Analysis of Emissions from Cattle Slurry using Time of FlightChemical Ionisation Mass Spectrometry (TOF-CIMS)

The use of animal-based fertilizers in the forms of manure and slurry is widespread throughout Europe. The process of spreading manure and slurry results in large emissions of greenhouse gases as well as inorganic gases and volatile organic compounds (VOCs). The non-methane VOCs emitted from manure and slurry are not well characterized, even though they are expected to result in the formation of important secondary pollutants such as ozone and secondary organic aerosols (SOA).

 

In this study, we conducted an initial small-scale laboratory measurement of VOCs emitted by cattle slurry using a Time of Flight Chemical Ionisation Mass Spectrometer. Dry purified air was passed through a small chamber containing the slurry and into the instrument, which was operated using both C₆H₆⁺ and I^- as reagent ions in order to detect a large range of oxygenated and hydrocarbon VOCs.

 

Using the I^- reagent ion, a number of low molecular weight carboxylic acids were detected, along with some phenolic compounds and hydrogen disulfide. A much larger number of compounds was detected using the C₆H₆⁺reagent ion, including the same phenolic compounds and a range of nitrogen-containing species. The timescales of the emitted species showed considerable variation, with some, e.g. hydrogen disulfide, being very intense and short-lived, and others, e.g. phenol, being continuously emitted at a roughly constant rate for several hours. Further work is currently underway to understand the factors controlling the nature of these emissions, their reactivity and SOA formation.