JOURNAL OF PHYCOLOGY, Issue 3 2004
Julia C. Phillips
The competitive ability for N uptake by four intertidal seaweeds, Stictosiphonia arbuscula (Harvey) King et Puttock, Apophlaea lyallii Hook. f. et Harvey, Scytothamnus australis Hook. f. et Harvey, and Xiphophora gladiata (Labillardière) Montagne ex Harvey, from New Zealand is described by the uptake kinetics for NO3,, NH4+, and urea. This is the first study to report uptake kinetics for N uptake by a range of southern hemisphere intertidal seaweeds in relation to season and zonation. Species growing at the highest shore positions had higher NO3, and urea uptake at both high and low concentrations and had unsaturable NH4+ uptake in both summer and winter. Although there was evidence of some feedback inhibition of Vmax for NO3, uptake by Stictosiphonia arbuscula growing at the lower vertical limits of its range, rates were high compared with species growing lower on the shore. Our results highlight the superior competitive ability for N uptake of certain high intertidal seaweeds, and consistent with our previous findings we can conclude that intertidal seaweeds in southeast New Zealand are adapted to maximizing N acquisition in a potentially N-limiting environment. [source]

EFFECTS OF NITRATE AND PHOSPHATE DISCHARGE FROM A FERTILIZER PRODUCTION PLANT IN A FJORD

JOURNAL OF PHYCOLOGY, Issue 2001
Article first published online: 24 SEP 200
Pedersen, A.1,2, Knutzen, J.2, Walday, M.2, Molvær, M.2 & Johnsen, T.2 1Department of Ecology and Evolutionary Biology, University of Connecticut at Stamford, Stamford, CT. 06901 U.S.A;. 2Norwegian Institute for Water Research, P.O.B. 173 Kjelsås, 0411 Oslo, Norway. "Hydro Agri Glomfjord" a fertilizer producer has been discharging large quantities of ammonium, nitrate and phosphate into Glomfjord (in northern Norway, N 66,48°, E 13,57°) since 1947. The effects of the nutrient load to the Fjord have resulted in classical eutrophication symptoms. Elevated nutrient levels have resulted in frequent plankton blooms and seasonally reduced O2 levels in the deep-water bodies as well as an eradication of the normal littoral assemblages. The fucoid belt had been replaced by various green algae 6 km from the outlet and outward the fjord. The effect is only seen on the northern side of the Fjord. After some improvement in the discharge loads in the 1980's, the condition in the pelagic column improved with regard to plankton blooms and deep water O2 concentration. The littoral communities didn't, show any indication of recovery and a pollution indication index based on algal composition, showed even increased eutrophication. [source]

WATERSHED SCALING EFFECT ON BASE FLOW NITRATE, VALLEY AND RIDGE PHYSIOGRAPHIC PROVINCE,

JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 5 2001
Bruce D. Lindsey
ABSTRACT: A study of stream base flow and NO3 -N concentration was conducted simultaneously in 51 subwatersheds within the 116-square-kilometer watershed of East Mahantango Creek near Klingerstown, Pennsylvania. The study was designed to test whether measurable results of processes and observations within the smaller watersheds were similar to or transferable to a larger scale. Ancillary data on land use were available for the small and large watersheds. Although the source of land-use data was different for the small and large watersheds, comparisons showed that the differences in the two land-use data sources were minimal. A land use-based water-quality model developed for the small-scale 7.3-square-kilometer watershed for a previous study accurately predicted NO3 -N concentrations from sampling in the same watershed. The water-quality model was modified and, using the imagery-based land use, was found to accurately predict NO3 -N concentrations in the subwatersheds of the large-scale 116-square-kilometer watershed as well. Because the model accurately predicts NO3 -N concentrations at small and large scales, it is likely that in second-order streams and higher, discharge of water and NO3 -N is dominated by flow from smaller first-order streams, and the contribution of ground-water discharge to higher order streams is minimal at the large scale. [source]

An In Situ Copper Plated Boron-Doped Diamond Microelectrode Array for the Sensitive Electrochemical Detection of Nitrate

ELECTROANALYSIS, Issue 20 2005
Sarah Ward-Jones
Abstract The first example of using a copper microelectrode array for use in electroanalysis is explored and exemplified with the electroanalytical quantification of nitrate. The analytical approach is based upon the in situ deposition of copper at a boron-doped diamond (BDD) microelectrode array. The immobilized copper layer is electrocatalytic for nitrate reduction and exhibits an analytically useful range from 1.2 to 124,,M with a marked selectivity for nitrate ion over nitrate, with a limit of detection of 0.76,,M. The analytical applicability was examined through standard addition determinations of nitrate in drinking and river water samples. [source]

Multiple influences of nitrate on uranium solubility during bioremediation of uranium-contaminated subsurface sediments

ENVIRONMENTAL MICROBIOLOGY, Issue 9 2002
Kevin T. Finneran
Summary Microbiological reduction of soluble U(VI) to insoluble U(IV) has been proposed as a remediation strategy for uranium-contaminated groundwater. Nitrate is a common co-contaminant with uranium. Nitrate inhibited U(VI) reduction in acetate-amended aquifer sediments collected from a uranium-contaminated site in New Mexico. Once nitrate was depleted, both U(VI) and Fe(III) were reduced concurrently. When nitrate was added to sediments in which U(VI) had been reduced, U(VI) reappeared in solution. Parallel studies with the dissimilatory Fe(III)-, U(VI)- and nitrate-reducing microorganism, Geobacter metallireducens, demonstrated that nitrate inhibited reduction of Fe(III) and U(VI) in cell suspensions of cells that had been grown with nitrate as the electron acceptor, but not in Fe(III)-grown cells. Suspensions of nitrate-grown G. metallireducens oxidized Fe(II) and U(IV) with nitrate as the electron acceptor. U(IV) oxidation was accelerated when Fe(II) was also added, presumably due to the Fe(III) being formed abiotically oxidizing U(IV). These studies demonstrate that although the presence of nitrate is not likely to be an impediment to the bioremediation of uranium contamination with microbial U(VI) reduction, it is necessary to reduce nitrate before U(VI) can be reduced. These results also suggest that anaerobic oxidation of U(IV) to U(VI) with nitrate serving as the electron acceptor may provide a novel strategy for solubilizing and extracting microbial U(IV) precipitates from the subsurface. [source]

Nitrate- and Nitrite-Assisted Conversion of an Acetonitrile Ligand Into an Amidato Bridge at an {Mo2(Cp)2(,-SMe)3} Core: Electrochemistry of the Amidato Complex [Mo2(Cp)2(,-SMe)3{,-,1,,1 -OC(Me)NH}]+

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 19 2005
Marc Le Hénanf
Abstract Treatment of [Mo2(Cp)2(,-SMe)3(MeCN)2]+ (1+) with NO3, or NO2, results in the conversion of one terminally bound acetonitrile ligand into an amidato bridge. The reaction produces [Mo2(Cp)2(,-SMe)3{,-,1,,1 -OC(Me)NH}]0/+ (20/+) and involves the formation of an intermediate, which was detected by cyclic voltammetry but which could not be isolated, and which likely arises from the substitution of the NOx anion for one MeCN ligand. The electrochemical behaviour of 2+ was studied by cyclic voltammetry in THF and MeCN. The reduction of 2+ in the presence of acid (HBF4/H2O or HBF4/Et2O) in these solvents leads to the release of the amidate bridge. Controlled-potential electrolysis of 2+ in MeCN in the presence of acid produces 1+ quantitatively; the charge consumed (>1 F,mol,1 of 1+) indicates that electrons are also used to reduce protons. This was confirmed by the formation of 2+ (in variable amounts depending on the conditions) on treating 2 with acid. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source]

Sources and transport of algae and nutrients in a Californian river in a semi-arid climate

FRESHWATER BIOLOGY, Issue 12 2007
NOBUHITO OHTE
Summary 1. To elucidate factors contributing to dissolved oxygen (DO) depletion in the Stockton Deep Water Ship Channel in the lower San Joaquin River, spatial and temporal changes in algae and nutrient concentrations were investigated in relation to flow regime under the semiarid climate conditions. 2. Chlorophyll- a (chl- a) concentration and loads indicated that most algal biomass was generated by in-stream growth in the main stem of the river. The addition of algae from tributaries and drains was small (c.15% of total chl- a load), even though high concentrations of chl- a were measured in some source waters. 3. Nitrate and soluble-reactive phosphorus (SRP) were available in excess as a nutrient source for algae. Although nitrate and SRP from upstream tributaries contributed (16.9% of total nitrate load and 10.8% of total SRP load), nutrients derived from agriculture and other sources in the middle and lower river reaches were mostly responsible (20.2% for nitrate and 48.0% for SRP) for maintaining high nitrate and SRP concentrations in the main stem. 4. A reduction in nutrient discharge would attenuate the algal blooms that accelerate DO depletion in the Stockton Deep Water Ship Channel. The N : P ratio, in the main stem suggests that SRP reduction would be a more viable option for algae reduction than nitrogen reduction. 5. Very high algal growth rates in the main stem suggest that reducing the algal seed source in upstream areas would also be an effective strategy. [source]

Aminopeptidase and phosphatase activities in basins of Lake Hiidenvesi dominated by cyanobacteria and in laboratory grown Anabaena

FRESHWATER BIOLOGY, Issue 9 2002
JAANA VAITOMAA
1.,Extracellular enzyme activities were examined in freshwater basins representing a transition from hypertrophy to mesotrophy and in axenic cyanobacterial cultures to evaluate the ecological role of extracellular enzyme activities of cyanobacteria. 2.,Aminopeptidase activity was related to the trophic status of the lake basins. The activity was highest in the most eutrophic basin and decreased in the less nutrient-rich basins. Cyanobacteria were the most important autotrophic organisms and aminopeptidase activity was positively associated with cyanobacterial biomass. 3.,In an axenic Anabaena batch culture, nitrogenase activity was several orders of magnitude higher than leucine aminopeptidase activity. Nitrate did not have an effect on aminopeptidase activity or growth, but significantly reduced the rate of nitrogen fixation. A high phosphorus concentration at the beginning of the Anabaena batch-culture experiment resulted in reduced phosphatase activity. 4.,In Lake Hiidenvesi, aminopeptidase activity probably originated mostly from attached bacteria and less so from cyanobacteria. [source]

Temporal coherence of two alpine lake basins of the Colorado Front Range, U.S.A.

FRESHWATER BIOLOGY, Issue 3 2000
J. I. L. L. S. Baron
1. Knowledge of synchrony in trends is important to determining regional responses of lakes to disturbances such as atmospheric deposition and climate change. We explored the temporal coherence of physical and chemical characteristics of two series of mostly alpine lakes in nearby basins of the Colorado Rocky Mountains. Using year-to-year variation over a 10-year period, we asked whether lakes more similar in exposure to the atmosphere be-haved more similarly than those with greater influence of catchment or in-lake processes. 2. The Green Lakes Valley and Loch Vale Watershed are steeply incised basins with strong altitudinal gradients. There are glaciers at the heads of each catchment. The eight lakes studied are small, shallow and typically ice-covered for more than half the year. Snowmelt is the dominant hydrological event each year, flushing about 70% of the annual discharge from each lake between April and mid-July. The lakes do not thermally stratify during the period of open water. Data from these lakes included surface water temper-ature, sulphate, nitrate, calcium, silica, bicarbonate alkalinity and conductivity. 3. Coherence was estimated by Pearson's correlation coefficient between lake pairs for each of the different variables. Despite close geographical proximity, there was not a strong direct signal from climatic or atmospheric conditions across all lakes in the study. Individual lake characteristics overwhelmed regional responses. Temporal coherence was higher for lakes within each basin than between basins and was highest for nearest neighbours. 4. Among the Green Lakes, conductivity, alkalinity and temperature were temporally coherent, suggesting that these lakes were sensitive to climate fluctuations. Water tem-perature is indicative of air temperature, and conductivity and alkalinity concentrations are indicative of dilution from the amount of precipitation flushed through by snowmelt. 5. In Loch Vale, calcium, conductivity, nitrate, sulphate and alkalinity were temporally coherent, while silica and temperature were not. This suggests that external influences are attenuated by internal catchment and lake processes in Loch Vale lakes. Calcium and sulphate are primarily weathering products, but sulphate derives both from deposition and from mineral weathering. Different proportions of snowmelt versus groundwater in different years could influence summer lake concentrations. Nitrate is elevated in lake waters from atmospheric deposition, but the internal dynamics of nitrate and silica may be controlled by lake food webs. Temperature is attenuated by inconsistently different climates across altitude and glacial meltwaters. 6. It appears that, while the lakes in the two basins are topographically close, geologically and morphologically similar, and often connected by streams, only some attributes are temporally coherent. Catchment and in-lake processes influenced temporal patterns, especially for temperature, alkalinity and silica. Montane lakes with high altitudinal gradients may be particularly prone to local controls compared to systems where coherence is more obvious. [source]

Nitrate leaching from three afforestation chronosequences on former arable land in Denmark

GLOBAL CHANGE BIOLOGY, Issue 6 2007
KARIN HANSEN
Abstract In regions dominated by agricultural activities, nitrogen (N) is recognized as a major pollutant in aquatic environments. In north-western Europe, afforestation of agricultural land is part of a strategy to improve water quality. In Denmark, former arable land has been afforested during the past 40,50 years. This study evaluated the effect of afforestation of former arable land on nitrate leaching, based on three afforestation chronosequences. Precipitation, canopy throughfall and soil water were collected and soil moisture was monitored at two Danish locations, Vestskoven (nutrient-rich, medium deposition) and Gejlvang (nutrient-poor, high deposition). Afforestation was performed using Norway spruce [Picea abies (Karst.) L.] and common oak (Quercus robur L.) at Vestskoven and Norway spruce at Gejlvang. The results suggest that afforestation of former arable land initially leads to lower nitrate leaching than that occurring under the former agricultural land use, and largely below the standard of 50 mg NO,3 L,1 for groundwater to be utilized as drinking water. Nitrate concentrations became almost negligible in forest stands of 5,20 years of age. However, after canopy closure (>20 years) nitrate concentrations below the root zone and nitrate leaching tended to increase. This was attributed to increased N deposition with increasing canopy development and decreased N demand once the most N-rich biomass compartments had been built up. Nitrate leaching started to increase at a throughfall deposition level of about 10 kg N ha,1 yr,1. Compared with nutrient-poor sandy soils, nutrient-rich clayey soils appeared more vulnerable to disturbance of the N cycle and to increased N deposition, leading to N saturation and enhanced nitrate leaching. In approximately the first 35 years after afforestation, nitrate leaching below the root zone was generally higher below oak than below Norway spruce. [source]

Nitrate leaching from cut grassland as affected by the substitution of slurry with nitrogen mineral fertilizer on two soil types

GRASS & FORAGE SCIENCE, Issue 1 2010
J. J. Schröder
Abstract A field experiment was conducted to find out whether there is any difference in risk of N leaching to groundwater when cattle slurry and/or mineral fertilizer-N was applied to cut grassland. The experiment was carried out over two consecutive years on two sites (one with a relatively wet sandy soil and one with a relatively dry sandy soil). Treatments were mineral fertilizer-N at annual rates of 0,510 kg N ha,1 year,1 and combinations of sod-injected cattle slurry (85, 170, 250 and 335 kg N ha,1 year,1) and mineral fertilizer-N (289, 238, 190 and 139 kg N ha,1 year,1). Yield responses indicated that in the short run, 0·44,0·88 (average 0·60) of the slurry-N was as available as mineral fertilizer-N. The total N input from mineral fertilizer and slurry was a worse predictor of nitrate leaching ( 0·11) than the N surplus (i.e. the difference between total N input and harvested N) ( 0·60). The effective N surplus, based on the difference between the summed inputs of the plant-available N and harvested N, proved to be the best indicator of leaching ( 0·86). Annual N application rates of up to 340 kg plant-available N ha,1 complied with the target nitrate concentration in groundwater of 11·3 mg N L,1 set by the European Union in both years on the wet sandy soil, whereas on the dry sandy soil none of the treatments did. [source]

Nitrate Removal Rates in a 15-Year-Old Permeable Reactive Barrier Treating Septic System Nitrate

GROUND WATER MONITORING & REMEDIATION, Issue 3 2008
W.D. Robertson
Permeable reactive barriers (PRBs) have gained popularity in recent years as a low-cost method for ground water remediation. However, their cost advantage usually requires that these barriers remain maintenance free for a number of years after installation. In this study, sediment cores were retrieved from a pilot-scale PRB consisting of a sand and wood particle (sawdust) mixture that has been in continuous operation for 15 years treating nitrate from a septic system plume in southern Ontario (Long Point site). Reaction rates for the 15-year-old media were measured in dynamic flow column tests and were compared to rates measured in year 1 using the same reactive mixture. Nitrate removal rates in the 15-year-old media varied, as expected, with temperature in the range of 0.22 to 1.1 mg N/L/d at 6 °C to 10 °C to 3.5 to 6.0 mg N/L/d at 20 °C to 22 °C. The latter rates remained within about 50% of the year 1 rates (10.2 ± 2.7 mg N/L/d at 22 °C). Near the end of the year 15 column test, media particles >0.5 mm in diameter, containing most of the wood particles, were removed from the reactive media by sieving. Nitrate removal subsequently declined by about 80%, indicating that the wood particles were the principal energy source for denitrification. This example shows that some denitrifying PRBs can remain maintenance free and be adequately reactive for decades. [source]

Helicobacter pylori Infection Increases Serum Nitrate and Nitrite More Prominently Than Serum Pepsinogens

HELICOBACTER, Issue 1 2002
Kanji Kodama
Abstract Background.Helicobacter pylori infection causes chronic gastritis and results in increased serum concentrations of pepsinogens I and II as well as gastrin, while the ratio of pepsinogen I to II (I : II) is decreased. Inducible nitric oxide synthase (iNOS) is induced in H. pylori -associated gastritis and may modulate inflammation. However serum nitrate and nitrite (NOx) concentrations in patients with H. pylori -induced chronic gastritis have not been reported. We examined differences in serum NOx between H. pylori -negative and positive volunteers relative to differences in pepsinogens and gastrin. Materials and methods. Sera from 80 healthy asymptomatic volunteers younger than 36 years were analyzed for anti- H. pylori antibody, NOx, gastrin and pepsinogens. Results. In H. pylori antibody-positive subjects serum NOx concentrations were higher than in negative subjects (p < .005). In H. pylori -negative subjects, NOx correlated with pepsinogen II (r = .405, p < .05). In subjects with low pepsinogen I or II, NOx was higher in H. pylori -positive than negative subjects (p < .001). In subjects with high pepsinogen I : II (6 or higher), serum NOx was higher in H. pylori -positive than in negative subjects. Conclusions.H. pylori -induced gastritis increases serum NOx concentrations more prominently than those of pepsinogen. In H. pylori -negative subjects, serum correlates with serum pepsinogen II. [source]

Efficient Regio- and Stereoselective Conversions of Oxiranes and Aziridines into , -(Nitrooxy)-Substituted Alcohols and Amines by Using Bismuth Nitrate,

HELVETICA CHIMICA ACTA, Issue 1 2007
Biswanath Das
Abstract Oxiranes and aziridines efficiently undergo ring opening with bismuth nitrate at room temperature to furnish the corresponding , -(nitrooxy)-substituted alcohols and amines respectively. The conversions are highly regio- and stereoselective and afford the nitrooxy-compounds in excellent yields within a short period of time. [source]

Effects of Varying Levels of Vegetable Juice Powder and Incubation Time on Color, Residual Nitrate and Nitrite, Pigment, pH, and Trained Sensory Attributes of Ready-to-Eat Uncured Ham

JOURNAL OF FOOD SCIENCE, Issue 6 2007
J.J. Sindelar
ABSTRACT:, Vegetable juice powder (VJP) and a starter culture containing Staphylococcus carnosus have been identified as necessary ingredients for the manufacture of uncured, no-nitrate/nitrite-added meat products with quality and sensory attributes similar to traditional cured products. The objectives of this study were to determine the effects of varying concentrations of VJP and incubation time (MIN-HOLD) on quality characteristics, including lipid oxidation, color, and cured meat pigment concentrations, of ham over a 90-d storage period, compare residual nitrate and nitrite content, and determine if differences exist in sensory properties of finished products. Four ham treatments (TRT) (TRT 1: 0.20% VJP, 0 MIN-HOLD; TRT 2: 0.20% VJP, 120 MIN-HOLD; TRT 3: 0.35% VJP, 0 MIN-HOLD; TRT 4: 0.35% VJP, 120 MIN-HOLD) and a sodium nitrite-added control (C) were used for this study. No differences (P > 0.05) were observed between TRTs and C for CIE L*, a*, b*, and cured color measured by reflectance ratio. Lipid oxidation (TBARS) for combined TRTs and C revealed little change over time while the C had less (P < 0.05) lipid oxidation than TRTs 2 and 4 for combined days. No differences (P > 0.05) were reported for cured pigment concentration between TRTs and C. Trained sensory panel intensity ratings for ham and vegetable aroma, and flavor, color, and firmness showed that a high concentration (0.35%) of VJP resulted in the highest scores for undesirable vegetable aroma and flavor. Treatment combinations with a low concentration (0.20%) of VJP were comparable to the C for all sensory attributes. [source]

NITROGEN LIMITATION EFFECTS OF DIFFERENT NITROGEN SOURCES ON NUTRITIONAL QUALITY OF TWO FRESHWATER ORGANISMS, SCENEDESMUS QUADRICAUDA (CHLOROPHYCEAE) AND SYNECHOCOCCUS SP. (CYANOPHYCEAE)

JOURNAL OF PHYCOLOGY, Issue 5 2003
Gunnel Ahlgren
Food quality for grazers has been related to mineral (nitrogen, phosphorus) and biochemical (amino acids, fatty acids) constituents. The aim of the study was to examine the influence of different nitrogen sources on these constituents in two organisms, the green alga Scenedesmus quadricauda Turp. and the cyanobacterium Synechococcus sp., commonly used in feeding experiments. The two organisms were grown in continuous cultures at different growth rates. Nitrate or ammonium salts were used as nitrogen sources under both replete and limited conditions. Carbon content (mg·g,1 dry weight) was stable in both organisms independent of nitrogen source, nitrogen limitation, and growth rate. Nitrogen content decreased with limitation and growth rate in Scenedesmus and to a lesser degree in Synechococcus, whereas changes in phosphorus content were not statistically significant. The relative proportions of amino acids (% of total amino acids) were relatively stable in both organisms, whereas the proportions of fatty acids varied with growth rate and limitation. Fatty acid content was much lower in Synechococcus than in Scenedesmus. At N limitation, polyunsaturated fatty acids (PUFAs) showed lower levels in both organisms. The change occurred in the ,3 PUFA (linolenic acid) of the green alga and in the ,6 PUFA (linoleic acid) of the cyanobacterium. The difference in the response of N limitation in the two organisms may be traced to the different composition of the chloroplast membranes (the prokaryotic way) and the microsomal membranes (the eukaryotic way) where the desaturation takes place. [source]

WATER QUALITY IN AGRICULTURAL, URBAN, AND MIXED LAND USE WATERSHEDS,

JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 6 2004
Chris B. Coulter
ABSTRACT: Water quality and nonpoint source (NPS) pollution are important issues in many areas of the world, including the Inner Bluegrass Region of Kentucky where urban development is changing formerly rural watersheds into urban and mixed use watersheds. In watersheds where land use is mixed, the relative contributions of NPS pollution from rural and urban land uses can be difficult to separate. To better understand NPS pollution sources in mixed use watersheds, surface water samples were taken at three sites that varied in land use to examine the effect of land use on water quality. Within the group of three watersheds, one was predominately agriculture (Agricultural), one was predominately urban (Urban), and a third had relatively equal representation of both types of land uses (Mixed). Nitrogen (N), phosphorus (P), total suspended solids (TSS), turbidity, pH, temperature, and streamflow were measured for one year. Comparisons are made among watersheds for concentration and fluxes of water quality parameters. Nitrate and orthophosphate concentrations were found to be significantly higher in the Agricultural watershed. Total suspended solids, turbidity, temperature, and pH, were found to be generally higher in the Urban and Mixed watersheds. No differences were found for streamflow (per unit area), total phosphorus, and ammonium concentrations among watersheds. Fluxes of orthophosphate were greater in the Agricultural watershed that in the Urban watershed while fluxes of TSS were greater in the Mixed watershed when compared to the Agricultural watershed. Fluxes of nitrate, ammonium, and total phosphorus did not vary among watersheds. It is apparent from the data that Agricultural land uses are generally a greater source of nutrients than the Urban land uses while Urban land uses are generally a greater source of suspended sediment. [source]

Nitrate modifies the assimilation pattern of ammonium and urea in wheat seedlings

JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 3 2010
Maria Garnica
Abstract BACKGROUND: In certain plant species, ammonium or urea nutrition can cause negative effects on plant development which can result in toxic symptoms. Some authors suggest that the presence of nitrate can alleviate these symptoms by increasing ammonium and urea assimilation, avoiding its accumulation. In order to study this hypothesis, wheat (Triticum aestivum L.) seedlings were grown with various nitrogen supplies containing the main nitrogen forms (ammonium, nitrate and urea). Amino acids content and the activity of the three main enzymes involved in nitrogen assimilation (nitrate reductase, glutamine synthetase and urease) were studied. RESULTS: The application of nitrate along with urea and/or ammonium was not associated with a time-sustained increase in the activity of glutamine synthetase and urease. Amino acid analysis revealed that nitrate induced changes in amino acid metabolism enhancing its concentration. Likewise the content of protein was also higher in nitrate-treated plants. CONCLUSION: These results suggest that the effect of nitrate is compatible with a rapid and transient increase in the activity of glutamine synthetase and urease during the first hour after the onset of treatments. Nevertheless, a possible effect of nitrate reducing ammonium accumulation through the activation of alternative metabolic pathways different from that involving glutamine synthetase cannot be ruled out. Finally, nitrate effects on amino acid concentration indicate that, whereas ammonium assimilation takes place principally in the root, urea and nitrate assimilation occurred in the shoot, under the conditions of the experiment. Copyright © 2009 Society of Chemical Industry [source]

Superficial Dermatomycoses Worldwide: Multinational Treatment Experience with a Combination of Isoconazole Nitrate and Diflucortolone Valerate

MYCOSES, Issue 2008
Viktor A. Czaika
[source]

Mechanismen und klinischer Stellenwert der Nitrattoleranz.

PHARMAZIE IN UNSERER ZEIT (PHARMUZ), Issue 5 2010
Diversität und Nebenwirkungen organischer Nitrate
Die wichtigste Beobachtung der letzten Jahre war, dass es sich bei den organischen Nitraten überraschenderweise um eine heterogene Gruppe von Vasodilatantien handelt, denen gemeinsam ist, dass sie die lösliche GC und die cGMP-abhängige Kinase aktivieren können. Alle klinisch wichtigen organischen Nitrate (GTN, ISDN und ISMN) außer dem PETN induzieren eine Toleranzentwicklung und eine endotheliale Dysfunktion bei chronischer Gabe. Aktuelle Arbeiten konnten insbesondere nach Gabe von GTN einen neuen Toleranz-Mechanismen identifizieren, der aus der Hemmung des Nitrat-bioaktivierenden Enzyms, der mitochondrialen Aldehyddehydrogenase (ALDH-2) sowie die Bildung reaktiver Sauerstoff- und Stickstoffspezies (RONS) in Mitochondrien besteht, die wiederum die Bioaktivierung des GTN hemmen. Damit konnten erstmals die beiden nun schon klassischen Konzepte der Nitrattoleranz, erhöhter oxidativer Stress und verminderte GTN-Biotransformation, in ein Konzept übergeführt werden. Aktuelle tierexperimentelle und humane Studien legen nahe, dass die organischen Nitrate nicht als einheitliche homogene Gruppe anzusehen sind, sondern eine beachtliche Diversität hinsichtlich Induktion der Gefäßdysfunktion und insbesondere in der Fähigkeit, oxidativen Stress in den Gefäßen zu induzieren, zeigen. In der Vergangenheit wurde versucht, die Nitratwirkung vor allem durch das so genannte "Nitrat-freie Intervall" zu erhalten, mit dem Nachteil des Stopps einer wichtigen antiischämischen Therapie. Momentan stellt das PETN, insbesondere mit seiner Fähigkeit, antioxidativ wirksame Enzymsysteme hochzuregulieren, das Nitrat der Wahl dar. Die klinische Wirksamkeit muss jedoch erst in großen "Multicenter-Trials" bei Patienten mit Herzinsuffizienz und pulmonaler Hypertonie sowie bei Patienten mit stabiler KHK untersucht werden. [source]

Nitrogen-assimilating enzymes in land plants and algae: phylogenic and physiological perspectives

PHYSIOLOGIA PLANTARUM, Issue 1 2002
Ritsuko Inokuchi
An important biochemical feature of autotrophs, land plants and algae, is their incorporation of inorganic nitrogen, nitrate and ammonium, into the carbon skeleton. Nitrate and ammonium are converted into glutamine and glutamate to produce organic nitrogen compounds, for example proteins and nucleic acids. Ammonium is not only a preferred nitrogen source but also a key metabolite, situated at the junction between carbon metabolism and nitrogen assimilation, because nitrogen compounds can choose an alternative pathway according to the stages of their growth and environmental conditions. The enzymes involved in the reactions are nitrate reductase (EC 1.6.6.1-2), nitrite reductase (EC 1.7.7.1), glutamine synthetase (EC 6.3.1.2), glutamate synthase (EC 1.4.1.13-14, 1.4.7.1), glutamate dehydrogenase (EC 1.4.1.2-4), aspartate aminotransferase (EC 2.6.1.1), asparagine synthase (EC 6.3.5.4), and phosphoenolpyruvate carboxylase (EC 4.1.1.31). Many of these enzymes exist in multiple forms in different subcellular compartments within different organs and tissues, and play sometimes overlapping and sometimes distinctive roles. Here, we summarize the biochemical characteristics and the physiological roles of these enzymes. We also analyse the molecular evolution of glutamine synthetase, glutamate synthase and glutamate dehydrogenase, and discuss the evolutionary relationships of these three enzymes. [source]

Control of Nitrate Uptake by Phloem-Translocated Glutamine in Zea mays L. Seedlings

PLANT BIOLOGY, Issue 4 2002
P. Pal'ove-Balang
Abstract: The putative role of glutamine, exported from leaves to roots, as a negative feedback signal for nitrate uptake was investigated in Zea mays L. seedlings. Glutamine (Gln) was supplied by immersion of the tip-cut leaves in a concentrated solution. Nitrate (NO3,) uptake was measured by its depletion in amino acid-free medium. The treatment with Gln resulted in a strong inhibition of nitrate uptake rate, accompanied by a significant enrichment of amino compounds in root tissue. The effect of N-availability on NO3, uptake was determined in split-root cultures. The plants were subjected to complete or localized N supply. Inducible NO3, uptake systems were also induced in N-deprived roots when the opposite side of the root system was supplied with KNO3. The inhibitory effect of Gln was unaffected by localized N supply on one side of the split-root. The potential role of Gln in the shoot-to-root control of NO3, uptake is discussed. [source]

Ceric Ammonium Nitrate Initiated Grafting of PEG to Plasma Polymers for Cell-Resistant Surfaces

PLASMA PROCESSES AND POLYMERS, Issue 2 2008
Naomi J. Vickers
Abstract The development of a facile method with general applicability and mild reaction conditions for grafting PEG onto surfaces to reduce bio-adhesion is described. The approach taken was to use CAN to graft PEG to plasma polymers coatings selected to give a high concentration of alcohol groups. The study showed that grafting required functional groups on surfaces, a minimum concentration of CAN initiator (0.05 M) and was time and initiator concentration dependent. Adhesion of fibroblasts and endothelial cells was reduced to negligible levels compared to the adhesion to tissue culture polystyrene and untreated plasma polymers of allyl alcohol following CAN induced PEG grafting. [source]

Determination of Urea Nitrate and Guanidine Nitrate Vapor Pressures by Isothermal Thermogravimetry

PROPELLANTS, EXPLOSIVES, PYROTECHNICS, Issue 3 2010
Jimmie Oxley
Abstract Since the bombing of Pan Am Flight 103 over Lockerbie, Scotland in 1988, detection of military explosives has received much attention. Only in the last few years has detection of improvised explosives become a priority. Many detection methods require that the particulate or vapor be available. Elsewhere we have reported the vapor pressures of peroxide explosives triacetone triperoxide (TATP), diacetone diperoxide (DADP), and 2,4,6-trinitrotoluene (TNT). Herein we examine the vapor signatures of the nitrate salts of urea and guanidine (UN and GN, respectively), and compare them to ammonium nitrate (AN) and TATP using an isothermal thermo-gravimetric method. The vapor signatures of the nitrate salts are assumed to be the vapor pressures of the neutral parent base and nitric acid. Studies were performed at elevated temperatures (80,120,°C for UN, 205,225,°C for GN, 100,160,°C for AN, and 40,59,°C for TATP), enthalpies of sublimation calculated and vapor pressures extrapolated to room temperature. Reported vapor pressure values (in Pa) are as follows: GN ,,UN ,[source]

Kinetic Regularities of the Heat Release for the Interaction of Some Organic Compounds with Ammonium Nitrate

PROPELLANTS, EXPLOSIVES, PYROTECHNICS, Issue 6 2006

Abstract Ammonium nitrate (AN) is used as an oxidant in a series of systems with a wide spectrum of applications, from explosive compositions up to smokeless stoichiometric self-burning compositions with low combustion temperature. The knowledge of the thermal stability of such compositions is of great importance in using them in practice. In this work the research of kinetics of heat release in the interaction of AN with different organic compounds has been performed using the automatic differential calorimeter. [source]

Calculation of the Detonation Velocities and Detonation Pressures of Dinitrobiuret (DNB) and Diaminotetrazolium Nitrate (HDAT-NO3)

PROPELLANTS, EXPLOSIVES, PYROTECHNICS, Issue 1 2004
Janna Geith
Abstract The enthalpies of combustion (,combH) of dinitrobiuret (DNB) and diaminotetrazolium nitrate (HDAT-NO3) were determined experimentally using oxygen bomb calorimetry: ,combH(DNB)=5195±200,kJ kg,1, ,combH(HDAT-NO3)=7900±300,kJ kg,1. The standard enthalpies of formation (,fH°) of DNB and HDAT-NO3 were obtained on the basis of quantum chemical computations at the electron-correlated ab initio MP2 (second order Møller-Plesset perturbation theory) level of theory using a correlation consistent double-zeta basis set (cc-pVTZ): ,fH°(DNB)=,353,kJ mol,1, ,1,829,kJ kg,1; ,fH°(HDAT-NO3)=+254,kJ mol,1, +1,558,kJ kg,1. The detonation velocities (D) and detonation pressures (P) of DNB and HDAT-NO3 were calculated using the empirical equations by Kamlet and Jacobs: D(DNB)=8.66,mm,,s,1, P(DNB)=33.9,GPa, D(HDAT-NO3)=8.77,mm,,s,1, P(HDAT-NO3)=33.3,GPa. [source]

Isolation and characterization of the "zooxanthellae" from soritid foraminifera and the giant clam Tridacna maxima

THE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 2 2005
JOHN J. LEE
Various methodological approaches are being used to characterize Symbiodinium spp isolated from Marginopora vertebralis and Amphisorus hemprichii and Amphisorus sp. from the Indo-pacific. While most of the cells in culture are non-motile vegetative cells, dinospores occur in batch cultures. We find consistant variance among the isolates in the duration and time of appearance of motile forms. Nitrate (0.146 mM) supports higher populations of the isolates than NH4 (0.146 mM). Higher concentrations of NH4 inhibit growth. Although Fensome et al. (1993) characterized the Order Suessiales (and Family Symbiodiniaceae) as gymnnodiniphycideans in which the amphiesmal vesicals are arranged in 7,10 longitudinal series we were unable to detect any plates on the surfaces of our isolates in the SEM. We were unsuccessful in revealing plates on non-motile forms by freeze fracture but they were present after treatment with various chemical agents (e.g. H2O2, HOCl,) and enzymes (cellulase, chitinase). They are not polygonal or arranged in the patterns anticipated for the Symbiodiniaceae. Polyclonal antibody studies of the Symbiodinium -like isolates are in agreement with molecular systematic studies in the sense that there is a common relation. The foram endosymbiotic dinoflagellates share some common surface antigens with each other and with the few invertebrate isolates we have tested. Studies of the foraminiferal symbionts' plastids revealed considerable morphological diversity. We isolated a diversity of endosymbionts from the mantle of Tridacna maxima from the Red Sea and the Marshall Islands. These included Symbiodinium, Amphidinium, Tetraselmis, and an unidentified chlorophyte. [source]

Use of white clover as an alternative to nitrogen fertiliser for dairy pastures in nitrate vulnerable zones in the UK: productivity, environmental impact and economic considerations

ANNALS OF APPLIED BIOLOGY, Issue 1 2007
M. Andrews
Abstract Perennial ryegrass and perennial ryegrass/white clover permanent dairy pastures are compared with respect to productivity, environmental impact and financial costs in nitrate vulnerable zones (NVZ) in the UK. With appropriate management, and utilisation of recommended perennial ryegrass and white clover cultivars, white clover is likely to stabilise at around 20% of total dry matter production in a mixed pasture. Plant dry matter production and milk production from a perennial ryegrass/white clover pasture are likely to be similar to that from a perennial ryegrass pasture receiving 200 kg N ha,1 annum,1 and around 70% of that obtained with perennial ryegrass supplied with 350,400 kg N ha,1 annum,1. Nitrate, phosphorus and methane losses from the system and decreases in biodiversity relative to a grazed indigenous sward are likely to be similar for a perennial ryegrass/white clover pasture and a perennial ryegrass pasture receiving 200 kg N ha,1 annum,1: nitrate leachate from both systems is likely to comply with European legislation. Greenhouse gas emissions resulting from nitrogen (N) fertiliser production would be avoided with the perennial ryegrass/white clover pasture. Within NVZ stocking rate restrictions, white clover can provide the N required by a pasture at a lower financial cost than that incurred by the application of N fertiliser. [source]

Paracoccus denitrificans for the effluent recycling during continuous denitrification of liquid food

BIOTECHNOLOGY PROGRESS, Issue 3 2010
Nils Tippkötter
Abstract Nitrate is an undesirable component of several foods. A typical case of contamination with high nitrate contents is whey concentrate, containing nitrate in concentrations up to 25 l. The microbiological removal of nitrate by Paracoccus denitrificans under formation of harmless nitrogen in combination with a cell retention reactor is described here. Focus lies on the resource-conserving design of a microbal denitrification process. Two methods are compared. The application of polyvinyl alcohol-immobilized cells, which can be applied several times in whey feed, is compared with the implementation of a two step denitrification system. First, the whey concentrate's nitrate is removed by ion exchange and subsequently the eluent regenerated by microorganisms under their retention by crossflow filtration. Nitrite and nitrate concentrations were determined by reflectometric color measurement with a commercially available Reflectoquant® device. Correction factors for these media had to be determined. During the pilot development, bioreactors from 4 to 250 mg·L,1 and crossflow units with membrane areas from 0.02 to 0.80 m2 were examined. Based on the results of the pilot plants, a scaling for the exemplary process of denitrifying 1,000 tons per day is discussed. © 2010 American Institute of Chemical Engineers Biotechnol. Prog. 2010 [source]

Containment of Biogenic Sulfide Production in Continuous Up-Flow Packed-Bed Bioreactors with Nitrate or Nitrite

BIOTECHNOLOGY PROGRESS, Issue 2 2003
Casey Hubert
Produced water from the Coleville oil field in Saskatchewan, Canada was used to inoculate continuous up-flow packed-bed bioreactors. When 7.8 mM sulfate and 25 mM lactate were present in the in-flowing medium, H2S production (souring) by sulfate-reducing bacteria (SRB) was prevented by addition of 17.5 mM nitrate or 20 mM nitrite. Changing the sulfate or lactate concentration of the in-flowing medium indicated that the concentrations of nitrate or nitrite required for containment of souring decreased proportionally with a lowered concentration of the electron donor lactate, while the sulfate concentration of the medium had no effect. Microbial communities were dominated by SRB. Nitrate addition did not give rise to changes in community composition, indicating that lactate oxidation and H2S removal were caused by the combined action of SRB and nitrate-reducing, sulfide-oxidizing bacteria (NR-SOB). Apparently the nitrite concentrations formed by these NR-SOB did not inhibit the SRB sufficiently to cause community shifts. In contrast, significant community shifts were observed upon direct addition of high concentrations (20 mM) of nitrite. Strains NO3A and NO2B, two newly isolated, nitrate-reducing bacteria (NRB) emerged as major community members. These were found to belong to the ,-division of the Proteobacteria, to be most closely related to Campylobacter lari, and to oxidize lactate with nitrate or nitrite as the electron acceptor. Thus the mechanism of microbial H2S removal in up-flow packed-bed bioreactors depended on whether nitrate (SRB/NR-SOB) or nitrite (SRB/NR-SOB as well as NRB) was used. However, the amount of nitrate or nitrite needed to completely remove H2S was dictated by the electron donor (lactate) concentration, irrespective of mechanism. [source]