Effects of macrophytes on lake‐water quality across latitudes: a meta‐analysis

Macrophytes are widely recognized for improving water quality and stabilizing the desirable clear‐water state in lakes. The positive effects of macrophytes on water quality have been noted to be weaker in the (sub)tropics compared to those of temperate regions. We conducted a global meta‐analysis using 47 studies that met our set criteria to assess the overall effects of macrophytes on water quality (measured by phytoplankton chlorophyll a concentration, total nitrogen concentration, total phosphorus concentration, Secchi depth and the trophic state index) and to investigate how these effects correlate with latitude using meta‐regressions. We also examined if the effects of macrophytes on lake‐water quality differ with growth form and study design in (sub)tropical and temperate areas by grouping the data and then comparing the effect sizes. We found that macrophytes significantly reduced phytoplankton chlorophyll a concentration, total nitrogen concentration, total phosphorus concentration, as well as the trophic state index, but they did not have a significant overall effect on Secchi depth. The effects of macrophytes on reducing phytoplankton chlorophyll a concentration, total nitrogen concentration and the trophic state index did not differ with latitude. However, the reduction of total phosphorus concentration was greater at lower latitudes. We showed that at lower latitudes, the positive effects of macrophytes on water quality are similar to or greater than those at higher latitudes, thus challenging the prevailing paradigm of macrophytes being less effective at enhancing lake‐water quality in the (sub)tropics. Furthermore, our data showed that the macrophyte effects vary by growth forms, and the growth forms that positively affect water quality differ between the (sub)tropical and temperate areas. We showed a lack of significant macrophyte effects in surveys within and outside macrophyte stands, suggesting difference in the sensitivities of study designs or possibly weaker effects of macrophytes in lakes compared to experimental settings.     

High Concentration of Fluoride Can Be Increased Risk of Abortion

The presence of fluoride in drinking water can be either beneficial or harmful for human health, depending on its concentration. Most adverse effects of fluoride are observed at high concentrations (above 1.5 mg/L). This study was aimed to evaluate the effect of fluoride concentrations in drinking water on spontaneous abortion in two regions: one with low fluoride concentration and another with high fluoride concentration. The results showed that there is a relationship between the concentration of fluoride in drinking water and abortion, so that the risk of abortion increased at high concentrations of fluoride. However, further studies are needed to clarify this relationship due to the small area and population in this study.     

Interaction of water with egg lecithin in benzene solution

Benzene solutions of purified egg lecithin, with small amounts of water added, have been examined by 60 MHz and 100 MHz NMR spectroscopy, infrared spectrophotometry and phase contrast microscopy. The transverse relaxation times of the water, N-methyl and OH protons are dependent on water concentration. This dependence changes sharply for the water proton at a level of one water molecule per lecithin monohydrate molecule. These results do not fully agree with those reported by other workers. Four mathematical models are examined which could account for the behaviour of the water protons. Models which assume a constant transverse relaxation time for water protons above a level of one water molecule per lecithin molecule cannot predict the behaviour observed. It is sufficient to assume that water protons above this concentration have a single relaxation time which is a linear function of water concentration. The added water associates primarily with the phosphate in the lecithin head group. Above nine water molecules per lecithin monohydrate molecule free water is present in the system.     

Possible ways of negative influence of acid gases on plants

The degree of negative influence of acid gases on plants is considered in dependence of their solubility in water. The linkage of water in the processes of hydration of gases forming acids can decrease the chemical potential of water in leaf apoplast. It causes the decrease in water inflow into leaf symplast. The more solubility of acid gases in water and the higher their concentration in the air, the lower water inflow from apoplast to symplast. At high concentration of toxicant water chemical potential in leaf apoplast is lower, than in symplast, and the water flows out into apoplast, i.e. plasmolis takes place. Plasmolis leads to the increase in toxicant concentration in leaf symplast and finally to the necrosis of cells. When air with acid gases are dissolving in apoplast water, "concentrating" of acid gases takes place because the acid components are more soluble in water than the main components of the air (nitrogen and oxygen). The lower acid dissociation in apoplast water, the higher speed of receipt from apoplast to symplast and even to inner cell compartments through cell membranes. It can explain why sulfur dioxide and fluoric hydrogen forming weak acids, are more toxic than nitric dioxide. Exogenous acids producing the hydrogen ions negatively influence on different metabolic processes of plants.     

Direct measurement of water availability in gelled plant tissue culture media

Summary Water constitutes nearly 100% of the volume and 95% of the mass of gelled plant tissue culture media. Even so, plant growth and development responses observed to occur with relatively small changes in gelling agent concentration (0.1% of media total mass) have been attributed to changes in media water availability. Measurements with three alternative direct techniques, specific for measuring physiochemical water availability indicated the effects of a change of this magnitude in gelling agent concentration negligibly affected the media water potential and water conductivity. Sensitive pressure membrane measurements indicated that incremental gelling agent concentration increases of 0.1% (of media total mass) within the range normally used for plant tissue culture media, depressed water matric potential only 1–2cm H₂O (1–2×10⁻⁴ MPa (mega pascal.)); these values were confirmed with equally sensitive tensiometer measurements. Moreover, no effect of concentration on water movement could be detected with a precise constant-head permeameter over a broader range of gelling agent concentrations. These results indicate that eitherin vitro plants are extremely sensitive to subtle shifts in water status, or other physiochemical factors that also change with gelling agent concentration are contributing to the reported effects on plant growth and development.     

Vibrational Properties of Cyclodextrin�CWater Solutions Investigated by Low-Frequency Raman Scattering: Temperature and Concentration Effects

Depolarized low-frequency Raman spectra from several cyclodextrin–water solutions have been investigated as a function of both temperature and macrocycle concentration. The differences between the vibrational spectra of solutions and pure water have been discussed, focusing the attention on the modifications of the vibrational bands assigned to the H-bond bending and stretching intermolecular modes of water. These features are in turn related to the structural changes occurring in the H-bonded water molecules allowing us to evince a destructuring effect on the tetrahedral hydrogen bonding arrangements induced in solution by increasing temperature and solute concentration.     

毛豹皮樟叶水提物的活性成分及其清除亚硝酸钠和阻断亚硝胺合成的作用

亚硝酸盐在食材、食品加工和食品储存过程中普遍存在,它是亚硝基化合物合成的前体物质,在一定条件下亚硝酸盐极易转化为亚硝胺,二者均可致癌[1-2],因此,清除亚硝酸盐和阻断亚硝胺合成对于预防和控制癌症的发生具有重要意义。关于清除亚硝酸盐和阻断亚硝胺合成的研究已有较多报道,一些植物含有的天然活性成分,如植物中所含的多酚和黄酮类物质等,具有抗氧化、抗菌、清除亚硝酸盐和阻断亚硝胺合成的作用。顶羽菊也Acroptilon repens ( Linn.) DC.页[3]、黄花菜(Hemerocallis citrina Baroni)[4]和簕菜也Acanthopanax trifoliatus ( Linn.) Merr.页[5]等提取物具有清除亚硝酸盐和阻断亚硝胺合成的作用;黄俊生[6]从南姜也Alpinia galanga ( Linn.) Willd.页表皮中提取的色素也具有较强的清除亚硝酸钠和阻断亚硝胺合成活性。     

Isotopic effects of low concentration of deuterium in water on biological systems

Isotopic effects of deuterium in water are studied in a broad range of concentrations on a number of biological objects of different organization levels. The results obtained show that biological objects are sensitive to variations of isotope composition in water. A decrease or increase in deuterium concentrations in water may cause activation or inhibition of biological functions. The values of biological isotopic effects of low deuterium concentration may even be higher than those of high deuterium concentration. No regularity in response for all the objects studied failed to find out in a range of deuterium concentration in water from 4 ppm to 1%.     

DNA polymerase β reveals enhanced activity and processivity in reverse micelles

Water is essential for the stability and functions of proteins and DNA. Reverse micelles are simple model systems where the structure and dynamics of water are controlled. We have estimated the size of complex reverse micelles by light scattering technique and examined the local microenvironment using fluorescein as molecular probe. The micelle size and water polarity inside reverse micelles depend on water volume fraction. We have investigated the different hydration and confinement effects on activity, processivity, and stability of mammalian DNA polymerase β in reverse micelles. The enzyme displays high processivity on primed single-stranded M13mp19 DNA with maximal activity at 10% of water content. The processivity and activity of DNA polymerase strongly depend on the protein concentration. The enzyme reveals also the enhanced stability in the presence of template-primer and at high protein concentration. The data provide direct evidence for strong influence of microenvironment on DNA polymerase activity.     

Ability to remove pesticides in the production of dialysis water (1)

In many cases it can be demonstrated that the amount of plant protective and plant treatment substances (pesticides) in drinking water exceeds the permitted levels of the drinking water ordinance which will come into effect on October 1st, 1989. Since some of these components are of toxicological relevance, an investigation was done on how far pesticides are removed during conventional purification of dialysis water, and especially during reverse osmosis. The retention rates of a reverse osmosis plant for 14 different pesticides applied in different concentrations and compositions were determined. Almost all of the substances examined were retained with an effectiveness of 92-98%. The elimination efficiency did not depend on the initial concentration of the pesticides. After an initial phase of 50 h duration, the concentration in the treated water reached a constant value which no longer changed even after more than 700 h. In part 1 of this contribution at first the fundamentals of dyalisis water purification are reviewed and a selection of the pesticides to be investigated is carried out. In addition experimental set up and procedure are described.     

基于水质管理目标的博斯腾湖生态水位研究

人类开发活动导致湖泊生态功能严重退化,研究湖泊生态水位对于维持湖泊生态系统健康意义重大。针对博斯腾湖化学需氧量(COD)浓度较高的水环境现状,分析博斯腾湖水位和COD浓度关系,研究提出基于水质管理目标的生态水位,以期为博斯腾湖水资源、水环境管理提供参考。结果表明,博斯腾湖水位与水体COD浓度显著负相关,但由于COD浓度空间差异较大以及影响因素不唯一,水位与COD浓度两者之间曲线估计结果不理想。为实现博斯腾湖COD浓度小于20 mg/L的水质管理目标,引入累计水位概念进行统计分析得到两个特征水位:所有COD浓度大于等于20 mg/L的数据对应水位的平均值为1046.02 m,该水位在历史丰水期水位的频率为60.83%,可作为最小生态水位;所有COD`浓度小于等于20 mg/L的数据对应水位的平均值为1046.4 m,该水位在历史丰水期水位的频率为44.70%,可作为适宜生态水位。适宜生态水位1046.4 m与已有研究成果基本相符,博斯腾湖在1046.4 m时既有利于水质管理,也可保障湖泊整体生态系统健康。     

Atrial natriuretic factor inhibits vasopressin secretion in conscious sheep

To test the hypothesis that atrial natriuretic factor (ANF) has a centrally mediated action on body fluid homeostasis, the effects of intracerebroventricularly (ICV) infused ANF on plasma vasopressin (AVP) concentration and urinary water and electrolyte excretion were investigated in euhydrated and water-deprived conscious sheep. ICV ANF decreased plasma AVP concentration and increased urinary free water excretion in euhydrated sheep, with excretion of Na and K unaltered. However, ICV ANF did not affect urinary volume, free water clearance, or excretion of Na and K in dehydrated animals, although plasma AVP concentration was significantly decreased. The relationship between urine volume and plasma AVP concentration was fitted by a power curve: urine volume = 0.79 X [AVP]-0.71; urine volume changes very little as a function of AVP concentration at the higher ranges. Intravenous infusion of the same amount of ANF was without effect on plasma AVP concentration or urinary excretion in both euhydrated and dehydrated animals. Mean arterial pressure was unchanged throughout all experiments. These results are consistent with the hypothesis that central ANF inhibits AVP secretion.     

Chloride and water secretion and absorption by the gills of the eel

Summary Perfusion experiments with the heart-gill preparation of the common eel, Anguilla vulgaris, are presented. Various concentrations of perfusion medium were used with eels from both sea water and fresh water. The external medium was sea water in the case of the sea water eels and fresh water in the other case.Perfusate was collected over a period of hours in each experiment and the exchange of chloride and water was studied.In the early experiments it was shown that normal permeability of the gills to these substances is small. The development of an extremely precise chloride method made it possible to evaluate the magnitudes of the exchanges in accurate quantitative terms.Experiments with fresh water as external medium showed that there is a small but perfectly significant change in chloride concentration in the perfusion medium as it passes through the gills so that it becomes more dilute. Reasons are adduced from which it is concluded that the dilution is due to the diffusion of water into the internal medium through the surface of the gills. This branchial water intake is calculated to be something like 40 cc. per kilogram of eel per day. This figure is in substantial agreement with Smith's measurements of the rate of urine formation in fresh water fishes.It was found that when the external medium is sea water, the chloride concentration of the internal medium decreases at a considerably faster rate than in the case where fresh water is present outside the gills. Experiments in which the external medium was analysed showed that chloride was being secreted into the concentrated sea water. It was found possible to measure volume changes in the external medium as well as the changes of chloride concentration in both mediums. These experiments demonstrated beyond doubt that a concentrated chloride solution is secreted by the gills in opposition to a large concentration gradient.Calculations made from several different bases showed that the measurements of volume and of chloride concentration consistently agree in yielding similar values for the volume and concentration of the chloride solution secreted by the gills of the sea water eel.It is shown that the magnitude of the concentration changes effected are related to the concentration of the internal medium used so that a small increase in the concentration of the perfusion medium results in a large increase in the amount of chloride concentration change occurring in the perfusion. Below a certain concentration of the internal medium the gills no longer give evidence of doing concentration work, and may even become permeable as evidenced by the internal medium increasing in concentration as it passes through the gills.Similarities between the activities of the gill of the sea water eel and of the normal mammalian kidney are pointed out. A rough calculation indicates that the work performed by the two organs is of the same order when computed in terms of grams of tissue involved.Experiments in which urea analyses were made showed that the gills of the eel are permeable to urea and that the amount of urea excreted through the gills as determined by direct measurement agrees quite well with Smith's figures for extfa-renal urea excretion.Possible objections to some of the conclusions are brought forth and their untenability demonstrated.Fellow of the National Research Council of America.     

Interfacial interactions of glutamate, water and ions with carbon nanopore evaluated by molecular dynamics simulations

Molecular dynamics simulations were used to assess the transport of glutamate, water and ions (Na(+) and Cl(-)) in a single wall carbon nanopore. The spatial profiles of Na(+) and Cl(-) ions are largely determined by the pore wall charges. Co-ions are repelled whereas the counter-ions are attracted by the pore charges, but this 'rule' breaks down when the water concentration is set to a level significantly below that in the physiological bulk solution. In such cases water is less able to counteract the ion-wall interactions (electrostatic or non-electrostatic), co-ions are layered near the counter-ions attracted by the wall charges and are thus layered as counter-ions. Glutamate is concentrated near the pore wall even at physiological water concentration, and irrespective of whether the pore wall is neutral or charged (positively or negatively), and its peak levels are up to 40 times above mean values. The glutamate is thus always layered as a counter-ion. Layering of water near the wall is independent of charges on the pore wall, but its peak levels near the wall are 'only' 6-8 times above the pore mean values. However, if the mean concentration of water is significantly below the level in the physiological bulk solution, its layering is enhanced, whereas its concentration in the pore center diminishes to very low levels. Reasons for such a 'paradoxical' behavior of molecules (glutamate and water) are that the non-electrostatic interactions are (except at very short distances) attractive, and electrostatic interactions (between the charged atoms of the glutamate or water and the pore wall) are also attractive overall. Repulsive interactions (between equally charged atoms) exist, and they order the molecules near the wall, whereas in the pore center the glutamate (and water) angles are largely randomly distributed, except in the presence of an external electric field. Diffusion of molecules and ions is complex. The translational diffusion is in general both inhomogeneous and anisotropic. Non-electrostatic interactions (ion-wall, glutamate-wall or water-wall) powerfully influence diffusion. In the neutral nanopore the effective axial diffusion constants of glutamate, water and Na(+) and Cl(-) ions are all <10% of their values in the bulk, and the electrostatic interactions can reduce them further. Diffusion of molecules and ions is further reduced if the water concentration in the pore is low. Glutamate(-) is slowed more than water, and ions are reduced the most especially co-ions. In conclusion the interfacial interactions influence the spatial distribution of glutamate, water and ions, and regulate powerfully, in a complex manner and over a very wide range their transport through nanosize pores.     

Aspects of petroleum hydrocarbon metabolism in marine animals

Studies on hydrocarbon composition of Black Sea musselsMytilus galloprovincialis sampled from different habitats indicate that the quantity and composition of hydrocarbons distributed in the molluscs depend on season and sea-water quality. The data obtained under experimental conditions testify to the possibility of hydrocarbon concentration in mussel tissues after death. During filtration in sea water containing oil and oil products, these pollutants are bound into faeces and pseudofaeces which contain a greater percentage of aromatic compounds than the oil initially present in sea water. Quantitative data are presented on hydrocarbon changes in mussel excretory products during transfer from oil-polluted to clean sea water. When Black Sea crabsEriphia verrucosa are fed with mussels containing fuel-oil components accumulated from sea water, the pollutants concentrate in the whole body of the crab. This is in contrast to parenteral oil uptake, which leads to a concentration of most of the hydrocarbon in the muscles.     

Fluorine content in natural water in the southern Ob-Irtysh interfluve

Fluorine content in 327 sources of surface, soil-ground and underground water in the southern Ob-Irtysh interfluve has been studied. Fluctuations of fluorine concentration in water are rather considerable; their possible geochemical origins are considered. A large region with high (exceeding MPC) fluorine concentration in the sources of underground water involved in water supply to inhabited areas was discovered in the western Baraba plain. The fluorine/calcium ratios in those water samples evidence a high danger of fluorosis in the population.     

光照对水环境变化和沉积物吸收磷酸盐的影响

在富氧和缺氧环境下室内模拟研究光照对清洁湖区沉积物吸收磷酸盐和对上覆水质变化的影响.结果表明,光照使缺氧环境上覆水体中的pH值显著提高,并增加其溶解氧的含量.上覆水体中磷酸盐浓度的变化在实验初期主要受水-沉积物界面溶解氧含量的影响,表现为富氧组磷酸盐的浓度下降迅速,但随实验时间的推移,光照逐渐起主要作用,表现为实验结束时有光条件下的磷酸盐浓度明显低于无光条件,磷酸盐的减少量和减少速度明显高于无光条件.无论是富氧、缺氧,还是有光、无光,当上覆水体中磷酸盐的浓度很高时,沉积物都能够吸收磷酸盐,但吸收量各不相同.光照对沉积物吸收上覆水中溶解性无机磷酸盐(DIP)的影响受缺氧和富氧环境的限制.     

Water Concentration and Activity Effects on Aminoacylase in Aqueous/Organic One-Liquid-Phase Systems

Aminoacylase has been employed as a model system to study its catalytic properties at low water concentrations/water activities with different water-miscible organic cosolvents. Cosolvents assayed were alcohols and polyols with pure logarithm of the partition coefficient (log P) values, on the standard water/octanol system, ranging between -5.2 and 0.24.

Experimental hydrolysis equilibrium constants (K_app), at a constant water concentration, decreased with the fall in log P of the cosolvent, as well as with reduction of the water concentration/water activity, as would be expected. The enzyme hydrolytic and synthetic activities, measured at a constant water concentration/water activity value, followed a sigmoidal dependence on log P of the cosolvent employed when the water concentration or water activity values were lower than 50% (w/w) or 0.66, respectively. This became a hyperbolic relationship at higher water concentration/water activity values. A linear relationship between the logarithm of the limiting water activity necessary to maintain enzyme activity and log P was obtained. Both hydrolytic and synthetic activities were suppressed for water activities higher than 0.66 and cosolvents with log P lower than -1.6.     

Role of proline and leaf expansion rate in the recovery of stressed white clover leaves with increased phosphorus concentration

Osmotic adjustment (OA) and increased cell-wall extensibility required for expansive leaf growth are well defined components of adaptation to water stress in dry soil, which might interact with soil phosphorus (P) concentration and defoliation frequency for intensively grazed white clover in legume-based pastures. Experiments were conducted with frequently and infrequently defoliated mini-swards of white clover growing in dry soil with low and high P concentrations. The higher yielding high-P plants were able to dry the soil to greater soil water suctions; their leaves had lower water potential values, yet they showed fewer water stress symptoms and underwent a more complete recovery from the water stress symptoms on rewatering, than the low-P plants. High- P plants had greater OA, proline concentration and leaf expansion rate. On the other hand, low-P plants showed an increased osmotic concentration when there was no change in the total solute content per unit of leaf d. wt, indicating more loss of water from the leaf tissue. The key measures that appeared to be directly associated with plant recovery over a short period following water stress were increased proline concentration and leaf expansion rate, probably resulting from increased cell-wall extensibility rather than increased production of cells for the high-P plants.     

Modelling of fish contamination with 90Sr in relation to the calcium concentrations in water

A set of data on the equilibrium concentration factors of 90Sr in fish in relation to the Ca concentrations in water was collected and analyzed. An empiric relationship was obtained on the basis of statistical processing of this dataset: CF(90Sr, Bq/kg w.w.) = 3940(1770-6110)/[Ca, mg/L]water. The range of observed data on the concentration factors of 90Sr in fish is from 20 to 4000 L/kg (about 200 times). The statistical relationship obtained in the paper allows one to reduce this uncertainty by more than 50 times. The formula adequately describes equilibrium concentration factors of 90Sr both in freshwater and in marine fish. A dynamics model approach is described for the cases of accidental contamination of water bodies, when the equilibrium approaches are not appropriate.