Aqueous Geochemistry Homework 1

Department of Earth Science |Northeastern Illinois University

AQUEOUS GEOCHEMISTRY
ESCI 406
Spring, 2005 Homework #1: Due Wednesday, January 19, 2005 Sanders

PART I: Chapter 1 Problems. Assignment: Complete any problems from the Jan 12 "pink sheet" that we did not solve in class.

PART II: Collecting Data for the Portfolio of Analyses

Changes to make for next time this course is taught: Ask for 4 analyses. The analysis sets must be from a variety of sources (limit to one set from stream analyses of the USGS). Have students write a one-paragraph description of each set and the general geologic setting. Insist on a full Discussion section in subsequent assignments; this was a weak point of this year's materials handed in.

Objectives of the Assignment

    1) Become familiar with the aqueous geochemistry journals;
    2) Learn to write a citation in standard scientific format;
    3) Collect data that will be used throughout the semester; and
    4) Gain some familiarity with the typical range of values of common water chemistry parameters.

The Assignment

Find five published sets of chemical analysis data that give the chemical composition of various waters. An analysis set refers to a group of several (three or more) analyses of samples taken from the same general study area, but varying with respect to time, space, geologic conditions, or hydrologic conditions. For example, samples may be taken from the same location in a lake in summer and winter (temporal variation), from the ocean at the surface and at depth (spatial variation), from water wells that tap a shallow aquifer and a deep aquifer (geologic variation), or from the same spot in a river during low flow and during high flow conditions (hydrologic variation). The point of this is to allow you to make comparisons of water chemistry in different conditions.

Each analysis reported must include concentrations of the seven major ions (what are they?), temperature, pH, and at least one other parameter (some examples: concentration of a metal, a nutrient, Eh, or an organic chemical). More interesting data sets will also include conductivity, concentration of other ions or constituents (for example, silica, halides, metals, more than one form of the same constituent, isotopes, gases).

In addition, it must be clear from the materials you hand in exactly how the samples vary. For example, you might wish to include a map showing the various locations of sampling to show spatial variation. If the sampling site was the same, but the times varied, you might include the date and time of sampling for each sample. For geologic variation, you might list the mineralogic composition of the aquifer from which each of a group of ground water samples were withdrawn.<>

Starting places to look for this information might be sites on the world wide web, the journals Ground Water, Geochimica et Cosmochimica Acta, Geochemistry International, GSA Bulletin, AAPG Bulletin, Water Resources Research, Environmental Science and Technology, or other journals in the library. Do not use analyses from the Eby textbook. Hint: You are going to have to return to these sources several times throughout the semester, so it might be worthwhile at this point to make a photocopy of the whole paper in which you find the analyses.

What to Hand In

For each analysis set, provide the complete analyses (a photocopy or printout will suffice) and the complete citation for the source.
Each analysis set should begin on a new page. Therefore, your final assignment should be at least five pages long.
Remember, this is going to go into your portfolio of analyses, so make it neat and well-organized.