The widespread occurrence of dense non-aqueous phase liquids (DNAPLs) in groundwater and in soil is of serious environmental concern. However, bare nanoiron particles have a strong tendency to agglomerate due to their high surface energies and intrinsic magnetic interactions, forming aggregates that plug and inhibit their flow through porous media. Effective in situ remediation of contaminated groundwater plume requires the successful delivery of reactive iron particles through soil. This study reports the transport characteristics of nanoscale zerovalent iron particles that are encapsulated in porous silica sub-micron particles through an aerosol-assisted technology. As seen in Figure 1, these particles are spherical with nanoiron evenly distributed throughout the silica matrix. These particles resist aggregation characteristics that are typical of nanoscale zerovalent iron, and are highly reactive. They can be transported through model soils (Ottawa sands) more efficiently than commercially available reactive nanoscale iron particle (RNIP). To explore the fate of particles in sands, macroscopic and microscopic methods were used. The result shows the composite particles elute readily while RNIP is trapped at the inlet of the column. Capillary experiments further prove that RNIP clogs the pores between sand grains due to rapid aggregation, but pore plugging does not occur for the composite particles. The partitioning characteristic of the particles was investigated by a capillary video microscopy technique. Our results again indicate that the iron/silica composite particle preferentially accumulate and localize at the TCE/water interface, making dechlorination more efficient. Such particles with enhanced mobility hold promise in new technologies for in-situ ground water remediation. Figure 1: Transmission electron micrograph of composite porous particles.