Ammonia

About: Ammonia is a research topic. Over the lifetime, 16217 publications have been published within this topic receiving 271940 citations. The topic is also known as: NH3 & azane.

Nitrification and its influence on biogeochemical cycles from the equatorial Pacific to the Arctic Ocean

Abstract: We examined nitrification in the euphotic zone, its impact on the nitrogen cycles, and the controlling factors along a 7500 km transect from the equatorial Pacific Ocean to the Arctic Ocean. Ammonia oxidation occurred in the euphotic zone at most of the stations. The gene and transcript abundances for ammonia oxidation indicated that the shallow clade archaea were the major ammonia oxidizers throughout the study regions. Ammonia oxidation accounted for up to 87.4% (average 55.6%) of the rate of nitrate assimilation in the subtropical oligotrophic region. However, in the shallow Bering and Chukchi sea shelves (bottom ⩽67 m), the percentage was small (0–4.74%) because ammonia oxidation and the abundance of ammonia oxidizers were low, the light environment being one possible explanation for the low activity. With the exception of the shallow bottom stations, depth-integrated ammonia oxidation was positively correlated with depth-integrated primary production. Ammonia oxidation was low in the high-nutrient low-chlorophyll subarctic region and high in the Bering Sea Green Belt, and primary production in both was influenced by micronutrient supply. An ammonium kinetics experiment demonstrated that ammonia oxidation did not increase significantly with the addition of 31–1560 nm ammonium at most stations except in the Bering Sea Green Belt. Thus, the relationship between ammonia oxidation and primary production does not simply indicate that ammonia oxidation increased with ammonium supply through decomposition of organic matter produced by primary production but that ammonia oxidation might also be controlled by micronutrient availability as with primary production.

Flow-injection analysis with fluorescence detection for the determination of trace levels of ammonium in seawater

Abstract: A method using flow-injection, gas-diffusion, derivatisation and then fluorescent detection has been established for ammonium ion determination in seawater. The fluorescent derivative formed by reacting ortho-phthaldialdehyde (OPA) and sulfite with ammonia gives high sensitivity while removing potential interferences. This is required to measure the low concentrations of ammonium often seen in the open ocean. The experimental conditions (flow-rate, reagent concentrations, membrane configurations, etc.) were manipulated to improve performance. For a sample throughput of 30 samples h−1, the limit of detection was 7 nM, the coefficient of variation was 5.7% at 800 nM, and the calibration curve was linear to at least 4 μmol L−1. Interferences were minimised by a gaseous diffusion step. Volatile small molecular-weight amines as interferents were discriminated against by this method. They neither passed through the membrane as efficiently as ammonia, nor reacted as readily with OPA when sulfite was the reductant. Contamination by ammonia from laboratory and shipboard sources complicates application of the method to natural waters, especially measurement of low concentrations (<100 nM) in open-ocean waters. Steps to overcome contamination are described in detail. Some results are presented for ammonium determination in Southern Ocean and Huon Estuary (Tasmania) waters.

The assimilation by plants of various forms of nitrogen

Abstract: SOME YEARS AGO (1926) the author became interested in the possible effect of hydrogen-ion concentration on the assimilation by plants of nitrogen as ammonia or as nitrate. In an experiment 2 designed to attack this problem, mineral nutrient solutions containing dextrose were prepared in which the nitrogen was furnished as ammonium nitrate, ammonium sulfate, or sodium nitrate, and the hydrogen-ion concentration of the solutions was varied by intervals of 0.2 or 0.3 pH from pH 4.0 to pH 7.6. The organism used, Rhizopus nigricans, grew well at all reactions in the solutions which contained ammonium sulfate or ammonium nitrate (somewhat better in the more alkaline solutions) but not at all in those which contained sodium nitrate. This confirmed earlier reports (Bach, 1927; Ritter, 1909) of the inability of Rhizopus nigricans to assimilate nitrogen as nitrate (at least under ordinary laboratory conditions) and encouraged the writer to plan an investigation of the ability of organisms to use various forms of nitrogen. Circumstances made it impossible to carry out the investigation as planned. Nevertheless, the preliminary work may be of sufficient interest to encourage further investigations in this field. A survey of the literature (space precludes summarizing all the available literature) suggested to the author that organisms may be arranged in four groups 3 according to their ability to assimilate various forms of nitrogen. GROIJP I. NITROGEN-FIXING ORGANISMS. These organisms are capable of assimilating gaseous nitrogen and also nitrates, ammonium salts, and certain organic nitrogenous compounds. Attention should be called to the assumption that everv organism capable of fixing gaseous nitrogen is capable also of assimilating nitrogen in the form of nitrates, ammonium compounds, and 'suitable forms of organic nitrogen. Though the evidence available supports it, this assumption needs further confirmation since considerably more attention has been devoted to the relation to gaseous nitrogen of the organisms generally accepted as nitrogen fixers than to their ability to assimilate combined nitrogen. However, it is generally agreed (Waksman, 1927; Lohnis, 1926; Stephenson, 1930) that Azotobacter can assimilate nitrogen as nitrates, as ammonium salts. and as orgLanic nitrogen (for