Cloud Processing of Atmospheric NitrogenEPA Grant Number: FP916355
Title: Cloud Processing of Atmospheric Nitrogen
Investigators: Hill, Kimberly A.
Institution: Purdue University
EPA Project Officer: Michaud, Jayne
Project Period: January 1, 2004 through December 31, 2004
Project Amount: $111,344
RFA: STAR Graduate Fellowships (2004) RFA Text | Recipients Lists
Research Category: Academic Fellowships , Air Quality and Air Toxics , Fellowship - Atmospheric Sciences
Forest uptake of carbon dioxide from the atmosphere constitutes one of the main uncertainties in predicting future climate, as trees may impact future global warming by consuming some of the emitted CO2. Nitrogen, which is necessary for normal tree growth, plays a significant role in the amount of carbon that forests consume. Forest growth often is limited by nitrogen availability, so an enhancement in nitrogen input to trees can fertilize and boost a forest’s ability to take up CO2. To date, measurement of nitrogen deposition to forests has involved the study of wet and dry deposition of various nitrogen species, nitric acid and ammonia being the most heavily studied. Wet deposition by precipitation and fog has been shown to account for 80-95 percent of total nitrogen deposition. The role of clouds in processing atmospheric nitrogen before deposition remains to be thoroughly studied. Clouds over forest environments may provide reaction surfaces and act as photochemical reactors for water-soluble nitrogen compounds, altering the amounts and speciation of inorganic and organic nitrogen deposited to the forest.
All previous studies of nitrogen in cloud water have been conducted using ground-based cloud water collectors from mountaintops. This study will expand on current studies of nitrogen by identifying the role of clouds and cloud chemistry in the nitrogen cycle in a forest environment through the use of aircraft-based cloud water sampling and cloud water analysis. The quantification of the concentrations of nitrogen in cloud water and interstitial air will expand our understanding of the ways clouds process nitrogen and remove it from the atmosphere. The project will involve two components: the collection and analysis of cloud water and the measurement of gas-phase NO, NO2, and NOy. Cloud water will be collected at different heights within the cloud, and the samples will be analyzed for total, inorganic, and organic nitrogen content to quantify the distribution of nitrogen in cloud water. Gas-phase measurements of NO, NO2, and NOy will be made both inside and outside of the cloud as a function of altitude within the cloud, using an NOy chemiluminescence analyzer, allowing us to observe changes in nitrogen speciation occurring within the cloud itself.