Ulrich Dämmgen

Ammonia Deposition Near Hot Spots: Processes, Models and Monitoring Methods

Atmospheric reduced nitrogen (NHx) mainly originates from hot spots, which can be considered as intensive area or point sources. A large fraction of the emitted NHx may be recaptured by the surrounding vegetation, hence reducing the contribution of these hot spots to long-range transport of NHx. This paper reviews the processes leading to local recapture of NHx near hot spots, as well as existing models and monitoring methods. The existing models range from research models to more operational models that can be coupled with long-range transport model provided the necessary information on emissions is available. Local recapture of NH3 ranges from 2% to 60% within 2 km of a hot-spot and it is sensitive to source height atmospheric stability, wind speed, structure of the surrounding canopies, as well as stomatal absorpton, which mainly depends on green leaf area index and stomatal NH3 compensation point of vegetation, and finally, cuticular deposition, which depends primarily on vegetation wetness. The main uncertainties and limitations on NHx recapture models and monitoring techniques are discussed. Due to the decrease of sulphur and nitrogen oxides emissions under a series of UNECE protocols, reduced nitrogen (NHx), has become the dominant pollutant in Western Europe contributing to acidification of ecosystems (e.g. Vestreng and Storen 2000). At the global scale NHx and NOx emissions are comparable, although large uncertainties exist on NHx emissions (Dentener and Crutzen 1994; Bouwman et al. 1997). Moreover, NHx deposition, with other nitrogen (N) deposition, leads to eutrophication and changes in the biodiversity of semi-natural ecosystems (Van Breemen and van Dijk 1988; Roelofs et al. 1985; Fangmeier et al. 1994; Krupa 2003; EEA 2003). Although atmospheric ammonia (NH3) is not a greenhouse gas (GHG), deposition of NHx may lead to increased GHG emissions (N2O) (Melillo et al. 1989) or reduced consumpton of CH4. Additionally, ammonium sulphate aerosols (NH4)2SO4, contribute to half of the negative radiatve forcing of the atmosphere due to aerosols (Houghton et al. 2001; Adams et al. 2001), as well as contriuting to impacts of secondary aerosol on human health.

The Atmospheric Sulphur Cycle

Emission, transmission and deposition of natural and anthropogenic air-borne S species are described with regard to their relevance to agriculture. Diurnal, annual and spatial patterns of emissions, concentrations and depositions are dealt with in detail. Trends of measured concentrations and depositions are presented. In Europe, the decrease of SO2 emissions has led to a considerable reduction in S deposition both from gaseous SO2 and particulate SO4 and SO3. All other S species are irrelevant for agricultural S balances. For agriculture, future depositions of sulphate S will be in the range of 5 to 10 kg ha−1 a−1. Depositions of gaseous SO2 will be in the same order of magnitude. As a considerable fraction of all S species is deposited outside the vegetation period, the future total plant available S deposition will be less than 10 kg ha−1 a−1 S.

Response of a grassland ecosystem to air pollutants: III—The chemical climate: Vertical flux densities of gaseous species in the atmosphere near the ground

The establishment of element balances for ecosystems presupposes a knowledge of the amounts of the respective element exchanged between the ecosystem and the atmosphere near the ground by determining their vertical flux densities. Any adequate approach to calculate flux densities of gaseous species in the atmosphere has to use micrometeorological techniques. The authors applied the ratiometric method, which is described in detail. Results of flux density calculations for sulfur dioxide, nitrogen dioxide, nitric oxide and ammonia obtained during two years of measurement are discussed with regard to their role in element balances. Flux densities and deposition velocities of ozone are interpreted as functions of meteorological parameters as well as of the biological activity of the canopy. The latter is characterized by the flux density and flux-to-concentration ratio of carbon dioxide.

Response of grassland ecosystem to air pollutants: I—Experimental concept and site of the braunschweig grassland investigation program

Between 1984 and 1991 in Braunschweig (South-east Lower Saxony, Germany) experiments concerning the influence of chronic stress by air pollutants to a permanent grassland ecosystem were performed, the conceptual background of which is dealt with in this paper. The site itself, the management practices and treatments applied, and the physical climate are described in detail.

Calculations of gaseous and particulate emissions from German agriculture 1990 - 2012 : Report on methods and data (RMD) Submission 2014

The report at hand (including a comprehensive annex of data) serves as additional document to the National Inventory Report (NIR) on the German green house gas emissions and the Informative Inventory Report (IIR) on the German emissions of air pollutants (especially ammonia). The report documents the calculation methods used in the German agricultural inventory model GAS-EM as well as input data, emission results and uncertainties of the emission reporting submission 2014 for the years 1990 - 2012. In this context the sector Agriculture comprises the emissions from animal husbandry and the use of agricultural soils. As required by the guidelines, emissions from activities preceding agriculture, from the use of energy and from land use change are reported elsewhere in the national inventories. The calculation methods are based in principle on international guidelines for emission reporting and have been continuingly improved during the past years. This concerns especially the calculation of energy requirements, feeding and the N balance of the most important animal categories. In addition, technical mitigation measures such as air scrubbing and digestion of slurry have been taken into account. [...]

Response of a grassland ecosystem to air pollutants. V. A toxicological model for the assessment of dose–response relationships for air pollutants and ecosystems

Abstract The principles of the interaction between gaseous air pollutants and ecosystems are investigated using a pharmacokinetic model. This model illustrates the importance of pollutant flux determinations by measurements and/or by modeling in order to provide a description of the adequate dose entity. It serves as a mechanistic base for the present discussion of flux-based versus concentration-based air quality guidelines. Consequently, the results obtained from chamber experiments can only be transferred to ambient conditions, if the function relating fumigation concentrations to absorbed fluxes is established. Adequate dose–response relationships for airborne pollutants and plant/soil systems presuppose a combination of flux measurements, free-air exposure systems and Soil-Vegetation-Atmosphere Transfer models.

Response of a grassland ecosystem to air pollutants. II: The chemical climate : fluxes of sedimenting airborne matter

Measurement of the deposition of sedimenting particles requires a sampling device, which avoids simultaneous deposition of gases and aerosols to the collection surface. A sampler constructed for the purpose of collecting rain and sedimenting particles is described and characterized in detail, in particular with regard to its collection efficiency for rain. Its collection properties for gases and aerosols are shown to be negligible. From two years of sampling at different heights it was found that resuspension of particles and co-condensation of gases near the plant canopy may lead to a major overestimation of bulk deposition. As a consequence, the extension towards the canopy of the constant flux layer for sedimenting particles has to be determined experimentally. Bulk deposition of sodium, potassium, magnesium, calcium, lead, copper, cadmium, manganese, iron, ammonium, nitrate, phosphate, sulfate, total sulfur and chloride at Braunschweig-Völkenrode, Southeast Lower Saxony, Germany, were recorded for six years. During this period a considerable decrease was observed in the deposition of lead, cadmium, nitrate, sulfate and total sulfur.

Trace gas emissions from German agriculture as obtained from the application of simpler or default methodologies

For the assessment of emission inventories matching pairs of activities (emission explaining variables) and emission factors are used. Simpler and detailed methodologies are proposed within the emission inventory handbooks. The data sets needed to serve the detailed methodologies have not been at public disposal so far. Therefore, this paper investigates the applicability of simpler methodologies to the statistical data sets of activities officially available in Germany. The statistical data base for the assessment of emissions from fertilised soils is adequate if one assumes that fertilisers sold in one financial year are applied in the same year. For grassland, statistical data describing the actual management do not exist. Lack of nitrogen inputs with crop residues and due to nitrogen fixation make it impossible to deduce the respective emissions. The assessment of indirect emissions due to reactions of leached nitrogen is also impossible. For extensively managed grasslands, data concerning fertiliser application or grazing are missing when calculating emissions. The determination of emissions from organic soils presupposes the knowledge of both the area concerned and the degree of mineralisation which has been attained at the time of the inventory. The results of the biennial animal census meet the requirements of the simpler methodologies. However, the assumptions made to evaluate the mean emission factors are not correct in many cases, as far as animal performance, housing, storage and application of animal excreta are concerned. The simpler methodologies are biassed, as the emission factors are (Northwest) European means. Changes in the raising of statistical data make the construction of meaningful time-series difficult.

Description, assessment and meaning of vertical fluxes of matter within ecotopes: a systematic consideration.

Ecotopes are the structural elements of landscapes for which matter and energy balances can be derived from measurements. Vertical flux densities are the typical entities governing their structure and function. Potential flux densities in ecotopes are discussed in detail using a complex circuit diagram that differentiates between transport and reaction columnar resistors. From this the locations and methods of measurement are deduced. Determination of flux densities between troposphere and phytosphere/pedosphere is restricted to the constant flux layer, by theory and practice.

Review of Published Studies Estimating the Abatement Efficacy of Reduced-Emission Slurry Spreading Techniques

The Gothenburg Protocol to reduce atmospheric pollution drawn up by the United Nations Economic Commission for Europe (UNECE) Convention on Long-Range Transboundary Air Pollution (LRTAP) limits national emissions of ammonia (NH 3 ). To help meet this agreement, the EU has agreed a National Emissions Ceilings Directive (NECD), under which the UK target for NH 3 emission is a maximum of 297 × 10 t NH 3 . By 2007, large pig and poultry units in the EU will be required to reduce NH 3 emission in consequence of the EU Directive on Integrated Pollution Prevention and Control (EEC 1996). Webb and Misselbrook (2004) estimated that c. 27 × 10 t NH 3 -N, c. 12% of UK NH 3 -N emissions from livestock production, arose following the application of slurries to land. Much effort has been directed toward reducing NH 3 emission following slurry application, however, few studies of reduced-emission slurry spreading techniques have been carried out using field-scale equipment and few balanced comparisons have been made of more than one abatement technique. In consequence it was considered useful to review published data.