G444 / G544 Methods in Analytical Geochemistry
Course Objectives:
Methods in Analytical Geochemistry is designed as an overview of
basic collection and preparation of water, soil and rock samples for
elemental analysis by analytical geochemical techniques used in
environmental and exploration geology, as well as, geochemical
studies.
Second, it is designed to give background and context to published
data sets for critical evaluation.
Third, it is an opportunity to develop scientific writing skills.
G444 / G544 Methods in Analytical Geochemistry
Course participant evaluation is based on:
a) bi-weekly lab book evaluations (including write-ups, data plots, analytical
accuracy, and neatness) [50%];
b) b) participation in summary lab/classroom/field discussions and activities
[20%];
c) c) including abstracts, field site summaries and evaluation of a final, threepage, method write-up [30%]*.
d) Graduate students taking the class for G544 (graduate credit) will have an
additional written assignment due after GSA week (TBA) involving
compilation, analysis and interpretation of a data set of their choosing,
that will be factored into the written assignment grade.
Website with resources for G444/G544 can be found by:
http://www.indiana.edu/~ereg444/index.htm
This website is a work in progress, feel free to make suggestions.
Date:
Weekly Schedule
Monday
8:00
9:00
~two additional hours per week to be
scheduled weekly
10:00
Lecture:
Geology 214
11:00
noon
MSBII 453 (lab)
1:00
2:00
3:00
4:00
5:00
Tuesday
Wednesday Thursday
Friday
Basic Field parameters
Temperature
pH
Specific Conductance
Dissolved Oxygen
Oxidation-Reduction Potential - Eh
Alkalinity
And water sampling.
pH
It is defined as the negative
common logarithm of the
concentration of hydrogen ions
[H+] in moles/liter:
pH = -log10 [H+].
The concentration of hydrogen
ions is commonly expressed in
terms of the pH scale. Low pH
corresponds to high hydrogen
ion concentration and vice versa.
a Pourbaix diagram, also known
as a potential/pH diagram or
Eh/pH diagram. The diagrams
are named after Marcel Pourbaix
(1904–1998), the Russian-born
chemist who invented them.
In sedimentary environments the
concept of geochemical facies is
best illustrated on an Eh-pH
diagram, a diagram delineating
the stability field of certain
minerals in terms of the proton
concentration (pH) and electron
concentration (Eh).
Eh and REDOX: the ability of an
environment to supply electrons
to an oxidizing agent, or to take
up electrons from a reducing
agent. Units are volts (V) or
millivolts (mV).
Eh-pH predominance diagram for aqueous
chromium (Cr) at 25 °C (Crtot = 1 µM).
Specific conductance (SpC) is a measure of the
concentration of soluble salts in solution.
Units are µSeimens/cm (µS/cm) or µmho/cm.
Conductance is also a readily available field test which
enables a worker to compare a new sample with previously
analyzed samples quickly and easily.
Irrigation Recommendations
Criteria
Values
Authority
Total Dissolved
Solids (TDS)
500 mg/l
EPA 440/9-76-023
Sodium plus
Potassium
200 mg/l
EPA 440/9-76-023
Chloride
250 mg/l
EPA 440/9-76-023
Nitrate
450 mg/l
EPA 440/9-76-023
Total Hardness
150 mg/l
EPA 440/9-76-023
Specific
Conductance
750 µmhos/cm
or µS/cm
U.S. Salinity Lab.
Alkalinity (AT) is a measure of the ability of a solution to
neutralize acids to the equivalence point of carbonate
or bicarbonate. Units are in milligrams/liter (mg/L) as
the carbonate species.
Typical ranges of values for some water field
measurements.
From: Sanders, L.L., 1998, A Manual of Field Hydrogeology: Prentice-Hall, NJ, 381p.
Type of waters:
rain water
freshwater
lakes/streams
ground water
brines
ocean water
landfill leachate
acid mine drainage
wetlands / bogs
Specific
Conductance
(µS/cm)
2 to 100
Eh
(millivolts)
pH
(pH units)
+400 to +600
4-7
2 to 100
+300 to +500
6.5 - 8.5
50 to 50,000
up to 500,000
~ 50,000
10,000
up to 500,000
50 to 50,000
-200 to +100
-300 to -600
+300 to +500
variable
+600 to +800
+100 to -100
6 - 8.5
near neutral
7.8 - 8.4
near neutral
below 5
variable
Note: 92 % of the world’s total freshwater consumption each year attributed to
agriculture, according to a study in the Proceedings of the National Academy of
Sciences 2012.
Hypothesis – as per Merriam-Webster
Etymology: Greek, from hypotithenai to put
under, suppose
1 a: an assumption or concession made for the sake of
argument b : an interpretation of a practical situation or
condition taken as the ground for action
2 : a tentative assumption made in order to draw out
and test its logical or empirical consequences
3 : the antecedent clause of a conditional statement