| Water and solute transport processes are the basic processes in soil-plant-atmosphere continuum.These processes are studied with the aim of understanding the law of nature and making good use of the water resources.Although a lot of methods have been applied to research the water and solute processes,an easy and reliable method is lacking in this field to systematically and automatically monitor these processes.In this paper,self-potential method that was an important supplement to hydrogeophysical methods was raised to study these processes and offered a new technique in this area.The first part of this paper focused on the porous media and contained four sections:(1)The hydraulic conductivity and dispersivity were trying to be inversed by monitoring the self-potential signals.(2)The salinity was tried to be gotten by the self-potential method.(3)The responses of self-potential due to rainfall and the variation of temperature were researched with the help of simulation experiments.(4)The self-potential probability tomography and current source inversion tomography were used to detect the infiltration area and the soil structure.The second part of this paper concentrated on the plant and included two parts:(1)The repetitive irrigations were constructed to study the relationship between the self-potential and the process of root water exaction.(2)The characteristics of the variation of the self-potential were investigated and the relationships between self-potential and plant physiology were studied.Through the research above,the following results were obtained.(1)The method of estimating the parameters was proposed based on the self-potential method in saline tests.The results were proved reliably.(2)The function expression of self-potential coupling coefficient was proposed and the mathematical relationship between salinity and self-potential was determined.In laboratory,the salinity was successfully inversed by free drainage experiments,(3)The relationship between streaming potential and the variation of soil parameters was built.The field experiment showed that self-potential pointed out the change of of water content in the soil,the direction of flow and the velocity of infiltration front.(4)The self-potential anomaly area corresponded with the area where soil water content increased.The self-potential probability tomography indicated that there was a sink hole and the self-potential current source tomography method gave the soil structure information.(5)There was an obvious action potential response in partial zone of the trunk after watering.Action potential signals spreaded through a dominant path.The amplitude of response of self-potential was larger in drought condition than the amplitude in moist condition.When the volume of irrigation water was similar,the larger volume created the stronger action signal.Meanwhile,while the water amount was close,the lower soil moisture content brought the stronger action signal.In addition,the velocity of action potential could be measured according to the time difference of the response of self-potential signals.(6)In the field experiment,the self-potential difference also showed diurnal variation.When the precipitation events happened,the self-potential decreased.Therefore,the processes of wetting and drying could be revealed by self-potential method.The above-mentioned research results showed that the hydraulic conductivity,dispersion,the salinity of solution,and the information of rainfall infiltration and temperature variation could be estimated by coupling the flow model,solute transport model and self-potential model.The self-potential probability tomography and current source tomography could reveal the infiltration area and soil structure.In plant,self-potential signals showed obvious responses to the plant physiology.In a word,self-potential method offered a new technique to study the hydrogeology and plant physiology,which might have important applications in the future. |
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