Biology Reference
In-Depth Information
According to the cores, the bay suffered its most extreme contamina-
tion between 1950 and 1970. In this period, the additives of choice were
both persistent and toxic. People sprayed DDT (dichlorodiphenyltri-
chloroethane) on their pest problems, cooled their electrical transformers
with PCBs (polychlorinated biphenyls), and smoothed various industrial
processes with heavy hitters like copper, lead, zinc, and chromium. These
additives were rarely removed from any effluent or by-products of human
activities. Though each of these contaminants may have only ended up in
the bay and its sediments in traces, scientists soon discovered that some
Copper and nickel loading from large dischargers to the bay
140,000
16,000
14,000
12,000
10,000
8,000
6,000
4,000
2,000
0
120,000
100,000
Total flow
Copper
80,000
Nickel
60,000
40,000
20,000
0
Bacteria in offshore waters
3,000
1,000
Above San Pablo Bay
South Bay
North Bay
2,500
800
2,000
600
1,500
400
1,000
200
500
0
0
Figure 9. Top: Copper and nickel loading from large discharges between 1986 and
2004. The bay's biggest discharger, the San Jose/Santa Clara wastewater plant,
reduced its copper loading by more than 90 percent with the help of a tertiary
treatment facility operational as of 1979. Bottom: Bacteria in offshore waters be-
tween 1962 and 1977, showing the dramatic reduction of contaminants due to the
initiation of wastewater treatment. Coliform bacteria are typically used as indica-
tors of disease-causing organisms. (S.F. Estuary Institute)
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