Flux measurements of NHx and NOy with a dual-channel converter above an intensively managed grassland on peat

<p>We designed a fast-response two-channel converter called NO<sub>y</sub>-TRANC for eddy covariance measurements of reduced and oxidized reactive nitrogen compounds (N<sub>r</sub>). It is a combination of the Total Reactive Atmospheric Nitrogen Converter (TRANC), which converts all reactive forms of nitrogen (ΣN<sub>r</sub>), except for nitrous oxide (N<sub>2</sub>O) and molecular nitrogen (N<sub>2</sub>), to nitrogen monoxide (NO), and a heated gold catalyst, which converts NO<sub>y</sub> to NO. NO<sub>x</sub>, which is the sum of NO and nitrogen dioxide (NO<sub>2</sub>), and higher oxidized nitrogen compounds are described by the term NO<sub>y</sub>. The NO<sub>y</sub>-TRANC is coupled to a two-channel chemiluminescence detector (CLD) for measuring NO. Due to a high sampling frequency and a fast response time, the system meets the requirements for flux calculation based on the eddy-covariance method. With this setup, a separation of ΣN<sub>r</sub> fluxes in reduced and oxidized nitrogen can be done.</p><p>We conducted flux measurements at a typically deeply drained, intensively managed grassland site on peat in an intensive dairy region in Northwest Germany for one year. ΣN<sub>r</sub> concentration was 12.4 ppb and NO<sub>y</sub> concentration was 6.3 ppb on average. We observed mostly emission fluxes at the site after the first fertilization in early spring. The winter month were characterized by slight nitrogen dry deposition. Monthly median of ΣN<sub>r</sub> fluxes ranged from -8 to 57 ng N m<sup>-2</sup>s<sup>-1</sup> with the exchange being enhanced during summer. We found that ΣN<sub>r</sub> and NO<sub>y</sub> dry emission were comparatively higher under dry conditions, i.e., low air humidity and soil moisture. The emission factors of applied nitrogen after the respective fertilization released as NH<sub>x</sub> can reach up to 2.0%.</p><p>Site management included five fertilization events and five grass cuts. The first fertilization event was at the end of March starting with mineral fertilizer followed by organic fertilizer a week later.  The fertilization scheme was the same for second and third event, but approximately two days were between the application of the fertilizer types. The second fertilization was at the end of May, subsequent fertilizations were done in intervals of 4-5 weeks. Only for the fourth and fifth event, organic fertilizer was used. Organic fertilizer was injected in slits made by v-shaped discs, mineral fertilizer was spread on the soil surface. The emission factor was lower after the first fertilization event compared to events in summer probably indicating a beginning nitrogen saturation after the first fertilization.</p><p>Our study demonstrates the application of a novel measurement technique for the determination reactive nitrogen compounds and gives insight into the exchange characteristics of reactive nitrogen under a common agricultural management.</p>

Sphagnum response to nitrogen deposition and nitrogen saturation – a meta-analysis

Background: Sphagnum plants are sensitive to nitrogen deposition changes. However, previous literature is inconclusive on the response of Sphagnum species to nitrogen deposition, little is known about the nitrogen saturation of Sphagnum growth, and the effects of climatic, spatial and fertilization variables on the response of Sphagnum plants are still unclear.Methods: We conducted a meta-analysis of 66 experiments on nitrogen application to Sphagnum plants. The combined effect size of a random-effects model was used to analyze the effect of nitrogen deposition on Sphagnum growth. A mixed-effects model was established to determine the significance of each factor for the response of Sphagnum plants to nitrogen deposition. The nitrogen saturation value for Sphagnum species was obtained by fitting the regression function.Results: Sphagnum growth is promoted by moderate nitrogen deposition, and when nitrogen deposition exceeds the saturation value, Sphagnum growth is inhibited. The current nitrogen deposition saturation value for Sphagnum species is 19.34 kg ha-2 yr-1 globally and varies in different latitudinal zones. When Sphagnum plants are affected by excessive nitrogen deposition, low-water-table microhabitats and excessive temperature and precipitation can all exacerbate Sphagnum growth inhibition.Conclusions: Excessive nitrogen deposition will inhibit Sphagnum growth, and the nitrogen saturation values we obtained for Sphagnum species can be used to adjust fertilizer applications to protect Sphagnum plants from excessive chemical fertilizer application.

SHS Processing of cyclone ferrosilicium dust

This paper offers a review of waste disposal techniques for disposing of dust generated by ferrosilicium industry. The paper examines the possibility of nitriding cyclone ferrosilicium dust through application of a high-pressure infiltration combustion process. The authors describe the key regularities of the ferrosilicium nitride SH-synthesis and demonstrate the potential applicability of the new technique. The findings show that the high-grade dusts resultant from ferrosilicium crushing and screening operations and identified as FeSi65 and FeSi75 consist of iron and silicon disilicides, whereas the dust coming from a 45 % alloy consists of FeSi2 and FeSi. Interaction of the initial alloys with nitrogen in a high-pressure combustion mode results in the generation of high-nitrogen material with the β-phase of silicon nitride at the basis. Such material can be used as unmolded refractory material for application in blast furnaces. Or it can be used to produce nitrogen containing steels, such as transformer steel. Thus, the dust grade PUD-75 would be optimum for application in refractories, and the dust grade PUD-65 — as an alloying component. The paper demonstrates that the composition of the cyclone ferrosilicium dust combustion products can be changed by changing the nitrogen pressure and the dispersity of the burden. Silicon nitride constitutes the main component in the composition of the combustion products (60–85%). It will be iron that will serve as a binder in this composite at the highest nitrogen saturation degree, whereas in the case of a lower nitrogen saturation degree it will iron silicides. It was found that nitrogen is absorbed in two stages during layer-by-layer combustion of ferrosilicium alloys. Passing of the combustion front is followed by the process of bulk post-reaction, during which the share of absorbed nitrogen can increase by 30%. This phenomenon explains why there exists no dependence between the concentration of nitrogen in the combustion products and the applied pressure.

Analysis of Species Characteristics of Laboratory Animals in Reaction to Hyperbaric Environmental Conditions

The aim of this work is to determine the dynamics of nitrogen saturation in small laboratory animals. Nitrogen was chosen as a model gas in this study because of its availability and characteristics, as it is not metabolised and is subject to passive diffusion. By subjecting different species of animals to hyperbaric exposures of increasing time and pressure, the study aimed to identify how rapid a decompression was possible to achieve an outcome that saw 50% of the animals surviving the ensuing acute decompression sickness. The basic parameters of hyperbaric exposure - pressure and time - made it possible to describe the saturation phenomena on the basis of partial saturation periods and to show whether a small animal organism can be considered as a single compartment model.

Isothermal treatment of nitrided layers formed on steels

This work was aimed at investigating the formation of nitrided layers during the isothermal transformation (austempering) and at describing the formed nitrided layer properties. The tested steels were characterized by a different content of carbon and alloying elements. In the case of the isothermal transformation, 4 variants of heat treatment parameters of nitrided layers were applied. The heat treatment differed in the austenitizing temperature (750°C–860°C) and the isothermal transformation temperature (390°C- 420°C). The microstructure and the mechanical properties (hardness) of the nitrided layers formed after the heat treatment processes were determined. After the nitriding process, during 30 hours in the nitriding atmosphere consisting only of ammonia, the high nitrogen saturation in the surface zone of the layers was obtained. The nitrided layers, after the heat treatment processes, were char-acterized by the diversified thickness, as evidenced by the hardness distributions at their cross-sections.