Skip to Main Content U.S. Department of Energy
Fundamental and Computational Sciences Directorate

Staff information


Ravi Kukkadapu

Environmental Dynamics & Simulations
Pacific Northwest National Laboratory
PO Box 999
MSIN: K8-96
Richland, WA 99352


Dr. Kukkadapu has been elemental in fostering international recognition of EMSL’s 57Fe-Mössbauer spectroscopy laboratory as a premier laboratory for biogeochemical sciences involving Fe-oxides and Fe-containing clays that are ubiquitous in subsurface. His expertise in application of Mössbauer spectroscopy coupled with electron microscopy and X-ray diffraction and absorption techniques on (bio)transformation of primary Fe(II)/(III)-oxides into secondary Fe(II)/(III)-minerals (carbonates, phosphates, and sulfides) and as well on redox transformation of Fe-clays under various biological, geochemical and hydrological conditions on attenuation or long-term stability of redox-sensitive contaminants has resulted in many fruitful collaborations and numerous publications.

Research Interests

  • Dr. Kukkadapu is recognized in the area of the role of soil Fe minerals on soluble radionuclide attenuation in subsurface. His current interests are: 1) the interplay of organic matter-mineral-bacteria interactions in subsurface and floodplain/terrestrial-aquatic interfaces on stability of soil organic matter (effect on greenhouse gases), nutrient cycling, and metal contaminant remediation, 2) the role of (bio)transformation/redox cycling of Fe-(oxyhydr)oxides/Fe-clays/Fe-sulfides (and Mn-oxides and zero-valent Fe ) in subsurface/floodplain/lake sediments on remediation of soluble metal contaminants, e.g., radionuclides, such as U, Tc and Pu, hazardous metals, such as, As, Cr, and Hg, and nitrate and phosphate nutrient cycling (water quality), 3) effect of soil organic matter on interfacial electron transfer between sorbed Fe(II) and clay Fe(III)/Fe-oxides, 4) development of stable materials for safe disposal of nuclear materials, e.g., garnets with large amounts of U loading, 5) geological CO2 sequestration, 6) reactive nano Fe phases, 7) Fe containing NH3-SCR catalysts, 8) application of 57Fe (and 119Sn) Mössbauer spectroscopy in geosciences, material synthesis, and catalysis areas, and 9) a general interest in, 151Eu and 129I Mössbauer spectroscopy.
  • Dr. Kukkadapu is extensively involved in programmatic research funded by the both Subsurface Biogeochemical Research (SBR) of DOE’s Office of Biological and Environmental Research (OBER) program and Geosciences Division of DOE’s Basic Energy Science (BES) program. He is also extensively involved with numerous University and other DOE Laboratory investigators in the area of subsurface biogeochemical research thru EMSL user proposals. His research has direct implications to DOE’s primary environmental mission-to assist in developing predictive biogeochemical transports models to better understand the fate and transport of radioactive and hazardous metal contaminants, such as, uranium (U), technetium (Tc), plutonium (Pu), and mercury (Hg), in subsurface/aquifers.

Education and Credentials

  • PhD, Inorganic Chemistry, Indian Institute of Chemical Technology, India

Affiliations and Professional Service

  • American Chemistry Society
  • American Geophysical Union
  • The Clay Minerals Society
  • Soil Science Society of America

Awards and Recognitions

  • 2011: Co-organizer of “The Sixth Nassau-Argonne International Mössbauer Symposium”, Garden City, NY
  • 2010: Featured as a Raising Star on the cover page of the “Mössbauer Effect Data Journal"
  • 2010: Cover of “Clays and Clay Mineral” Journal
  • 2010: Associate Editor of the “Clays and Clay Minerals” journal
  • 2009: Keynote speaker of the “Annual meeting of Clay Minerals Group of Mineralogical Society of United Kingdom”, New Castle, U. K - FuturoClay symposium
  • 2009: PNNL Outstanding Performance Award for bringing in external visibility to EMSL Mössbauer capability
  • 2009: Recognized as an Emerging Scientist in the Mössbauer Spectroscopy field at the “International Conference on Applications of the Mössbauer effect conference”, Vienna, Austria
  • 2009: Science Magazine Editor’s Choice, July 3, 2009 of the article “Reduction of Hg(II) to Hg(0) by Magnetite” , that appeared in Environmental Science and Technology
  • 2004: Co-organizer of the “Magnetic Resonance Spectroscopic studies of Clay Minerals” session at the 41st Annual Meeting of the Clay Minerals Society
  • 2000: Best poster award at the “International Symposium on the Industrial Applications of Mössbauer effect”, Virginia Beach
  • 1987-1990: Robert R. Welch foundation’s postdoctoral research fellowship, University of Houston

PNNL Publications


  • Chen C, RK Kukkadapu, OV Lazareva, and DL Sparks. 2017. "Solid-phase Fe Speciation along the Vertical Redox Gradients in Floodplains using XAS and Mössbauer Spectroscopies." Environmental Science & Technology 51(14):7903-7912.  doi:10.1021/acs.est.7b00700
  • Elsaidi SK, MA Sinnwell, D Banerjee, A Devaraj, RK Kukkadapu, TC Droubay, Z Nie, L Kovarik, V Murugesan, S Manandhar, MI Nandasiri, BP McGrail, and PK Thallapally. 2017. "Reduced Magnetism in Core-Shell Magnetite@MOF Composites." Nano Letters 17(11):6968-6973.  doi:10.1021/acs.nanolett.7b03451
  • Ilgen AG, RK Kukkadapu, DR Dunphy, K Artyushkova, JM Cerrato, JN Kruichak, M Janish, CJ Sun, JM Argo, and RE Washington. 2017. "Synthesis and characterization of redox-active ferric nontronites." Chemical Geology 470:1-12.  doi:10.1016/j.chemgeo.2017.07.010
  • Kaur M, JS Mccloy, RK Kukkadapu, CI Pearce, J Tucek, ME Bowden, MH Engelhard, E Arenholz, and Y Qiang. 2017. "TETRAGONAL LIKE PHASE IN CORE-SHELL IRON IRON-OXIDE." Journal of Physical Chemistry C 121(21):11794-11803.  doi:10.1021/acs.jpcc.7b01469
  • Kovarik L, NM Washton, RK Kukkadapu, A Devaraj, A Wang, Y Wang, J Szanyi, CHF Peden, and F Gao. 2017. "Transformation of active sites in Fe/SSZ-13 SCR catalysts during hydrothermal aging: a spectroscopic, microscopic and kinetics study." ACS Catalysis 7(4):2458-2470.  doi:10.1021/acscatal.6b03679
  • Noel V, KE Boye, RK Kukkadapu, SE Bone, JS Lezama Pacheco, E Cardarelli, N Janot, S Fendorf, KH Williams, and J Bargar. 2017. "Understanding the controls on redox processes in floodplain sediments of the Upper Colorado River Basin." Science of the Total Environment 603-604:663-675.  doi:10.1016/j.scitotenv.2017.01.109
  • Wu T, AM Griffin, CA Gorski, E Shelbolina, H Xu, RK Kukkadapu, and EE Roden. 2017. "Interactions Between Fe(III)-oxides and Fe(III)-phyllosilicates During Microbial Reduction 2: Natural Subsurface Sediments." Geomicrobiology Journal 34(3):231-241.  doi:10.1080/01490451.2016.1174758
  • Xu J, H Veeramani, N Qafoku, G Singh, MV Riquelme Breazeal, A Pruden, RK Kukkadapu, BN Gartman, and MF Hochella, Jr. 2017. "Efficacy of Acetate-Amended Biostimulation for Uranium Sequestration: Combined Analysis of Sediment/Groundwater Geochemistry and Bacterial Community Structure." Applied Geochemistry 78:172-185.  doi:10.1016/j.apgeochem.2016.12.024
  • Xu J, H Veeramani, N Qafoku, G Singh, MV Riquelme Breazeal, A Pruden, RK Kukkadapu, BN Gartman, and MF Hochella, Jr. 2017. "Efficacy of Acetate-Amended Biostimulation for Uranium Sequestration: Combined Analysis of Sediment/Groundwater Geochemistry and Bacterial Community Structure." Applied Geochemistry 78:172-185.  doi:10.1016/j.apgeochem.2016.12.024


  • Gao F, Y Zheng, RK Kukkadapu, Y Wang, ED Walter, B Schwenzer, J Szanyi, and CHF Peden. 2016. "Iron loading effects in Fe/SSZ-13 NH3-SCR catalysts: nature of the Fe-ions and structure-function relationships ." ACS Catalysis 6(5):2939-2954.  doi:10.1021/acscatal.6b00647
  • Guo X, A Navrotsky, RK Kukkadapu, MH Engelhard, A Lanzirotti, M Newville, ES Ilton, SR Sutton , and H Xu. 2016. "Structure and Thermodynamics of Uranium-Containing Iron Garnets." Geochimica et Cosmochimica Acta 189:269-281.  doi:10.1016/j.gca.2016.05.043
  • Guo X, E Tiferet, L Qi, J Solomon, A Lanzirotti, M Newville, MH Engelhard, RK Kukkadapu, D Wu, ES Ilton, MD Asta, S Sutton, H Xu, and A Navrotsky. 2016. "U(v) in Metal Uranates: A Combined Experimental And Theoretical Study of MgUO4, CrUO4 and FeUO4." Dalton Transactions 45(11):4622-4632.  doi:10.1039/C6DT00066E
  • Kaplan DI, RK Kukkadapu, JC Seaman, BW Arey, A Dohnalkova, S Buttner, D Li, T Varga, KG Scheckel, and PR Jaffe. 2016. "Iron Mineralogy and Uranium-Binding Environment in the Rhizosphere of a Wetland Soil." Science of Total Environment 569-570:53-64.  doi:10.1016/j.scitotenv.2016.06.120
  • Lao D, RK Kukkadapu, L Kovarik, BW Arey, DJ Heldebrant, and SK Nune. 2016. "Switchable Ionic Liquids: An Environmentally-friendly Medium to Synthesize Nanoparticulate Green Rust." Current Inorganic Chemistry 6(2):92-99.  doi:10.2174/1877944106999160317160621
  • Long GJ, F Grandjean, X Guo, A Navrotsky, and RK Kukkadapu. 2016. "Mössbauer Spectral Properties of Yttrium Iron Garnet, Y3Fe5O12, and its Isovalent and Nonisovalent Yttrium-Substituted Solid Solutions." Inorganic Chemistry 55(7):3413-3418.  doi:10.1021/acs.inorgchem.5b02769
  • Nune SK, D Lao, DJ Heldebrant, J Liu, MJ Olszta, RK Kukkadapu, LM Gordon, MI Nandasiri, GA Whyatt, CK Clayton, DW Gotthold, MH Engelhard, and HT Schaef. 2016. "Anomalous Water Expulsion from Carbon-Based Rods at High Humidity." Nature Nanotechnology 11(9):791-797.  doi:10.1038/nnano.2016.91
  • Ruby C, S Naille, G Ona-Nguema, G Morin, M Mallet, D Guerbois, K Barthelemy, M Etique, A Zegeye, Y Zhang, H Boumaiza, M Al-Jaberi, A Renard, V Noel, P Binda, K Hanna, C Despas, M Abdelmoula, RK Kukkadapu, J Sarrias, M Albignac, P Rocklin, F Nauleau, N Hyvrard, and JM Genin. 2016. "Use Of Ferrihydrite-coated Pozzolana And Biogenic Green Rust To Purify Waste Water Containing Phosphate And Nitrate." Current Inorganic Chemistry 6(2):100-118.  doi:10.2174/1877944106999160603125459
  • Starcher AN, W Li, RK Kukkadapu, EJ Elzinga, and DL Sparks. 2016. "Fe(II) Sorption On Pyrophyllite: Effect Of Structural Fe(III) (impurity) In Pyrophyllite On Nature Of Layered Double Hydroxide (LDH) Secondary Mineral Formation." Chemical Geology 439:152-160.  doi:10.1016/j.chemgeo.2016.06.017
  • Wu T, RK Kukkadapu, AM Griffin, CA Gorski, H Konishi, H Xu, and EE Roden. 2016. "Interactions Between Fe(III)-Oxides and Fe(III)-Phyllosilicates during Microbial Reduction 1: Synthetic Sediments." Geomicrobiology Journal 33(9):793-806.  doi:10.1080/01490451.2015.1117546
  • Zhang W, D Banerjee, J Liu, HT Schaef, JV Crum, CA Fernandez, RK Kukkadapu, Z Nie, SK Nune, RK Motkuri, KW Chapman, MH Engelhard, JC Hayes, KL Silvers, R Krishna, BP McGrail, J Liu, and PK Thallapally. 2016. "Redox-Active Metal-Organic Composites for Highly Selective Oxygen Separation Applications." Advanced Materials 28(18):3572-3577.  doi:10.1002/adma.201600259


  • Abrecht DG, JM Schwantes, RK Kukkadapu, BS McDonald, GC Eiden, and LE Sweet. 2015. "Real-Time Noise Reduction for Mossbauer Spectroscopy through Online Implementation of a Modified Kalman Filter." Nuclear Instruments and Methods in Physics Research. Section A, Accelerators, Spectrometers, Detectors and Associated Equipment 773:66-71.  doi:10.1016/j.nima.2014.10.053
  • Chen C, RK Kukkadapu, and DL Sparks. 2015. "Influence of Coprecipitated Organic Matter on Fe2+(aq) -Catalyzed Transformation of Ferrihydrite: Implications for Carbon Dynamics." Environmental Science & Technology 49(18):10927-10936.  doi:10.1021/acs.est.5b02448
  • Gao F, M Kollar, RK Kukkadapu, NM Washton, Y Wang, J Szanyi, and CHF Peden. 2015. "Fe/SSZ-13 as an NH3-SCR Catalyst: A Reaction Kinetics and FTIR/Mössbauer Spectroscopic Study." Applied Catalysis. B, Environmental 164:407-419.  doi:10.1016/j.apcatb.2014.09.031
  • Gartman BN, N Qafoku, JE Szecsody, RK Kukkadapu, Z Wang, DM Wellman, and MJ Truex. 2015. "Uranium Fate in Hanford Sediment Altered by Simulated Acid Waste Solutions ." Applied Geochemistry 63(December 2015):1-9.  doi:10.1016/j.apgeochem.2015.07.010
  • Guo X, RK Kukkadapu, A Lanzirotti, M Newville, MH Engelhard, SR Sutton , and A Navrotsky. 2015. "Charge-coupled Substituted Garnets (Y3-xCa0.5xM0.5x)Fe5O12 (M = Ce, Th): Structure and Stability as Crystalline Nuclear Waste Forms." Inorganic Chemistry 54(8):4156-4166.  doi:10.1021/acs.inorgchem.5b00444
  • Liu Y, C Liu, RK Kukkadapu, JP McKinley, JM Zachara, AE Plymale, MD Miller, T Varga, and CT Resch. 2015. "99Tc(VII) Retardation, Reduction, and Redox Rate Scaling in Naturally Reduced Sediments." Environmental Science & Technology 49(22):13403-13412.  doi:10.1021/acs.est.5b03273
  • Mccloy JS, NM Washton, PL Gassman, J Marcial, JL Weaver, and RK Kukkadapu. 2015. "Nepheline crystallization in boron-rich alumino-silicate glasses as investigated by multi-nuclear NMR, Raman, & Mössbauer spectroscopies." Journal of Non-crystalline Solids 409:149-165.  doi:10.1016/j.jnoncrysol.2014.11.013
  • Sunendra JR, RK Kukkadapu, DJ Burdige, ME Bowden, DL Sparks, and DP Jaisi. 2015. "Organic Matter Remineralization Predominates Phosphorus Cycling in the Mid-Bay Sediments in the Chesapeake Bay." Environmental Science & Technology 49(10):5887-5896.  doi:10.1021/es5059617
  • Zhao L, H Dong, RK Kukkadapu, Q Zeng, RE Edelmann, M Pentrak, and A Agrawal. 2015. "Biological Redox Cycling Of Iron In Nontronite And Its Potential Application In Nitrate Removal." Environmental Science & Technology 49(9):5493-5501.  doi:10.1021/acs.est.5b00131


  • Qafoku N, BN Gartman, RK Kukkadapu, BW Arey, KH Williams, PJ Mouser, SM Heald, JR Bargar, N Janot, SB Yabusaki, and PE Long. 2014. "Geochemical and Mineralogical Investigation of Uranium in Multi-element Contaminated, Organic-rich Subsurface Sediment ." Applied Geochemistry 42:77-85.  doi:10.1016/j.apgeochem.2013.12.001
  • Fan D, R Anitori, BM Tebo, PG Tratnyek, JS Lezama Pacheco, RK Kukkadapu, L Kovarik, MH Engelhard, and ME Bowden. 2014. "Oxidative Remobilization of Technetium Sequestered by Sulfide-Transformed Nano Zerovalent Iron." Environmental Science & Technology 48(13):7409-7417.  doi:10.1021/es501607s
  • Felmy AR, DA Moore, EC Buck, SD Conradson, RK Kukkadapu, LE Sweet, DG Abrecht, and ES Ilton. 2014. "The Solubility of 242PuO2 in the Presence of Aqueous Fe(II): The Impact of Precipitate Preparation." Radiochimica Acta 102(10):861-874.  doi:10.1515/ract-2013-2187
  • Guo X, AH Tavakoli, S Sutton, RK Kukkadapu, L Qi, A Lanzirotti, M Newville, MD Asta, and A Navrotsky. 2014. "Cerium Substitution in Yttrium Iron Garnet: Valence State, Structure, and Energetics." Chemistry of Materials 26(2):1133-1143.  doi:10.1021/cm403444f
  • Matyas J, JE Amonette, RK Kukkadapu, DK Schreiber, and AA Kruger. 2014. "THE EFFECTS OF GLASS DOPING, TEMPERATURE AND TIME ON THE MORPHOLOGY, COMPOSITION, AND IRON REDOX OF SPINEL CRYSTALS." Chapter 14 in Advances in Materials Science for Environmental and Energy Technologies III, October 27-31, 2013, Montreal, Quebec, Canada. Ceramic Transactions, vol. 250, ed. T Ohji, et al, pp. 147-156.  John Wiley & Sons, Inc., Hoboken, NJ.  doi:10.1002/9781118996652.ch14
  • Shao H, RK Kukkadapu, EJ Krogstad, MK Newburn, and KJ Cantrell. 2014. "Mobilization of Metals from Eau Claire Siltstone and the Impact of Oxygen under Geological Carbon Dioxide Sequestration Conditions." Geochimica et Cosmochimica Acta 141:62-82.  doi:10.1016/j.gca.2014.06.011


  • Bi Y, SP Hyun, RK Kukkadapu, and KF Hayes. 2013. "Oxidative Dissolution of UO2 in a Simulated Groundwater Containing Synthetic Nanocrystalline Mackinawite." Geochimica et Cosmochimica Acta 102:175-190.  doi:10.1016/j.gca.2012.10.032
  • Fan D, R Anitori, BM Tebo, PG Tratnyek, JS Lezama Pacheco, RK Kukkadapu, MH Engelhard, ME Bowden, L Kovarik, and BW Arey. 2013. "Reductive Sequestration Of Pertechnetate (99TcO4-) By Nano Zerovalent Iron (nZVI) Transformed By Abiotic Sulfide." Environmental Science & Technology 47(10):5302-5310.  doi:10.1021/es304829z
  • Fox PM, JA Davis, RK Kukkadapu, DM Singer, JR Bargar, and KH Williams. 2013. "Abiotic U(VI) Reduction by Sorbed Fe(II) on Natural Sediments." Geochimica et Cosmochimica Acta 117:266-282.  doi:10.1016/j.gca.2013.05.003
  • Shah M, CC Lin, RK Kukkadapu, MH Engelhard, X Zhao, Y Wang, T Barkay, and N Yee. 2013. "Syntrophic Effects in a Subsurface Clostridial Consortium on Fe(III)-(Oxyhydr)oxide Reduction and Secondary Mineralization." Geomicrobiology Journal 31(2):101-115.  doi:10.1080/01490451.2013.806610
  • Veeramani H, A Scheinost, N Monsegue, N Qafoku, RK Kukkadapu, M Newville, A Lanzirotti, A Pruden, M Murayama, and MF Hochella, Jr. 2013. "Abiotic Reductive Immobilization of U(VI) by Biogenic Mackinawite." Environmental Science & Technology 47(5):2361-2369.  doi:10.1021/es304025x
  • Zhao L, H Dong, RK Kukkadapu, A Agrawal, D Liu, J Zhang, and RE Edelmann. 2013. "Biological Oxidation of Fe(II) in Reduced Nontronite Coupled with Nitrate Reduction by Pseudogulbenkiania sp. Strain 2002." Geochimica et Cosmochimica Acta 119:231-247.  doi:10.1016/j.gca.2013.05.033


  • Pearce CI, O Qafoku, J Liu, E Arenholz, SM Heald, RK Kukkadapu, CA Gorski, CMB Henderson, and KM Rosso. 2012. "Synthesis and properties of titanomagnetite (Fe3-xTixO4) nanoparticles: A tunable solid-state Fe(II/III) redox system." Journal of Colloid and Interface Science 387(1):24-38.  doi:10.1016/j.jcis.2012.06.092
  • Qafoku O, L Kovarik, RK Kukkadapu, ES Ilton, BW Arey, J Tucek, and AR Felmy. 2012. "Fayalite Dissolution and Siderite Formation in Water-Saturated Supercritical CO2." Chemical Geology 332-333:124-135.  doi:10.1016/j.chemgeo.2012.09.028
  • Campbell KM, RK Kukkadapu, N Qafoku, AD Peacock, E Lesher, KH Williams, JR Bargar, MJ Wilkins, LA Figueroa, J Ranville, J Davis, and PE Long. 2012. "Geochemical, mineralogical and microbiological characteristics of sediment from a naturally reduced zone in a uranium-contaminated aquifer." Applied Geochemistry 27(8):1499-1511.  doi:10.1016/j.apgeochem.2012.04.013
  • Lee JH, JK Fredrickson, RK Kukkadapu, MI Boyanov, KM Kemner, X Lin, DW Kennedy, BN Bjornstad, A Konopka, DA Moore, CT Resch, and JL Phillips. 2012. "Microbial Reductive Transformation of Phyllosilicate Fe(III) and U(VI) in Fluvial Subsurface Sediments." Environmental Science & Technology 46(7):3721-3730.  doi:10.1021/es204528m
  • Peretyazhko T, JM Zachara, RK Kukkadapu, SM Heald, IV Kutnyakov, CT Resch, BW Arey, CM Wang, L Kovarik, JL Phillips, and DA Moore. 2012. "Pertechnetate (TcO4-) reduction by reactive ferrous iron forms in naturally anoxic, redox transition zone sediments from the Hanford Site, USA." Geochimica et Cosmochimica Acta 92:48-66. 
  • Shelobolina ES, H Xu, H Konishi, RK Kukkadapu, T Wu, M Blothe, and EE Roden. 2012. "Microbial Lithotrophic Oxidation of Structural Fe(II) in Biotite." Applied and Environmental Microbiology 78(16):5746-5752. 
  • Um W, HS Chang, JP Icenhower, WW Lukens, RJ Serne, N Qafoku, RK Kukkadapu, and JH Westsik, Jr. 2012. "Iron Oxide Waste Form for Stabilizing 99Tc." Journal of Nuclear Materials 429(1-3):201-209.  doi:10.1016/j.jnucmat.2012.06.004
  • Wu T, ES Shelobolina, H Xu, H Konishi, RK Kukkadapu, and EE Roden. 2012. "Isolation and microbial reduction of Fe(III) phyllosilicates from subsurface sediments." Environmental Science & Technology 46(21):11618-11626.  doi:10.1021/es302639n
  • Yang J, RK Kukkadapu, H Dong, ES Shelobolina, J Zhang, and J Kim. 2012. "Effects of Redox Cycling of Iron in Nontronite on Reduction of Technetium." Chemical Geology 291:206-216.  doi:10.1016/j.chemgeo.2011.10.013


  • Bishop ME, H Dong, RK Kukkadapu, C Liu, and RE Edelmann. 2011. "Bioreduction of Fe-bearing clay minerals and their reactivity toward pertechnetate (Tc-99)." Geochimica et Cosmochimica Acta 75(18):5229-5246.  doi:10.1016/j.gca.2011.06.034
  • Campbell KM, JA Davis, JR Bargar, DE Giammar, R Bernier-Latmani, RK Kukkadapu, KH Williams, H Veramani, KU Ulrich, JB Stubbs, SB Yabusaki, LA Figueroa, E Lesher, MJ Wilkins, AD Peacock, and PE Longg. 2011. "Composition, stability, and measurement of reduced uranium phases for groundwater bioremediation at Old Rifle, CO." Applied Geochemistry 26:S167-S169.  doi:10.1016/j.apgeochem.2011.03.094
  • Jaisi DP, RK Kukkadapu, LM Stout, T Varga, and RE Blake. 2011. "Biotic and abiotic pathways of phosphorus cycling in minerals and sediments: insights from oxygen isotopes in phosphate." Environmental Science & Technology 45(15):6254-6261.  doi:10.1021/es200456e
  • McCloy JS, RK Kukkadapu, JV Crum, BR Johnson, and TC Droubay. 2011. "Size Effects on Gamma Radiation Response of Magnetic Properties of Barium Hexaferrite Powders." Journal of Applied Physics 110(11):Article No. 113912.  doi:10.1063/1.3665769
  • Qafoku N, PE Dresel, JP McKinley, ES Ilton, W Um, CT Resch, RK Kukkadapu, and SW Petersen. 2011. Geochemical Characterization of Chromate Contamination in the 100 Area Vadose Zone at the Hanford Site - Part 2PNNL-17865, Pacific Northwest National Laboratory, Richland, WA. 
  • Zachara JM, RK Kukkadapu, T Peretyazhko, ME Bowden, CM Wang, DW Kennedy, DA Moore, and BW Arey. 2011. "The Mineralogic Transformation of Ferrihydrite Induced by Heterogeneous Reaction with Bioreduced Anthraquinone Disulfonate (AQDS) and the Role of Phosphate." Geochimica et Cosmochimica Acta 75(21):6330-6349.  doi:10.1016/j.gca.2011.06.030


  • Bishop ME, DP Jaisi, H Dong, RK Kukkadapu, and J Ji. 2010. "Bioavailability of Fe(III) in Loess Sediments: An Important Source of Electron Acceptors." Clays and Clay Minerals 58(4):542-557.  doi:10.1346/CCMN.2010.0580409
  • Hixon AE, YJ Hu, DI Kaplan, RK Kukkadapu, H Nitsche, O Qafoku, and BA Powell. 2010. "Influence of Iron Redox Transformations on Plutonium Sorption to Sediments." Radiochimica Acta 98(9-11):685-692.  doi:10.1524/ract.2010.1769
  • Hu YJ, LK Schwaiger, CH Booth, RK Kukkadapu, E Cristiano, DI Kaplan, and H Nitsche. 2010. "Molecular Interactions of Plutonium(VI) with Synthetic Manganese-Substituted Goethite." Radiochimica Acta 98(9-11):655-663.  doi:10.1524/ract.2010.1766
  • Jaisi DP, RE Blake, and RK Kukkadapu. 2010. "Fractionation of Oxygen Isotopes in Phosphate during its Interactions with Iron Oxides." Geochimica et Cosmochimica Acta 74(4):1309-1319.  doi:10.1016/j.gca.2009.11.010
  • Kukkadapu RK, N Qafoku, BW Arey, CT Resch, and PE Long. 2010. "Effect of Extent of Natural Subsurface Bioreduction on Fe-mineralogy of Subsurface Sediments." Journal of Physics: Conference Series 217(1):012047 1-8.  doi:10.1088/1742-6596/217/1/012047
  • Moon HS, L McGuinness, RK Kukkadapu, AD Peacock, J Komlos, Jr., L Kerkhoff, PE Long, and PR Jaffe. 2010. "Microbial Reduction of Uranium under Iron- and Sulfate-reducing Conditions: Effect of Amended Goethite on Microbial Community Composition and Dynamics." Water Research 44(14):4015-4028. 
  • Rastogi G, S Osman, RK Kukkadapu, MH Engelhard, PA Vaishampayan, GL Andersen, and RK Sani. 2010. "Microbial and Mineralogical Characterizations of Soils Collected from the Deep Biosphere of the Former Homestake Gold Mine, South Dakota." Microbial Ecology 60(3):539-550.  doi:10.1007/s00248-010-9657-y
  • Um W, H Chang, JP Icenhower, N Qafoku, SC Smith, RJ Serne, EC Buck, RK Kukkadapu, ME Bowden, JH Westsik, Jr, and WW Lukens. 2010. Immobilization and Limited Reoxidation of Technetium-99 by Fe(II)-GoethitePNNL-19833, Pacific Northwest National Laboratory, Richland, WA. 


  • Qafoku N, RK Kukkadapu, JP McKinley, BW Arey, SD Kelly, CM Wang, CT Resch, and PE Long. 2009. "Uranium in Framboidal Pyrite from a Naturally Bioreduced Alluvial Sediment ." Environmental Science & Technology 43(22):8528-8534 .  doi:10.1021/es9017333
  • Smith SC, M Douglas, DA Moore, RK Kukkadapu, and BW Arey. 2009. "Uranium Extraction From Laboratory Synthesized, Uranium-Doped Hydrous Ferric Oxides ." Environmental Science & Technology 43:2341-2347. 
  • Wiatrowski HA, S Das, RK Kukkadapu, ES Ilton, T Barkay, and N Yee. 2009. "Reduction of Hg(II) to Hg(0) by Magnetite." Environmental Science & Technology 43(14):5307-5313.  doi:10.1021/es9003608
  • Zhang G, H Dong, H Jiang, RK Kukkadapu, J Kim, DD Eberl, and Z Xu. 2009. "Biomineralization Associated with Microbial Reduction of Fe3+ and Oxidation of Fe2+ in Solid Minerals ." American Mineralogist 94(7):1049-1058. 


  • Peretyazhko T, JM Zachara, SM Heald, BH Jeon, RK Kukkadapu, C Liu, DA Moore, and CT Resch. 2008. "Heterogeneous Reduction of Tc(VII) by Fe(II) at the Solid-Water Interface." Geochimica et Cosmochimica Acta 72(6):1521-1539.  doi:10.1016/j.gca.2008.01.004
  • Peretyazhko T, JM Zachara, SM Heald, RK Kukkadapu, C Liu, AE Plymale, and CT Resch. 2008. "Reduction of Tc(VII) by Fe(II) Sorbed on Al (hydr)oxides." Environmental Science & Technology 42(15):5499-5506.  doi:10.1021/es8003156
  • Bank TL, RK Kukkadapu, AS Madden, ME Baldwin, and PM Jardine. 2008. "Effects of gamma-sterilization on the physico-chemical properties of natural sediments." Chemical Geology 251(1-4):1-7.  doi:10.1016/j.chemgeo.2008.01.003
  • Komlos J, Jr., A Peacock, RK Kukkadapu, and PR Jaffe. 2008. "Long-Term Dynamics of Uranium Reduction/Reoxidation under Low Sulfate Conditions." Geochimica et Cosmochimica Acta 72(15):3603-3615.  doi:10.1016/j.gca.2008.05.040
  • Mohanty SR, B Kollah, DB Hedrick, AD Peacock, RK Kukkadapu, and EE Roden. 2008. "Biogeochemical Processes In Ethanol Stimulated Uranium Contaminated Subsurface Sediments." Environmental Science & Technology 42(12):4384-4390. 


  • Borch T, Y Masue, RK Kukkadapu, and S Fendorf. 2007. "Phosphate Imposed Limitations on Biological Reduction and Alteration of Ferrihydrite Mineralization." Environmental Science & Technology 41(1):166-172. 
  • Heald SM, JM Zachara, BH Jeon, JP McKinley, RK Kukkadapu, and DA Moore. 2007. "XAFS Study of the Chemical and Structural States of Technetium in Fe(III) Oxide Co-precipitates." In X-RAY Absorption Fine Structure - XAFS13: 13th International Conference. AIP Conference Proceedings, vol. 882, pp. 173-175.  American Institute of Physics, Melville, NY.  doi:10.1063/1.2644465
  • Komlos J, Jr., RK Kukkadapu, JM Zachara, and PR Jaffe. 2007. "Biostimulation of Iron Reduction and Subsequent Oxidation of Sediment Containing Fe-silicates and Fe-oxides: Effect of Redox Cycling on Fe(III) Bioreduction." Water Research 41(13):2996-3004.  doi:10.1016/j.watres.2007.03.019
  • Zachara JM, JK Fredrickson, RK Kukkadapu, and YA Gorby. 2007. "Anaerobic Microbial-Mineral Processes with Fe(III) Oxides: Experimental Considerations and Approaches." Chapter 4 in Methods for Investigating Microbial-Mineral Interactions: CMS Workshop Lectures, vol. 14, ed. Patricia A. Maurice and Leslie A. Warren, pp. 117-165.  The Clay Minerals Society, West Lafayette, IN. 
  • Zachara JM, SM Heald, BH Jeon, RK Kukkadapu, C Liu, JP McKinley, A Dohnalkova, and DA Moore. 2007. "Reduction of Pertechnetate [Tc(VII)] by Aqueous Fe(II) and the Nature of Solid Phase Redox Products." Geochimica et Cosmochimica Acta 71(9):2137-2157.  doi:doi:10.1016/j.gca.2006.10.025


  • Kukkadapu RK, JM Zachara, JK Fredrickson, JP McKinley, DW Kennedy, SC Smith, and H Dong. 2006. "Reductive Biotransformation of Fe in Shale-Limestone Saprolite Containing Fe(III) Oxides and Fe(II)/Fe(III) Phyllosilicates." Geochimica et Cosmochimica Acta 70(14):3662-3676.  doi:10.1016/j.gca.2006.05.004
  • Seabaugh JL, H Dong, RK Kukkadapu, DD Eberl, JP Morton, and J Kim. 2006. "Microbial Reduction of Fe(III) in the Fithian and Muloorina Illites : Contrasting Extents and Rates of Bioreduction." Clays and Clay Minerals 54(1):67-79.  doi:10.1346/CCMN.2006.0540109
  • Weber KA, MM Urrutia, PF Churchill, RK Kukkadapu, and EE Roden. 2006. "Anaerobic Redox Cycling of Iron by Freshwater Sediment Microorganisms." Environmental Microbiology 8(1):100-113. 


  • Liu C, JM Zachara, L Zhong, RK Kukkadapu, JE Szecsody, and DW Kennedy. 2005. "Influence of Sediment Bioreduction and Reoxidation on Uranium Sorption." Environmental Science and Technology 39(11):4125-4133. 
  • Cooper DC, AL Neal, RK Kukkadapu, D Brewe, AJ Coby, and FW Picardal. 2005. "Effects of Sediment Iron Mineral Composition on Microbially Mediated Changes in Divalent Metal Speciation: Importance of ferrihydrite." Geochimica et Cosmochimica Acta 69(7):1739-1759. 
  • Deutsch WJ, KM Krupka, KJ Cantrell, CF Brown, MJ Lindberg, HT Schaef, SM Heald, BW Arey, and RK Kukkadapu. 2005. Advances in Geochemical Testing of Key Contaminants in Residual Hanford Tank Waste PNNL-15372, Pacific Northwest National Laboratory, Richland, WA. 
  • Jaisi DP, RK Kukkadapu, DD Eberl, and H Dong. 2005. "CONTROL OF FE(III) SITE OCCUPANCY ON THE RATE AND EXTENT OF MICROBIAL REDUCTION OF FE(III) IN NONTRONITE." Geochimica et Cosmochimica Acta 69(23):5429-5440.  doi:10.1016/j.gca.2005.07.008
  • Kukkadapu RK, JM Zachara, JK Fredrickson, DW Kennedy, A Dohnalkova, and DE McCready. 2005. "Ferrous Hydroxy Carbonate is a Stable Transformation Product of Biogenic Magnetite." American Mineralogist 90(2-3):510-515. 
  • Punnoose A, J Hays, A Thurber, MH Engelhard, RK Kukkadapu, CM Wang, V Shutthanandan, and S Thevuthasan. 2005. "Development of High-Temperature Ferromagnetism in SnO2 and Paramagnetism in SnO by Fe Doping." Physical Review. B, Condensed Matter and Materials Physics 72(5):054402 (14 p.). 
  • Punnoose A, J Hays, A Thurber, MH Engelhard, RK Kukkadapu, CM Wang, V Shutthanandan, and S Thevuthasan. 2005. "Development of high-temperature ferromagnetism in SnO2 and paramagnetism in SnO by Fe doping." Virtual Journal of Nanoscale Science & Technology 12(7):,


  • Kukkadapu RK, JM Zachara, JK Fredrickson, and DW Kennedy. 2004. "Biotransformation of Two-Line Silica-Ferrihydrite by a Dissimilatory Fe(III)-Reducing Bacterium: Formation of Carbonate Green Rust in the Presence of Phosphate." Geochimica et Cosmochimica Acta 68(13):2799-2814. 
  • Fredrickson JK, JM Zachara, DW Kennedy, RK Kukkadapu, JP McKinley, SM Heald, C Liu, and AE Plymale. 2004. "Reduction of TcO4- by sediment-associated biogenic Fe(II)." Geochimica et Cosmochimica Acta 68(15):3171-3187. 
  • Norberg NS, KR Kittilstved, JE Amonette, RK Kukkadapu, DA Schwartz, and DR Gamelin. 2004. "Synthesis of Colloidal Mn2+:ZnO Quantum Dots and High-TC Ferromagnetic Nanocrystalline Thin Films." Journal of the American Chemical Society 126(30):9387-9398. 
  • Strawn DG, NE Palmer, LJ Furnare, C Goodell, JE Amonette, and RK Kukkadapu. 2004. "Copper Sorption Mechanisms on Smectites." Clays and Clay Minerals 52(3):321-333. 
  • Zachara JM, RK Kukkadapu, PL Gassman, A Dohnalkova, JK Fredrickson, and T Anderson. 2004. "Biogeochemical Transformation of Fe Minerals in a Petroleum-Contaminated Aquifer." Geochimica et Cosmochimica Acta 68(8):1791-1805. 


  • Kukkadapu RK, H Li, GLL Smith, JV Crum, JS Jeoung, WH Poisl, and MC Weinberg. 2003. "Mossbauer and Optical Spectroscopic Study of Temperature and Redox Effects on Iron Local Environments in a Fe-Doped (0.5 mol% Fe2O3) 18Na(2)O-72SiO(2) Glass ." Journal of Non-crystalline Solids 317(3):301-318. 
  • Amonette JE, RK Kukkadapu, EE Alp, W Sturhahn, and TS Toellner. 2003. "Heterogeneous Electron-Transfer Kinetics with Synchrotron 57Fe Mossbauer Spectroscopy." Geochimica et Cosmochimica Acta 67(12):2109-2116. 
  • Dong H, RK Kukkadapu, JK Fredrickson, JM Zachara, DW Kennedy, and HM Kostandarithes. 2003. "Microbial Reduction of Structural Fe(III) in Illite and Goethite." Environmental Science and Technology Vol. 37(7):1268-1276 . 
  • Fredrickson JK, S Kota, RK Kukkadapu, C Liu, and JM Zachara. 2003. "Influence of Electron Donor/Acceptor Concentrations on Hydrous Ferric Oxide (HFO) Bioreduction." Biodegradation 14(2):91-103. 
  • Hansel CM, SG Benner, J Neiss, A Dohnalkova, RK Kukkadapu, and S Fendorf. 2003. "Secondary Mineralization Pathways Induced by Dissimilatory Iron Reduction of Ferrihydrite Under Advective Flow." Geochimica et Cosmochimica Acta 67(16):2977-2992. 
  • Kukkadapu RK, JM Zachara, JK Fredrickson, SC Smith, A Dohnalkova, and CK Russell. 2003. "Transformation of 2-line Ferrihydrite to 6-line Ferrihydrite under Oxic and Anoxic Conditions." American Mineralogist 88(11-12):1903-1914 pt. 2. 


  • Zachara JM, RK Kukkadapu, JK Fredrickson, YA Gorby, and SC Smith. 2002. "Biomineralization of Poorly Crystalline Fe(III) Oxides by Dissimilatory Metal Reducing Bacteria (DMRB)." Geomicrobiology Journal 19:179-207. 


  • Fredrickson JK, JM Zachara, RK Kukkadapu, YA Gorby, SC Smith, and CF Brown. 2001. "Biotransformation of Ni-Substituted Hydrous Ferric Oxide by an Fe(III)-Reducing Bacterium." Environmental Science and Technology 35(4):703-712. 
  • Kukkadapu RK, JM Zachara, SC Smith, JK Fredrickson, and C Liu. 2001. "Dissimilatory Bacterial Reduction of Al-Substituted Goethite in Subsurface Sediments." Geochimica et Cosmochimica Acta 65(17):2913-2924. 
  • Matocha CJ, DL Sparks, JE Amonette, and RK Kukkadapu. 2001. "Kinetics and Mechanism of Birnessite Reduction by Catechol." Soil Science Society of America Journal 65:58-66. 
  • Wang Z, RC Moore, AR Felmy, MJ Mason, and RK Kukkadapu. 2001. "A Study of the Corrosion Products of Mild Steel in High Ionic Strength Brines." Waste Management 21:335-341. 
  • Zachara JM, NS Foster, JE Amonette, EJ Bylaska, AR Felmy, PL Gassman, SM Heald, RK Kukkadapu, C Liu, MJ Mason, KM Rosso, CK Russell, JR Rustad, SC Smith, Z Wang, and TW Wietsma. 2001. Annual Report 2000 Environmental Dynamics and SimulationPNNL-13456, Pacific Northwest National Laboratory, Richland, WA. 


  • Dong H, JK Fredrickson, DW Kennedy, JM Zachara, RK Kukkadapu, and TC Onstott. 2000. "Mineral Transformations Associated with the Microbial Reduction of Magnetite." Chemical Geology 169:299-318. 
  • Zachara JM, NS Foster, JE Amonette, EJ Bylaska, AR Felmy, PL Gassman, SM Heald, RK Kukkadapu, C Liu, MJ Mason, KM Rosso, CK Russell, JR Rustad, SC Smith, Z Wang, and TW Wietsma. 2000. Annual Report 1999 Environmental Dynamics & Simulation PNNL-13206, Pacific Northwest National Laboratory, Richland, WA. 


  • Maxwell RS, RK Kukkadapu, JE Amonette, and HM Cho. 1999. "2H Solid-State NMR Investigation of Terephthalate Dynamics and Orientation in Mixed-Anion Hydrotalcite-like Compounds." Journal of Physical Chemistry B 103:5197-5203. 

Science at PNNL

Core Research Areas

User Facilities

Centers & Institutes

Research Highlights

View All Research Highlights & Staff Accomplishments

RSS Feed