Adaptation of a speciation sampling cartridge for measuring ammonia flux from cattle feedlots using relaxed eddy accumulation

作者：Baum K A; Ham J M^*

来源：Atmospheric Environment, 2009, 43(10): 1753-1759.

DOI：10.1016/j.atmosenv.2008.12.021

• Animal feeding operation
• NH(3) emission
• Aerosol fluxes
• Denuder
• REA

Improved measurements of ammonia losses from cattle feedlots are needed to quantify the national NH(3) emissions inventory and evaluate management techniques for reducing emissions. Speciation cartridges composed of glass honeycomb denuders and filter packs were adapted to measure gaseous NH(3) and aerosol NH(4)(+) fluxes using relaxed eddy accumulation (REA). Laboratory testing showed that a cartridge equipped with four honeycomb denuders had a total capture capacity of 1800 mu g of NH(3). In the field, a pair of cartridges was deployed adjacent to a sonic anemometer and an open-path gas analyzer on a mobile tower. High-speed valves were attached to the inlets of the cartridges and controlled by a datalogger so that up- and down-moving eddies were independently sampled based on direction of the vertical wind speed and a user-defined deadband, Air flowed continuously through the cartridges even when not sampling by means of a recirculating air handling system. Eddy covariance measurement of CO(2) and H(2)O, as measured by the sonic and open-path gas analyzer, were used to determine the relaxation factor needed to compute REA-based fluxes. The REA system was field tested at the Beef Research Unit at Kansas State University in the summer and fall of 2007. Daytime NH(3) emissions ranged between 68 and 127 mu g m(2) s(-1); fluxes tended to follow a diurnal pattern correlated with latent heat flux. Daily fluxes of NH(3) were between 2.5 and 4.7 g m(2) d(-1) and on average represented 38% of fed nitrogen. Aerosol NH(4)(+) fluxes were negligible compared with NH(3) emissions. An REA system designed around the high-capacity speciation cartridges can be used to measure NH(3) fluxes from cattle feedlots and other strong sources. The system could be adapted to measure fluxes of other gases and aerosols.

• 出版日期2009-3