45641-AC2
Phosphate Oxygen Isotope Systematics of PO4-Fe-Oxide Interactions
Over the past year, our research has focused on making oxygen isotope analyses of phosphate associated with naturally-occurring Fe-oxides, using methods developed in Year. 1 of the grant period. Funding from this ACS grant was used primarily, to support postdoctoral associate Saejung Chang (for both years) who developed protocols for the analysis of small amounts of phosphate in 3.2-3.4 billion-year-old ferruginous chert and banded iron formations (BIF’s) samples from the Barberton Greenstone Complex in S. Africa. Results of her analyses, have provided new information about water temperature, biological activity and biogeochemical cycling of phosphorus in the Archean ocean. This research was done in collaboration with Aivo Lepland of the Geological Survey of Norway. This work as well as Dr. Chang’s studies of phosphate in cave apatite deposits conducted during Year. 1 of the grant period, has been submitted for publication. ACS-PRF funds also supported Dr. Chang’s work related to my research on the P-redox cycle , specifically, on the oxygen isotope systematics of phosphite (HPO32-)oxidation by the bacterium Desulfotignum phosphitoxidans, the enzyme phosphite dehydrogenase (PtxD) and by UV radiation. This research is being done in collaboration with Bernhard Schink (U. of Konstanz) and William Metcalf (U. of Illinois-Urbana Champaign).
In addition, ACS-PRF grant funds supported the purchase of supplies and analytical costs for work conducted by postdoctoral fellow Deb Jaisi, whose research during the second year of funding was focused on analysis of natural marine phosphates associated with iron-oxide deposits produced from ferrous iron in hydrothermal vent fluids by marine Fe-oxidizing bacteria at Loihi Seamount. This research was conducted in collaboration with Craig Moyer (Western Washington University) and Olivier Rouxel (Woods Hole Oceanographic Institution) who are lead PI’s on the NSF-funded FeMO Microbial Observatory at the Loihi undersea volcano. Results from this research complement experimental studies on O isotope fractionation during dissolved phosphate-Fe-oxide interactions performed by Dr. Jaisi during Year 1 of the grant period, which has been submitted for publication. Results of Dr. Jaisi’s research on phosphate in microbial iron mats and dissolved phosphate in ambient seawater and hydrothermal vent fluids provides new insight into the biological cycling of phosphorus within microbial Fe-oxide mats and in subsurface vent fluids, and on the temperature of Fe-oxide mat formation.
