Tavs Nyord

Application of PTR-MS for measuring odorant emissions from soil application of manure slurry.

Odorous volatile organic compounds (VOC) and hydrogen sulfide (H2S) are emitted together with ammonia (NH3) from manure slurry applied as a fertilizer, but little is known about the composition and temporal variation of the emissions. In this work, a laboratory method based on dynamic flux chambers packed with soil has been used to measure emissions from untreated pig slurry and slurry treated by solid-liquid separation and ozonation. Proton-transfer-reaction mass spectrometry (PTR-MS) was used to provide time resolved data for a range of VOC, NH3 and H2S. VOC included organic sulfur compounds, carboxylic acids, phenols, indoles, alcohols, ketones and aldehydes. H2S emission was remarkably observed to take place only in the initial minutes after slurry application, which is explained by its high partitioning into the air phase. Long-term odor effects are therefore assessed to be mainly due to other volatile compounds with low odor threshold values, such as 4-methylphenol. PTR-MS signal assignment was verified by comparison to a photo-acoustic analyzer (NH3) and to thermal desorption GC/MS (VOC). Due to initial rapid changes in odorant emissions and low concentrations of odorants, PTR-MS is assessed to be a very useful method for assessing odor following field application of slurry. The effects of treatments on odorant emissions are discussed.

Contribution of livestock H 2 S to total sulfur emissions in a region with intensive animal production

Hydrogen sulfide (H2S) from agricultural sources is generally not included in sulfur emission estimates even though H2S is the major sulfur compound emitted from livestock production. Here we show that in a country with intensive livestock production (Denmark), agriculture constitute the most important sulfur source category (~49% of all sources of sulfur dioxide), exceeding both the production industry and energy categories. The analysis is based on measurements of H2S using proton-transfer-reaction mass spectrometry. National emissions are obtained using ammonia as a reference pollutant with the validity of this approach documented by the high correlation of ammonia and hydrogen sulfide emissions. Finisher pig production is the most comprehensively characterized agricultural source of sulfur and is estimated to be the largest source of atmospheric sulfur in Denmark. The implication for other locations is discussed and the results imply that the understanding and modeling of atmospheric sulfate sources should include agricultural H2S.Hydrogen sulfide (H2S) from agricultural sources is generally omitted from sulfur emission estimates despite its abundance in livestock emissions. Here, the authors show that agriculture is the most important source of sulfur in Denmark using proton-transfer-reaction mass spectrometry measurements of H2S.

Real-time quantification of emissions of volatile organic compounds from land spreading of pig slurry measured by PTR-MS and wind tunnels

Volatile organic compounds (VOC) and hydrogen sulfide are emitted from land spreading of manure slurry to the atmosphere and contribute to odour nuisance, particle formation and tropospheric ozone formation. Data on emissions is almost non-existing partly due to lack of suitable quantitative methods for measuring emissions in full scale. Here we present a method based on application of wind tunnels for simulation of air exchange combined with the use of online mass spectrometry (PTR-MS). The focus was on odorous VOC but all relevant VOC were included. A method for quantification of VOC emission based on calculated proton-transfer reaction rate constants was validated by comparison to reference concentrations for typical VOC emitted from pig manure slurry. Wall losses of volatile sulfur compounds in the wind tunnels were assessed to be insignificant and recoveries >95% were observed for these compounds. An influence of air exchange rate was clearly observed highlighting the need to identify realistic air exchange rates for future application of the method. Emission data was obtained for spreading of pig manure slurry as an example of an important source of gases. Emissions were monitored for ~37u202fh following land spreading and time-resolved emission data was presented for the first time. Highest emissions were observed for short-chain volatile carboxylic acids (C2-C6) with acetic acid being the most abundant compound. Emission peaks were observed immediately following application and were followed by declining emissions until the second day at which emissions reached a second peak for several compounds. This second emission peak was speculated to be caused by a temperature-induced diurnal effect. Emissions of volatile sulfur compounds occurred on a short time-scale and ceased shortly after application. Odour activity values were dominated by C4-C5 carboxylic acids and 4-methylphenol with a less pronounced influence of 4-methylphenol on day 2.

Developing a New Management Tool—a Holistic View on the Nitrogen Cycle

New agricultural technologies can reduce the emissions of ammonia associated with e.g. manure spreading. Reduced emissions to the atmosphere have the potential to limit the negative impacts of reactive nitrogen (Nr) on terrestrial ecosystems and human health. But could the new technologies transfer more Nr to the watershed instead and hence lead to increased eutrophication in the aquatic environment? In order to answer questions like this a holistic approach is necessary. Therefore a new management tools is under development at the Danish Center for Energy and Environment (DCE), Aarhus University, where models describing the fate of Nr in the relevant compartments (atmosphere, watershed and aquatic systems) are linked.

Testing a New Holistic Management Tool for Nitrogen—Environmental Impacts of Using Manure Acidification in the Danish Agricultural Sector

The fate of anthropogenic reactive nitrogen (N) is often described as a cascade of different nitrogen forms and effects throughout the environment. In order to describe the fate in detail, a holistic approach covering the flow between the main environmental compartments is needed. Therefore a new management tools has been setup for an area in Denmark. A holistic approach is attempted by linking models for the main compartments (atmosphere, watershed and aquatic) and including a common emission scenario. The scenario describes a new technique for reducing ammonia emissions and at the same time increase N availability for crops using acidification of liquid manure and use of air cleaners in pig and poultry houses. Here the first results from a pilot study in Northern Jutland, Denmark, will be presented.