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The application of differential pulse stripping voltammetry in the determination of trace metals in wet precipitation
Author(s)
Le Roux, Shirley Theodora Rose
Date Issued
1999
Type
Thesis
Publisher
Peninsula Technikon
Abstract
Wet deposition of toxic trace metals is the dominant mode of deposition in
terrestrial ecosystems and contributes very significantly to their pollution burden.
Wet deposited metals are dissolved in rainwater. They reach the vegatation in a
form most favourable for uptake. Reliable analysis of toxic trace metals in
rainwater is important in order to determine the impact they make on the
environment.
In this study, trace metals in rainwater and in dry deposition (as a control
measure), have been analysed over a period of a year. These metals include
cadmium, copper, cobalt, lead, nickel and zinc. The rainwater was filtered,
acidified to pH2 and irradiated with UV-light. Dry deposition samples, were
digested by heating in nitric acid before analysis. Differential-pulse anodic
stripping voltammetry was used to determine cadmium, lead and zinc. Copper
was determined by adsorptive cathodic stripping at pH7 after complexation with
catechol. Cobalt and nickel were measured at pH9 by adsorptive cathodic
stripping after formation of their dimethylglyoximes. Sampling was done on a
daily basis from April 1996 to March 1997, on the campus of the Peninsula
Technikon. The samples were collected over a 24-hour period. The total
average concentration for the metals was 16.11 flg/dm3 for rainwater and
427flg/dm3 for dry deposition. Meteorological factors such as wind speed,
humidity and temperature affect the distribution of pollutants and thus the trace
metal levels. The levels of the metallic pollutants were thus evaluated against
meteorological data. Differential-pulse stripping voltammetry is shown to be
applicable for heavy metal analysis of rainwater.
terrestrial ecosystems and contributes very significantly to their pollution burden.
Wet deposited metals are dissolved in rainwater. They reach the vegatation in a
form most favourable for uptake. Reliable analysis of toxic trace metals in
rainwater is important in order to determine the impact they make on the
environment.
In this study, trace metals in rainwater and in dry deposition (as a control
measure), have been analysed over a period of a year. These metals include
cadmium, copper, cobalt, lead, nickel and zinc. The rainwater was filtered,
acidified to pH2 and irradiated with UV-light. Dry deposition samples, were
digested by heating in nitric acid before analysis. Differential-pulse anodic
stripping voltammetry was used to determine cadmium, lead and zinc. Copper
was determined by adsorptive cathodic stripping at pH7 after complexation with
catechol. Cobalt and nickel were measured at pH9 by adsorptive cathodic
stripping after formation of their dimethylglyoximes. Sampling was done on a
daily basis from April 1996 to March 1997, on the campus of the Peninsula
Technikon. The samples were collected over a 24-hour period. The total
average concentration for the metals was 16.11 flg/dm3 for rainwater and
427flg/dm3 for dry deposition. Meteorological factors such as wind speed,
humidity and temperature affect the distribution of pollutants and thus the trace
metal levels. The levels of the metallic pollutants were thus evaluated against
meteorological data. Differential-pulse stripping voltammetry is shown to be
applicable for heavy metal analysis of rainwater.
Additional information
Thesis (MTech (Physical Sciences))--Peninsula Technikon, Cape Town, 1999
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