ARL initiates Atmospheric Deposition of Ammonia study (ADAM)
Air Resources Laboratory (ARL) has partnered with the University of Tennessee (UT) to launch a series of experiments to quantify ammonia air-surface exchange over an agricultural ecosystem. The experiments are being conducted through the end of April 2010 at the UT Plant Sciences Unit near Knoxville, TN with various real-time and integrated measurement techniques. ARL scientists from the Atmospheric Turbulence and Diffusion Division have installed and will operate a suite of instrumentation, including annular denuder systems; laser spectroscopy analyzers; ion mobility spectrometers; and supplementary micrometeorological equipment. The overall goal of the study is to determine the suitability and robustness of the ammonia measurement systems to quantify exchange processes of ammonia over crops, especially post-fertilization. The Plant Sciences Unit manages experimental plots of agronomic and horticultural crops through routine distribution of urea fertilizers, which have been shown to increase local ammonia emissions by several orders of magnitude.
Background: For years, ARL has been a key player in air-surface exchange research. Recent field studies in agricultural ecosystems have revealed that integrated measurement techniques are often unsuccessful in capturing rapid changes in ammonia exchanges rates. Environmental conditions such as meteorology and soil chemistry can alter the ability of plants to absorb nutrients from fertilizers, which can lead to excess ammonia being emitted into the air. Scientists from UT use their knowledge of canopy dynamics and plant structure to develop best management practices for crops that are beneficial economically and environmentally. The ADAM study was proposed as an opportunity to approach agricultural ammonia emissions from a multi-disciplinary perspective.
Significance: Ammonia is a form of reactive nitrogen (a nutrient) that can contribute to a ‘cascade of effects’ in terrestrial and aquatic ecosystems, including soil acidification, coastal water eutrophication, and loss of biodiversity. It also contributes to air quality issues by playing a role in the formation of fine particulate matter. Ammonia emissions from agriculture have increased dramatically in recent years and account for more than 80% of total emissions worldwide. This experiment will facilitate the determination of suitable techniques for measuring air-surface exchange of ammonia, and it will contribute to a better understanding of how fertilized crops can be a sink (deposition) or a source (emission) of atmospheric ammonia. The outcomes of the study will inform ARL’s planned studies in the northern San Joaquin Valley, as part of the upcoming NOAA Biennial Field Campaign, CalNex 2010.
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