Effects Of Nitrate Concentrations Research Articles

Effects of nitrate concentrations on As(III) immobilization via new ferric arsenite hydroxynitrate precipitates

The Fe(III)-As(III)-anion precipitation as layered double hydroxide-like compounds such as tooeleite and ferric arsenite hydroxychloride (FC) has been found in As(III)-contaminated acidic mine soils. However, the question of whether As(III) is immobilized by Fe(III) in aqueous nitrate media, a common constituent in soils and metallurgical wastewater, remains unclear. Herein, we investigated the effects and mechanism of nitrate on As(III) immobilization via Fe(III)-As(III)-nitrate precipitation. Our results indicated that new ferric arsenite hydroxynitrate (FN) with variable Fe(III)/As(III)/nitrate molar ratios crystallized in an initial nitrate content range of 11,160–74,400 mg·L−1 at pH 2.3. This FN precipitation resulted in 60.3–87.9% of As(III) removal and a fall-rise immobilization trend as a function of the initial nitrate concentration. The optimal initial nitrate concentration for As(III) fixation was 44,640 mg·L−1. Although FN shared similar morphology and crystal structure with tooeleite and FC, the substitution of NO3− for SO42− and Cl− in the FeO6-AsO3 interlayers caused a significant local structural distortion due to different ionic radii. The characteristic infrared and Raman bands of the nitrate group in FN occurred at 1,363 cm−1, 1,384 cm−1 and 152 cm−1, 722 cm−1, 1,055 cm−1, respectively. The FN induced significantly enhanced As(III) immobilization relative to its tooeleite and FC counterparts at equimolar concentrations of NO3−, SO42−, and Cl− as the media.

Health effects of nitrate concentrations in the groundwater of Al-Manara village, north-east of Mosul city, Iraq

Health effects of nitrate concentrations in the groundwater of Al-Manara village, north-east of Mosul city, Iraq

Removal of co-contaminants Cu (II) and nitrate from aqueous solution using kaolin-Fe/Ni nanoparticles

Treatment of wastewater containing co-contaminants poses a significant challenge because heavy metal and inorganic anion contaminants in wastewater have different fates and transport mechanisms. In this paper, bimetallic Fe/Ni nanoparticles supported by kaolinite (K-Fe/Ni) were used to simultaneously remove Cu (II) and nitrate. Results show that the removal of either Cu (II) or nitrate using K-Fe/Ni was mutually affected. Specifically, 42.5% of nitrate was degraded in the presence of 200mg/L Cu (II), while only 26.9% of nitrate was reduced when Cu (II) was absent. Similar results were also obtained for the removal of Cu (II) in the absence or presence of nitrate. However, the effect of nitrate concentrations on the removal of Cu (II) was less than that for Cu (II) concentrations regarding the degradation of nitrate. To better understand this process, the K-Fe/Ni before and after reacting with Cu (II) and nitrate was characterized with specific surface area, X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray energy-dispersive spectrometer (EDS), and X-ray photoelectron spectroscopy (XPS). These results show that there were the formation of iron oxide, metallic Cu and Ni, after reacting with Cu (II) and nitrate. This indicates that Cu (II) was reduced to Cu0 onto the surface of K-Fe/Ni, and then a novel catalyst such as K-Fe/Ni/Cu formed. Finally, a possible mechanism for the simultaneous removal of Cu (II) and nitrate is proposed, based on Fe0 as the reductive agent, whilst both Ni and Cu act as the catalysts for the hydrogen generated from water, and kaolin serves as a support.

Differential Production of Tropane Alkaloids in Hairy Roots and in vitro Cultured Two Accessions of Atropa belladonna L. under Nitrate Treatments

Plants are a potential source of a large number of valuable secondary metabolites. In vitro cultures are being considered as an alternative to agricultural processes for studying valuable secondary metabolites. In this way, nutritive factors are important parameters influencing the production of these compounds in plants. Effects of nitrate concentrations (KNO3) on the production of two tropane alkaloids, hyoscyamine and scopolamine, and the growth of aerial parts and roots of two in vitro propagated accessions of Atropa belladonna and hairy roots were investigated. As hairy roots cultures are able to keep a stable production of alkaloids over long periods of subculturing, they are considered as an interesting option for the study of alkaloid biosynthesis. A hairy roots culture of Atropa belladonna was established by transformation with Agrobacterium rhizogenes strain AR15834. The results of our study showed that a rise in KNO3 concentration caused a decline in hairy roots growth, and had a remarkable effect on the alkaloid content. The alkaloid concentrations obtained in the hairy roots were 3-20 times higher than that in the plants at 35 mM of KNO3. Increasing the nitrate concentration in the medium of hairy roots also improved the hyoscyamine/scopolamine ratio, while it increased the scopolamine/hyoscyamine ratio in the studied plants.

The anoxic extractive membrane bioreactor

The extractive membrane bioreactor (EMB) employs a dense silicone rubber membrane to selectively extract hydrophobic organic compounds from industrial wastewaters into a bioreactor in order to biodegrade them. The major drawback of the EMB is excess biofilm growth on the membrane, which limits mass transfer and creates oxygen limitations. In this work, nitrate has been used as an electron acceptor instead of oxygen. Due to the high solubility of nitrate in water, it is hypothesised that nitrate penetrates the whole biofilm, preventing the formation of inactive zones of bacteria. Four experiments have been performed with toluene as a model substrate under anoxic conditions. The effect of nitrate concentrations on the biofilm and on the toluene flux have been investigated. In addition, the production of soluble microbial products (SMPs), and bacterial hydrophobicity were studied. Under high nitrate concentrations, the performance of the anoxic EMB was stable and no biofilm was formed. The bacteria metabolised toluene, and the toluene flux remained approximately constant. Conversely, at low nitrate concentration, a decrease in pollutant flux concomitant with biofilm growth was observed. The production of SMPs increased under limiting nitrate concentrations, but the hydrophobicity of the suspended bacteria remained constant. However, the bacterial hydrophobicity of the attached cells was significantly greater than that of the suspended cells.

ホウレンソウのシュウ酸含量に及ぼす窒素肥料の影響

Effects of nitrate concentrations and the ratio of NO3-: NH4+ in nutrient solutions on the oxalate content of spinach (Spinacia oleracea L. cv. Shoryoku) leaves were examined Solutions containing 0 to 100 ppm of NO3- were used to grow the plants. When the ni trate level of nutrient solutions was lower than 10 ppm, plants grew poorly and the total nitrogen and oxalate contents of the leaves were low.When grown on the solutions containing different ratios of NO3- : NH4+, the total and watersoluble oxalate contents decreased as the ratio was decreased. The effects of different nitrogen sources and concentrations on the growth of plants varied depending on the seasons of the year. Generally when the ratio exceeded 1 : 3 (75% NH4+), plant growth was depressed. However, when the ratio was less than 3 : 1 (25% NH4+), the plants grew well. Thus, the oxalate content of spinach leaves can be reduced without depressing plant growth.

Effect of high nitrate concentrations on growth and nitrate uptake by free-living and immobilizedChlorella vulgaris cells

Growth and nitrate uptake were studied on free-living and immobilizedChlorella vulgaris cells cultivated in medium containing different nitrate concentrations. First, the effect of nitrate concentrations on growth indicated that cells can live in the presence of high concentrations as high as 97 mM. Although no lethal effect on cells was observed such concentration a slow down in growth and a decrease in biomass produced was observed. The rate of nitrate uptake increased with the nitrate concentration in the medium. The maximum uptake rate was reached in first days of culture in both free-living and immobilized cells. The rate dropped more rapidly for cells growing in 2 mM nitrate than for cells growing in higher nitrate concentration. The maximum rate was very much the same for free-living and immobilized and was within the order of 0.45 to 0.57 μg NO3 h−1 10−6 cells. Immobilization modified the changes of nitrate uptake rate for concentration higher than 2 mM.

Effect of nitrate concentrations and additional amino acids on the susceptibility of wheat to chlorsulfuron

Effect of nitrate concentrations and additional amino acids on the susceptibility of wheat to chlorsulfuron