Impact of Nanoscale Zero Valent Iron on Geochemistry and Microbial Populations in Trichloroethylene Contaminated Aquifer Materials

• Published in: Environmental science & technology 2010-05, Vol.44 (9), p.3474-3480
• Main Authors: Kirschling, Teresa L, Gregory, Kelvin B, Minkley, Jr, Edwin G, Lowry, Gregory V, Tilton, Robert D
• Format: Article
• Language: English
• Subjects: Animal, plant and microbial ecology; Applied sciences; Aquifers; Biological and medical sciences; Bioremediation; Chemical compounds; Chemistry - methods; Earth sciences; Earth, ocean, space; Electrodes; Electrophoresis - methods; Engineering and environment geology. Geothermics; Environmental impact; Environmental science; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; Geochemistry; Geology - methods; Groundwater pollution; Groundwaters; Hydrogen - chemistry; Iron; Iron - chemistry; Metals, Heavy - chemistry; Microbial ecology; Models, Chemical; Nanoparticles; Nanotechnology - methods; Natural water pollution; Oxygen - chemistry; Pollution; Pollution, environment geology; Polymerase Chain Reaction; Remediation and Control Technologies; Sulfates - chemistry; Trichloroethylene - chemistry; Various environments (extraatmospheric space, air, water); Water Pollutants, Chemical - analysis; Water Purification - methods; Water treatment and pollution
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es903744f

Nanoscale zerovalent iron (NZVI) particles are a promising technology for reducing trichloroethylene (TCE) contamination in the subsurface. Prior to injecting large quantities of nanoparticles into the groundwater it is important to understand what impact the particles will have on the geochemistry and indigenous microbial communities. Microbial populations are important not only for nutrient cycling, but also for contaminant remediation and heavy metal immobilization. Microcosms were used to determine the effects of NZVI addition on three different aquifer materials from TCE contaminated sites in Alameda Point, CA, Mancelona, MI, and Parris Island, SC. The oxidation and reduction potential of the microcosms consistently decreased by more than 400 mV when NZVI was added at 1.5 g/L concentrations. Sulfate concentrations decreased in the two coastal aquifer materials, and methane was observed in the presence of NZVI in Alameda Point microcosms, but not in the other two materials. Denaturing gradient gel electrophoresis (DGGE) showed significant shifts in Eubacterial diversity just after the Fe0 was exhausted, and quantitative polymerase chain reaction (qPCR) analyses showed increases of the dissimilatory sulfite reductase gene (dsrA) and Archaeal 16s rRNA genes, indicating that reducing conditions and hydrogen created by NZVI stimulate both sulfate reducer and methanogen populations. Adding NZVI had no deleterious effect on total bacterial abundance in the microcosms. NZVI with a biodegradable polyaspartate coating increased bacterial populations by an order of magnitude relative to controls. The lack of broad bactericidal effect, combined with the stimulatory effect of polyaspartate coatings, has positive implications for NZVI field applications.