CHAPTER 2
River and Stream Sediments
2.1
Metals
2.1.1
Antimony
Beauton and Patrick [1] give details of the distribution and mobility of antimony in
river sediments. They showed in leaching experiments that antimony is easily leached
from the sediment under anaerobic conditions but not under aerobic conditions.
When the sediments were incubated anaerobically, there was evidence of the release
of volatile sulphur compounds.
2.1.2
Arsenic
Cutter [2] has described a selective hydride generation technique as the basis for the
differential determination of total arsenic in oxidatively digested river sediments.
A direct spectrophotometric procedure has been described for the determination of
parts per billion of hydrochloric acid releasable arsenic in river sediments and soils
[3]. In this method the arsenic in the sediment sample is reduced by stannous chloride
and zinc to arsine which is then swept from the generator into silver diethyldithiocarbamate chromogenic reagent to be evaluated spectrophotometrically at 535 nm. Only
inorganic arsenic is included in this determination. Organically bound arsenic is not
determined unless the sample is oxidized. No significant change in the recovery of
6 J.lg of arsenic(V) added to 5.0 g of sediment was observed when the samples were
also spiked with either 200 J.lg (40 mg kg-I) of chromium(VI), 300 J.lg (60 mg kg-I) of
copper(II), 300 J.lg (60 mg kg-I) of nickel(II), 15 J.lg (3 mg kg-I) of mercury(II) or 2J.lg
(0.4 mg kg-I) of antimony(III). Interference by combinations of various metal ions
was also studied. It appears that the recovery of arsenic generally is not affected up to
a combined metal ion concentration of 300 J.Lg per 5 g of soil that had also been spiked
with 6.0 J.lg of arsenic(V). Whereas higher concentrations of antimony(III) and mercury(II) enhance the apparent recovery of arsenic, the other metal ions at levels
greater than the concentrations listed above decrease the recovery of arsenic. In Table
2.1 the native arsenic levels found in three river sediments and the results of arsenic
spiking experiments are shown. Between 95.5 and 101.5 % of the added arsenic was
recovered with a standard deviation between 4.2 and 4.9 %.
River and Stream Sediments
2.1
Metals
2.1.1
Antimony
Beauton and Patrick [1] give details of the distribution and mobility of antimony in
river sediments. They showed in leaching experiments that antimony is easily leached
from the sediment under anaerobic conditions but not under aerobic conditions.
When the sediments were incubated anaerobically, there was evidence of the release
of volatile sulphur compounds.
2.1.2
Arsenic
Cutter [2] has described a selective hydride generation technique as the basis for the
differential determination of total arsenic in oxidatively digested river sediments.
A direct spectrophotometric procedure has been described for the determination of
parts per billion of hydrochloric acid releasable arsenic in river sediments and soils
[3]. In this method the arsenic in the sediment sample is reduced by stannous chloride
and zinc to arsine which is then swept from the generator into silver diethyldithiocarbamate chromogenic reagent to be evaluated spectrophotometrically at 535 nm. Only
inorganic arsenic is included in this determination. Organically bound arsenic is not
determined unless the sample is oxidized. No significant change in the recovery of
6 J.lg of arsenic(V) added to 5.0 g of sediment was observed when the samples were
also spiked with either 200 J.lg (40 mg kg-I) of chromium(VI), 300 J.lg (60 mg kg-I) of
copper(II), 300 J.lg (60 mg kg-I) of nickel(II), 15 J.lg (3 mg kg-I) of mercury(II) or 2J.lg
(0.4 mg kg-I) of antimony(III). Interference by combinations of various metal ions
was also studied. It appears that the recovery of arsenic generally is not affected up to
a combined metal ion concentration of 300 J.Lg per 5 g of soil that had also been spiked
with 6.0 J.lg of arsenic(V). Whereas higher concentrations of antimony(III) and mercury(II) enhance the apparent recovery of arsenic, the other metal ions at levels
greater than the concentrations listed above decrease the recovery of arsenic. In Table
2.1 the native arsenic levels found in three river sediments and the results of arsenic
spiking experiments are shown. Between 95.5 and 101.5 % of the added arsenic was
recovered with a standard deviation between 4.2 and 4.9 %.