Reactive nitrogen compounds in the Arctic

Abstract. Total ammonium (tot-NH4+) and total nitrate (tot-NO3−) provide a chemically conservative quantity in the measurement of exchange processes of reactive nitrogen compounds ammonia (NH3), particulate ammonium (NH4+), nitric acid (HNO3), and particulate nitrate (NO3−), using the aerodynamic gradient method. Total fluxes were derived from concentration differences of total ammonium (NH3 and NH4+) and total nitrate (HNO3 and NO3−) measured at two levels. Gaseous species and related particulate compounds were measured selectively, simultaneously and continuously above a spruce forest canopy in south-eastern Germany in summer 2007. Measurements were performed using a wet-chemical two-point gradient instrument, the GRAEGOR. Median concentrations of NH3, HNO3, NH4−, and NO3− were 0.57, 0.12, 0.76, and 0.48 μg m−3, respectively. Total ammonium and total nitrate fluxes showed large variations depending on meteorological conditions, with concentrations close to zero under humid and cool conditions and higher concentrations under dry conditions. Mean fluxes of total ammonium and total nitrate in September 2007 were directed towards the forest canopy and were −65.77 ng m−2 s−1 and −41.02 ng m−2 s−1 (in terms of nitrogen), respectively. Their deposition was controlled by aerodynamic resistances only, with very little influence of surface resistances. Including measurements of wet deposition and findings of former studies at the study site on occult deposition (fog water interception), the total N deposition in September 2007 was estimated to 5.86 kg ha−1.

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Emissions of reactive nitrogen compounds (RNCs) from two vehicles with turbo-charged spark ignition engines over cold start driving cycles

Combustion Engines ◽

10.19206/ce-135811 ◽

2021 ◽

Author(s):

Joseph Woodburn

Keyword(s):

Cold Start ◽

Spark Ignition ◽

Reactive Nitrogen ◽

Nitrogen Compounds ◽

Ammonia Emissions ◽

Spark Ignition Engines ◽

Passenger Cars ◽

Test Procedures ◽

Automotive Market ◽

Driving Cycles

This paper reviews the emissions of reactive nitrogen compounds (RNCs) from modern vehicles fitted with spark ignition en-gines and three-way catalysts. Specific aspects of the pollutants involved – and their formation – are discussed. Cold start driving cycles are scenarios under which emissions of all four RNCs can be significant; the mechanisms behind emissions trends are ex-plored. Experimental data obtained from two vehicles tested over two different cold start driving cycles are presented and analysed. The use of gravimetric and molar metrics are explored. Ammonia, a species which is currently not regulated for passenger cars in any automotive market, is identified as forming the majority of the RNC emissions over the entire driving cycle. While ammonia emissions are strongly linked to aftertreatment system warmup and periods of high load, significant ammonia emissions were also measured under certain hot-running, low load conditions, and even at idle. For the majority of the duration of the test procedures employed, the RNC profile was dominated by ammonia, which accounted for between 69% and 86% of measured RNCs in the ex-haust gas. Emissions are compared to the available legislative precedents (i.e. emissions limits currently in force in various jurisdic-tions). Finally, possibilities for control of exhaust emissions of currently unregulated RNCs are briefly discussed.

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On-road emission measurements of reactive nitrogen compounds from heavy-duty diesel trucks in China

Environmental Pollution ◽

10.1016/j.envpol.2020.114280 ◽

2020 ◽

Vol 262 ◽

pp. 114280 ◽

Cited By ~ 16

Author(s):

Liqiang He ◽

Shaojun Zhang ◽

Jingnan Hu ◽

Zhenhua Li ◽

Xuan Zheng ◽

...

Keyword(s):

Reactive Nitrogen ◽

Nitrogen Compounds ◽

Heavy Duty ◽

Heavy Duty Diesel ◽

Diesel Trucks ◽

Road Emission

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Fate and transport of nitrogen in soils, sediment and water of the Lena Delta, Northeast Siberia

10.5194/egusphere-egu2020-21011 ◽

2020 ◽

Author(s):

Tina Sanders ◽

Matthias Fuchs ◽

Kirstin Dähnke

Keyword(s):

Organic Matter ◽

Arctic Ocean ◽

Inorganic Nitrogen ◽

Organic Matter Content ◽

The Arctic ◽

Nitrous Oxide Emissions ◽

Reactive Nitrogen ◽

Particulate Nitrogen ◽

Incubation Experiments ◽

Lena Delta

Soils and sediments in the Lena Delta in Northeast Siberia store large amounts of organic matter including organic bound nitrogen. This nitrogen is not directly available for plants and primary production, but can be remineralised in the soils or in sediments after erosion to the Lena River. Our study aims to estimate the load of reactive nitrogen from terrestrial sources into the Arctic Ocean. Therefore, water and sediment samples were collected along a transect (~200 km) from the centre of the Delta to the open Laptev Sea in summer 2019. On the collected samples, we will measure dissolved organic and inorganic nitrogen, particulate nitrogen and CN ratio. In addition, the 15N stable isotope values of these components will be determined to identify nitrogen sources, sinks and processes of nitrogen transformation. Additionally, we carried out incubation experiments in the field to determine the potential remineralisation rates of various soil types in Lena water and nutrients fluxes of the sediments. The load of dissolved inorganic nitrogen in the Lena water in the delta was very low and low nitrate and silicate concentration indicate uptake by phytoplankton. Outside the Lena Delta, a lens of nutrient depleted freshwater covered the salty Arctic Ocean water, which had higher loads of reactive nitrogen. The organic matter content of the soils and sediment is highly variable and ranges from 1 to 45 %. This organic matter is the source of reactive nitrogen, which is determined in incubation experiments and using nitrogen stable isotopes. We found that especially the unvegetated soils and sediment are sources of reactive nitrogen in the end of vegetation period, and are potentially sources of nitrous oxide emissions.

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Validation of nitrogen dry deposition modelling above a mixed forest using high-frequency flux measurements

10.5194/egusphere-egu2020-3559 ◽

2020 ◽

Author(s):

Pascal Wintjen ◽

Frederik Schrader ◽

Martijn Schaap ◽

Burkhard Beudert ◽

Christian Brümmer

Keyword(s):

Dry Deposition ◽

High Frequency ◽

Transport Model ◽

Mixed Forest ◽

Reactive Nitrogen ◽

Nitrogen Compounds ◽

Chemical Transport Model ◽

Flux Measurements ◽

Deposition Models

Reactive nitrogen (Nr) compounds comprise essential nutrients for plants. However, a large supply of nitrogen by fertilization through atmospheric deposition may be harmful for ecosystems such as peatlands and may lead to a loss of biodiversity, soil acidification and eutrophication. In addition, nitrogen compounds may cause adverse human health impacts. Large parts of Nr emissions originate from anthropogenic activities. &#160;Emission hotspots of &#931;Nr, i.e. the sum of all Nr compounds, are related to crop production and livestock farming (mainly through ammonia, NH3) and fossil fuel combustion by transport and industry (mainly through nitrogen oxides, NO2 and NO). Such additional amount of Nr will enhance its biosphere-atmosphere exchange, affect plant health and can influence its photosynthetic capacity. Therefore, it is necessary to thoroughly estimate the nitrogen exchange between biosphere and atmosphere.For measuring the nitrogen mixing ratios a converter for reactive nitrogen (TRANC: Total Reactive Atmospheric Nitrogen Converter) was used. The TRANC converts all reactive nitrogen compounds, except for nitrous oxide (N2O), to nitric oxide (NO) and is coupled to a fast-response chemiluminescence detector (CLD). Due to a low detection limit and a response time of about 0.3s the TRANC-CLD system can be used for flux calculation based on the eddy covariance (EC) technique. Flux losses, which are related to the experimental setup, different response characteristics and the general high reactivity of most N gases and aerosols, occur in the high frequency range. We estimated damping factors of approximately 20% with an empirical cospectral approach.For getting a reliable prediction of &#931;Nr fluxes through deposition models, long-term flux measurements offer the possibility to verify the nitrogen uptake capacity and to investigate exchange characteristics of &#931;Nr in different ecosystems.In this study, we compare modelled dry deposition fluxes using the deposition module DEPAC (DEPosition of Acidifying Compounds) within the chemical transport model LOTOS-EUROS (LOng Term Ozone Simulation &#8211; EURopean Operational Smog) against &#931;Nr flux measurements of the TRANC-CLD for a remote mixed forest site with hardly any local anthropogenic emission sources. This procedure allows to determine the background load and the natural exchange characteristics of nitrogen under low atmospheric concentrations. Therefore, the broad-scale dry deposition predicted directly by LOTOS-EUROS was compared to site-specific modelling results obtained using measured meteorological input data as well as the directly measured &#931;Nr fluxes. In addition, the influence of land-use weighting in LOTOS-EUROS was examined. We further compare our results to &#931;Nr deposition estimates obtained with canopy budget techniques. Measured &#931;Nr dry deposition at the site was 4.5 kg N ha-1 yr-1, in close agreement with modelled estimates using DEPAC with measured drivers (5.2 kg N ha-1 yr-1) and as integrated in the chemical transport model LOTOS-EUROS (5.2 kg N ha-1 yr-1 to 6.9 kg N ha-1 yr-1 depending on the weighting of land-use classes).Our study is the first one presenting 2.5 years flux measurements of &#931;Nr above a remote mixed forest. Further verifications of long-term flux measurements against deposition models are useful to improve them and result in better understanding of exchange processes of &#931;Nr.

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