LMWOA (low molecular weight organic acid) exudation by salt marsh plants: Natural variation and response to Cu contamination

This work aimed to evaluate, in vitro, the capability of roots of two salt marsh plants to release low molecular weight organic acids (LMWOAs) and to ascertain whether Cu contamination would stimulate or not organic acids exudation. The sea rush Juncus maritimus and the sea-club rush Scirpus maritimus, both from the lower Douro river estuary (NW Portugal), were used. Plants were collected seasonally, four times a year in 2004, during low tide. After sampling, plant roots were washed for removal of adherent particles and immersed for 2 h in a solution that matched salinity (3) and pH (7.5) of the pore water from the same location to obtain plant exudates. In one of the seasons, similar experiments were carried out but spiking the solution with different amounts of Cu in order to embrace the range between 0 and 1600 nM. In the final solutions as well as in sediment pore water LMWOAs were determined by high performance liquid chromatography. Plants were able to release, in a short period of time, relatively high amounts of LMWOAs (oxalate, citrate, malate, malonate, and succinate). In the sediment pore water oxalate, succinate and acetate were also detected. Therefore, plant roots probably contributed to the presence of some of these organic compounds in pore water. Exudation differed between the plant species and also showed some seasonally variation, particularly for S. maritimus. The release of oxalate by J. maritimus increased with Cu increase in the media. However, exudation of the other LMWOAs did not seem to be stimulated by Cu contamination in the media. This fact is compatible with the existence of alternative internal mechanisms for Cu detoxification, as denoted by the fact that in media contaminated with Cu both plant species accumulated relatively high amounts (29–83%) of the initially dissolved Cu. This study expands our knowledge on the contribution of globally dominant salt marsh plants to the release of LMWOAs into the environment.     

Dynamic racking tests of curtain wall glass elements with in-plane and out-of-plane motions

This project was conducted to investigate the breakage and fallout behaviour of various types of architectural glass elements in a dry-glazed curtain wall system under in-plane and out-of-plane dynamic motions. The project was a follow-up to an earlier project that focused exclusively on in-plane dynamic racking performance of curtain wall glass elements. The recent data indicated that adding out-of-plane motions caused significantly higher amounts of glass breakage and subsequent glass fallout in most glass types that were found during the in-plane tests to be prone to glass fallout. Specifically, 1/4 in (6 mm) annealed monolithic glass, 1/4 in annealed monolithic glass with a 0·004 in (0·10 mm) PET film (not anchored to the mullions), and 7/16 in (11 mm) fully tempered laminated glass exhibited comparable or higher fallout rates than the already substantial fallout rates that were observed during the in-plane only racking tests. Unanchored window film was found to be ineffective in resisting post-breakage glass fallout under dynamic racking motions. In contrast, 1/4 in (6 mm) annealed laminated glass and 7/16 in (11 mm) heat-strengthened laminated glass exhibited no glass fallout during the out-of-plane tests, just as they exhibited no fallout during the in-plane tests. Out-of-plane test results also showed that 3/8 in (10 mm) heat-strengthened monolithic glass exhibited no fallout, while 3/8 in annealed monolithic glass exhibited very negligible glass fallout. The addition of torsional motions was not found to induce glass fallout in those glass types that resisted glass fallout in previous tests performed without torsional motions.     

Die Matrix der Fische

Summary An apparatus has been developed and demonstrated, which may be used for measuring the motility and the vitality of fish and other animals under the action of different influences, for instance poisons. Under favorable experimental conditions, the energy can be estimated, which is shown by the animals in theirmilieu extérieur.      

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.