Microbial Ecology and Geo-electrical Responses across a Groundwater Plume

We have used geophysics, microbiology, and geochemistry to link large-scale (30+ m) geophysical self-potential (SP) responses at a groundwater contaminant plume with its chemistry and microbial ecology of groundwater and soil from in and around it. We have found that microbially mediated transformation of ammonia to nitrite, nitrate, and nitrogen gas was likely to have promoted a well-defined electrochemical gradient at the edge of the plume, which dominated the SP response. Phylogenetic analysis demonstrated that the plume fringe or anode of the geobattery was dominated by electrogens and biodegradative microorganisms including Proteobacteria alongside Geobacteraceae, Desulfobulbaceae, and Nitrosomonadaceae. The uncultivated candidate phylum OD1 dominated uncontaminated areas of the site. We defined the redox boundary at the plume edge using the calculated and observed electric SP geophysical measurements. Conductive soils and waste acted as an electronic conductor, which was dominated by abiotic iron cycling processes that sequester electrons generated at the plume fringe. We have suggested that such geoelectric phenomena can act as indicators of natural attenuation processes that control groundwater plumes. Further work is required to monitor electron transfer across the geoelectric dipole to fully define this phenomenon as a geobattery. This approach can be used as a novel way of monitoring microbial activity around the degradation of contaminated groundwater plumes or to monitor in situ bioelectric systems designed to manage groundwater plumes

Stress-testing of the Russian Banking Sector: Contingent Claims Analysis Approach

This study aims to perform stress-testing of the Russian banking sector with a focus on credit risk measures derived by using contingent claims analysis, an extension of Black-Scholes and Merton option pricing theory. Risk exposure indicators are linked to a number of macroeconomic variables that describe global and domestic economic and financial development. To reduce the dimension of the dataset, principal component analysis is applied. The derived factors of financial stability, economic growth, and interest rates together with credit risk measures are used in vector autoregressions so as to draw impulse response functions, which allows for stress-testing of the analyzed banks by estimating the effect of adverse and severe adverse shocks to the factors specified by 95% and 99% VaR. Stress test analysis revealed that shock to the economic growth factor shows more persistence compared to the financial stability factor. Surprisingly, shock to the interest rates factor resulted to be insignificant at a chosen lag length. The results also suggest high degree of banks’ heterogeneity, which complicates a derivation of a parsimonious model suitable for the whole system. While international banks are barely affected by the proposed shocks, domestic banks, regardless of their size, may react rather strongly to the financial stability and economic growth shocks – to the point of reaching distress level within several months after the adverse event