[1] Although recent research suggests that contaminant plumes behave as geobatteries that produce an electrical current in the ground, no associated model exists that honors both geophysical and biogeochemical constraints. Here, we develop such a model to explain the two main electrochemical contributions to self-potential signals in contaminated areas. Both contributions are associated with the gradient of the activity of two types of charge carriers, ions and electrons. In the case of electrons, bacteria act as catalysts for reducing the activation energy needed to exchange the electrons between electron donors and electron acceptors. Possible mechanisms that facilitate electron migration include iron oxides, clays, and conductive biological materials, such as bacterial conductive pili or other conductive extracellular polymeric substances. Because we explicitly consider the role of biotic processes in the geobattery model, we coined the term ''biogeobattery.'' After theoretical development of the biogeobattery model, we compare model predictions with self-potential responses associated with laboratory and field scale investigations conducted in contaminated environments. We demonstrate that the amplitude and polarity of large (>100 mV) self-potential signatures requires the presence of an electronic conductor to serve as a bridge between electron donors and acceptors. Small self-potential anomalies imply that electron donors and electron acceptors are not directly interconnected, but instead result simply from the gradient of the activity of the ionic species that are present in the system.

Health literacy, a more complex concept than knowledge, is a required capacity to obtain, understand, integrate and act on health information [1], in order to enhance individual and community health, which is defined by different levels, according to the autonomy and personal capacitation in decision making [2]. Medium levels of Health literacy in an adolescent population were found in a study conducted in 2013/2014, being higher in sexual and reproductive health and lower in substance use. It was also noticed that the higher levels of health literacy were in the area adolescents refer to have receipt more health information. The health literacy competence with higher scores was communication skills, and the lower scores were in the capacity to analyze factors that influence health. Higher levels were also found in younger teenagers, but in a higher school level, confirming the importance of health education in these age and development stage. Adolescents seek more information in health professionals and parents, being friends more valued as a source information in older adolescents, which enhance the importance of peer education mainly in older adolescents [3]. As a set of competences based on knowledge, health literacy should be developed through education interventions, encompassing the cultural and social context of individuals, since the society, culture and education system where the individual is inserted can define the way the development and enforcement of the health literacy competences [4]. The valued sources of information should be taken into account, as well as needs of information in some topics referred by adolescents in an efficient health education. Schizophrenia is a serious and chronic mental illness which has a profound effect on the health and well-being related with the well-known nature of psychotic symptoms. The exercise has the potential to improve the life of people with schizophrenia improving physical health and alleviating psychiatric symptoms. However, most people with schizophrenia remains sedentary and lack of access to exercise programs are barriers to achieve health benefits. The aim of this study is to evaluate the effect of exercise on I) the type of intervention in mental health, II) in salivary levels of alpha-amylase and cortisol and serum levels of S100B and BDNF, and on III) the quality of life and selfperception of the physical domain of people with schizophrenia. The sample consisted of 31 females in long-term institutions in the Casa de Saúde Rainha Santa Isabel, with age between 25 and 63, and with diagnosis of schizophrenia according to the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV-TR). Physical fitness was assessed by the six-minute walk distance test (6MWD). Biological variables were determined by ELISA (Enzyme-Linked Immunosorbent Assay). Psychological variables were assessed using SF-36, PSPP-SCV, RSES and SWLS tests. Walking exercise has a positive impact on physical fitness (6MWD -p = 0.001) and physical components of the psychological test...

International audienceNegative self-potential anomalies can be generated at the ground surface by ore bodies and ground water contaminated with organic compounds. These anomalies are connected to the distribution of the redox potential of the ground water. To study the relationship between redox and self-potential anomalies, a controlled sandbox experiment was performed. We used a metallic iron bar inserted in the left-hand side of a thin Plexiglas sandbox filled with a calibrated sand infiltrated by an electrolyte. The self-potential signals were measured at the surface of the tank (at different time lapses) using a pair of non-polarizing electrodes. The self-potential, the redox potential, and the pH were also measured inside the tank on a regular grid at the end of the experiment. The self-potential distribution sampled after six weeks presents a strong negative anomaly in the vicinity of the top part of the iron bar with a peak amplitude of −82 mV. The resulting distributions of the pH, redox, and self-potentials were interpreted in terms of a geobattery model combined with a description of the electrochemical mechanisms and reactions occurring at the surface of the iron bar. The corrosion of iron yields the formation of a resistive crust of fougerite at the surface of the bar. The corrosion modifies both the pH and the redox potential in the vicinity of the iron bar. The distribution of the self-potential is solved with Poisson's equation with a source term given by the divergence of a source current density at the surface of the bar. In turn, this current density is related to the distribution of the redox potential and electrical resistivity in the vicinity of the iron bar. A least-squares inversion method of the self-potential data, using a 2D finite difference simulation of the forward problem, was developed to retrieve the distribution of the redox potential

Natural self-potential (SP) fields observed in the vicinity of conductive orebodies can be explained in terms of electrochemical reactions in which the conductors participate. Battery-like models assume that a buried conductor creates an anode-cathode pair by conveying a flow of electrons to oxidizing areas in the shallow subsurface from reducing areas at depth. For conductors with invariant composition (behaving as an inert electrode), a quantitative formulation is already available. Numerical Green’s functions are used to allow one-step evaluation of SP fields from an inert electrode model. The model is used to simulate geoelectric targets in mineral exploration and to test a procedure to obtain current source terms by inverting an SP data set. Data inversion is constrained by charge conservation and prescribes source terms at the target surface. A background resistivity model is assumed to be known and is used to recognize interfaces and evaluate numerical Green’s functions in forward and inverse modeling. The inversion procedure is applied to interpret 2D data from two gold deposits of the Yanacocha district, Peru.

In contaminant plumes or in the case of ore bodies, a source current density is produced at depth in response to the presence of a gradient of the redox potential. Two charge carriers can exist in such a medium: electrons and ions. Two contributions to the source current density are associated with these charge carriers (i) the gradient of the chemical potential of the ionic species and (ii) the gradient of the chemical potential of the electrons (i.e., the gradient of the redox potential). We ran a set of experiments in which a geobattery is generated using electrolysis reactions of a pore water solution containing iron. A DC power supply is used to impose a difference of electrical potential of 3 V between a working platinum electrode (anode) and an auxiliary platinum electrode (cathode). Both electrodes inserted into a tank filled with a well-calibrated sand infiltrated by a (0.01 mol L(-1) KCl+0.0035 mol L(-)(1) FeSO(4)) solution. After the direct current is turned off, we follow the pH, the redox potential, and the self-potential at several time intervals. The self-potential anomalies amount to a few tens of millivolts after the current is turned off and decreases over time. After several days, all the redox-active compounds produced initially by the electrolysis reactions are consumed through chemical reactions and the self-potential anomalies fall to zero. The resulting self-potential anomalies are shown to be much weaker than the self-potential anomalies observed in the presence of an electronic conductor in the laboratory or in the field. In the presence of a biotic or an abiotic electronic conductor, the self-potential anomalies can amount to a few hundred millivolts. These observations point out indirectly the potential role of bacteria forming biofilms in the transfer of electrons through sharp redox potential gradient in contaminant plumes that are rich in organic matter.