My research is focused on development and applications of synchrotron X-ray fluorescence microscopy and X-ray absorption spectroscopy, especially of lighter elements Si, P, S and Ca, in Earth, planetary and environmental sciences. I use X-ray microspectroscopyto characterize element-specific chemistry and local structure in complex, heterogeneous natural materials, in the “tender” energy range (1-5 keV, between “hard” >5 keV and “soft” <2 keV classifications of X-ray energy), primarily utilizing the National Synchrotron Light Source II (NSLS-II) at Brookhaven National Lab. Specific areas of interest include the following.
- Mission-returned asteroid samples, interplanetary dust particles and carbonaceous chondrite meteorites: Recent space missions Hayabusa2 (Japan) and OSIRIS-REx (NASA) have retrieved samples from primitive carbonaceous asteroids Ryugu and Bennu. These pristine samples of primitive material from the early solar system preserve information about early materials and processes from nebular condensation to planet formation more than 4.5 billion years ago. They also contain prebiotic organic compounds and essential nutrients P and S, which may represent a source for the building blocks for development and sustenance of life on early Earth -- and potentially elsewhere.
- The grain-scale distribution and chemical speciation of phosphorous in soils and sediments: Phosphorus is an essential agricultural nutrient, but can also become a pollutant in ground- and surface-waters, causing harmful algae blooms and fishkills. Its grain-scale chemical speciation controls whether the P is bioavailable to plants/crops or bound up in inert forms, or is so free as to readily wash away into waterways. A new direction for this research is the potential release of bound P when coastal soils are inundated by rising sea levels.
- Critical minerals, trace elements and geochronology: microcharacterization of trace element chemistry and oxidation state, combined with isotope-based geochronology, is used to explore the geochemical processes resulting in the mobilization, transport and concentration of critical elements such as Rare Earth Elements and lithium. Better understanding these processes will improve our search for, and safe exploitation of, these resources.
- Development of new instrumentation and analysis techniques: To address the above research interests, I developed the first tender-energy microprobe at NSLS/NSLS-II (the TES beamline), followed by development of a new tender-energy microspectroscopy program at the XFM beamline. My research also develops methods to utilize low-energy absorption edges of heavier elements, such as the uranium M5 and zirconium L3 edges, and advanced data-analysis approaches for XAS in these complex systems.
Selected publications:
P. Northrup, 2019. The TES Beamline (8-BM) at NSLS-II: tender-energy spatially resolved
X-ray absorption spectroscopy and X-ray fluorescence imaging. J. Synch. Rad., 26,
2064-2074.
https://doi.org/10.1107/S1600577519012761
S. Bowie, C. Mottram, E.T. Rasbury, P. Northrup, R. Tappero, D. Kellett. 2025. U redox
state tracked in mineralized hydrothermal carbonate with implications for U-Pb geochronology.
Commun. Earth Environ., 6, 362.
https://doi.org/10.1038/s43247-025-02194-4
P. Northrup, R. Tappero, T. Glotch, G.J. Flynn, M. Yesiltas, Y. Kebukawa, L. Flores,
M. Gemma, G. Piccione. 2024. Chemistry in Retrieved Ryugu Asteroid Samples Revealed
by Non-Invasive X-Ray Microanalyses: Pink-Beam Fluorescence CT and Tender-Energy Absorption
Spectroscopy. Geosciences, 14, 111.
https://doi.org/10.3390/geosciences14040111
K. Szerlag, M. Siebecker, F. Izaditame, P. Northrup, R. Tappero, D. Sparks. 2024.
Multi-modal, micro-spectroscopic speciation of legacy phosphorus in two U.S. mid-Atlantic
agricultural soils. Soil Sci. Soc.Am. J. 88, pp1992-2012.
https://doi.org/10.1002/saj2.20765
P. Northrup, T. Glotch, G.J. Flynn, O. Koren, M. Gemma, R. Tappero, M. Yesiltas, Y.
Kebukawa, K. Horvat, 2025. Heterogeneity of Materials and Textures in Ryugu Samples,
but a Common Story of Evolving Fluid Chemistry and fO 2 . LPI Contributions,
https://www.hou.usra.edu/meetings/lpsc2025/pdf/2715.pdf
I. Reddell, C. Shackelford, P. Northrup, R. Tappero, H. Coker, K. Szerlag, 2025. Exploring
Phosphorus and Sulfur Speciation in Extraterrestrial Materials in Contrast to Manufactured
Martian and Lunar Regolith Simulants via Synchrotron-Based X-Ray Microspectroscopy.
LPI Contributions,
https://www.hou.usra.edu/meetings/lpsc2025/pdf/2820.pdf
M. Yesiltas, T. Glotch, Y. Kebukawa, B. Sava, Y. Durmaz, P. Northrup. 2024. Nanoscale
spectroscopic identification and characterization of minerals and organic matter in
Ryugu particles. J. Geophys. Res.: Planets 129, e2023JE008090.
https://doi.org/10.1029/2023JE008090
C. Gu, S. Joshi, M. Fischel, E. Tomaszewski, P. Northrup, D. Sparks, 2024. Saltwater
intrusion increases phosphorus abundance and alters availability in coastal soils
with implications for future sea level rise. Science of the Total Environment, 172624.
https://doi.org/10.1016/j.scitotenv.2024.172624
J. Kleinsasser, B. Konecke, A. Simon, P. Northrup, A. Lanzirotti, M. Newville, C.
Borca, T. Huthwelker, F. Holtz. 2024. Sulfur speciation in dacitic melts using X-ray
absorption near-edge structure spectroscopy of the S K-edge (S-XANES): Consideration
of radiation-induced changes and the implications for sulfur in natural arc systems.
American Mineralogist 109, 1359-1374.
https://doi.org/10.2138/am-2022-8833
T. Present, E. Niespolo, C. Clarke, A. Behrensmeyer, L.M. Leakey, M. Leakey, C. Mongle,
A. Du Plessis, P. Northrup, R. Tappero, D. Yang, E.T. Rasbury, F. Grine, 2024. Nondestructive
geochemical characterization of fossil hominin taphonomy and burial history. Quaternary
Science Reviews, 328, 108525.
https://doi.org/10.1016/j.quascirev.2024.108525
D. Schaub, P. Northrup, H. Nekvasil, T. Catalano, R. Tappero. 2023. Gas-mediated trace
element incorporation into rhyolite-hosted topaz: a synchrotron microbeam XAS study.
American Mineralogist, 108, 2153-2163.
https://doi.org/10.2138/am-2022-8417
G. Piccione, T. Blackburn, S. Tulaczyk, E. Rasbury, M .Hain, D. Ibarra, K. Methner,
C. Tinglof, B. Cheney, P. Northrup, K. Licht. 2022. Subglacial precipitates record
Antarctic ice sheet response to late Pleistocene millennial climate cycles. Nat. Comm.
13, 5428.
https://doi.org/10.1038/s41467-022-33009-1
P. Northrup, 2024, Non-Invasive Synchrotron X-ray Microprobes for Chemical Characterization
of Extraterrestrial Materials: Tender-Energy Microspectroscopy, Pink-Beam Fluorescence
CT, and Microbeam X-Ray Absorption Spectroscopy. LPI Contributions.
https://www.hou.usra.edu/meetings/lpsc2024/pdf/2374.pdf
T. Glotch, P. Northrup, M. Yesiltas, Y. Kebukawa, M. Gemma, L. Flores-Andrade, 2024.
Phosphorus and Sulfur Speciation in Ryugu Particles. LPI Contributions.
https://www.hou.usra.edu/meetings/lpsc2024/pdf/2279.pdf
G. J. Flynn, P. Northrup, 2024. Phosphorus, Sulfur, and Potassium as Tracers of Aqueous
Alteration onRyugu. LPI Contributions.
https://www.hou.usra.edu/meetings/metsoc2024/pdf/6066.pdf
S. Hemming, T. Liu, P. Northrup, S. Nicholas, E. Rasbury, H. Chen, A. Warden, A. Chen,
R. Li, R. Tappero, S. Cox, J. Everard, S. Wang, M. Deluca, B. Bostick, A. Halliday.
2023. Synchrotron Microanalytical Characterization and K/Ar Dating of the GL-O-1 Glauconite
Reference Material at the Single Pellet Scale and Reassessment of the Age of Visually
Mature Pellets. Minerals 13, 773.
https://doi.org/10.3390/min13060773
P Northrup, S Wirick, GJ Flynn. 2021. Tender Energy X-Ray Microspectroscopy Reveals
Microscale Heterogeneity of P and S Chemistry in CM2 Chondrite. LPI Contributions.
https://www.hou.usra.edu/meetings/lpsc2021/pdf/2480.pdf
A. Gamble, P. Northrup, D. Sparks. 2019. Elucidation of Soil Phosphorus Speciation
with Synchrotron-Based Microspectroscopic Techniques. J. Environm. Qual., 49, 184-193.
https://doi.org/10.1002/jeq2.20027
E. Ingall, J. Brandes, J. Diaz, M. deJonge, D. Paterson, McNulty, C. Elliott, P. Northrup,
2011.Phosphorus K-edge XANES Spectroscopy of Mineral Standards, J. Synch. Rad., 18,
189–197.
http://journals.iucr.org/s/issues/2011/02/00/hi5614/hi5614.pdf
database of spectra:
https://scripts.iucr.org/cgi-bin/sendsupfiles?hi5614&file=hi5614sup1.xls&mime=application/vnd.ms-excel
D Abdala, P Northrup, Y Arai, D Sparks. 2015. Surface Loading Effects on Orthophosphate
SurfaceComplexation at the Goethite/water Interface as Examined by Extended X-rayAbsorption
Fine Structure(EXAFS) Spectroscopy, J. Colloid Interface Sci., 437, 297-303.
https://doi.org/10.1016/j.jcis.2014.09.057
D Abadala, P Northrup, E Cesar Vicentin, D Sparks, 2015. Residence Time and pH Effects
on the Bonding Configuration of Orthophosphate Surface Complexes at the Goethite/water
Interface as Examined by Extended X-ray Absorption Fine Structure (EXAFS) Spectroscopy,
J. Colloid Interface Sci., 442, 15-21.
https://doi.org/10.1016/j.jcis.2014.11.048
A Leri, L Mayer, K Thornton, P Northrup, M Dunigan, K Ness, A Gellis, 2015. A Marine
Sink for Chlorine in Natural Organic Matter, Nature Geosci., 8, 620-624.
https://doi.org/10.1130/GES02139.1
G Piccione, E T Rasbury, B Elliott, J R Kyle, S Jaret, A Acerbo, A Lanzirotti, P Northrup,
K Wooton, R Parrish, 2019. Vein Fluorite and Calcite U-Pb Dating Demonstrates Post
5 Ma REE Mobilization Associated with Rio Grande Rifting. Geosphere, 15, 1958-1972.
https://doi.org/10.1130/GES02139.1
G Flynn, S Wirick, P Northrup, 2019. P Speciation in Large, Cluster Interplanetary
Dust Particles. LPI Contributions.
https://www.hou.usra.edu/meetings/lpsc2019/pdf/1403.pdf
G Flynn, S Wirick, P Northrup. Phosphorous Speciation in Primitive Interplanetary
Dust: Clues to Grain Formation in the Solar Protoplanetary Disk. LPI Contributions.
https://www.hou.usra.edu/meetings/metsoc2019/pdf/6321.pdf
M Schoonen, J Hill, J Thieme, Y Chu, R Tappero, P Northrup, G Flynn, L Keller, K Chen-Wiegart,
L Li, E Nazaretski, G Williams, S Wirick, H Yan, 2016. Planetary Science Capabilities
at National Synchrotron Light Source-II, Brookhaven National Laboratory, LPI Contributions.
https://www.hou.usra.edu/meetings/lpsc2016/pdf/2951.pdf
N Vidavsky, J Kunitake, A Chiou, P Northrup, T Porri, L Ling, C Fischbach, L Estroff,
2018. Studying Biomineralization Pathways in a 3D Culture Model of Breast Cancer Microcalcifications,
Biomaterials, 179, 71-82.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6747704/
P Northrup, A Leri, R Tappero, 2016. Applications of “Tender” Energy (1-5 keV) X-ray
Absorption Spectroscopy in Life Sciences, Protein Peptide Lett., 23(3), 300-308.
https://doi.org/10.2174/0929866523666160107114505
R. Reeder, G. Lamble, and P. Northrup, 1999. XAFS study of the coordination and local
relaxation around Co 2+ , Zn 2+ , Pb 2+ , and Ba 2+ , trace elements in calcite, Am.
Min., 84, 1049-1060.
http://www.minsocam.org/MSA/AmMin/TOC/Articles_Free/1999/Reeder_p1049-1060_99.pdf
Z Shadike, H-S Lee, C Tian, K Sun, L Song, E Hu, I Waluyo, A Hunt, S Ghose ,Y Hu,
J Zhou, J Wang, P Northrup, S-M Bak and X-Q Yang. 2019. Design and Synthesis of a
New Organodisulfide and its Characterization as Cathode Material for High Performance
Lithium Batteries. Adv. En. Mat.
https://doi.org/10.1002/aenm.201900705
BNL Science Highlight: https://www.bnl.gov/newsroom/news.php?a=115516
T Wang, G-X Ren, Z Shadike, J-L Yue, M-H Cao, J-N Zhang, M-W Chen, X-Q Yang, S-M Bak,
P Northrup, P Liu, X-S Liu, Z-W Fu. 2019. Anionic redox reaction in layered NaCr 2/3
Ti 1/3 S 2 through electron holes formation in addition to the dimerization of S-S.
Nature Comm. 10, 4458.
https://doi.org/10.1038/s41467-019-12310-6
C-H Lin, M Topsakal, K Sun, J Bai, C Zhao, E Dooryhee, P Northrup, H Gan, D Lu, E
Stavitski, Y Chen-Wiegart. 2020. Operando structural and chemical evolutions of TiS
2 in Na-ion batteries. J. Mater. Chem. A 8, 12339-12350.
https://doi.org/10.1039/D0TA00226G
X Yu, H Pan, Y Zhou, P Northrup, J Xiao, S Bak, M Liu, K Nam, X Yang, D Qu, J Liu,
T Wu, X-Q Yang, 2015. Direct Observation of the Redistribution of Sulfur and Polysufides
in Li-S Batteries During First Cycle by In Situ X-ray Fluorescence Microscopy, Adv.
Energy Mater., 5, 1500072.
https://onlinelibrary.wiley.com/doi/abs/10.1002/aenm.201500072
J Moon, P Kalb, L Milian, P Northrup. 2016. Characterization of a sustainable sulfur
polymer concrete using activated fillers. Journal of Cement and Concrete Composites.
67, 20-29.
https://doi.org/10.1016/j.cemconcomp.2015.12.002
P Gregoire, A Engelbrektson, C Hubbard, Z Metlagel, R Csencsits, M Auer, M Conrad,
J Thieme, P Northrup, J Coates, 2014. Control of Sulfidogenesis Through Bio-oxidation
of H 2 S Coupled to (per)chlorate Reduction, Environmental microbiology reports 6,
558-564.
https://doi.org/10.1111/1758-2229.12156
F Riquelme, P Northrup, J Ruvalcaba-Sil, V Stojanoff, D P Siddons, J Alvarado-Ortega,
2013. Insights into restricted organic preservation in Chiapas amber using IR microimaging,
PIXE/RBS and Sulfur K-edge XANES spectroscopy, Applied Physics A. 116, 97-109.
https://doi.org/10.1007/s00339-013-8185-2
Mengqiang Zhu, Paul Northrup, Chenyang Shi, Simon Billinge, Donald Sparks, and Glenn
Waychunas, 2013. The Structure of Sulfate Adsorption Complexes on Ferrihydrite, Env.
Sci. & Tech. Lett. 1, 97-101.
https://doi.org/10.1021/ez400052r
Y. Zhu, J. Zhang, L. Wu, A. Frenkel, J. Hanson, P. Northrup, W. Ku, 2007. Nanoscale
Disorder in CaCu 3 Ti 4 O 12 : A New Route to Enhanced Dielectric Response, Phys.
Rev. Lett., 99:037602.
https://doi.org/10.1103/PhysRevLett.99.037602
P. Voyles, P. Citrin, D. Chadi, D. Muller, J. Grazul, P. Northrup, and H.-J. Gossmann,
2003. Evidence for a New Class of Defects in Highly n-doped Si: Donor-pair-vacancy-interstitials,
Phys. Rev. Lett., 91.
https://doi.org/10.1103/PhysRevLett.91.125505
P. Citrin, P. Northrup, R. Birkhahn, A. Steckl, 2000. Local Structure and Bonding
of Er in GaN: A Contrast with Er in Si, Appl. Phys. Lett., 76: 2865.
https://doi.org/10.1063/1.126499
P. Citrin, D. Muller, H.-J. Gossmann, R. Vanfleet and P. Northrup, 1999. Geometric
frustration of 2D dopants in silicon: surpassing electrical saturation, Phys. Rev.
Lett. 18, 3234-3237.
https://doi.org/10.1103/PhysRevLett.83.3234
T. Inoue, D. Weidner, P. Northrup, J. Parise, 1998. Elastic properties of hydrous
ringwoodite (-phase) in Mg 2 SiO 4 , Earth and Planetary Sci. Lett. 160:107-113.
https://doi.org/10.1016/S0012-821X(98)00077-6
P Northrup and R Reeder, 1995. Relationship between the structure and growth morphology
of topaz [Al 2 SiO 4 (OH,F) 2 ] using the periodic bond chain method, J. of Crystal
Growth, 156, 433-442.
https://doi.org/10.1016/0022-0248(95)00287-1
P. Northrup and R. Reeder, 1994. Evidence for the importance of growth-surface structure
to trace element incorporation in topaz, Am. Min., 79, 1167-1175.
http://www.minsocam.org/ammin/AM79/AM79_1167.pdf
P. Northrup, K. Lienenweber, and J. Parise, 1994. The location of H in the high-pressure
synthetic Al2SiO4(OH)2 topaz analogue, American Mineralogist, 79, 401-404.
http://www.minsocam.org/ammin/AM79/AM79_401.pdf
P Northrup, J Parise, LK Cheng, LT Cheng and E McCarron, 1994. High temperature single-crystal
X-ray diffraction studies of potassium and (cesium, potassium) titanyl arsenates,
Chem. Mat., 6, 434-440.
https://doi.org/10.1021/cm00040a017
J Parise, D Corbin, L Abrams, P Northrup, J Rakovan, T M Nenoff, and G D Stucky, 1994.
Structural relationships between some BePO-, BeAsO- and AlSiO-RHO frameworks, Zeolites,
14, 25-34.
https://doi.org/10.1016/0144-2449(94)90050-7