Dr. Chauhan has recently secured two significant grants from the Savannah River Nuclear Solutions (SRNS) to investigate remediation of Uranium and heavy metals from the Savannah River Site (SRS), which is an approximately 800-km2 former nuclear weapons production facility located along the Savannah River near Aiken, SC.
Briefly, metals and radionuclides are transported into the environment as a function of nuclear energy activities, accidental spills from nuclear power plants, and the production of nuclear weapons and their testing. Inadvertent release of radionuclides represents a serious threat for both, environmental and human health, since they are easily integrated into the food chain. Therefore, environmental monitoring and ecosystem rehabilitation is required and ongoing at contaminated facilities such as the Savannah River Site (see photo below).
At such sites, the toxic chemicals are mainly monitored by chemical characterization, which generally provides the total concentration of contaminants and circumvents the more relevant aspect of chemical speciation and how much of the contaminant(s) are available for microbially-mediated bioconversion.
Microbial biosensors, that are genetically engineered to detect a toxic pollutant, can be an effective monitoring mechanism because of their strong potential for detecting the bioavailable fraction of the toxic compound, thus providing a direct estimation of toxicity (See flow diagram below).
Thus, FAMU and UGA participants will collaboratively monitor natural attenuation processes by evaluating the bioavailable metal(s) (mainly Nickel) and radionuclide (Uranium) from the subsurface environment of SRS, a nuclear legacy waste site, such that bottlenecks in the attenuation processes can be identified and better management practices can be recommended.
Specifically, PI at Florida A&M University supported by Co-PI at The University of Georgia, Dr. Seaman will collaboratively:
1) use newly designed whole cell bacterial biosensors with the ability to precisely identify the dominant metals and radionuclides such that hotspots of bioavailable contamination can be identified and correlated to the total chemical fraction to bin contaminated samples as high (H), medium (M) and low (L) levels;
2) obtain 16S gene based functional metagenomics information from H, M and L samples to identify and isolate the dominant bacterial-fungal communities, and correlate with concentrations and genes for metals resistance and U bioconversion such that predictions on Ni and U bioremediation across sites using predictive relative metabolic turnover (PRMT) can be obtained;
3) delineate factors that limit Ni and U bioremediation using lab controlled microcosms; and
4) train a steady stream of under-represented undergraduate and graduate students in the field of environmental monitoring and rehabilitation using rigorously intertwined research objectives.
- Three dozen soil/sediment samples (≈ 50 gm) were collected from within the Steed Pond/Tims Branch watershed on the SRS. The samples, SP101, SP101S and SP104, were then returned to the lab, homogenized, and air-dried. The materials were then loaded into a portable x-ray fluorescence unit to screen samples for contaminant metals and U according to EPA Method 6200. Uranium was found at 801 ppm in SP101, 222 ppm in SP104 and 143 ppm in SP101S, respectively.
- Multivariate analysis was performed using Primer6 on the range of contaminants documented from 3 locations within the Steed Pond area, shown below. Principal components analysis (PCA) on the metals and Uranium (U) concentrations sampled at Steed Pond showed that site SP101 correlated positively with both U and Nickel (Ni) concentrations. Moreover, both U and Ni clustered together and away from other heavy metals, indicating that the sampled site should be restored for these two contaminants relative to the other metals that were also found in the Steed Pond site. Site specific analysis for metals and Uranium are shown below.
Furthermore, bacterial community profiling was performed using PCR with primers 515aF and 926R, using conditions described previously (Walters et al. 2015). Similarly, fungal community profiling was performed using primers ITS1f and ITS2 (e.g.Walters et al. 2015). Archaeal community profiling was performed using primers Arc344F and Arc806R, with conditions described previously (e.g. Takahashi et al. 2014). Shown below are data obtained on the bacteria, archaea and fungi from the Uranium impacted SRS sites, which revealed a diverse assemblage of communities regardless of contamination levels.