Horizontal transfer of genes in soil and on surfaces in general has recently been linked to to a range of important and some alarming phenomena ranging from bacterial adaptation and evolution, to bioremediation and development of metal tolerance among subsurface microbes, to development of antibiotic resistance by pathogens in the environment, to risk analysis associated with gene flow between native soil microfauna and genetically-modified crop cells. However very little is known about the processes that control rates of horizontal transfer in the environment and there is no agreed-upon form for governing kinetic expressions. Furthermore, conjugative, e.g. cell-to-cell, gene transfer is partly controlled by the physics of bacterial transport and attachment to surfaces in porous media. Here we review recent data on and conceptual models of conjugative transfer of genes in environmental microbial communities, in both aqueous and surface-attached phases, and we develop a differential-difference equation for kinetics that accommodates lags. We incorporate these kinetics into preliminary modeling for design of small-scale experiments to quantify rates of conjugative gene transfer in porous media within a microflow chamber. The model combines the new kinetics with Levy flight representation of bacterial motility and with colloid filtration-based attachment to surfaces, to simulate the rates of gene transfer over the space and time dimensions associated with the microflow chamber experiments.