Simulation of the seismoelectric effect serves as a useful tool to capture the observed seismoelectric conversion phenomenon in porous media, thus offering promising potential in underground exploration activities to detect pore fluids such as water, oil and gas. The static electromagnetic (EM) approximation is among the most widely used methods for numerical simulation of the seismoelectric responses. However, the static approximation ignores the accompanying electric field generated by the shear wave, resulting in considerable errors when compared to analytical results, particularly under high salinity conditions. To mitigate this problem, we propose a spatial high-order finite-difference time-domain (FDTD) method based on Maxwell's full equations of time-varying EM fields to simulate the seismoelectric response in 2D mode. To improve the computational efficiency influenced by the velocity differences between seismic and electromagnetic waves, different time steps are set according to the stability conditions, and the seismic feedback values of EM time nodes are obtained by linear approximation within the seismic unit time step. To improve the simulation accuracy of the seismoelectric response with the time-varying EM calculation method, finite-difference coefficients are obtained by solving the spatial high-order difference approximation based on Taylor expansion. The proposed method yields consistent simulation results compared to those obtained from the analytical method under different salinity conditions, thus indicating its validity for simulating seismoelectric responses in porous media. We further apply our method to both layered and anomalous body models and extend our algorithm to 3D. Results show that the time-varying EM calculation method could effectively capture the reflection and transmission phenomena of the seismic and EM wavefields at the interfaces of contrasting media. This may allow for the identification of abnormal locations, thus highlighting the capability of seismoelectric response simulation to detect subsurface properties.

Persistent organic pollutants (POPs) has the typical features of persistence, long-range transport, biological accumulation and high toxicity, so that POPs contaminated sites have posed much risk to human health and environment, which is in urgent need of improvement. At present, there are many international advanced remediation methods and engineering practices, but it has not formed the mature remediation technology system in China. Through studying the international concrete examples of remediation technologies, the paper completely reviews the attributes and characteristics of various technology methods, puts forward preliminary technology management system for the remediation of POPs contaminated sites, then provides methodology process for screening the treatment technologies for POPs contaminated sites in China.

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The frequency domain (FD) electromagnetic method (FDEM) describes the underground electrical distribution by frequency and apparent resistivity, this approach has been successfully applied in mineral exploration, geothermal exploration and oil exploration applications (