface waters. It has been estimated that the annual lead inputs to
Boundary Bay
Gil
•
• Year 1
PugetSound
xo •
x Year 2
o Year 3
Cape Flattery
~
Grays Harbor
0
•
Willapa Bay
•
Columbia River
ox
•
Tillamook Bay
x
•
Yaquina Head
0
•
Coos Bay
xO •
Gold Beach
•
Pt. SI. George
exo
Humboldt Bay
xO
•
Cape Mendocino
>0)
•
Pont Arena
>G)
•
Farallon lsI.
x
O.
S. S. F. Bay
• x
N. S. F. Bay
ox •
Soberanes Point
x. 0
Santa Cruz
x
. 0
Diabolo Canyon
x
«l
San Simeon
Gil
•
Santa Catalina
.ox
Oceanside
xo •
San Pedro Harbor
•
x
0
Point Arguello
ox
•
Rincon Cliffs
0
xe
Point Fermin
xc
San Diego Harbor
•
x
Point La Jolla
x
•
0
I
I
I I
I
I
I
I
I
I
0
2
4
6
8 10 12 14 16 18
ppm Pb by dry weight
Fig.8.5
Lead contents in mussels taken from u.s. West Coast stations going from Boundary
Bay, Washington, south to Point La Jolla, California (from [564)).