Analyses plan Module 19 Conductivity {H+} determined using pH electrode Major base cations to be determined by ICP-AES Major anions to be determined by IC Total organic carbon Al fractionation

Conductivity Master student lab V150 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+} determined using pH electrode Master student lab V160 Thermo Orion model 720 pH-meter with a Blueline 11-pH electrode. The pH-meter is calibrated with pH = 4.00 and 7.01 buffer solutions Presented by Xie

Major base cations to be determined by ICP-AES Ca2+, Mg2+, Na+, K+ Method will be demonstrated in Module 24 Appropriate calibration solutions are prepared by Xie Conducted by Anne-Marie Skramstad

Major anions to be determined by Ion Chromathograph (IC) Analytical Chemistry lab Ø109 Tot-F, Cl-, NO3-, SO42- Principle The sample is injected in a flow of eluent The analyte ions are separated by different degree of binding to the active sites on the ion exchange material Ions with opposite charge of the analyte is exchanged with H+ or OH- The activity of the analyte is and accompanied H+ or OH- in the eluent stream is measured by means of a conductometer Presented by Hege Lynne et al

Total organic carbon Analytical chemistry lab Ø 104 High temperature (680C) catalytic combustion analysis on a Shimadzu TOC-5000A instrument Principle: The organic carbon is combusted to CO2 by high temperature and catalysis. The amount of CO2 produced is measured using av IR detector Presented by Hege Lynne et al. Analytes measured may include: TC, IC, TOC, NPOC, and POC

Al fractionation Download manual from Master student lab V160 Method presented as example in Lecture 1 (slide 15) Presented by Xie) Download manual from http://folk.uio.no/rvogt/KJM_MEF_4010/

QC of data After the analysis the data must be compiled and quality controlled by ion balance and agreement between measured and calculated conductivity For this purpose you may use the Data compilation and QC worksheet available at http://folk.uio.no/rvogt/KJM_MEF_4010/

Species in natural freshwater Central equilibriums in natural water samples KJM MEF 4010 Module 19

Inorganic complexes Major cations in natural waters H+, Ca2+, Mg2+, Na+, K+ Common ligands in natural systems: OH-, HCO3-, CO32-, Cl-, SO42-, F- & organic anions In anoxic environment: HS- & S2- Dominating species in aerobic freshwater at pH 8 are: The table shows the % of the aqueous ligand relative to the sum of the M species Free hydroxyl only at pH > 8 though cations of weak bases hydrolyse Bicarbonate and carbonate only at pH>5 Significant amounts of F only where there is high conc. of Al

Hydrolysis In aqueous systems, hydrolysis reactions are important Hydrolysis reactions are controlled by {H+} The higher the pH, the stronger the hydrolysis of metal cations E.g. Aluminium Al3+aq denotes Al(H2O)63+ This is especially the case for amphoteric species The hydrolysis is actually a removal of a proton as the more electronegative oxygen and central atom has taken the electron cloud.

Concentrations of dissolved Fe3+ species Two total Fe concentrations, FeT = 10-4M and FeT = 10-2M

Dissolved Organic Matter Low molecular weight (LMW) < 1000Da (e.g. C32H80O33N5P0.3) E.g.: High molecular weight 1000 - > 100 000Da Humic substance Very complex and coloured substances Enhances weathering The protolyzation of weak organic acids Complexation of Al and Fe Total congruent dissolution Commonly 2-6 mg C/L Secondary synthesis products of the decomposition of organic matter No clear distinctions (boarders). Poorly defined The colour is due to conjugated double bounds Since the humic substances have multiple functional groups that may be used to complexbind metal ions . Such polydentate chelates are very stable (See Soil chemistry, slide 31). Enhances the mobility of heavy (transition) metals (Cd, Ni, Co, Zn) and lipophilic micro pollutants The amount of colour increaeses in many parts of Northern Europe and North America

Concentrations and activities

Not possible to calculate further than I=0.1 Activity {X}=X · [X] {X} is the activity to X [X] is the concentration to X X is the activity coefficient to X X are dimensionless It is determined by: The diameter (å) of the hydrated X Its valence (nX) The ionic strength (I) Not possible to calculate further than I=0.1 n=1 n=2 ”I” is expressed in mol/L Apply the square root of charge to simplify the DH equation and since the  is proportional to the square root of n On the blackboard: c Molar of the salt give rise to an I equals; AgCl: ½(c·1²+c·1²) = ½ · 2c Ba(IO3)2 : ½(c·2²+2c·1²)= ½ · 6c BaSO4: ½(c·2²+c·2²) = ½ · 8c Al(NO3)3: ½(c·3²+3c·1²)= ½ ·12c I can be roughly estimated based on the amount of solved material (TDS): I=2.5•10-5 •TDS (mg/L) or charge: I=1.7•10-5 • SpC (S/cm) n=3 n=4   when I  0   1 when I<10-5M Anions + cations

Debye Huckel (DH) equation For ionic strengths (I) < 0.1M the X can be calculated by means of e.g. the Debye Huckel equation: I < 0.1 I < 0.005 0.5 & 0.33 are temperature dependent table values Presented values are for 25°C åX is a table value for the specie in question Notice the denomination of the å in nm or Ångstrøm in both factors An alternative equation for the extended DH is the Günterberg equation In this equation the expression 3.3å is replaced by 1 (i.e. å is given the Value of 0.3) A other equation is the Davis equation