We have developed polymer-templated gold nanoparticles as a contrast agent for X-CT imaging in soil, exploiting the known biocompatibility of gold in comparison with competitors such as iodine-based reagents or other heavy metals. The particle synthesis is a single step process that can be performed at high concentrations. In combination with then production of diblock copolymers by GTP, this generates a nanoparticle system that is scalable and practicable for soil applications. The polymer-templated gold nanoparticles show high stability in the soil environment, and enable labelling of the soil aqueous phase with good contrast in X-CT. Diffusion measurements confirmed the ability of this new contrast system to be used in transport studies, and reveals that diffusion is slower than typical ionic species,