The reasons for the deviation between two models are not only due to the thin EDL assumption to get electrical potential and charge distribution in pores but also to some other approximations for integral evaluations. The results suggest that the model developed in this work can be used with arbitrary capillary/pore scale and thus is not restricted to the thin EDL assumption. | VNU Journal of Science: Mathematics – Physics, Vol. 34, No. 4 (2018) 9-18 Effective Excess Charge Density in Water Saturated Porous Media Luong Duy Thanh* Thuy Loi University, 175 Tay Son, Dong Da, Ha Noi, Vietnam Received 03 October 2018 Revised 28 OCtober 2018; Accepted 01 November 2018 Abstract: A model for the effective excess charge in a capillary as well as in porous media is developed for arbitrary pore scales. The prediction of the model is then compared with another published model that is limited for a thin electric double layer (EDL) assumption. The comparison shows that there is a deviation between two models depending on the ratio of capillary/pore radius and the Debye length. The reasons for the deviation between two models are not only due to the thin EDL assumption to get electrical potential and charge distribution in pores but also to some other approximations for integral evaluations. The results suggest that the model developed in this work can be used with arbitrary capillary/pore scale and thus is not restricted to the thin EDL assumption. Keywords: Zeta potential, porous media, electric double layer, effective excess charge. 1. Introduction The self-potential (SP) method is a passive geophysical method based on the measurements of the natural electrical potentials at the ground surface of the Earth. The SP survey has the advantage of being non-destructive, fast, inexpensive and very simple to perform in the field requiring only a high impedance millivoltmeter and at least two non-polarizable electrodes connected through a reel of wire. The SP method has been used for a variety of geophysical applications. For example, the SP measurements could be used to characterize active volcanic areas [1, 2], to detect and monitor groundwater flow [3, 4], contaminant plumes [5, 6] or to study landslides [7, 8]. In natural porous media, several main mechanisms proposed to explain SP signals are associated with streaming potential, electrochemical, .
