You are here:
FACTORS INFLUENCING THE DEPOSITION OF A COMPOUND THAT PARTITIONS BETWEEN GAS AND PARTICULATE PHASES
Citation:
Hutzell, W T. FACTORS INFLUENCING THE DEPOSITION OF A COMPOUND THAT PARTITIONS BETWEEN GAS AND PARTICULATE PHASES. Presented at Fall 2000 Meeting of the American Geophysical Union, San Francisco, CA, December 15-19, 2000.
Impact/Purpose:
The goal of this research is to develop and test appropriate chemical and physical mechanisms for use in EPA's Models-3 chemical/transport models. These models will be addressing issues of tropospheric photochemistry, fine particles, toxic and semi-volatile substances, and acid deposition. As such, scientifically credible mechanisms for atmospheric gas- and aqueous-phase chemistry as well as heterogeneous chemistry, applicable to the particular pollutant regimes must be included in Models-3.
Description:
How will atmospheric deposition behave for a compound when it reversibly sorbs between gas and atmospheric particulate phases? Two factors influence the answer. What physical mechanisms occur in the sorption process? What are the concentration and composition of atmospheric particulate matter that is the sorbent? The factors combine to produce deposition behaviors associated with both phases. They also infer a dependence on the compound's physical properties and meteorological variables such as temperature and humidity. The result makes difficult identifying what phase dominates atmospheric deposition at any time or location. Numerical modeling is a method that can qualitatively define the changes in deposition versus this dominance.
This research investigates how sorption affects deposition by using an Eulerian model for particulate matter and deposition. The model includes an algorithm that partitions mass between gas and particulate phases based on equilibrium isotherms for sorption. The algorithm, itself, depends on concentrations of simulated particulate matter and includes parameters that control a compound's potential to sorb onto particulate matter. In the investigation, these parameters are varied to examine the effects on wet and dry deposition, separately. The results provide insights on how deposition changes when the ratio changes between concentrations in gas and particulate phases. The information may support future modeling of compounds that undergo the gas to particulate sorption. Several such compounds are relevant in assessing environmental health.