In 2012, roughly 8.2% of all feedlot animals in the U.S. were in Colorado (Food & Water Watch 2015). With just under a quarter of a million head of beef cattle, the manure from Weld County, CO alone is equivalent to the sewage generated from 24.5 million people. More cattle means more excrement and more excrement leads to high emissions of undesired gases. One of the many emitted gases from cattle excrement is ammonia, which comes from urine.
I study the transport of ammonia gases through the atmosphere, which often end up in Rocky Mountain National Park by settling as gaseous ammonia or getting into clouds and precipitating out as ammonium-containing compounds. One effect of too much nitrogen is fertilization of the mountain ecosystems (think “plant fertilizers”), which are not used to having so much available nitrogen. Ultimately, this nutrient loading can lead to loss of biodiversity in fragile mountain ecosystems–some species are able to adapt quickly to large amounts of nutrients better than others.
In 2007, a Memorandum of Understanding amongst state and federal agencies, known as the Nitrogen Deposition Reduction Plan (NDRP), was signed to work towards reducing nitrogen emissions along the Front Range of Colorado. The NDRP outlines a series of actions to reduce nitrogen deposition levels below a threshold that is harmful to mountain ecosystems by 2032.
My work of studying nitrogen transport, as a result of the NDRP, began in 2011 as a Masters student at Colorado State University in the Department of Atmospheric Science.
Specifically, I study the transport of emissions from cattle feedlots in eastern Colorado into the Rocky Mountain National Park via upslope winds. I use a weather model to study how pollutants move from feedlots into clouds and deposit on the Rocky Mountains (blue arrow in the figure above).
I work with the Weather Research and Forecasting (WRF) model to study the importance of the convective component (red arrow in the figure above) of ammonia/ammonium transport during summertime deposition events. Summers along the Front Range of Colorado are unique because surface winds blow from east to west and carry pollutants from the plains (including urban pollution as well as ammonia from feedlots and croplands) into the Rocky Mountains. Below is an animation* of output (18-20 August 2006) from the WRF model. The figure below the animation is a wind rose from observations of wind speed and direction for 18-20 August 2006 MDT. More information on wind roses and the wind observations can be found at the Iowa Environmental Mesonet website.
*A passive tracer (colored) and cloud fraction (gray) are shown above. The time step between each frame, which takes 1 second real-time, is 10 minutes. Imagery was produced by VAPOR (www.vapor.ucar.edu), a product of the Computational Information Systems Laboratory at the National Center for Atmospheric Research.