Travel distance and transformation of injected emulsified zerovalent iron nanoparticles in the subsurface during two and half years Chunming Su a, *, Robert W. Puls a,1 , Thomas A. Krug b , Mark T. Watling b , Suzanne K. O’Hara b , Jacqueline W. Quinn c , Nancy E. Ruiz d a Ground Water and Ecosystems Restoration Division, National Risk Management Research Laboratory, Office of Research and Development, United States Environmental Protection Agency, 919 Kerr Research Drive, Ada, OK 74820, United States b Geosyntec Consultants Inc., 130 Research Lane, Suite 2, Guelph ON N1G 5G3, Canada c Mail Stop NE-S-2, NASA Kennedy Space Center, FL 32899, United States d Naval Facilities Engineering Command Engineering Service Center, 1100 23rd Avenue, ESC31, Port Hueneme, CA 93043, United States article info Article history: Received 1 June 2012 Received in revised form 3 December 2012 Accepted 18 December 2012 Available online 21 March 2013 Keywords: Travel distance Emulsified zerovalent iron Pneumatic injection Direct injection Nanoiron corrosion Groundwater remediation Magnetite Lepidocrocite Ferrihydrite Goethite abstract Nanoscale zerovalent iron (NZVI) such as Toda Kogyo RNIP-10DS has been used for site remediation, yet information is lacking regarding how far injected NZVI can travel, how long it lasts, and how it transforms to other minerals in a groundwater system. Previously we reported effective mass destruction of chlorinated ethenes dominated by tetra- chloroethene (PCE) using emulsified zerovalent iron (EZVI) nanoparticles of RNIP-10DS in a shallow aquifer (1e6 m below ground surface, BGS) at Site 45, Marine Corps Recruit Depot, Parris Island, South Carolina, USA. Here we report test results on transport and trans- formation of injected EZVI in the subsurface. We employed two EZVI delivery methods: pneumatic injection and direct injection. Effective delivery of EZVI to the targeted zone was achieved with pneumatic injection showing a travel distance from injection points of up to 2.1 m and direct injection showing a travel distance up to 0.89 m. X-ray diffraction and scanning electron microscopy studies on particles harvested from well purge waters indicated that injected black colored NZVI (a-Fe 0 ) was transformed largely to black colored cube-like and plate-like magnetites (Fe 3 O 4 , 0.1e1 mm, 0e9 months), then to orange colored irregularly shaped lepidocrocite (g-FeOOH, 0.1e1 mm, 9 months to 2.5 years), then to yellowish lath-like goethite (a-FeOOH, 2e5 mm, 2.5 years) and ferrihydrite-like spherical particles (0.05e0.1 mm) in the top portion of the aquifer (1e2 m BGS). No a-Fe 0 was found in most monitoring wells three months after injection. The formed iron oxides appeared to have a wider range of particle size (submicron to 5 mm) than the pristine NZVI (35e140 nm). Injected NZVI was largely transformed to magnetite (0.1e1 mm) during two and half years in the lower portion of the aquifer (3e6 m). Published by Elsevier Ltd. * Corresponding author. Tel.: þ1 5804368638; fax: þ1 5804368703. E-mail address: su.chunming@epa.gov (C. Su). 1 Present address: Oklahoma Water Survey, University of Oklahoma, 201 David L. Boren Blvd., Suite 2920, Norman, OK 73072, United States. Available online at www.sciencedirect.com journal homepage: www.elsevier.com/locate/watres water research 47 (2013) 4095 e4106 0043-1354/$ e see front matter Published by Elsevier Ltd. http://dx.doi.org/10.1016/j.watres.2012.12.042