The dissolution of calcite in acid waters: mass transport versus surface control

SUMMARY. 1. A new experimental method for the study of kinetics and mechanism of reactions at the solid-liquid interface has shown that the dissolution of calcite in acidic waters is, under conditions of high mass transport, controlled by the first order heterogeneous reaction of H⁺ at the interface and not by diffusion as previously thought.
2. The implications of this for lake liming strategies (aimed at countering the effects of 'acid rain') are significant in that under typical liming conditions, the rate of calcite dissolution will be surface controlled and consequently appreciably slower than previously considered.     

Role of glandular kallikreins as growth factor processing enzymes: structural and evolutionary considerations

Hormones and growth factors are generally released from larger precursors by limited proteolysis. The causative agents remain poorly defined with respect to location and properties. One subset of proteases, the glandular kallikreins, have been implicated in a few cases, in part because of their specific association with mature forms of some hormones. However, limited distribution and low copy number in some species cast doubt on this hypothesis, and they may well play other physiological functions that remain to be elucidated.     

Urban and rural river restoration in France: a typology

River restoration (RR) is widely practiced in both rural and urban contexts by combining various goals and measures. The theoretical discourse on RR not yet adequately reflects this breadth of restoration practice. In this study, we investigated 110 French RR projects implemented between 1980 and 2015. We analyzed projects considering eight key design features, main project motivation, restoration goals, project dates, costs, size, funding, river annual discharge, and implemented evaluation procedures. The study (1) provides a detailed account of the French RR effort, (2) compares restoration efforts in urban and rural contexts, and (3) establishes a RR project typology. The results also show that urban RR comprises a wider range of goals and measures than its rural counterpart, includes restoration of riparian habitats, and integrates ecological and social goals. A hierarchical multiple factor analysis yielded five types of projects, Fish RR (14% of the urban and 53% of the rural projects), Blue RR (4%, 7%), Water Framework Directive RR (36%, 40%), Flood protection RR (14%, 0%), and Human RR (32%, 0%). We suggest that the restoration community needs databases that use a project typology as developed in this study. This approach would take into account the multiple facets of RR projects, enabling more transparency into their communication and allow more suitable project comparisons.     

Typification of vessel-induced waves and their interaction with different bank types,including management implications for river restoration projects

Restoration projects often aim to initiate side erosion processes in order to improve the ecological situation, leading to banks of gentle slopes which positively affect biotic habitats. However, within navigable reaches such measures have to be planned under consideration of the impact of vessel-generated waves on YOY-fish. Hence an extensive study was conducted at different bank types to analyze and describe waves, induced by passing vessels. A high resolution wave gauge was exposed, to obtain wave data of different vessel types over a broad discharge range. Simultaneously vessel passage was recorded using an automatic identification system. Attributed to the ships, different wave types could be distinguished and their specific parameters (e.g., wave height) were described. Additionally we analyzed by which of these parameters wave height is primarily affected. For passenger ships a speed reduction of 5 km h^?1 results in a reduction of wave height of 14 cm at the Danube. A morphological analysis was accomplished to identify habitat loss and shift of the water’s edge based on ship induced maximum drawdown. Habitat loss, expressed as retrogression of the water’s edge, ranged between 0.88 and 35 m for the highest drawdown recorded.     

Assessment of interaction between sheep and poorly palatable grass: a key tool for grassland management and restoration

Invasion of poorly palatable grasses due to abandonment or improper grazing management decreases pastures feeding value and biodiversity. With the aim to control their spread, we assessed the relationship between sheep foraging behavior and changes in aboveground phytomass, leaf traits, and chemical features of the tall grass Brachypodium rupestre and evaluated the effects of a B. rupestre-based diet on epithelium keratinization of rumen. Our results demonstrated that sheep became less selective throughout the experimental trials and B. rupestre decreased its aboveground phytomass. Some leaf traits showed significant changes (LDMC, LA, and ADL were higher in ungrazed areas; leaf nitrogen content was higher in the grazed ones). In addition, we detected an increase of the degree of epithelium keratinization of sheep. Thus high grazing pressure can be used to control the spread of B. rupestre, but negative effects on animal welfare due to the increase of rumen keratinization might be expected.     

Intracellular transport of lymphoid surface glycoproteins: Role of the Golgi complex

The biosynthesis of the heavy chains of two membrane glycoproteins, identified as immunoglobulin M and histocompatibility antigens, has been studied in [³⁵S]methionine pulse-chase experiments by one and two-dimensional gel electrophoresis. Terminal sugar addition results in marked shifts in gel mobility that are mainly due to sialic acid addition, since they are sensitive to neuraminidase. These shifts are prevented when the ionophore monensin is present during the chase incubation. We conclude that both membrane IgM² and H2 heavy chains normally pass through the Golgi subsite defined by monensin and acquire terminal sialic acid distal to this site. Analysis of surface-iodinated control and monensin-treated cells indicates that, in the presence of monensin, newly synthesized, incompletely glycosylated IgM and H2 are not transported to the cell surface. Thus these membrane proteins appear to follow the same intracellular pathway as secretory proteins.     

Hydrologic and geomorphic considerations in restoration of river-floodplain connectivity in a highly altered river system,Lower Missouri River,USA

Planning for restoration of river-floodplain systems requires understanding how often and how much of a floodplain may be inundated, and how likely the floodplain is to retain the water once flooded. These factors depend fundamentally on hydrology and geomorphology of the channel and floodplain. We discuss application of an index of river-floodplain connectivity, the Land Capability Potential Index (LCPI), to regional-scale restoration planning along 600 km of the Lower Missouri River. The LCPI integrates modeled water-surface elevations, floodplain topography, and soils to index relative wetness of floodplain patches. Geomorphic adjustment of the Lower Missouri River to impoundment and channel engineering has altered the natural relations among hydrology, geomorphology, and floodplain soils, and has resulted in a regional upstream to downstream gradient in connectivity potential. As a result, flow-regime management is limited in its capacity to restore floodplain ecosystems. The LCPI provides a tool for identifying and mapping floodplain restoration potential, accounting for the geomorphic adjustment. Using simple criteria, we illustrate the utility of LCPI-like approaches in regional planning for restoration of plains cottonwood (Populus deltoides) communities, hydrologically connected floodplain wetlands, and seasonal floodplain wetlands.     

Glucose transport into rat skeletal muscle: interaction between exercise and insulin

This study was done to evaluate the effect of insulin on sugar transport into skeletal muscle after exercise. The permeability of rat epitrochlearis muscle to 3-O-methylglucose (3-MG) was measured after exposure to a range of insulin concentrations 30, 60, and 180 min after a bout of exercise. Thirty and 60 min after exercise, the effects of exercise and insulin on 3-MG transport were additive over a wide range of insulin concentrations, with no increase in sensitivity or responsiveness to insulin. After 180 min, when approximately 66% of the exercise-induced increase in sugar transport had worn off, both the responsiveness and sensitivity of the glucose transport process to insulin were increased. These findings appear compatible with the hypothesis that the actions of exercise and insulin result in activation and/or translocation into the plasma membrane of two separate pools of glucose transporters in mammalian skeletal muscle.     

Nitrogen transformations in microenvironments of river beds and riparian zones

The soil of flooded riparian zones, the rhizosphere of riparian plants, biofilms at solid surfaces in the river, and the surface layer of sediments all constitute important environments for the oxidative or reductive transformations of inorganic nitrogen compounds. The exact microzonation and coupling of the processes have recently been studied intensively with ¹⁵N enrichment methods and microsensors for NH₄⁺, NO₂⁻, NO₃⁻, and N₂O. Microsensor analyses of gradients in sediments and biofilms have shown that nitrate production takes place in an aerobic surface zone that has a maximum thickness of a few millimeters in most shallow-water sediments and may be as thin as 100 μm in biofilms from very eutrophic environments. In the anoxic zone, denitrification is also concentrated in a zone of maximum a few millimeters, and typically half of the nitrate produced by nitrification is denitrified while the other half escapes to the water. The supply of nitrate from above is primarily controlled by the oxic layer acting as a diffusion barrier, and therefore denitrification is generally a linear function of the nitrate concentration in the water. The overlying water is thus a much more important source of nitrate for denitrification if the concentration is high. The rate and location of denitrification are also affected by bioturbating animals, benthic microphytes, plants, and bacteria performing dissimilatory nitrate reduction to ammonium (DNRA).     

Enterococci in river Ganga surface waters: Propensity of species distribution, dissemination of antimicrobial-resistance and virulence-markers among species along landscape

Background  

Surface waters quality has declined in developing countries due to rapid industrialization and population growth. The microbiological quality of river Ganga, a life-sustaining surface water resource for large population of northern India, is adversely affected by several point and non-point sources of pollution. Further, untreated surface waters are consumed for drinking and various household tasks in India making the public vulnerable to water-borne diseases and outbreaks. Enterococci, the 'indicator' of water quality, correlates best with the incidence of gastrointestinal diseases as well as prevalence of other pathogenic microorganisms. Therefore, this study aims to determine the distribution of species diversity, dissemination of antimicrobial-resistance and virulence-markers in enterococci with respect to rural-urban landscape along river Ganga in northern India.     

Blue sucker habitat use in a regulated Texas river: implications for conservation and restoration

Environmental Biology of Fishes - Species conservation requires a clear understanding of habitat availability and subsequent use of those habitats. In cases where species declines have occurred and...     

干热河谷主要植被恢复树种蒸腾作用

以金沙江干热河谷区10多种自然生长树种为试材,探讨了不同季节典型晴天里各树种叶片水平的蒸腾速率日动态规律,以揭示极端干热生境条件下供试树种蒸腾作用的动态特征.实验结果表明:在干旱生境(3月份)转向干热生境(5月份)时,大多数供试树种蒸腾速率的日变化峰值有所提前,蒸腾作用受到明显限制,而当干热胁迫解除、湿润生境(10月份)来临时,蒸腾作用受限程度减轻或消失,多数供试树种呈现出比较典型的峰状曲线;在干旱、干热以及湿润季节里,供试树种均可分为高、亚高、亚低和低蒸腾速率树种等4个类别,且随着季节的变化,树种所属类别或蒸腾速率大小排序存在明显变动,体现了树种特性在水分生理反应上的多样性表达;随着干热胁迫的加深,供试树种蒸腾速率的变化可分为增强型、减弱型及稳定型3种;树种蒸腾速率的变化方向与气孔导度的变化方向存在不一致的现象,树种蒸腾速率的季节性增减可能表现为气孔因素为主与非气孔因素为主两种控制形式.     

Dynamic disturbance regime approach in river restoration: concept development and application

In recent years, numerous restoration measures have been initiated to ecologically and morphologically improve rivers based on self-dynamic development. A wealth of monitoring studies has been implemented to evaluate these restoration measures. Such restored river systems, however, must develop for years to decades to achieve a (dynamic) equilibrium, with an equally lengthy period before serious evaluation is possible. Thus, modelling approaches that accurately quantify the underlying processes and their manifold interactions are useful tools for river management. This paper presents a new conceptual approach for analyzing the interrelationship among plant succession, morphology, and hydrological impacts. Based on the dynamic disturbance regime approach, the model concept addresses interdisciplinary processes in river morphodynamics. The development of the concept is outlined, and the approach is applied considering three different process types: (1) metastable, (2) oscillation, and (3) acyclic. All three describe the relationship between vegetation succession/retrogression and the impact of disturbances. We show that addressing these three different process types helps the prediction of intermediate and long-term river system development by going beyond steady-state monitoring results to consider future dynamic developments. Moreover, classifying these process types and comparing them with reference (natural) conditions helps evaluation of the river system and subsequently definition of management strategies.     

Study of interaction between calcium and zinc ond-galactose intestinal transport

Zinc is an essential trace element necessary to life. This metal may exert some of its physiological effects by acting directly on cellular membranes, either by altering permeability or by modulating the activity of membrane-bound enzymes. On the other hand, calcium is an essential element in a wide variety of cellular activities. The aim of the present work was to study a possible interaction between zinc and calcium on intestinal transport ofd-galactose in jejunum of rabbit in vitro. In media with Ca²⁺, when ZnCl₂ was present at 0.5 or 1 mM, zinc was found to reduce thed-galactose absorption significantly. In Ca²⁺-free media, where CaCl₂ was omitted and replaced isotonically with choline chloride, the sugar transport was not modified by zinc. Verapamil at 10⁻⁶ M (blocking mainly Ca²⁺ transport) did not modify the inhibitory effect of zinc ond-galactose transport. When 10⁻⁶ M of A 23187 (Ca²⁺-specific ionophore) was added with/without Ca²⁺ to the media, ZnCl₂ produced no change in sugar transport. These results could suggest a possible interaction of calcium and zinc for the same chemical groups of membrane, which could affect the intestinal absorption of sugars.     

Similarities and differences between measured and predicted concentrations of pesticides in Dutch surface waters

In order to have a thorough evaluation of the progress and effectiveness of Dutch crop protection policy, both model predictions and measured pesticide concentrations in surface waters are considered. To this purpose, monitoring data obtained by various water boards and other monitoring institutes were processed. Data were aggregated over a two year time period and over space (at 1x1 km-grid). A geographic view is given in the Dutch Pesticides Atlas (www.pesticidesatlas.nl). The model used for the predictions was the Dutch National Environmental Indicator NMI version 2 (www.nmi.alterra.nl) that has input data regarding spray drift data, crop interception, soil and climate and many more. Information on aggregation steps over time and space, grid sizes, information on crop areas was geared to one another for both instruments. Results on measured pesticide concentrations in surface waters and model predictions were compared to each other at the national scale. For this study, 10 different cases were selected covering a large range of pesticides' characteristics and pesticides' use. In 60% of the cases, the results were largely in agreement with each other when expressed as absolute numbers of measurements exceeding the environmental quality standard. This is very accurate and useful for policy purposes. Based on concentrations and on the order of magnitude, no significant agreement between measurements and model predictions was found. Differences were explained by various factors, and an overview of predominant systematic differences between the measurements and the model predictions was presented. Using both measurements and model predictions in supporting environmental policy evaluations is warranted, because of higher Weight-of-Evidence. Combining both can assist in optimizing the knowledge on pesticides behaviour, fate and ecological problems and therefore this is the preferred evaluation method.