Eddy-Correlation Measurement of Size-Segregated and Composition-Resolved Aerosol Depositional Flux Using an Aerosol Mass Spectrometer

EPA Grant Number: R828172
Title: Eddy-Correlation Measurement of Size-Segregated and Composition-Resolved Aerosol Depositional Flux Using an Aerosol Mass Spectrometer
Investigators: Smith, Kenneth A.
Institution: Massachusetts Institute of Technology
EPA Project Officer: Shapiro, Paul
Project Period: July 24, 2000 through July 23, 2002 (Extended to July 23, 2004)
Project Amount: $225,000
RFA: Exploratory Research - Engineering, Chemistry, and Physics) (1999) RFA Text |  Recipients Lists
Research Category: Engineering and Environmental Chemistry , Water , Land and Waste Management , Air

Description:

The deposition of aerosol particles is a substantial input of acidic, nitrogen- containing, and toxic compounds to natural environments. Many of these compounds are associated with fine aerosol particles, those with diameters smaller than 2.5~m. Further, the ambient concentration of fine particulate matter (PM2.5) depends on the depositional flux of these particles. To date, measurements of fine particle deposition have only been performed in the laboratory using idealized deposition surfaces. However, the flux of fine particles is expected to be sensitive to the actual deposition surface and ambient conditions which depend on surface vegetation, water content, relative humidity and local meteorology. We propose to measure depositional flux of fine particles in natural environments directly using the well established eddy correlation technique with a recently developed aerosol mass spectrometer (AMS). The data collected with this technique will provide the first direct comparisons with deposition velocity parameterizations necessary to estimate the flux of fine particles from the atmosphere.

Objectives/Hypothesis:

The depositional flux of fine particles has long been the subject of intense research effort; and properly so because it is an important removal mechanism of fine particles from the air in arid climates and it is an important mechanism of surface water acidification in areas with more generous rainfall. Nevertheless, estimates of the flux are subject to considerable uncertainty and it is not now possible to measure the flux of particular species such as SO4= and NO3- or PAH.

Our objective is to build an instrument which will measure species flux as a function of particle size and do it in real time.

Approach:

We will build a new instrument which will consist of an Aerodyne Aerosol Mass Spectrometer, a sonic anemometer, and an infrared hygrometer. After laboratory testing it will be deployed in the field to measure fluxes of SO4=, NO3- and PAH as a function of weather conditions and particle size. We anticipate testing at two sites: one will be covered with low vegetation and the other will be an over-water site.

Expected Results:

At the end of this project, an instrument proven to measure fine particle depositional fluxes in real-time will be available to the research and regulatory communities. Subsequent studies with such instruments could measure deposition fluxes of these species at sites with different climatology and vegetation.

Publications and Presentations:

Publications have been submitted on this project: View all 8 publications for this project

Journal Articles:

Journal Articles have been submitted on this project: View all 2 journal articles for this project

Supplemental Keywords:

PM2.5, air toxics, sulfate, nitrate, PAHs, RFA, Scientific Discipline, Air, Toxics, Water, Nutrients, particulate matter, Environmental Chemistry, climate change, HAPS, Environmental Monitoring, Engineering, Engineering, Chemistry, & Physics, nutrient supply, aerosol particles, fine particles, mass spectrometry, toxicology, hydrocarbon, PM 2.5, air sampling, chemical composition, PAH, atmospheric nitrogen deposits, circulation model, airborne aerosols, PM2.5, monitoring of organic particulate matter, nitrogen removal, meterology, acid rain, climatology, atmospheric deposition, eddy-correlation, humidity, vegetative surfaces

Progress and Final Reports:

  • 2001
  • 2002 Progress Report
  • 2003
  • Final Report