What Happens to Iron in the River?


Evidence for a photochemically driven iron cycle in the East Fork of the Jemez River, 2012

June 19 Iron Formation
July 25 Iron Formation

Dr. Cooray wanted to find out what drives the iron cycle in the East Fork of the Jemez River. He took water samples using an instrument he designed and built himself to measure iron formation. Then he looked for correlations between the iron formation rate and various environmental conditions. The graphs below show the iron formation rate (red squares, measured on the left y-axis) and the solar radiation (blue diamonds, measured on the right y-axis) for two days in 2012, June 19 and July 25.

Iron is one of the most redox active elements in aquatic systems. Fe(II) is more bioavailable and considered as a transient species between thermodynamically stable Fe(III) compounds and iron oxides. The biogeochemistry of iron can be driven by both chemical reactions (photochemical or thermal) and by microbial mediated reactions.


Asitha T. Cooray and Michael J. Pullin, New Mexico Intitute of Mining and Technology, Socorro, New Mexico, USA

East Fork of the Jemez River
About the Researchers: 

Asitha T. Cooray received his PhD in Chemistry from New Mexico Institute of Mining and Technology in 2013. He received his BSc in Chemistry in 2005 from University of Sri Jayewardenepura, Sri Lanka. He also graduated in 2005 as a Graduate Chemist from the Institute of Chemistry, Ceylon. His research interests are in the field of aqueous environmental chemistry with emphasis on redox cycling of iron in natural waters. He also enjoys developing analytical methods to determine the concentrations of chemical constituents in aquatic environments.


Reading the Graph

1.What is the amount of solar radiation at 2pm on July 25?

2. What is the normalized Fe(II) formation rate at 1pm on June 19?

Making Inferences

3. Which day shows the most total solar radiation?

4. Looking at the June data, what is the relationship between solar radiation and Fe(II) concentrations?

Digging Deeper

5. What are some possible reasons for the July data not showing a pattern similar to the one in June? How could you find out?

click here to view the answers.