Electro-chemical mineralization of recalcitrant indole by platinum-coated titanium electrode: multi-response optimization,mechanistic and sludge disposal study

Indole is a highly recalcitrant aromatic heterocyclic organic compound consisting of a five-membered nitrogen-containing pyrrole ring fused to a six-membered benzene ring. This study presents the results of the electro-chemical mineralization of indole in an aqueous solution using platinum-coated titanium (Pt/Ti) electrode. A central composite design was used to investigate the effect of four parameters namely initial pH (pH_o), current density (j), conductivity (k) and treatment time (t) at 5 levels. Multiple responses namely chemical oxygen demand (COD) removal (Y ₁) and specific energy consumption (Y ₂) were simultaneously maximized and minimized, respectively, by optimizing the parameters affecting the mineralization of indole by using the desirability function approach. At the operating conditions of pH 8.6, j = 161 A/m², k = 6.7 mS/cm and t = 150 min, 83.8% COD removal with specific energy consumption of 36.3 kWh/kg of COD removed was observed. Ultra performance liquid chromatography, UV–visible spectroscopy, Fourier transform infrared spectroscopy and cyclic voltammetry of the indole solution were performed at the optimum condition of the treatment so as to report a plausible mechanism of indole degradation. Field emission scanning electron microscopy analysis of electrodes before and after treatment was performed for determining the changes on anode surface during the treatment. Thermal analysis of the solid residue (scum) obtained was also performed for exploring its disposal prospects. Present study shows that electro-chemical oxidation can be used for mineralization of nitrogenous heterocyclic compounds such as indole.     

New seismogenic source and deep structures revealed by the 1999 Chia-yi earthquake sequence in southwestern Taiwan

In a tectonically active setting large earthquakes are always threats; however, they may also be useful in elucidating the subsurface geology. Instrumentally recorded seismicity is, therefore, widely utilized to extend our knowledge into the deeper crust, especially where basement is involved. It is because the earthquakes are triggered by underground stress changes that usually corresponding to the framework of geological structures. Hidden faults, therefore, can be recognized and their extension as well as orientation can be estimated. Both above are of relevance for assessment on seismic hazard of a region, since the active faults are supposed to be re-activated and cause large earthquakes. In this study, we analysed the 1999 October 22 earthquake sequence that occurred in southwestern Taiwan. Two major seismicity clusters were identified with spatial distribution between depths of 10 and 16 km. One cluster is nearly vertical and striking 032°, corresponding to the strike-slip Meishan fault (MSF) that generated the 1906 surface rupture. Another cluster strikes 190° and dips 64° to the west, which is interpreted as west-vergent reverse fault, in contrast to previous expectation of east vergence. Our analysis of the focal solutions of all the larger earthquakes in the 1999 sequence with the 3-D distribution of all the earthquakes over the period 1990–2004 allows us reinterpret the structural framework and suggest previously unreognized seismogenic sources in this area. We accordingly suggest: (1) multiple detachment faults are present in southwestern Taiwan coastal plain and (2) additional seismogenic sources consist of tear faults and backthrust faults in addition to sources associated with west-vergent fold-and-thrust belt.     

The geography of the elderly in a modernizing society: the Hong Kong case

The characteristics of the elderly population of Hong Kong are first described. Recent changes in the spatial distribution of the elderly are also detailed. The spatial distribution and internal migration patterns of the elderly are shown to be very similar to those of the population as a whole. The problems posed by the fact that many of the elderly are poorly educated and lowly paid are considered.     

Preface: Proceedings of the 5th International Symposium on Lithographic Limestone and Plattenkalk

Magmatic rocks from the pre-Mesozoic basements of the Sambuco and Maggia nappes have been dated by U–Pb zircon ages with the LA-ICPMS technique. Several magmatic events have been identified in the Sambuco nappe. The mafic banded calc-alkaline suite of Scheggia is dated at 540 Ma, an age comparable to that of mafic rocks in the Austroalpine Silvretta nappe. The Sasso Nero peraluminous augengneiss has an age of 480–470 Ma, like many other “older orthogneisses” in Alpine basement units. It hosts a large proportion of inherited zircons, which were dated around 630 Ma, a Panafrican age indicating the Gondwanan affiliation of the Sambuco basement. The calc-alkaline Matorello pluton yielded ages around 300 Ma, similar to numerous Late Carboniferous intrusions in other basement units of the Lower Penninic (Monte Leone, Antigorio, Verampio) and Helvetic domains (Gotthard and other External Crystalline Massifs). Associated lamprophyric dykes are slightly younger (300–290 Ma), like similar dykes sampled in gneiss blocks included in the sedimentary cover of the underlying Antigorio nappe (290–285 Ma). The Cocco granodiorite and Rüscada leucogranite, both intruding the basement of the neighbouring Maggia nappe, yielded ages of ca. 300–310 Ma, identical within errors to the age of the Matorello pluton. They are significantly older than former age determinations. This age coincidence, coupled with remarkable petrologic similarities between the Cocco and Matorello granodiorites, strongly suggests paleogeographic proximity of the Sambuco and Maggia nappes in Late Carboniferous times. In recent publications these two nappes have been interpreted as belonging to distinct Mesozoic paleogeographic domains: “European” for Sambuco and “Briançonnais” for Maggia, separated by the “Valais” oceanic basin. In this case, the similarity of the Matorello and Cocco intrusions would demonstrate the absence of any significant transcurrent movement between these two continental domains. Alternatively, according to a more traditional view, Sambuco and Maggia might belong to a single large Alpine tectonic unit.     

Exploiting historical rainfall and landslide data in a spatial database for the derivation of critical rainfall thresholds

Critical rainfall thresholds for landslides are powerful tools for preventing landslide hazard. The thresholds are commonly estimated empirically starting from rainfall events that triggered landslides in the past. The creation of the appropriate rainfall–landslide database is one of the main efforts in this approach. In fact, an accurate agreement between the landslide and rainfall information, in terms of location and timing, is essential in order to correctly estimate the rainfall–landslide relationships. A further issue is taking into account the average moisture conditions prior the triggering event, which reasonably may be crucial in determining the sufficient amount of precipitation. In this context, the aim of this paper is exploiting historical landslide and rainfall data in a spatial database for the derivation of critical rainfall thresholds for landslide occurrence in Sicily, southern Italy. The hourly rainfall events that caused landslides occurred in the twentieth century were specifically identified and reconstructed. A procedure was proposed to automatically convert rain guages charts recorded on paper tape into digital format and then to provide the cumulative rainfall hyetograph in digital format. This procedure is based on a segmentation followed by signal recognition techniques which allow to digitalize and to recognize the hyetograph automatically. The role of rainfall prior to the landslide events was taken into account by including in the analysis the rainfall occurred 5, 15 and 30 days before each landslide. Finally, cumulated rainfall duration thresholds for different exceedance probability levels were determined. The obtained thresholds resulted in agreement with the regional curves proposed by other authors for the same area; antecedent rainfall turned out to be particularly important in triggering landslides.     

Environmental conditions for gravelly and pebbly dunes and sorted bedforms on a moderate-energy inner shelf (Marettimo Island,Italy, western Mediterranean)

Side scan sonar records, sediment textural characteristics, and in-situ field observations were used to study gravelly and pebbly dunes and sorted bedforms on the inner shelf of Marettimo Island, along the northwestern Sicilian shelf. The dunes are composed of coarse sands, gravels and pebbles (D50: 2–16 mm), displaying a symmetrical shape with a wavelength in the range of 1–2.5 m and a height of 0.15–0.30 m. The bedforms are distributed in a patchy pattern in a depth range of 10–50 m, and are described for the first time on a Mediterranean inner shelf. Sorted bedforms are linear morphological features developed almost perpendicular to the coast in the eastern sector of the island between 15 and 50 m water depth. Bottom shear stresses required for sediment entrainment and the generation of the shallower dunes can be reached during strong storms (Hs=5–6 m; Tp=9–11 s), which are not common in the Mediterranean Sea. However, wave storm events recorded in the study area during the last 17 years are not able to generate the coarsest and deeper dunes, suggesting that the stirring mechanism for dune formation is associated with severe storms that have a recurrence interval of more than 17 years. The long-term stability of the coarse bedforms is supported by the permanence of sorted bedforms without significant morphological changes for long periods (>13 years). Therefore, it is shown that processes forming coarse bedforms can occur in tideless and moderate-energy settings like those of the Mediterranean continental shelves, although the morphological features are probably less dynamic and remain unaltered for longer periods than on higher-energy shelves.