H. Yoon, Valocchi, A. J., Werth, C. J., and Dewers, T., “Pore-scale simulation of mixing-induced calcium carbonate precipitation and dissolution in a microfluidic pore network,” Water Resour. Res., vol. 48, 2012.
D. C. McCalman, Kelley, K. H., Werth, C. J., Shapley, J. R., and Schneider, W. F., “Aqueous N2O reduction with H2 over Pd-based catalyst: Mechanistic insights from experiment and simulation,” Topics Catal., vol. 55, pp. 300–312, 2012.
B. P. Chaplin, Reinhard, M., Schneider, W. F., Schüth, C., Shapley, J. R., Strathmann, T. J., and Werth, C. J., “A critical review of Pd-based catalytic treatment of priority contaminants in water,” Environ. Sci. Technol., vol. 46, pp. 3655–3670, 2012.
D. Shuai, Choe, J. K., Shapley, J., and Werth, C. J., “Enhanced activity and selectivity of carbon nanofiber supported Pd catalysts for nitrite reduction,” Environ. Sci. Technol., vol. 46, pp. 2847–2855, 2012.
Y. Guo, Li, W., Yan, J., Moosa, B., Amad, M., Werth, C. J., and Khashab, N. M., “Fullerene-catalyzed reduction of azo derivatives in water under UV irradiation,” Chem. Asian J., vol. 7, pp. 2842–2847, 2012.
A. Marruffo, Yoon, H., Schaeffer, D. J., Barkan, C. P. L., Saat, M. R., and Werth, C. J., “

NAPL source zone depletion model and its application to railroad-tank-car spills

,” Ground Water, vol. 50, no. 4, pp. 627-632, 2012.
D. Shuai, Wang, C., Genc, A., and Werth, C. J., “A new geometric method based on two-dimensional transmission electron microscopy for analysis of interior versus exterior Pd loading on hollow carbon nanofibers,” J. Phys. Chem. Lett., vol. 2, pp. 1082–1087, 2011.
C. Zhang, Kang, Q., Wang, X., Zilles, J., Muller, R. H., and Werth, C. J., “Effects of pore-scale heterogeneity and transverse mixing on bacterial growth in porous media,” Environ. Sci. Technol., vol. 44, pp. 3085–3092, 2010.
Y. Yang, Metre, V. P., Mahler, B., Wilson, J., Ligouis, B., Razzaque, M., Schaeffer, D., and Werth, C. J., “The influence of coal-tar sealcoat and other carbonaceous materials on polycyclic aromatic hydrocarbon loading in an urban watershed,” Environ. Sci. Technol., vol. 44, pp. 1217–1223, 2010.
J. K. Choe, Shapley, J. R., Strathmann, T. J., and Werth, C. J., “Influence of rhenium speciation on the stability and activity of Re/Pd bimetal catalysts used for perchlorate reduction,” Environ. Sci. Technol., vol. 44, pp. 4716–4721, 2010.
C. Zhang, Dehoff, K., Hess, N., Oostrom, M., Wietsma, T. W., Valocchi, A. J., Fouke, B. W., and Werth, C. J., “Pore-scale study of transverse mixing induced CaCO3 precipitation and permeability reduction in a model subsurface sedimentary system,” Environ. Sci. Technol., vol. 44, pp. 7833–7838, 2010.
Y. Yang, Mahler, B. J., VanMetre, P. C., Ligouis, B., and Werth, C. J., “Potential contributions of asphalt and coal tar to black carbon quantification in urban dust,” soils, and sediments, {Geochimica} et {Cosmochimica} {Acta}, vol. 74, pp. 6830–6840, 2010.
T. W. Willingham, Zhang, C., Werth, C. J., Valocchi, A. J., Oostrom, M., and Wietsma, T. W., “Using dispersivity values to quantify the effects of pore-scale flow focusing on enhanced reaction along a transverse mixing zone,” Adv. Water Resour., vol. 33, pp. 525–535, 2010.
D. Shuai, Chaplin, B. P., Shapley, J. R., Menendez, N. P., McCalman, D. C., Schneider, W. F., and Werth, C. J., “Enhancement of Oxyanion and Diatrizoate Reduction Kinetics Using Selected Azo Dyes on Pd-Based Catalysts,” Environmental Science & Technology, vol. 44, no. 5, pp. 1773–1779, 2010. Publisher's VersionAbstract
Azo dyes are widespread pollutants and potential cocontaminants for nitrate; we evaluated their effect on catalytic reduction of a suite of oxyanions, diatrizoate, and N-nitrosodimethylamine (NDMA). The azo dye methyl orange significantly enhanced (less than or equal to a factor of 5.24) the catalytic reduction kinetics of nitrate, nitrite, bromate, perchlorate, chlorate, and diatrizoate with several different Pd-based catalysts; NDMA reduction was not enhanced. Nitrate was selected as a probe contaminant, and a variety of azo dyes (methyl orange, methyl red, fast yellow AB, metanil yellow, acid orange 7, congo red, eriochrome black T, acid red 27, acid yellow 11, and acid yellow 17) were evaluated for their ability to enhance reduction. Hydrogenation energies of azo dyes were calculated using density functional theory and a volcano relationship between hydrogenation energies and reduction rate enhancement was observed. A kinetic model based on Brønsted−Evans−Polanyi (BEP) theory matched the volcano relationship and suggests sorbed azo dyes enhance reduction kinetics through hydrogen atom shuttling between reduced azo dyes (i.e., hydrazo dyes) and oxyanions or diatrizoate. This is the first research that has identified this synergetic effect, and it has implications for designing more efficient catalysts and reducing Pd costs in water treatment systems.
C. J. Werth, Zhang, C., Brusseau, M., Oostrom, M., and Baumann, T., “A review of non-invasive imaging methods and applications in contaminant hydrogeology research,” Journal of Contaminant Hydrology, vol. 113, no. 1-4, pp. 1–24, 2010. Publisher's VersionAbstract
Contaminant hydrogeological processes occurring in porous media are typically not amenable to direct observation. As a result, indirect measurements (e.g., contaminant breakthrough at a fixed location) are often used to infer processes occurring at different scales, locations, or times. To overcome this limitation, non-invasive imaging methods are increasingly being used in contaminant hydrogeology research. Four of the most common methods, and the subjects of this review, are optical imaging using UV or visible light, dual-energy gamma radiation, X-ray microtomography, and magnetic resonance imaging (MRI). Non-invasive imaging techniques have provided valuable insights into a variety of complex systems and processes, including porous media characterization, multiphase fluid distribution, fluid flow, solute transport and mixing, colloidal transport and deposition, and reactions. In this paper we review the theory underlying these methods, applications of these methods to contaminant hydrogeology research, and methods' advantages and disadvantages. As expected, there is no perfect method or tool for non-invasive imaging. However, optical methods generally present the least expensive and easiest options for imaging fluid distribution, solute and fluid flow, colloid transport, and reactions in artificial two-dimensional (2D) porous media. Gamma radiation methods present the best opportunity for characterization of fluid distributions in 2D at the Darcy scale. X-ray methods present the highest resolution and flexibility for three-dimensional (3D) natural porous media characterization, and 3D characterization of fluid distributions in natural porous media. And MRI presents the best option for 3D characterization of fluid distribution, fluid flow, colloid transport, and reaction in artificial porous media. Obvious deficiencies ripe for method development are the ability to image transient processes such as fluid flow and colloid transport in natural porous media in three dimensions, the ability to image many reactions of environmental interest in artificial and natural porous media, and the ability to image selected processes over a range of scales in artificial and natural porous media.
K. A. Guy, Xu, H., Yang, J. C., Werth, C. J., and Shapley, J. R., “Catalytic nitrate and nitrite reduction with Pd-Cu/PVP colloids in watewr: Composition,” structure, and reactivity correlations, {J}. {Phys}. {Chem}. {C}., vol. 113, pp. 8177–8185, 2009.
B. P. Chaplin, Shapley, J. R., and Werth, C. J., “Catalytic nitrate reduction using pd-in catalysts in a packed-bed reactor: the effect of solution composition on ammonia production,” Catalysis Letters, pp. 56–62, 2009.
G. Gopalakrishnan, Burken, J., and Werth, C. J., “Lignin and lipid impact on sorption and diffusion of trichloroethylene in tree branches for determining contaminant fate during plant sampling and phytoremediation,” Environ. Sci. Technol., vol. 43, 2009.
G. Gopalakrishnan, Werth, C. J., and Negri, M. C., “Mass recovery methods for trichloroethylene in plant tissue,” Environ. Toxic. & Chem., {DOI}:, vol. 10., 2009.
H. Yoon, Oostrom, M., Wietsma, T. W., Werth, C. J., and Valocchi, A. J., “Numerical and experimental investigation of DNAPL removal mechanisms in a layered porous medium by means of soil vapor extraction,” J. Contam. Hydrol., pp. 1–13, 2009.