60th Annual Report on Research 2015

PROPOSED RESEARCH SUMMARY

Smectite-illite interstratified clay minerals are ubiquitous in many sedimentary basins. Progressive transformation of smectite to illite via mixed layer illite/smectite has been correlated with petroleum generation and therefore this reaction is considered as a proxy for hydrocarbon exploration.  More recently, formation of illite from smectite was found to occur in biologically catalyzed reactions in short time and bypassed high temperature, pressure and long time required for this transformation in natural environments.  If the smectite-illite reaction is biologically catalyzed in natural environments, it will require a paradigm shift in our fundamental understanding of this reaction as well as its relationship with petroleum maturation. The proposed research seeks to fill in this important gap between controlled lab and natural environments by applying phosphate-oxygen isotope ratios as a tracer and recorder of biological activities during this transformation using sediment records from Mississippi Delta, LA and Fithian, IL. It will combine sequential extraction of sediment P phases with Nuclear Magnetic Resonance (NMR) and phosphate oxygen isotope ratios (d¹⁸O_P) to identify biotic/abiotic environment and temperature of illite (or mixed layer I/S) formation. The outcome of the proposed research, whether it corroborates the laboratory findings or not, will significantly advance our understanding of this reaction as well as broaden the application of d¹⁸O_P as a tracer of this reaction pathway.

ACHIEVEMENTS MADE SO FAR FROM THE FUNDED GRANT

What was accomplished under these goals? (Note this includes achievements from years 1 and 2 combined)

Sediment sampling across the geochemical gradient in Mississippi Delta was completed in July 2014. Additionally sediment samples from Fithian, IL were obtained and analyzed in 2014-15. Sediments, pore waters along with mineralogical composition of sediment were being analyzed.  We attempted to identify layered smectite and illite minerals including interstratified (I/S) in these sediments. Our results have some interesting findings. However, results were not very conclusive. While additional analyses are being done for these samples and will be compared to that of Fithin Illite, we thought similar sediments from other site could provide additional insights into the S/I layer interstratification. Therefore we added Chesapeake Bay as the third site to be compared for the S/I interstratification.

We have been comparing three sites in the Chesapeake Bay where the different degree of authigenesis have been reported in the past. It consists of a 30-m-thick, smectite- and illite-rich interval that overlies the Exmore Formation on the impact crator. Biological and abiotic formation of S-I mineral in this site could provide unique insights into the major question sought to be addressed in this research.

In the second year, we focused more on biogeochemistry and authigenic mineral formation in the sediment column in contrasting environments in the Chesapeake Bay. Our results indicate the active formation of authigenic apatite in sediment column. Discrimination of biological and chemical mediated reaction on the formation of apatite is under investigation. Better understanding of authigenic mineral formation is hoped to pave way to further study smectite-illite transformation, which we plan to execute in the third year of the project.

What opportunities for training and professional development has the project provided?

·         A PhD graduate student (Sunendra R. Joshi) has been funded by this research. Sunendra work on additional aspects of comparing the mineral formation in his research.

·         A PhD graduate student (Hui Li) has been funded in this grant since Sept 1, 2015. Additional progress on her research will be reported in the future progress report.

·         A summer intern (Awet Negusse) graduated: now working as a chemist in Evans Analytical Group.

How have the results been disseminated to communities of interest?

Book chapter published and presentations are made on the professional society meetings

PUBLICATIONS:

Book:

1.      Jaisi, D.P., Blake, R.E., Liang, Y. and Chan, S.J. Exploration of compound-specific organic-inorganic phosphorus transformation using stable isotope ratios in phosphate. In: Applied manure and nutrient chemistry for sustainable agriculture and environment. Eds Z. He and H. Zhang. ISBN 978-94-017-8806-9. pp 267-292.

Published abstracts/presentations in conferences/annual meeting of the professional societies:

1.    Jaisi, D.P., Joshi, S.R.^†, Kukkadapu, R.K., and Sparks, D.L. Scaling up molecular reactions to ecosystem processes: Organic matter degradation controlled phosphorus cycling in the Chesapeake Bay. 249th National Meeting, American Chemical Society. Denver, CO (March 22‒26, 2015).

2.    Li, J.*, Reardon, P., Joshi, S.R. ^†, Bai, Y. ^†, Bear, K. ^†, Washton, N., Jaisi, D.P. Remineralization of organic phosphorus and precipitation of authigenic phosphate in the mid-Chesapeake Bay water column. Geological Society of America Annual Meeting, Baltimore MD (Nov 1-4, 2015).

3.    Joshi, S.R. ^†, Risal, S. ^††, Li, W., Jaisi, D.P. Coupled Fe-P or C-P pathways of P cycling in the Chesapeake Bay sediments: Comparison of three sites with contrasting bottom water hypoxia. Geological Society of America Annual Meeting, Baltimore MD (Nov 1-4, 2015).

*Postdoctoral associate

^†Graduate student

^††Undergraduate student/summer intern