Calcium (Ca) Availability to Ecosystems: Weathering of Limestone

Biswas

Geological Processes

Calcium Availability Laboratory

Calcium (Ca) availability to ecosystems: Weathering of limestone,

apatite, and Ca-plagioclase (anorthite)

à Data Analysis

àLab notebook and Data analysis (this handout) due Thursday 5/31

Please include answers/discussion of the following questions in your lab notebook. Make sure to show your work—eg. formulas and/or steps of calculations-- that you followed to convert the original masses of samples and absorbance data (of analyzed dilutions of leach samples) all the way to moles of Ca and % weathering of each mineral.

Please make sure to mention whether you are working with the group A or group B data.

Class data

(1) How much % Ca weathered out of each mineral (% weathering) on average for the Group A/Group B data—provide the average and the standard deviationfor each mineral the entire Group A/B data.

-Please produce a (horizontal) bar graph with error bars for the 3 %Ca weathered values of each mineral (use categories for the y-axis with 3 minerals as the names of the categories)

-Are there are outliers in this data set? If the error is greater than 2-fold, this data is likely erroneous due to errors in laboratory methods or calculations.

-Aside from outliers, there is a range of data being produced—why is each group getting a different value for % weathering?

(2) Are there differences in the degree of weathering (% weathering) of the 3 mineral samples ? Did the degree to which each mineral was weathered match your expectations (ie. did minerals weather in the order you expected) ?
(3) Does the amount of Ca weathered out of the limestone appear to have been limited by acid (as I think you hypothesized) ?

(4) On short time scales (10s-100 yrs), which mineral(s) will weather sufficiently quickly to offer Ca to biota (eg. plants & animals) ? What data do you have to support your statement?

(5)On long time scales (1000s yrs)-- which mineral(s) will still be available to contribute Ca to biota ? What data do you have to support your statement?

Your data
Does your sample fall within the range of the rest of the class? Or were your samples very different than the rest of class… such that you would not include them in calculating the average and standard deviation for the class data.

How do you feel about your lab technique, now that you have the class’s data. What steps could you have taken in lab to improve your lab technique?