River Rock Research Articles

Distribution of Pb isotopic signatures in a hydrographic sub-basin of the Poços de Caldas Plateau, Minas Gerais, Brazil

The Taquari River Basin, located in the Alkaline Complex of Poços de Caldas, in the south of Minas Gerais, Brazil, is situated in an old volcanic caldera. In the study area there are fields and pastures; agriculture with cultivation of vegetables; rose plantations; and native forest, in addition to the Mineral Treatment Unit of Caldas (UTM-Caldas), which is part of the Industrial Complex of Poços de Caldas (CIPC), a uranium mining and processing facility. The main objective of this work was to investigate the isotopic Pb signatures of river sediments, rocks, mining tailings and fertilizer samples collected in the region surrounding UTM-Caldas in order to identify environments with influences from geogenic and / or anthropogenic sources. The results showed that there is an anthropic contribution (fertilizers and mining tailings) in some sectors of the Taquari river basin, generating possible concerns about the amount of elements that can be transferred to the water bodies. In addition, there is a significant geogenic contribution of naturally enriched areas, which have distinct situations that also generate an increase in the concentration of chemical elements in water bodies.

Plant growth and pollutant removal from wastewater in domiciliary constructed wetland microcosms with monoculture and polyculture of tropical ornamental plants

This study investigated pollutants (fluoride, chloride, nitrate, ammonia, phosphates, sulphate and total and volatile solids) removal efficiency from domestic wastewater and plant growth during 195 days in domiciliary constructed wetland (DCWs) microcosms. DCWs were planted with monoculture of Canna hybrid, Alpinia purpurata and Hedychium coronarium and polyculture of the same ornamental flowering plants (OFP), having river rock as a porous substrate. All OFP survived in the DCWs conditions without physical damage. C. hybrid showed the highest length and volume of roots and the highest height and number of flowers than other species in both, mono and polyculture systems. H. coronarium, did not produce flowers. A. purpurata grew better in monoculture than polyculture. Ammonia nitrogen removal was significantly higher in DCW microcosms with monocultures of C. hybrid than with monocultures of A. purpurata (p = .037), but no significantly different than monocultures of H. coronarium (p = .466), Contrary, removal efficiency of this ion was significantly higher in polyculture than mocultures of A. purpurata (p = .024) and H. coronarium (p = .0.032) but no significantly different than monoculture of C. hybrid.The other parameters were removed similarly in both cultures of plants (20–81%; p > .05). Polycultures of OFP are a good option for wastewater treatment in DCWs.

Anopheles larval species composition and characterization of breeding habitats in two localities in the Ghibe River Basin, southwestern Ethiopia

BackgroundDocumentation of the species composition of Anopheles mosquitoes and characterization of larval breeding sites is of major importance for the implementation of larval control as part of malaria vector control interventions in Ethiopia. The aims of this study were to determine the Anopheles larval species composition, larval density, available habitat types and the effects of related environmental and physico-chemical parameters of habitats in the Ghibe River basin of southwestern Ethiopia.MethodsAnopheles larvae were sampled from November 2014 to October 2016 on a monthly basis and 3rd and 4th instars were identified microscopically to species. The larval habitats were characterized based on habitat perimeter, water depth, intensity of light, water current, water temperature, water pH, water turbidity, distance to the nearest house, vegetation coverage, permanence of the habitat, surface debris coverage, emergent plant coverage, habitat type and substrate type.ResultsIn total, 9277 larvae of Anopheles mosquitoes and 494 pupae were sampled from borrow pits, hoof prints, rain pools, pools at river edges, pools in drying river beds, rock pools, tire tracks and swamps. Anopheles larval density was highest in pools in drying river beds (35.2 larvae per dip) and lowest in swamps (2.1 larvae per dip) at Darge, but highest in rain pools (11.9 larvae per dip), borrow pits (11.2 larvae per dip) and pools at river edges (7.9 larvae per dip), and lowest in swamps (0.5 larvae per dip) at Ghibe. A total of 3485 late instar Anopheles mosquito larvae were morphologically identified. Anopheles gambiae sensu lato was the primary Anopheles mosquito found in all larval habitats except in swamps. Temperature at the time of sampling and emergent vegetation, were the most important variables for Anopheles mosquito larval density. Anopheles gambiae density was significantly associated with habitats that had smaller perimeters, were sunlit, had low vegetation cover, and a lack of emergent plants. Generally, Anopheles mosquito larval density was not significantly associated with water pH, water temperature, water turbidity, algal content, and larval habitat depth.ConclusionDifferent species of Anopheles larvae were identified including An. gambiae s.l., the main malaria vector in Ethiopia. Anopheles gambiae s.l. is the most abundant species that bred in most of the larval habitat types identified in the study area. The density of this species was high in sunlit habitat, absence of emergent plants, lack of vegetation near habitat and habitats closer to human habitation. Rainfall plays a great role in determining the availability of breeding habitats. The presence of rain enable to create some of the habitat types, but alter the habitats formed at the edge of the rivers due to over flooding. Controlling the occurrence of mosquito larvae through larval source management during the dry season, targeting the pools in drying river bed and pools formed at the edge of the rivers as the water receded can be very crucial to interrupt the re-emergence of malaria vectors on the onset of rainy season.

Impact of Ornamental Vegetation Type and Different Substrate Layers on Pollutant Removal in Constructed Wetland Mesocosms Treating Rural Community Wastewater

Improving water quality is a relevant environmental aspect, and using constructed wetlands (CWs) is a sustainable option for this; both porous material filled cells and plants that collectively remove contaminants must be readily available and inexpensive. This study evaluated CWs and their functionality by comparing two ornamental plants (Spathiphyllum wallisii and Hedychium coronarium) planted in experimental mesocosm units filled with layers of porous river rock, tepezil, and soil, or in mesocosms with layers of porous river rock, and tepezil, without the presence of soil. The findings during the experiments (180 days), showed that the removal of pollutants (chemical oxygen demand (COD), total solids suspended (TSS), nitrogen as ammonium (N-NH4), as nitrate (N-NO3), and phosphate (P-PO4) was 20–50% higher in mesocosms with vegetation that in the absence of this, and those mesocosms with the soil layer between 33–45% favored removal of P-PO4. Differences regarding of vegetation removal were only observed for N-NH4, being 25–45% higher in CWs with H. coronarium, compared with S. wallisii. Both species are suitable for using in CWs, for its functionality as phytoremediation, and aesthetic advantages could generate interest for wastewater treatment in rural communities, parks, schools or in domiciliary levels like floral flower boxes in the backyard. The study also revealed that a soil layer in CWs is necessary to increase the removal of P-PO4, an ion hardly eliminated in water treatment.

Effect of Ornamental Plants, Seasonality, and Filter Media Material in Fill-and-Drain Constructed Wetlands Treating Rural Community Wastewater

The effects of Canna indica (P1), Pontederia sagittata (P2), and Spathiphyllum wallisii (P3) growing in different filter media materials (12 using porous river rock and 12 using tepezyl) on the seasonal removal of pollutants of wastewater using fill-and-drain constructed wetlands (FD-CWs) were investigated during 12 months. Three units of every media were planted with one plant of P1, P2, and P3, and three were kept unplanted. C. indica was the plant with higher growth than the other species, in both filter media. The species with more flower production were: C. indica > P. sagittate > S. wallisii. Reflecting similarly in the biomass of the plants, C. indica and P. sagittata showed more quantity of aerial and below ground biomass productivity than S. wallisii. With respect to the removal efficiency, both porous media were efficient in terms of pollutant removal performance (p > 0.05). However, removal efficiency showed a dependence on ornamental plants. The higher removal of chemical oxygen demand (COD), biochemical oxygen demand (BOD5), total kjeldahl nitrogen (TKN), nitrates (NO3−-N), ammonium (NH4+-N), and phosphates (PO4−3-P) oscillated between 81% to 83%, 80% to 84%, 61% to 69%, 61% to 68%, 65% to 71%, 62% to 68%, and 66% to 69%, respectively, in P1 and P2, removals 15% to 30% higher than P3. The removal in planted microcosms was significantly higher than the unplanted control units (p = 0.023). Nitrogen and phosphorous compounds were highly removed (60%–80%) because in typical CWs, such pollutant removals are usually smaller, indicating the importance of FD-CWs on wastewater treatments using porous river rock and tepezyl as porous filter media. (BOD5), chemical oxygen demand (COD), (NO3−-N), (NH4+-N), (TKN), and (PO4−3-P).

Egg masses of some stream‐dwelling caddisflies (Trichoptera: Hydrobiosidae) from Victoria, Australia

AbstractEggs are a largely neglected life stage in most ecological studies of aquatic insects, despite the importance of oviposition behaviour and fecundity estimates for many research questions. Incorporating egg stages into ecological research requires that ecologists can identify and quantify eggs, but descriptions of eggs and egg masses are scarce for many groups and particularly for Australian taxa. This paper focusses on stream‐dwelling caddisflies in the family Hydrobiosidae and provides species‐level identifications, morphological descriptions and images of egg masses of some species that commonly occur in south‐eastern Australia. All the species we identified laid plaque‐shaped egg masses attached to the underside of river rocks that protrude above the water surface. These egg masses can be identified in the field with the naked eye or the aid of a low‐magnification hand lens. Interspecific variations in egg mass morphology were primarily thickness and firmness of the spumaline layer, egg mass size and arrangement of eggs within the mass. We also provide some ecological information on clutch sizes and the physical characteristics of oviposition sites, and we discuss various ways in which these taxa could be exploited as model systems for ecological research.

UJI DENSITAS DAN POROSITAS SERTA KARAKTERISASI MENGGUNAKAN XRD DAERAH MATA AIR PANAS SEMURUP SUNGAI MEDANG KABUPATEN KERINCI PROVINSI JAMBI

Test Density and Porosity of rock have been done to see the relation to temperature influence 100 ᵒC, 200 ᵒC and 300 ᵒC. Rocks that will be tested first heated temperature with furnace tool then weighed with a digital balance. Density and Porosity measurement data were analyzed using Matlab Software with ASTMC373 equation. The result of Matlab in the form of graph shows average temperature change to Semurup rock density of 0.03 g / cm3 and the effect of temperature on Semurup rock porosity at 300 ᵒC is 30.29%. The average temperature change to Medang River rock density is 0.003 g / cm3 and the effect of temperature on Medang River rock porosity at 300 ᵒC is 0,55%. Looking at the rock crystal structure used XRD. Data from Characterization using XRD was analyzed with High Score Plus software. The result of rock characterization using XRD, from semurup showed that component of CaCO3 is 94%, crystal structure not yet fully formed and still in amorphous form, meanwhile rock from medang river show that component of CaCO3 is with 98%, crystalline structure have formed crystal.

Natural and by-product materials for thermocline-based thermal energy storage system at CSP plant: Structural and thermophysical properties

Thermal energy storage (TES) technology is currently considered as a key solution to improve the performance of Concentrated Solar Power (CSP) plants in terms of their flexibility and dispatchability. Particularly, thermocline packed-bed single-tank configuration was shown to be a promising and economically appropriate solution, which utilizes low cost filler materials as TES working media. In this work, some natural and by-product materials, i.e. Basic Oxygen Furnace (BOF)-Slag, Magnetite ore and River rock, were evaluated as filler materials for a pre-industrial 20 MWhth TES system that will be coupled to a 1 MWel commercial pilot CSP plant. Through their structural characterization, thermophysical properties and comparison with already applied materials for this type of configuration the most promising one in terms of its specifications for sensible TES is selected. The most promising material will be validated at a 200 kWhth (1/100 real scale) laboratory scale TES prototype that is being constructed within the framework of the Organic Rankine Cycle (ORC) – Plus project.

Epilithic Chamaesiphon (Synechococcales, Cyanobacteria) species in mountain streams of the Alps\u2014interspecific differences in photo-physiological traits

Many alpine streams inhabit conspicuous epilithic biofilms on pebbles and rocks that are formed by members of the cyanobacterial genus Chamaesiphon (Synechococcales). In the Austrian Alps, some Chamaesiphon species can even overgrow up to 70% of the surface of river rocks, and hence they must play an important but still unstudied ecological role in the organic matter flux. Since photo-biological traits have not been investigated so far, photosynthetic features, pigments, and UV-sunscreen compounds were studied in three Chamaesiphon morphospecies (C. geitleri, C. polonicus, C. starmachii). These species form conspicuously differently colored spots on cobbles and boulders in the alpine streams. While C. polonicus typically forms red crusts on flat pebble conglomerate, C. geitleri and C. starmachii are characterized by dark brown and black biofilms in the field, respectively. Photosynthesis-irradiance (PE) curves indicate that all three Chamaesiphon species have different light requirements for photosynthesis, with C. starmachii and C. polonicus preferring high and low photon fluence rates, respectively, while C. geitleri takes a position in between. This low-light requirement of C. polonicus is also reflected in ca. ten-times lower chlorophyll a, zeaxanthin, and ß-carotene concentrations, as well as in a lack of the UV-sunscreen scytonemin. All Chamaesiphon morphospecies exhibit the mycosporine-like amino acid porphyra-334. The physiological and biochemical data indicate strong intraspecific differences in photosynthetic activity and pigment patterns, which explain well the distinct preferences of the three studied Chamaesiphon morphospecies for sun-exposed or shaded habitats.

Modeling of Entrainment in Debris Flow Analysis for Dry Granular Material

Debris flow entrainment refers to the increase in mass by way of erosion of the channel beds or undermining the channel banks. Entrainment makes the calculation of travel distance and velocities of debris flow much more complex and difficult. Shear failure of the material in the channel bed is usually considered to be the dominant mechanism in entrainment analysis. However in granular flow, material at the surface of the channel bed can be eroded by progressive scouring under the base of the debris. This may result in more material being eroded and entrained than just considering the shear failure mechanism. A new analytical model is proposed to calculate entrainment in debris flow analysis by considering both rolling and shearing motion. Newton’s Law of Motion is used to calculate accelerations, velocities, and displacements of granular particles. To study the entrainment process inside granular flow and to verify the new entrainment model, numerical experiments have been carried out using the Discrete Element Method (DEM). Velocities, including translational velocity, rotational velocity and average velocity, total volume, shear stresses are monitored using measurement circles in the numerical experiment. Variations of the depth of erosion at specific locations along the debris flow channel are monitored and the average entrainment rates are calculated. By comparing the numerical experimental results with the analytical solutions, it is found that results from the analytical model agree well with that from the numerical experiments. In order to use the new entrainment model into debris flow runout calculation, the new entrainment model has been incorporated in a runout model based on an energy approach. Entrainment calculation governed by a second order partial differential equation is solved using the finite difference method. The total mass and profile of the channel bed are adjusted during the entrainment calculation. Sensitivity analyses have been carried out on the new model by varying the model parameters including internal friction angle, basal friction angle, turbulent coefficient and mean of Probability Density Function (PDF) etc. Back analysis of historical cases is carried out using the new model. Several case histories have been studied which include the Tsingshan debris flow, Niumian Rock Avalanche, Fjaerland debris flow, Faucon debris flow and Zymoetz River rock avalanche. An extremely large rock avalanche occurred on April 9, 2000 at Yigong is also studied in the thesis. Measurements obtained from site investigation, including flow velocity, flow height, entrainment depth at specific locations, run-out distance and total volume at deposition fan, have been used to evaluate the model. The results are encouraging based on comparisons of the run-out distance, front velocity and total volume of the debris. Improvements are required on the entrainment depth and total volume in some cases when lateral spreading of the debris is significant.

The Kawa Model in occupational therapy and its application in the rehabilitation of a mentally challenged patient

Abstract Introduction: The article aims to provide information on the Kawa Model and its application in occupational therapy. The model uses the metaphor of a river to depict a human life journey. Particular constructs connected with a river such as water, river side walls, driftwood or rocks represent elements of individuals′ social environment as well as their resources and limitations. Case study: The application of the Kawa Model in occupational therapy makes it possible to recognize and interpret the state of a patient taking into account social and cultural contexts. It also helps to structure an individual’s narration. Description: The situation of a patient diagnosed with paranoid schizophrenia is analysed according to the presented model and shown in both graphic and descriptive versions. Conclusions: As well as analysing theoretical aspects of implementing the Kawa Model, the present study shows elements of practical applications of this concept when working with a schizophrenic patient.

The Technology of the Early Oakhurst Lithic Techno-Complex from Klipdrift Cave, Southern Cape, South Africa

The analysis of the lithics recovered from the layers dating between cal bp 10,700 and cal bp 13,700 at Klipdrift Cave, southern Cape, South Africa, provides new information on the Oakhurst techno-complex. A comparison with contemporary sites such as Matjes River Rock Shelter indicates not only technological similarities, but also unexpected differences. The Klipdrift Cave Oakhurst shares many characteristics typical of this techno-complex from the southern Cape, for example, in the dominance of quartzite, irregular and unstandardised flakes; the occurrence of irregular cores; and typical large side and end scrapers. It differs from most coastal Oakhurst sites however, in the more intensive exploitation of quartz, and the presence of a blade component, especially in the lowermost layers. Palaeoenvironmental data, derived from stable isotope analysis of ostrich eggshell, suggest that it was dry in this region during this time period. This was partially a result of the colder conditions that prevailed during the Younger Dryas. The lithic technological production techniques are stable at Klipdrift Cave during the period that the site was occupied from cal bp 13,700 to cal bp 10,700. Our data suggest that the lithic technology did not change in response to possible climatic variability.

Oyster reef restoration: substrate suitability may depend on specific restoration goals

AbstractA limited supply of oyster shell for restoration practices has prompted investigations of alternative substrates used in construction of artificial oyster reefs. The success of oyster reef restoration projects is increasingly focused not only on oyster densities, but also on habitat provisioning for associated fauna. A subtidal oyster reef complex (0.24 km2) was restored in the Mission‐Aransas Estuary, Texas, U.S.A., in July 2013 using replicated mounds of concrete, limestone, river rock, and oyster shell substrates. Oyster and reef‐associated fauna characteristics were quantified quarterly for 15 months, using sampling trays that were deployed 3 months after construction. The highest densities of oyster spat occurred 9 months after tray deployment (July 2014, 1,264/m2), whereas juvenile oyster densities increased throughout the study period to 283/m2. Concrete (1,022/m2) and limestone (939/m2) supported the highest number of oysters over all dates. Oyster shell (1,533/m2) and concrete (1,047/m2) substrates supported the highest densities of associated motile fauna. Faunal diversity (Hill's N1) did not vary by substrate material, but did show seasonal variation. A simple benefit–cost ratio was used to indicate the localized monetary value for each of the substrates. Oyster shell and concrete substrates returned the highest benefit–cost ratio for motile fauna, while concrete yielded the highest benefit–cost ratio for oyster abundance. Incorporating benefit–cost ratios in restoration planning will allow practitioners to better integrate substrate‐specific ecological values with economic considerations and project goals to maximize return on restoration investments.

Assessment of the Hydrogeochemistry of Groundwater Using Multivariate Statistical Analysis in Erode Taluk, Tamilnadu, India

The geochemistry of ground water in Erode Taluk, Cauvery River and hard rock terrain in Erode Taluk covers an area of about 752.61 km2 and has been investigated to understand the hydro-geochemistry of the area. The challenge was made to study using multivariate statistical analysis like Factor Analysis (FA) and Cluster Analysis (CA). 103 groundwater samples are collected from Erode Taluk, for the period of pre and post monsoon season were analyzed for various physicochemical factors such as pH, Electrical Conductivity (EC), Total Dissolved Solids (TDS), Total Hardness (TH), Na+, Mg2+, HCO3−, Ca2+, CO32-, Cl−, SO42-, NO3−, F− and Fe2+ are determined. Hydro geochemical data for 103 groundwater samples were subjected to Q and R mode FA and CA. R and Q-mode analysis reveals that inter-relations between the variables and samples studied. The application of R-mode factor, however, has been more effective than the use of either one of them alone. The CA and Q-mode factor indicates that swap over between the surface water and the groundwater plays a dominant role in the hydro geochemical evolution of groundwater.

Three Poems

Three Poems Sarah Gordon (bio) Threshold The open door beckonsa way out or a way in when all else seemsnarrowly walled and white The open door is a framefor a painting, precisely measured, carefully cut,handmade, man-made with power to close offas a rope or an eye cordons off or includes everythingpertinent to the scene A clean aesthetic, simplyoffering what it offers seeing what it seesand allows you to see the river, the road,the long line of trees behind which the soldiersstare, then languish [End Page 584] You see them theretheir arms weary with holding the gunswithholding their fire You see them in the lightand think of them at night, your soft gownblowing against you as you sketch yourselfinto Life, entering its scarred and beautiful bodyits wide and open eye Shades The old aunts are still standingin turn, backs to the fireplace,skirts lifted to warm their veiny legs. Out on the front lawn, the crowscall to some distant power, plantingtheir crows’ feet in the grassy crows’ paradise, green and wormy.The father is a boy still, slinginghis rifle, a toy still, over his soft shoulder and heading into the woodswhere he’ll remain for years on end,forever seeking the slippery vagabondage [End Page 585] of freedom, fine fall afternoonscrisping into chill, the winter just ahead.The mother is ever herself, at home and alone, pots boiling overbut retrieved in time, her blue eyesbrimming a melancholy she can’t serve up. Just overhead in the dining room: clouds.Just overheard, the old bickering,with its raised brows, burning words. Someone abruptly pushes back a chair,rising from the table, a tearful tenwho won’t forget, ever, her heart carving a question markat the end of every breath. Tactile Matters Roundness is all. Smooth surfaces,the fat ball you wrap your hand around, that sleeps in your open palmuntil you decide what to do with it, cars that curve and satisfy, lowto the ground, slick as river rocks ahead on the road, which quietlypublishes its next move so that you turn the vehicleas you turn the page [End Page 586] or the potter’s wheel, embracingthe wet clay, shaping it your way. The wild-haired Einstein told ushow space is curved, like a canopy, how the apple doesn’t drop straightdown, but rather rolls down the slope toward the spinning earth, a freefall that takes our breath away. What he didn’t say was howcurves can please, how the whorl of the shell and the full-term bellymesmerize, how we trace the arc with our fingers, to be a part of it,as the soprano’s voice follows the golden stream easily upcurrentand home again, resting in the sweet familiar, while we, the clumsy, off-key children,climb the sides of the ropey hammock, giggling and trying to hold on,to stay right-side-up, the getting in and getting outour scariest maneuvers. [End Page 587] Sarah Gordon Sarah Gordon’s poetry has appeared in a number of publications, including the Georgia Review, Shenandoah, Southern Poetry Review, Confrontation, Arts & Letters, and Christianity and Literature. Her collection, Distances, appeared from Brito & Lair in 1999. She is founding editor of the Flannery O’Connor Review and author of Flannery O’Connor: The Obedient Imagination (UGA Press, 2000) and A Literary Guide to Flannery O’Connor’s Georgia (UGA Press, 2008). Copyright © 2016 Sarah Gordon

Use of normal-density high-absorption limestone aggregate as internal curing agent in concrete

A common practice to provide additional water for the hydration process of cement is to use special aggregates that act as agents incorporating water to the concrete (lightweight natural aggregates or polymers). Previous studies have suggested that normal-density high-absorption limestone aggregates may produce a similar effect. The aim was to determine if they can function as an internal curing agent. The methodology consisted of concrete specimens employing two types of aggregates and subjected to three different curing treatments. Results showed similar values of compressive strength and porosity among the concrete cured under wet and dry treatments for the high-absorption limestone aggregate but not for the river rock aggregate. Thus, this effect was attributed to the internal curing properties of the high-absorption limestone aggregate.

Oyster reef restoration: effect of alternative substrates on oyster recruitment and nekton habitat use

Eastern oysters (Crassostrea virginica) in Gulf of Mexico estuaries create complex reefs and provide important habitat for fish and crustaceans. Oyster reefs have suffered historic losses due to overharvest, disease, and degraded water quality, and recent efforts have focused on restoring reefs to benefit nekton populations. Oyster shell is the preferred substrate for oyster reef restoration, but as a consequence of its limited supply, a variety of alternative substrates are being used. We used field experiments to quantify the effects of substrate type (concrete, porcelain, limestone, river rock, and oyster shell) on oyster recruitment, growth, and nekton habitat use in St. Charles Bay, TX. After 4 months, oyster spat recruitment density, nekton density and community structure were similar across substrate types—and analogous to those on natural reefs—but differed from samples collected on bare sediment. To determine refuge value of the alternative substrates, we tested mud crab (Panopeidae) prey mortality with and pinfish (Lagodon rhomboides) or blue crab (Callinectes sapidus) predators. Prey mortality was similar across substrate types for both predators, and was significantly lower than no substrate and bare sand controls. Alternative substrates can provide important structural materials to support the development of oyster populations and nekton assemblages, and may be used to promote sustainable management of oyster reef resources via restoration.

Magnesium isotopes in permafrost-dominated Central Siberian larch forest watersheds

To unravel the Mg isotope fractionation pathways within the continuous permafrost zone in the larch deciduous forest of Central Siberia, we measured the Mg isotopic composition of two large Siberian rivers (Nizhnaya Tunguska and Kochechum, which flow into the Yenisey), a small forested stream, and the major fluid and solid sources of Mg in the watershed: atmospheric precipitates, surface suprapermafrost flow, interstitial soil solutions, plant biomass, litter and mineral soils. The obtained results indicate a significant seasonal variation in riverine water Mg isotope signatures. During the winter baseflow, the Mg isotope composition of large rivers is significantly lighter than the source basaltic rocks and the atmospheric depositions. These differences support the presence of fluids enriched in lighter Mg isotopes, such as those affected by the mineral precipitation of secondary silicates or fluids that dissolve sedimentary carbonate rocks. During the spring flood and in the summer and fall seasons, the river fluid δ26Mg values increased by 0.2–0.3‰ and approached the Mg isotope composition of the ground vegetation (dwarf shrubs, mosses) and the soil organic horizon. Overall, the riverine waters were 0.3–0.7‰ lighter than the unaltered bedrock and the deep minerals soil horizons.The Mg isotopic compositions of Larix gmelinii organs (i.e., stem wood, roots and needles) exhibit a low variability. However, an enrichment of 0.2–0.3‰ in the δ26Mg of larch needles in the course of the growing season, from June to September can be observed. This enrichment most likely demonstrates uptake of isotopically heavier Mg by the plant in addition to the progressive thawing of the mineral soil (deepening of the active layer of the soil). Overall, the Mg isotope approach indicates the important contribution of vegetation (larch needles, mosses and dwarf shrubs) to the riverine Mg isotope signature and helps to reveal the contribution of isotopically light carbonate rocks in the large rivers of the Central Siberian Plateau.

Micropropagation of the native species Anthurium antioquiense Engl. for conservation purposes

Anthurium antioquiense Engl. is a native plant belonging to the Araceae family. It grows on rocks in clear-water rivers and well-protected zones, similar to the waters in certain watersheds of the Antioquia Department, Colombia. Loss of habitat has threatened this promising ornamental plant species, which is also important because of its role in the ecosystem. In vitro tissue culture is considered an efficient alternative for the propagation of endangered species with the aim of establishing short-, medium- and long-term conservation programs. In the present research, in vitro introduction and shoot induction from A. antioquiense seedlings were performed. The highest production of shoots was obtained in a ½ MS (half-salt content) medium with 1 mg L-1 of BAP, which attained a 23.7 shoots/explant per month multiplication rate. The in vitro plants generated from shoots were individualized and transferred to a growth regulator-free medium. Rooting did not require the presence of growth regulators, and the adaptation of the in vitro plants to ex vitro conditions achieved a 98% survival rate.

Neotypification of Brachyscome assamica C.B. Clarke (Asteraceae)

Brachyscome assamica C.B. Clarke (1876: 40) is a small shrubby herb, restricted to Assam State of northeast India and it is the only known species of the genus Brachyscome Cassini (1816: 199) occurring in India. It can be readily recognized by its 1–2-seriate elliptic involucral bracts with scarious margins, longer, whitish, violet-tinged ligules, beaked achenes, and the absence of a pappus. Clarke (1876) described the species based on material seen at the Calcutta Herbarium (CAL) collected from Dihing River Rocks, Namsang, in Upper Assam, India. Hooker (1881: 249) mentioned that he knew “nothing of this plant, which exists only in the Calcutta Herbarium, where Clarke described it”. Hajra (1995: 102), in revision of the family Asteraceae in “Flora of India”, indicated that no relevant material could be found at the CAL.