CHAPTER 3
Lake and Pond Sediments
Many of the methods described in Chap. 1 for analysis would be applicable without
modification to lake and pond sediments. The methods described in this chapter have
been specifically applied to lake and pond sediments, and are grouped together here
for convenience. Many methods specifically designed for lake sediment analysis take
account of the fact that such samples contain higher concentrations of sulphide than
do river sediments.
3.1
Metals
3.1.1
Cadmium
The determination of various forms of cadmium in sediments is discussed in Sect.
2.1.4. Table 3.1 presents the results obtained in the determination of the various
species of cadmium in a sediment taken from Lake Ontario.
3.1.2
Mercury
Pillay et al. [194] applied neutron activation analysis to the determination of 1.96.1 mg kg-l mercury in Lake Erie. The errors of this procedure were less than 15 % at
the 0.01 mg kg-l level and less than 5 % at the 2 mg kg-l level. Standard deviations at
these two levels were 17 % and 7 0/0. No losses of mercury occurred during the freeze
drying of specimens. Losses of 10-20 % did however occur during low temperature
oven drying which must be avoided to ensure accurate results.
Table 3.1
Distribution of
chemical forms of cadmium
suspended sediments taken
from Lake Ontario (from [7])
Exchangeable forms
Carbonate and surface oxide bound
Bound to iron and manganese oxides
Bound to organic matter
Residual forms
Total cadmium concentration
%
17 ± 6
31 ± 10
34 ± 7
12 ± 5
6 ± 3
3.5 - 8.0 mg kg- 1