REMOTE MONITORING OF
HEAVY METALS INN IN
NATURAL WATER AND
EFFLUENTS
Department of Chemistry, NTNU
Motivation
During the last years an increasing focus has been
turned on the quality of water and environmental
surveillance. This has also been founded in
international agreements and conferences like The
Johannesburg Summit and EU Water Framework
Directive.
Motivation
An extensive activity and interest for the safety
and protection of water resources is shown in
general from WFD, UN and WHO
Motivation
Additionally the importance of the water
security is also shown through the large number
of different world-wide organizations which
focus on water quality and safety, e.g.
GARNET, GESI, GEF, GREEN, GWP, Global
Water, IWRN, IAEH, IAWQ, ICWQ, IGRAC,
IRC, IWMI, IWRA, WEF, WFP, WQA, WRI
etc.
Motivation
There is a strong linkage between the state of
environment of freshwater resources in a
country and its capacity for poverty eradication
and development.
Motivation
Even though water is probably the most
important resource and commodity we have,
pollution of important water recourses is still a
problem. In future it should be focus even more
to protect and monitor the water quality
Challenge
Making low-cost instruments with high
sensitivity and reproducibility, which can
operate automatically for long time of periods
out in the field with little maintenance.
Methods for trace analyses
Atomic Absorption Spectrometry and
Atomic Emission Spectrometry
Inductive Couple Plasma – Mass Spectroscopy
Electrochemical techniques
Ion Chromatography (with a proper detector)
Neutron Activation Analysis
UV/VIS Spectrometry
Classical analytical methods
Methods for trace analyses
A great number of analytical methods are able
for measuring water quality and water pollution.
However, all these methods have to be used in
laboratories and only a few parameters (e.g. pH,
conductivity, nitrate, phosphate) can be
monitored out in the field.
This fact represents a large problem in
environmental monitoring in general.
Methods for trace analyses
For instance, it is not possible to detect short
time pollutions and accidental spills of
environmental poisons, and it often takes a long
time from sampling to the answer of the analysis
is finish.
Methods for trace analyses
A better way to perform environmental
monitoring is to combine continuous monitoring
in the filed by use of automatic equipment
together with manually sampling and analyses
in laboratories.
Then a more complete monitoring program can
be established, which both can detect short time
pollutions, but also the different methods can
verify each other.
Methods for trace analyses
Through several years of research within this
field, automatic equipment for continuous
monitoring of heavy metals and trace metals
have now been developed in our research group
at NTNU. The scientific interest is large and the
commercial potential is worldwide
Methods for trace analyses
Electrochemical techniques offers an interesting
group of methods for remote monitoring of
heavy metals.
Electrochemical techniques
Good detection limit, possible for use in natural
water, moderate price, fast, and simultaneously
detection of several metals
Well known and accepted theory
A problem is to find a suitable electrode
materials for use in field (avoid liquid mercury)
Properties for electrode materials
High overvoltage towards HER
Wide working window
Non toxic
Slow passivitation
Possible to make nano-dimension
Resistant against fouling of biological material
Low price, easy to produce and cast
Easy to operate in field equipment
Sensor materials
Metal electrodes
Mercury, Gold, Silver, Iridium, Palladium,
Platinum
Carbon substrate
Diamond (e.g. Boron doped), Glassy carbon,
Graphite (heat treated electrode graphite)
Film electrodes / Meniscus
Bismuth film, Mercury film, Hg-Ag, Hg-Au…
Mixed electrodes
Alloying a metal with high hydrogen
overvoltage with a metal with low hydrogen
overvoltage.
A significant increase in the hydrogen
overvoltage is observed for the alloyed metal,
even for small additions.
Silver electrodes added bismuth
Silver electrodes contaminated with 2, 4, 6, 10, 15 % (w/w) bismuth.
DPSAV in 0.05 M NH4Ac solution (pH 4,6).
Solid dental amalgam electrodes
500
0
-1.60
-500
-1.40
-1.20
-1.00
-0.80
-0.60
-0.40
-0.20
0.00
0.20
0.40
2%Hg
40%Hg
-1000
51%Hg
-1500
-2000
Silver electrodes containing 2, 40, and 51 % (w/w) mercury. CV in
0.01 M HNO3 solution, scan rate 100 mV/s.
Voltammetric apparatus for use
in field
Voltammetric apparatus for
use in field, small scale tests
Field Apparatus
Field Apparatus
Sampling
Avoiding contamination
Accuracy in pumping installation
Analyses
Cleaning of the electrodes and the cell system
Field instrument, advantage
Low risk for contamination or changes in the
samples due to time
Speciation studies possible in the field
Possibilities to detect short time pollution and
react immediately
Unique data for biological and / or geological
studies
Pilot projects in Norway
TBS
HVS
Løkken
Polluted river water, Løkken Verk, Norway
Løkken pyrite ore
Slag heap
Løkken Verk is an old mining area in middle part of Norway
Løkken pyrite ore, composition
Placing of the monitoring system
Raubekken, a middle large river passing through
the mining area
Instrument mounted in the field.
Results
Typical voltammetric scan of water sample from the river
Raubekken added NH4Cl (0.05 M) . DPASV, scan rate 20 mV/s,
modulation pulse 75 mV, deposition time 30 s at – 1450 mV.
Calibration
60
30
Zn
Pb
50
20
R2 = 0.9998
I (  A)
I (  A)
R2 = 0.9969
40
10
30
20
500
0
700
160
900
1100
Conc (g/L)
1300
1500
0
200
60
Fe
400
Conc (g/L)
600
800
Cu
50
140
I (  A)
I (  A)
R2 = 0.9516
40
R2 = 0.999
120
30
20
100
10
80
1000
0
1200
1400
Conc (g/L)
1600
1800
0
200
400
Conc (g/L)
600
800
Calibration by standard addition was performed once or twice a
month.
Calibration values
Zn
Cu
Fe
250 mg/L
250 mg/L
220 mg/L
I (mA)
21,7
16,0
23,1
Std. Dev
1,3
1,5
1,2
Rel. Std. Dev
6,0
9,6
5,2
Std.s Conc
Average peak heights for added standards during the period
Measurements of Zn, Fe, and Cu
3500
Zn
Cu
3000.0
3000
2500.0
Conc (  g/L)
2500
2000.0
2000
1500.0
1500
1000.0
1000
500.0
500
0
14.1.
3.2.
23.2.
14.3.
Date
3.4.
23.4.
13.5.
3.2.04
23.2.04
14.3.04
3.4.04
Fe
3000.0
8
0.0
14.1.04
A
Temp (C)
6
High [Fe]
2500.0
4
Low [Zn]
2
0
14.1.
3.2.
23.2.
2000.0
14.3.
3.4.
23.4.
1500.0
Date
20
B
Temp (C)
10
1000.0
0
500.0
-10
-20
-30
4.1.
24.1.
13.2.
4.3.
24.3.
13.4.
3.5.
0.0
14.1.04
3.2.04
23.2.04
14.3.04
3.4.04
Date
Continuous measurements from January to May 2004.
One measurement every 30 minutes.
23.4.04
13.5.04
23.4.04
13.5.04
Comparison with ICP-MS
Continuous analyses of zinc, iron, and
copper for a time period of four months
(middle of January to middle of May,
2004), in polluted river water at Løkken
Verk. Sampling performed every 30
minutes, DPASV with 30 s plating time,
scan rate was 20 mV/s, and modulation
pulse 75 mV. NH4Cl (0.015 M) added to
the sample.
Comparison of voltammetric
measurements against ICP-MS
Seawater and brackish water
Costal seawater, Trondheim
Results
Voltammogram of costal seawater. DPASV, scan rate 20 mV/s,
modulation pulse 75 mV, deposition time 540 s at – 1450 mV.
Zinc in seawater
Avg. [Zn] = 2.3 g/L
Results from continuous measurements of iron in seawater.
One measurement every 30 minutes.
Iron in seawater
Fe
1.4
Conc ( g/L)
1.2
1
0.8
0.6
0.4
0.2
0
22.1.
22.1.
23.1.
23.1.
24.1.
24.1.
25.1.
Date
Results from continuous measurements of iron in seawater.
One measurement every 30 minutes.
25.1.
26.1.
Falconbridge, Nickel refinery
Waste Incineration Plant
Monitoring of heavy
metals in purified
scrubbing water at
Heimdal varmesentral,
Trondheim, Norway.
Waste Incineration Plant
Detection of zinc, cadmium and lead in scrubbing wastewater added NH4Cl
(to 0.05M). DPASV, 120 s dep. time at -1300mV, scan rate 15 mV s-1, mod.
pulse 50 mV.
Mercury in wastewater, HVS
Concentrations plotted against time
Waste Incineration Plant
25
Conc (  g/L)
20
15
10
5
0
08-aug-03
18-aug-03
28-aug-03
07-sep-03
17-sep-03
27-sep-03
07-okt-03
17-okt-03
Date
Continuous monitoring of mercury in
purified scrubbing water at Heimdal
incineration plant Trondheim, Norway.
DPASV by use of Au-Bi (4%) electrode,
deposition time 300 s at 100 mV, scan
rate 15 mV/s, modulation pulse 50 mV.
Boliden, Odda. Zinc refinery, Norway
Field instrument, maintenance
Field instrument, maintenance
Refill of supporting electrolyte solution
Polish of electrode
Cleaning cell and filter systems
Calibration
Maintenance of titanium pump
Continuous measurements have to frequently be
verified by performing manual sampling and detection
with other analytical techniques (e.g. once or twice a
months)
Collaboration with Fugro Oceanor
Than you for your attention
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