Senior Scientists

Dr. Callura is an environmental engineer with expertise in sorption chemistry, contaminant fate and transport, and numerical modeling.  He has worked on projects involving a wide range of contaminants, including metals, radioactive elements, hydrocarbons, chlorinated solvents, and nitrosamines.  Prior to joining Gradient, Dr. Callura completed his doctoral research at Carnegie Mellon University, where he developed novel adsorbent materials for the selective extraction of rare earth metals from fluid mixtures and industrial wastes.  He previously worked for the Georgia Department of Natural Resources, where he oversaw remediation of contaminated sites for the State Superfund and Voluntary Remediation programs. Dr. Callura has several years of laboratory experience, including projects involving the fate and transport of veterinary antibiotics in the environment and the formation of carcinogenic disinfection byproducts in water and wastewater treatment systems.

Metal Remediation:  Identified regional standards and best practices for remediation of lead in soil and water.  Reviewed literature regarding metal complexation by sediments and humic substances.

Radionuclide Remediation:  For a CERCLA cost recovery claim, reviewed site investigation and remediation plans.  Investigated potential sources of radionuclides in soil at the site, identified appropriate soil standards, and provided independent cost estimates for remediation.

Metals and Organic Pollutants in River Sediments:  For a CERCLA cost allocation, evaluated potential impacts of manufacturing operations on soil and river sediments.  Reviewed site history, soil and sediment data, and other nearby industrial activity to determine the likelihood that the client’s operations contributed to metals, PAHs, PCBs, and other contaminants detected in a nearby river.

Hydraulic Fracturing Fluids in Groundwater:  Evaluated potential composition of groundwater exposed to hydraulic fracturing fluids.  Calculated concentrations of metals, radionuclides, and other fluid components under a range of mixing conditions.

PCBs in Soil and Sediments:  Assessed historical use of PCBs in a region with impacted soil and sediments.  Performed literature review to highlight industrial activities that are known sources of metals and PCBs and evaluated transport pathways from potential upland sources to the impacted region.

Metal Adsorption:  Studied adsorption and chelation of metals and radionuclides from saline solutions.  Developed new adsorbent materials and designed fixed-bed column systems to selectively extract and recover target metals from aqueous feedstocks.