Angel Cuellar

Date of Award


Degree Name

Master of Science


Geological and Environmental Sciences

First Advisor

Dr. Carla M. Koretsky

Second Advisor

Dr. Daniel Cassidy

Third Advisor

Dr. Johnson Haas

Access Setting

Masters Thesis-Campus Only


Co and Cd bioavailability and mobility in the natural environment are strongly influenced by interactions with soil substrates, including co-precipitation into mineral lattices and sorption onto mineral and microbial surfaces. The goal of this study is to develop a targeted extraction scheme to distinguish metals sorbed on microbes or minerals from metals bound in mineral lattices. To do this, a variety of laboratory experiments were completed to test a series of extracting reagents on several Co- and Cd-doped substrates. Specifically, four extraction reagents (MgCl2, C2H3NaO2, NHOH2∙HCl, and H2O2) described by (Tessier et al., 1979) were used to extract Co or Cd sorbed on Shewanella putrefaciens cells walls or hydrous ferric oxide (HFO), and Co or Cd co-precipitated with HFO. MgCl2 did not dissolve the HFO, but did strip up to 96% of the co-precipitated or adsorbed metals from HFO and Shewanella. C2H3NaO2 also removed up to 84% of the metals from the HFO and the Shewanella and slowly released Fe from the HFO over time (up to 13% after 5 days). NHOH2∙HCl reductively dissolved the iron oxide releasing essentially all of the Fe from the HFO lattice, together with most of the Cd or Co. NHOH2∙HCl also released most of the adsorbed Co and Cd. H2O2 liberated metals from bacteria, but concentrations dropped with time.

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