Search results for "ammonium"
showing 10 items of 1070 documents
Detailed internal characterisation of two Finnish landfills by waste sampling
2006
The aim of this study was to characterise the internal structure and composition of landfilled waste at two Finnish landfills to provide information for active and post-landfill operations. The two sites, Ammässuo and Kujala, have been in operation for 17 and 48 years, respectively. Waste was sampled (total 68 samples) and analysed for total solids (TS), volatile solids (VS), total Kjeldahl nitrogen (TKN), biological methane potential (BMP) and leaching of organic material (determined as chemical oxygen demand, COD) and ammonium nitrogen (NH(4)-N). The results showed high vertical and horizontal variability, which indicated that both the waste composition and state of degradation varied gre…
The relaxant effects of cromakalim (BRL 34915) on human isolated airway smooth muscle
1992
Cromakalim (BRL 34915) is a potassium channel opener with therapeutic potential as a bronchodilator in asthma. Cromakalim (0.1–30 μmol/l) inhibited the spontaneous tone of human isolated bronchi n a concentration-related manner being nearly as effective as isoprenaline or theophylline. The order of relaxant potencies (expressed as -log10 IC50 mol/l; mean ±SEM) was isoprenaline (7.29 ± 0.27; n = 8) > cromakalim (5.89 ± 0.12; n = 7) > theophylline (4.07 ±0.13; n = 10). In human bronchi where tone had been raised by addition of histamine (0.1 mmol/l), acetylcholine (0.1 mmol/l) or leukotriene D4 (LTD4, 0.1 μmol/l), the relaxant effect of cromakalim was substantially reduced. Cromakalim suppres…
The essential identity of the framework structures of ZSM-8 and ZSM-5
1994
The crystal structures of TEA-ZSM-8 and its calcined template-free form have been studied by Rietveld analyses based on X-ray powder diffraction data. The results show that the aluminosilicate framework structure of ZSM-8 is essentially identical to that of ZSM-5. The tetraethylammonium molecule could be located in the difference Fourier analysis yielding positions similar to its TPA counterpart in ZSM-5. Lattice constants of ZSM-8 are in the same range as for ZSM-5. Contrary results are related to incorrectly indexed powder patterns. Optical investigations of ZSM-5 and ZSM-8 crystals showed that the zeolites studied here are both twinned exhibiting differently shaped twin individuals.
Dimeric capsules of tetraurea calix[4]arenes. MD simulations and X-ray structure, a comparison
2002
The single crystal X-ray structure of a homodimer of a tetra(tolylurea) calix[4]arene including a tetraethylammonium cation as guest shows an expansion of the capsule and a distortion of its shape, in comparison to the structure of a similar dimer with an encapsulated benzene molecule. Thus, only 8 of 16 possible hydrogen bonds are present in the hydrogen bonded belt holding together the two hemispheres. The encapsulated cation is disordered over two equivalent positions with two methyl groups pointing to the equator, while two methyl groups pointing to the poles form CH–π interactions with the inner surfaces of the calixarene cavities. MD simulations are in agreement with the distorted X-r…
Azolium and acetate ions in DMF: Formation of free N-heterocyclic carbene. A voltammetric analysis
2016
In order to reveal the possible formation of free N-heterocyclic carbene (NHC) in DMF-azolium and acetate solutions, the proton exchange equilibrium between azolium cations and CH3COO− was investigated (by cyclic voltammetry) by adding CH3COOH or tetrabutylammonium acetate to DMF solutions of imidazolium or thiazolium salts of different acidity.The voltammetric analysis confirms that the deprotonation of the azolium cation by CH3COO− (with the formation of free NHC) is significant in the case of the more acidic thiazolium cations, while it is not effective with the less acidic imidazolium ones.Accordingly, the NHC-catalyzed benzoin condensation was carried out in DMF solutions of azolium sa…
Subsurface nitrate reduction under wetlands takes place in narrow superficial zones
2017
This study aims to investigate the depth distribution of the Nitrate Reduction Potential (NRP) on a natural and a re-established wetland. The obtained NRP provides a valuable data of the driving factors affecting denitrification, the Dissimilatory Nitrate Reduction to Ammonium (DNRA) process and the performance of a re-established wetland. Intact soil cores were collected and divided in slices for the determination of Organic Matter (OM) through Loss of Ignition (LOI) as well as Dissolved Organic Carbon (DOC) and NRP spiking nitrate in batch tests. The Nitrate Reduction (NR) was fitted as a pseudo-first order rate constant (k) from where NRPs were obtained. NR took place in a narrow superfi…
High Nitrogen Removal in a Constructed Wetland Receiving Treated Wastewater in a Cold Climate
2018
Constructed wetlands provide cost-efficient nutrient removal, with minimal input of human labor and energy, and their number is globally increasing. However, in northern latitudes, wetlands are rarely utilized, because their nutrient removal efficiency has been questioned due to the cold climate. Here, we studied nutrient retention and nitrogen removal in a boreal constructed wetland (4-ha) receiving treated nitrogen-rich wastewater. On a yearly basis, most of the inorganic nutrients were retained by the wetland. The highest retention efficiency was found during the ice-free period, being 79% for ammonium-nitrogen (NH4+-N), 71% for nitrate-nitrogen (NO3--N), and 88% for phosphate-phosphorus…
N2O emission in maize-crops fertilized with pig slurry, matured pig manure or ammonium nitrate in Brittany
2008
International audience; N2O is a potent greenhouse gas and solutions have to be sought to reduce its emission from agriculture. This work evaluates N2O emission from maize-crop (Zea mays) fields submitted to different organic or mineral fertilizers (pig slurry, matured pig manure or ammonium nitrate) in Brittany (France). N2O emission was evaluated along a year in two experimental sites receiving 110 or 180 kg N ha−1 as ammonium nitrate or pig slurry and 180 or 132 kg N ha−1 as ammonium nitrate or matured pig manure at Champ Noel and Le Rheu experimental plots, respectively. N2O emission was evaluated by interpolation method of periodic fluxes on the field scale and by simulation with NOE a…
Optimization of Nitrification Process by a Bacterial Consortium in the Submerged Biofiltration System with Ceramic Bead Carrier
2014
Laboratory-scale solid phase submerged system was developed to study the process of ammonium biodegradation. Ceramic beads were found to be an appropriate carrier material for the attachment of thePNN bacterial consortium (Pseudomonas sp., Nitrosomonas sp., Nitrobacter sp.) exhibiting nitrification/denitrification activity. This consortium was previously isolated from a biological activated sludge process at a fish factory wastewater treatment plant. Three organic amendments - molasses, humic acid extract, and malt extract - were used for the ceramic bead pretreatment. Molasses significantly enhanced (p<0.05) the process of bacteria attachment onto the ceramic carrier and further ammonium r…
Rapid evaluation of ammonium in different rain events minimizing needed volume by a cost-effective and sustainable PDMS supported solid sensor.
2020
Abstract The presence of ammonium ion in rainwater is due to atmospheric processes which involve its scavenging from gas phase and particulate matter. The fractionated samplings of rainwater can provide information about these processes and their potential sources. However, only a low sample volume may be available, which constrained the analysis in general and more particularly in situ mode. For minimizing this limitation, this work proposes a polydimethylsiloxane (PDMS)-salicylate sensor that produces a color change. The embedding of solid reagents into PDMS was optimized. Good analytical characteristics (analysis time of 10 min, sample volume of 500 μL, limit of detection 0.03 μgmL−1) we…