Monitoring a marine ecosystem in introductory chemistry

Rachel Narehood AustinACS Meeting

Boston August 2002

Context for change: Introduce new intro chem sequence (CHEM

107b/CHEM 108b)

CHEM 107 “Atomic and molecular structure”

CHEM 108 “Chemical Reactivity”

CHEM 107b “Chemical Structure and its importance in the environment”

CHEM 108b “Chemical Reactivity in environmental systems”

CHEM 108b “Chemical Reactivity in Environmental Systems”

Using biogeochemical cycles to teach chemistry Nitrogen cycle: thermodynamics Carbon cycle: equilibria (including

solubility and acid base) Sulfur cycle: redox chemistry Oxygen: kinetics

N2

Basicprinciples

Logistics

60 students – 3 sections of 20

125 gallon salt water aquarium w/UV sterilizer, acrylic tank, sump, ballasts with actinic and lanthanide bulbs on timers, submersible heater, venturi protein skimmer

11 weeks of lab Week 1: intro to excel,

Beer’s law refresher Week 2: technical training Weeks 3,4, & 5: rotation 1 Weeks 6, 7, & 8: rotation 2 Weeks 9, 10, & 11: rotation 3 Modified from Ken Hughes –

Analytical chemistry

Lab Structure Group tasks

Nitrogen cycle (NH3, NO2-, NO3

-) Minerals Alkalinity, pH, [O2(aq)]

Weekly cycle Week 1: calibration curve + data point Week 2: data point Week 3: data point + quality control

test

Methods PO4

3- + (NH4)6Mo7O24 [Mo12O36(PO4)]

3- + 3 NH4+

[Mo12O36(PO4)]3- +

SnCl2Molybdenum Blue (

NO2- + sulfanilamide + N-(1-

napthyl)-ethyelendiamine dihydrochloride (NED dihydrochloride) azo dye (

OH

NH3 + HOCl + MnSO4 N OHO

Indophenol

(

Standard Methods for the Examination of Water and Wastewater 20th Ed

Methods Dissolved oxygen

(Winkler method)4 Mn(OH) 2 + O2 + 2 H2O 4

Mn(OH)3

4Mn(OH)3 + 4 I- + 12 H+ 4 Mn2+ + 2I2 + 12 H2O

2Starch-I 2 + 4 S2O32- 4 I- +

2S4O62-

Standard Methods for the Examination of Water and Wastewater 20th Ed

Methods UV determination

of NO3- coupled to

IC determination (=220)

Lab Manual Detailed procedures given

Students are encouraged to check other sources Detailed procedures for hazardous waste

Minimal background (refs. on reserve)Natural Reef Aquariums , by Tullock, ISBN 1-890087-01-7The Conscientious Marine Aquarist, by Fenner, ISBN 1-890087-02-5

The New Marine Aquarium, by Paletta, ISBN 1-890087-52-1 Several appendices

 General Technical Comments (units, concentration/dilution, beers law, titrations, pipetters, quadratic equations)

Chemical Concentration Volume Waste Location

MnSO4*.H2O 0.05% Amount

DisposedDRAIN

Marine Aquarium Weekly Report

Week of _________________

Test Monday PM Tuesday AM Tuesday PM

Group A Ammonia < 1 ppm

Nitrite < 1 ppm

Nitrate 0-20 ppm (lower is better)

Group B Phosphate 1.0-3.0 ppm

Sulfate 2700 ppm

Calcium 400 ppm

Magnesium 1350 ppm

Group C Salinity 19 ppt Cl

Alkalinity 125-250 ppm CaCO3

Dissolved Oxygen 5-7 ppm

Overview pH Temp Specific gravity

Selected Data

0

1

2

3

4

5

6

7

0 2 4 6 8 10

weeks

[ ]

pp

m ammonia

nitrate

average for one class

standard deviation (+/-) for one class

2.2

2.3

2.4

2.5

2.6

2.7

2.8

2.9

1 2

[Nit

rate

] p

pm

Student data facilitates detailed monitoring of tank

Variability is large between groups

Assessment Required sections (10-15 pages, one per group)

Abstract Introduction Experimental Section Results. Discussion and Conclusion

Grading Each lab 100 points - 10 points: title/signatures; abstract; intro;

exp.; results; discussion, graphs/data presentation; writing/typos; effort

Peer review of rough draft (each student does one per semester) Final grade 90% lab grade, 10% effort – individual assessment,

group assessment, peer review, my assessment

Acknowledgements

Lab development: Ken Hughes, Michael Danahy, Lorna Clark, Gary Starzynski, Kathy Covert,

Images: Hilary Domush, Brent Mann, Dana DiGiando, Elizabeth Lewis, Gary Starzynski

Funding: NSF (CCLI), NSF (Molecular Sciences Institute), Bates College (faculty development funds), Bates College/AACU (SENCER development funds), Kroepsch Teaching Award