Chemical methods in geology
2a.
Hydrogeochemical Diagrams
Tento učební materiál vznikl v rámci projektu Rozvoj doktorského studia chemie
č. CZ.02.2.69/0.0/0.0/16_018/0002593
Topics
• Diagrams in hydrogeochemistry
– Stiff diagram
– Piper diagram
– Durov diagram
– pH- Eh
DIAGRAMS
Diagrams
• Clearer presentation of a larger number of samples
• Usually plot of basic ions (Mg2+, Ca2+, K+, Na+ and Cl−, HCO3
−,
SO4
2−, NO3
−)
• Visual comparison – quick recognition of the same types of
water
• Maps
• Point graphs expressing correlations are also handy (e.g. Na+
and Cl−)
R² = 0,0054
0,00
0,05
0,10
0,15
0,20
0,25
0,30
0 0,05 0,1 0,15 0,2 0,25 0,3
Na+[mmol/L]
Cl-[mmol/L]
Korelace Na-Cl
R² = 0,5527
0,060
0,065
0,070
0,075
0,080
0,085
0,090
0,095
0,100
0,105
0,100 0,110 0,120 0,130 0,140 0,150
Mg[mmol/L]
Si [mmol/L]
Mg-Si correlation
XY dot charts – Scatterplot
Basic diagrams
• Bar
– In miliequivalents
– Cation (left) and anion (right) part
– They should be equal =
electroneutrality
• Pie
– In milliequivalents
– Circle size represents total
mineralization
– Cation (top) and anion (bottom)
part – electroneutrality
• Quick recognition of the same
water typesAppelo & Postma (2005)
Stiff diagram
• Qualitative and
quantitative composition
• Three to four axes
• On each axis a cation on
left and an anion on the
right in meq /L
• A characteristic shape is
formed
Seawater
Dissolving carbonates
The other two main components of water
+ sometimes 4 axes (according to the needs of the given study)
What are the properties of the waters shown?
What environment will they match?
Which one will correspond to rainwater?
Calcite karst?
Dolomite karst?
Appelo & Postma (2005)
Goal 2013
How are the waters different?
Stiff on the map
EnviroInsite
Piper diagram
• Especially suitable for large amounts
of samples
• We present the percentages of total
meq/l of cations and anions
separately
• Main cations in the left triangle
• Main anion in the right triangle
• Projection into the central rhombus as a
single point
• Qualitative diagram
• Assessment of water types
• Quantity added through the shape or
size of symbols
– Typically total mineralization via size
Appelo & Postma (2005)
Water classification
By Kvgunten - Own work , CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=56008459
Legend
A: Calcium type
B: No dominant type
C: Magnesium type
D: Sodium and potassium type
E: Bicarbonate type
F: Sulphate type
G: Chloride type
1: Alkaline earths exceed alkalies
2: Alkalies exceed alkaline earths
3: Weak acids exceed strong acids
4: Strong acids exceed weak acids
5: Magnesium bicarbonate type
6: Calcium chloride type
7: Sodium chloride type
8: Sodium bicarbonate type
9: Mixed type
Appelo & Postma (2005)
Forejtová 2008
Forejtová 2008
Láznička 2016
Seifertová 2014
Seifertová 2014
Jeřábková 2013
Durov diagram
• Application similar to a Piper diagram
• Especially suitable for large amounts
of data
• The percentages of total meq/l of
cations and anions plotted separately
• Projection into the center square
• Projection into pH and TDS rectangles
• Semi-quantitative diagram
Láznička 2016
Ušelová 2014
Říčka 2010
Schoeller diagram
• Quantitative comparison of the hydrochemical nature of waters
• A smaller number of samples
Clark (2015)
Piper diagram construction
Pleiades of paid
software
• GWB
Free tools
(Diagrammes,
GW_Plot) – older,
not recommended
On paper
In Excel - extremely
impractical, but
doable
Macros for Python,
R and other
solutions
Construction of diagrams in GWB
• Data in GSS
• Plot – Piper diagram, Stiff etc.
Data from Clark 2015 (Table 7.2) – file Data_diagram.gss
meq/L
Sample
Discharge
(m3/s) TDS Ca2+ Mg2+ Na+K HCO3- SO42- ClChloride
spring 2869 2.7 1.84 45.6 4.41 4.76 35.1
Carbonate spring 170 2.3 0.21 0.04 1.95 0.01 0.02
Sulfate spring 287 2.5 1.37 0.33 1.28 2.8 0.007
River water
January 1.8 2607 2.7 1.8 41.1 4.1 4.5 31.6
February 1.6 2791 2.7 1.8 44.2 4.3 4.7 34
March 2 2341 2.6 1.6 36.5 3.9 4.1 28.1
April 4 1308 2.6 1.4 18.4 2.6 3.3 14
May 151.7 203 2.3 0.3 0.5 1.9 0.2 0.4
June 52.5 274 2.4 0.5 1.5 1.9 0.7 1.1
July 19.9 421 2.4 0.7 3.8 1.9 1.2 2.8
August 10.6 622 2.4 0.9 7 2.1 1.8 5.3
September 6.4 903 2.5 1.2 11.6 2.2 2.6 8.8
October 2.9 1689 2.6 1.5 25.2 3.1 3.5 19.3
November 2.1 2218 2.6 1.7 34.3 3.7 4.1 26.3
December 1.9 2476 2.7 1.8 41.1 4.1 4.5 31.6
20%
20%
20%
40%
40%
40%
60%
60%
60%
80%
80%
80%
Mg
Ca
20%
20%
20%
40%
40%
40%
60%
60%
60%
80%
80%
80%
SO4
Cl
SO
4+Cl
Ca+Mg
HCO
3+CO
3
Na+K
80%
80%
60%
60%
40%
40%
20%
20%
I I
I
J
J
J
K
K
K
L L
L
M M
M
O
O
O
P
P
P
A A
A
B
B
B
C
C
C
D
D
D
E
E
E
G
G
G
H
H
H
I I
I
I Chloride spring
J Carbonate spring
K Sulfate spring
L January
M February
O March
P April
A May
B June
C July
D August
E September
G October
H November
I December
Eh -pH diagrams
• Visualization of acid-base and redox conditions in the
environment
• Assessment of speciation
– Mobility, toxicity, environmental connections, geochemical evolution
• Data plot
Natural conditions
Appelo & Postma (2005)
Adapted from Ryan (2014)
Hydrogeochemistry
Appelo & Postma (2005)
Speciation of Al
• Construct an Eh-pH diagram for aluminum
• Al concentration = 10−7.8 mol/L
Speciation of Fe
• Construct an Eh-pH diagram for iron
• Fe2+ activity = 10−5
• The presence of sulfur (10−3) and carbonates (10−3)
Speciation diagrams
• Visualization of the
dependence of speciation
on the composition of the
system
Tento učební materiál vznikl v rámci projektu Rozvoj doktorského studia
chemie
č. CZ.02.2.69/0.0/0.0/16_018/0002593
References
• Presented diagrams are created for this material or used from
theses available online at: https://is.muni.cz/thesis/
• Other sources:
• APPELO, CAJ and Dieke POSTMA. Geochemistry , groundwater and
pollution :. _ 2nd ed . Leiden: AA Balkema publishers , c2005. ISBN
0-415-36421-3.
• CLARK, I. (2015): Groundwater Geochemistry and
Isotopes.BocaRaton , Florida: CRC Press.
• Ryan, P. (2014). Environmental and low temperature geochemistry.
John Wiley and Sons. 402p. ISBN 978-1-4051-8612-4 ( pbk .)