Analyses planAnalyses planModule 19Module 19

Conductivity and temperatureConductivity and temperature{H{H++} determined using pH electrode } determined using pH electrode

UV/VIS MASUV/VIS MAS Sample pre-treatmentSample pre-treatment

Sample filtrationSample filtration• Total organic carbon Total organic carbon • Major anions and cations Major anions and cations

to be determined by ICto be determined by IC UV oxidationUV oxidation

ConductivityConductivity

Ecoscan Con5 (Eutech instruments) conductivity meter.

The instrument is calibrated using 1000 and 1433 µS calibration solutions

The measurements are done for quality control purposes in order to compare measured and calculated conductivity

{H{H++} determined using pH } determined using pH electrodeelectrode

Thermo Orion model 720 Thermo Orion model 720 pH-meter with a Blueline pH-meter with a Blueline 11-pH electrode. 11-pH electrode. The pH-meter is calibrated The pH-meter is calibrated

with with pH = 4.00 and 7.01 buffer pH = 4.00 and 7.01 buffer solutionssolutions

Major anions and cations to be Major anions and cations to be determined by Ion Chromatograph determined by Ion Chromatograph

(IC)(IC) PrinciplePrinciple• The sample is injected in The sample is injected in

a flow of eluenta flow of eluent• The analyte ions are The analyte ions are

separated by different separated by different degree of binding to the degree of binding to the active sites on the ion active sites on the ion exchange materialexchange material

• Ions with opposite charge Ions with opposite charge of the analyte is of the analyte is exchanged with exchanged with HH++ or OH or OH--

• The activity of the analyte The activity of the analyte along with along with HH++ or OH or OH-- in the eluent in the eluent stream are measured by stream are measured by means of a means of a conductometerconductometer

Total organic carbonTotal organic carbon Analytical chemistry lab Ø 104Analytical chemistry lab Ø 104 High temperature (680High temperature (680ººC) catalytic C) catalytic

combustion analysis on a Shimadzu combustion analysis on a Shimadzu TOC-5000A instrumentTOC-5000A instrument

Principle:Principle: The organic carbon is combusted to The organic carbon is combusted to

COCO22 by high temperature and by high temperature and catalysis. The amount of COcatalysis. The amount of CO22 produced is measured using produced is measured using an IR detectoran IR detector

Analytes measured may include: TC, Analytes measured may include: TC, IC, TOC, NPOC, and POC IC, TOC, NPOC, and POC

Al fractionationAl fractionation

Fractionation of Fractionation of monomeric aluminium monomeric aluminium from polymeric forms from polymeric forms is accomplished by is accomplished by 20 sec. complexation 20 sec. complexation with 8-hydroxyquinoline with 8-hydroxyquinoline at pH 8.3 with subsequent extraction into MIBK organic phaseat pH 8.3 with subsequent extraction into MIBK organic phase

Organic bound monomeric aluminium is separated from inorganic Organic bound monomeric aluminium is separated from inorganic aluminium (mainly labile) by trapping the latter fraction on an aluminium (mainly labile) by trapping the latter fraction on an Amberlight IR-120 ion exchange columnAmberlight IR-120 ion exchange column

The Al concentrations in the organic extracts are determined The Al concentrations in the organic extracts are determined photometrically photometrically Download manual from Download manual from

• http://folk.uio.no/rvogt/KJM_MEF_4010/http://folk.uio.no/rvogt/KJM_MEF_4010/

P fractionationP fractionation

- The oxidation by UV is intended to mimic the photooxidation occurring in the lake during ice free season.

- Filtration through 0,45μm filter (or rather 0,2μm) filter removes algae.

P determinationP determination

- Orthophosphate reacts with - Orthophosphate reacts with ammoniummolybdateammoniummolybdate to a to a yellow-colouredyellow-coloured phosphorousmolybdate acid, that is reduced with phosphorousmolybdate acid, that is reduced with ascorbic acid in the presence of antimony to a ascorbic acid in the presence of antimony to a strongly strongly blue colouredblue coloured complex. This colour is complex. This colour is measured photometrically as described in measured photometrically as described in Norwegian Standard (NS 4724).Norwegian Standard (NS 4724).

QC of dataQC of data After the analysis the After the analysis the

data must be compiled data must be compiled and quality controlled by and quality controlled by ion balance and ion balance and agreement between agreement between measured and calculated measured and calculated conductivityconductivity

For this purpose you may For this purpose you may use the Data compilation use the Data compilation and QC worksheet and QC worksheet available at available at http://folk.uio.no/rvogt/KJhttp://folk.uio.no/rvogt/KJM_MEF_4010/M_MEF_4010/

SpeciesSpeciesin natural freshwaterin natural freshwater

Central equilibriums in natural water samplesCentral equilibriums in natural water samples KJM MEF 4010KJM MEF 4010

Module 19Module 19

Inorganic complexesInorganic complexes

Major cations in natural watersMajor cations in natural waters HH++, Ca, Ca2+2+, Mg, Mg2+2+, Na, Na++, K, K++

Common ligands in natural systems:Common ligands in natural systems: OHOH--, HCO, HCO33

--, CO, CO332-2-, Cl, Cl--, SO, SO44

2-2-, F, F- - & organic anions& organic anions IIn anoxic environment: HSn anoxic environment: HS-- & S & S2-2-

Dominating species in Dominating species in aerobic freshwater aerobic freshwater at pH 8 are:at pH 8 are:

Metal ion Dominating species % Mn+aq of

total amount of M

Mg(II) Mg(H2O)62+ 94

Ca(II) Ca(H2O)62+ 94

Al(III) Al(OH)2(H2O)4+, Al(OH)3(H2O)3

0, Al(OH)4(H2O)2- 1•10-7

Mn(IV) MnO2(H2O)20 -

Fe(III) Fe(OH)2(H2O)4+, Fe(OH)3(H2O)3

0, Fe(OH)4(H2O)2- 2•10-9

Ni(II) Ni(H2O)62+, NiCO3(H2O)5

0 40 Cu(II) CuCO3(H2O)2

0, Cu(OH)2(H2O)20 1

Zn(II) Zn(H2O)42+, ZnCO3(H2O)2

0 40 Pb(II) PbCO3(H2O)4

0 5

HydrolysisHydrolysis

85.22 H4Al(OH)OH4Al

25.17 H3Al(OH)OH3Al

55.10 H2Al(OH)OH2Al

954 H Al(OH) OH Al

6.5 HAl(OH)OHAl(OH)

75.6 HAl(OH)OHAl(OH)

6.5 HAl(OH)OHAl(OH)

954 HAl(OH)OHAl

43214aq

42aq3

3213aq 0

32aq3

212aq22aq3

11aq2

2aq3

4aq42aq0

3

3aq0

32aq2

2aq22aq2

1aq2

2aq3

pKpKpKpKp

pKpKpKp

pKpKp

.pKp

pK

pK

pK

.pK

In aqueous systems, hydrolysis reactions are important In aqueous systems, hydrolysis reactions are important Hydrolysis reactions are controlled by {HHydrolysis reactions are controlled by {H++}}

• The higher the pH, The higher the pH, the stronger the hydrolysis of metal cationsthe stronger the hydrolysis of metal cations

• E.g. AluminiumE.g. Aluminium

• AlAl3+3+aqaq denotes Al(H denotes Al(H22O)O)66

3+3+

Concentrations of dissolved FeConcentrations of dissolved Fe3+3+ species speciesTwo total Fe concentrations, Two total Fe concentrations, FeFeTT = 10 = 10-4-4M and FeM and FeTT = 10 = 10-2-2MM

FeT = 10-4 M

%Fe

0

20

40

60

80

100

FeT = 10-2 M

pH1 2 3 4

%Fe

0

20

40

60

80

100

Fe3+

FeOH2+

Fe(OH)2+

Fe2(OH)24+

Fe3+

FeOH2+

Fe(OH)2+

810121416

0 2 4 6 8 10 12 14pH

pX

pFepFe(OH)pFe(OH)2pFe(OH)3pFe(OH)4

Dissolved Organic MatterDissolved Organic Matter Low molecular weight (LMW)Low molecular weight (LMW)

< 1000Da (e.g. C< 1000Da (e.g. C3232HH8080OO3333NN55PP0.30.3)) E.g.: E.g.:

High molecular weightHigh molecular weight 1000 - > 100 000Da1000 - > 100 000Da Humic substanceHumic substance

• Very complex and coloured substancesVery complex and coloured substances Enhances weatheringEnhances weathering

The protolyzation of weak organic acidsThe protolyzation of weak organic acids Complexation of Al and Fe Complexation of Al and Fe

• Total congruent dissolution Total congruent dissolution

Concentrations and Concentrations and activitiesactivities

ActivityActivity {X} = {X} = XX · [X] · [X]

{X} is the activity to X{X} is the activity to X [X] is the concentration to X[X] is the concentration to X XX is the activity coefficient to X is the activity coefficient to X

XX are dimensionless are dimensionless • It is determined by: It is determined by:

The diameter (å) The diameter (å) of the hydrated Xof the hydrated X

Its valence (nIts valence (nXX)) The ionic strength (I)The ionic strength (I)

n=1

n=2

n=3n=4

• when I 0 1 when I<10-5MAnions + cations

Not possible to calculate further

than I=0.1

Debye HuckelDebye Huckel (DH) (DH) equationequation

For ionic strengths (I) For ionic strengths (I) << 0.1M 0.1M the the XX can be calculated by means of can be calculated by means of e.g. the e.g. the Debye HuckelDebye Huckel equation: equation: I < 0.1I < 0.1

I < 0.005 I < 0.005

becausebecause 0.5 & 0.33 are temperature 0.5 & 0.33 are temperature

dependent table values dependent table values • Presented values are for 25°CPresented values are for 25°C

ååXX is a table value for the specie in question is a table value for the specie in question

))33.01/((5.0log 2 IåIn xxx

Inxx25.0log

1)005.033.01( xå