Influence of biotic-abiotic factors on the degradation of novaluron in tropical soil

In this study, the degradation of novaluron (benzoylphenyl urea insect growth regulator) was investigated under controlled laboratory conditions in clay loam alluvial and coastal saline soils of West Bengal, India. The application rates were field rate (FR); 2FR and 10FR. The incubation study was carried out at 30 °C and 60% of maximum water holding capacity of both the soils. Degradation of novaluron in both the soils followed first order reaction kinetics at all application rates under non-sterile and sterile conditions. The half-lives of novaluron in non-sterilized soils ranged from 17.0–17.8 days (alluvial soil) and 11.4–12.7 days (coastal saline soil), while the values in case of the sterilized soils were 53.7–59.0 days (alluvial soil) and 28.9–29.8 days (coastal saline soil) respectively. The novaluron degradation patterns were found to be highly influenced by soil types, application rates, and biotic abiotic factors. Abiotic factors strongly influenced novaluron degradation in both the soils. Biotic degradation was higher in alluvial soil compared to the coastal saline soil.     

Geobotany of red sanders (Pterocarpus santalinus) – a case study from the southeastern portion of Andhra Pradesh

 RedSanders in their natural distribution occur almost exclusively in quartzites and shales. This indicates the geobotanical response to these rock types in the semi-arid tract of the southeastern portion of Andhra Pradesh in the tropical dry deciduous forests of Chittoor, Cuddapah and Nellore districts. Thus Red Sanders are important from a commercial point of view and also a useful tool to demarcate stratigraphic formations. Received: 27 April 1998 · Accepted: 21 July 1998     

Seismicity in the vicinity of Ross Island, Antarctica

Earthquakes in the Ross Sea, Antarctica, are of two types: volcanic, and those which appear to be of tectonic origin. Volcanic events in the vicinity of Ross Island are associated exclusively with Mount Erebus, Ross Island; this volcano erupts regularly, generating several earthquakes per day whose characteristics are quite distinct from non-volcanic events. These nonvolcanic earthquakes are recognizable by their distinct P- and S-wave arrivals, and a lack of the high frequency, often monochromatic character typical of Erebus events.One hundred fifty-seven tectonic microearthquakes (M < 2.0) were recorded in 1983 and 1984 by the ten station network on Ross Island; these events were located using the least-squares routine, HYPOELLIPSE. Of these events, 106 have RMS residual traveltime errors of less than or equal to 0.6 seconds; they are clustered in the vicinity of Ross Island, but are not restricted to it. There is a linear trend of epicenters cutting across the island and continuing northward. Most activity seems to center beneath Mount Terra Nova, between Mount Erebus and Mount Terror. Mean depth for events is 8.2 km; however, depths are rather evenly distributed over a range of 0 to 25 km.Modelling based on Bouger gravity anomalies and seismic refraction studies indicates a depth to the Moho of about 40 km beneath the continent, shallowing to 27 km beneath the Ross Sea. This 27 km depth is approximately equal to the lower limit of the tectonic seismicity detected by the Erebus network; hence, events are of crustal origin. These data suggest, with the rift-type geochemistry of Erebus' magma, that the Ross Sea is a site of active crustal extension and rifting.     

The Ribeira fluorite district,southern Brazil

The origin and evolution of different ore deposits grouped in the same district are often complex and may involve inheritance from crustal or mantle geochemical anomalies, remobilization of former ore deposits and a polyphase hydrothermal history. Localized in a Proterozoic basement in the Parana state, the Ribeira fluorite district is such an example composed of three deposit types with distinct geological and geochemical characters. Emplaced at different periods from the late Proterozoic to the Cretaceous, they are roughly aligned along a belt nearly 10 km in width and 50 km in length, the southern boundary of which is a transcurrent fault. Two main ore facies are present: (1) microcrystalline ore (< 0.1 mm grains) and (2) macrocrystalline ore (with a grain size of several millimetres). The former results from the replacement of metalimestones or internal karstic sediments and the latter from microcrystalline ore dissolution and pore precipitation or recrystallization. At least two different groups of source rocks can be proposed for the trapped REE in CaF₂: (1) fluorite samples associated with the Mato Preto carbonatitic rocks display a slightly negative ɛNd compatible with a mantle source and a REE pattern with the higher ΣREE and La/Yb ratio in the district; (2) other fluorites have a strongly negative ɛNd (− 14 to − 20) which indicates a crustal source. That fluorine and REE have the same source is possible in strata-bound and fracture-filling deposits, but is doubtful at Mato Preto, the only economic fluorite deposit associated with carbonatite rocks in Brazil. This occurrence within a Precambrian fluorite belt suggests that remobilization of a former strata-bound deposit was a more significant metallogenic process than magmatic differentiation. Editorial handling: DR     

The Deep Geoelectrical Section of the Avacha–Koryak Zone of Contemporary Volcanism,Kamchatka

The methods and results of magnetotelluric sounding in the range of 0.0001–1000 s and more with the use small portable magnetotelluric stations are considered. Data on the distribution of electrical conductivity at depths beneath the Avacha–Koryak zone of contemporary volcanism are obtained. The obtained data are interpreted using the modern techniques and methods.

     

Geochemical Evidence for Subduction Fluxes, Mantle Melting and Fractional Crystallization Beneath the South Sandwich Island Arc

The volcanoes of the South Sandwich island arc follow threedistinct series: low-K tholeiitic (followed by Zavodovski, Candlemas,Vindication, Montagu and Bristol), tholeiitic (followed by Visokoi,Saunders and Bellinghausen) and calcalkaline (followed by Leskov,Freehand and part of Cook and Thule). Flux calculations indicatethat the percentage contribution of the subduction componentto the mantle source of all three series varies from undetectable(e.g. Zr) through small (e.g. Nd=20%) and moderate (e.g. La,Ce, Sr=50–80%) to dominant (e.g. Pb, K, Ba, Rb, Cs >90%)with little change along the arc. Isotope systematics (Pb, Nd,Sr) show that this subduction component obtains a greater contributionfrom altered oceanic crust than from pelagic sediment. Elementsfor which the subduction contribution is small show that themantle is already depleted relative to N-MORB mantle (equivalentto loss of an 2•5% melt fraction) before melting beneaththe arc. After addition of the subduction component, dynamicmelting of this depleted mantle then causes the variations inK that distinguish the three series. The estimated degree ofpartial melting (20%) is slightly greater than that beneathocean ridges, though geothermometry suggests that the primarymagma temperature (1225C) is similar to that of primary MORB.About half of the melting may be attributed to volatile addition,and half to decompression. Dynamic melting involving three-dimensional,two-phase flow may be needed to explain fully the inter-islandvariations. KEY WORDS: geochemistry; petrology; fluxes; melting; subduction ^*Corresponding author     

Structural Variations of Bottom Sediments in the Rybinsk Reservoir

Long-standing variations in the structure of bottom sediments within typical habitats of the aquatic life are characterized using the Volzhskii Pool of the Rybinsk Reservoir as an example. The role of hydrodynamic processes of the littoral zone in the formation of the ground complex of shallow water areas of the pool is discussed. The trends in variation in the quality of bottom substrate in fish habitats are analyzed. The peculiarities of long-standing variations in the distribution of types of bottom sediments in the entire reservoir are shown.     

On a homogeneous representation of seismic history in large regions

The possibility to obtain a more complete and unbiased long-term history of seismic shakings over large territories than is explicitly reported from inhabited localities is discussed in the paper. An approach proposed for this purpose consists in complementing the spatial distribution of the macroseismic effect of earthquakes by calculated intensities at localities where information on felt shakings is absent. The calculated intensity is obtained on the basis of data on the epicentral intensity and location of epicenters provided by earthquake catalogs. This approach is applied to the analysis of the history of seismic shaking in Spain. The calculated intensities are shown to be comparable in accuracy with the ordinary practice of intensity determinations at national seismological centers.     

Two tiltmeters and an integrating seismometer for the monitoring of volcanic activity, and the results of some trials on Mount Etna

Two types of continuously recording tiltmeter and a new “integrating seismometer” were tested on Etna during the period September to December 1976. The primary object was the investigation of techniques for the surveillance and prediction of volcanic activity, but some information on the internal structure and mechanism of Etna was also obtained. It was concluded that a network of tiltmeters combined with seismic monitoring (using standard and/or integrating seismometers) offers the best dual approach to the problem of determining the true state of dormant volcanoes, and predicting the date and site of possible future eruptions.     

Untersuchung der Sorptionseigenschaften des Kationenaustauschers KB-2M mit Makronetzstruktur zur Abtrennung von Zinkionen aus Ab- und Spülwässern

Study of Sorptional Properties of the Cation Exchanger KB-2M with Macroreticular Structure for Recovery of Zinc Ions from Sewage and Rinsing Water Although a number of ion-exchange methods have been employed for the recovery of some transition metals from industrial effluents, knowledge about ion-exchange resins with macroreticular structure is poor. The present paper describes the mechanism of sorption on such exchangers and their application for recovery of zinc from sewage rinsing water. Ion exchanger of macroreticular structure are polymers with long-chained cross-linking agents. We have synthesized carboxylic ion-exchange resins by hydrolysis of copolymerisates of methyl acrylate with different cross-linking agents: divinylbenzene, divinyl sulfide, divinyl ester of ethylene glycol and divinyl ester of di- or triethylene glycol. The sorption process on modifications of the carboxylic resins KB-2 of various structure was studied with different methods: potentiometric titration, infrared spectroscopy, electron microscopy, X-ray structural analysis. The initial zinc concentration in rinsing water was 0.05 mol/L at pH from 3 to 6. For the sorption, 0.2…1.0 g of resin were equilibrated with 100 mL of zinc solution. After equilibrium (12 h), the resin was separated from solution. The zinc ions were determined by atomic absorption spectrometry after stripping with 100 mL of 10% sulfuric acid. The distribution ratio D was calculated (D: mmole of Zn sorbed per gram of resin divided by mmole of Zn per millilitre of solution). By means of infrared spectroscopy, the mechanism of sorption of zinc ions from rinsing water was determined. There may be a possibility of the formation of complexes in the cation-exchange resin phase. It was found out in this paper that the cation-exchanger KB-2M of macroreticular structure is the most effective for the sorption of the Zn²⁺-ions from sewage and rinsing water.