Geology Reference
In-Depth Information
Scale (miles)
FIGURE 14.1 Concentration of mercury in sediment on the bottom of Lake Erie in 1971. (Numbered dots are sample sites; italicized
numbers are selected mercury values in ppm. The 0.25 and 0.5 ppm isolines are given.)
FIGURE 14.2 Concentration of chromium in sediment on the bottom of Lake Erie in 1971. (Numbered dots are sample sites; italicized
numbers are selected chromium values in ppm. The 20 ppm isoline is given.)
c.
in general for mercury at the same or similar sampling
11.
Did the concentration of mercury in the harbor at Cleve-
sites
land improve between 1971 and 1997/98?
12.
At station 11 (approximately equal to station 74) the value
for
chromium
went from 18 to 56 ppm over the period.
(There are no chromium values shown in Table 14.2 for 1997/98.)
a.
What was the change in
mercury
values for this period
at this site?
10.
Are the regulations against dumping or release of heavy
metals working to improve the sediment in the lake?
Explain.
