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1999 Progress Report: Partitioning of Semivolatile Organic Compounds in Organic and Inorganic Aerosols: A Unified Approach
EPA Grant Number: R826771Title: Partitioning of Semivolatile Organic Compounds in Organic and Inorganic Aerosols: A Unified Approach
Investigators: Kamens, Richard M. , Chandramouli, Bharadwaj , Jang, Myoseon , Jaoui, Mohammed , Lee, Sangdon
Current Investigators: Kamens, Richard M. , Chandramouli, Bharadwaj , Jang, Myoseon
Institution: University of North Carolina at Chapel Hill
EPA Project Officer: Shapiro, Paul
Project Period: October 1, 1998 through September 30, 2001
Project Period Covered by this Report: October 1, 1998 through September 30, 1999
Project Amount: $562,536
RFA: Air Pollution Chemistry and Physics (1998)
Research Category: Engineering and Environmental Chemistry
Description:
Objective:The objective of this project is to provide a unified model to predict the equilibrium gas-particle partitioning (G/P) of semivolatile organic compounds (SVOCs) on both organic and inorganic aerosols. To do this, it is necessary to: (1) implement new models for both SVOC gas-liquid (absorptive) and gas-solid (adsorptive) behavior, (2) provide an experimental database to test these models, and (3) demonstrate that these models can be used and applied to a variety of different ambient situations. This work will provide a theoretical framework and user-friendly procedure for estimating the G/P phase distribution of almost any semivolatile organic, whether it is a new environmental chemical for which only chemical structural information exists, a carcinogenic compound, an environmental estrogen, or an environmental endocrine disrupter.
Progress Summary:Implementation of Hansen Activity Coefficient Method. We implemented a user-friendly method of calculating absorptive partitioning coefficients on organic aerosols. The Hansen method of calculating activity coefficients uses solubility parameters to calculate activity coefficients.
where 
is the average molar
volume of the sorbing liquid, the solubility parameters for the SVOC are
dispersion 
, polar 
, and hydrogen bonding 
, and ib, the
weighing factor. We implemented a FORTRAN software program using group
contribution techniques to calculate the activity coefficient of the SVOC in
organic aerosol. This program calculates solvent and solute solubility
parameters using structure information and composition of the aerosol and uses
this to calculate the activity coefficient of an SVOC in a given organic
aerosol. This gives us the ability to easily calculate partitioning coefficients
of almost any SVOC in a given aerosol (like diesel particles or wood soot
particles), and this can be used as a supplement/substitute to the UNIFAC
techniques already available. Figure 1 shows the results of one typical
calculation on a test, single component hexadecane aerosol. The Hansen
calculation gives good fits with the measured KPs.
Implementation of a Gas-Phase Reaction/Gas-Particle Partitioning Model on Inorganic Aerosols. We developed a photochemical reaction/adsorptive gas-particle partitioning scheme to model the formation and partitioning of hydroxyl oxidation products of decamethyl cyclopentasiloxane (D5) and decamethyl tetrasiloxane (L4). This work used a photochemical simulation model, PKSS, to simulate the reactions of D5 and L4 in an urban smog atmosphere, and partitioning of products on Arizona road dust particles into the model. The results from these simulations were compared with daytime experiments conducted in our 190-m3 outdoor smog chamber. One such comparison is shown in Figure 2. We were able to successfully predict the formation and uptake of D4TOH (the hydroxyl reaction product of D5). This is a useful tool as it addresses, for the first time, a reaction/partitioning sequence onto an inorganic particle and can, in conjunction with advances in prediction of adsorptive partitioning coefficients, be used to predict the fates of reactive SVOCs in the atmosphere.
Prediction of Particle Formation From the 
Pinene-Ozone Reaction. We implemented new
reaction schemes to predict the formation of secondary aerosol particles from
the reactions of Pinene in the
atmosphere. We incorporated daylight reaction schemes into a preexisting dark,
pinene-O3
reaction mechanism and used a reaction/partitioning scheme to estimate particle
mass. Figure 3 shows some preliminary results from this work. The model predicts
total particle mass quite well and tracks photochemical parameters like NOx and O3 very reasonably. The estimation of
biogenic aerosol mass is very important in determining total particle load in
the atmosphere, and hence, the partitioning properties of the aerosol.
Our future activities will include the following:
1. We will continue chamber experiments to vigorously test the absorptive
partitioning model. Experiments will be carried out with emissions from gasoline
engine exhaust and meat grilling and added to our extensive database of diesel
particles, wood smoke, Pinene
measured KPs, and used to validate the model.
2. We will develop and implement user-friendly programs to estimate KPs on different particle types. These programs will include a database of compound properties like boiling point, vapor pressure, and group contributions for the most important SVOCs to facilitate ease of use and also the ability to take in user inputs for new compounds/aerosol compositions and estimate vapor pressures and KPs.
3. We will conduct experiments with Arizona road dust and estimate KPs on these particles. We will implement new group contribution parameters for polarizability, dipolarity, and Lewis-Acidity and Basicity to refine the existing physico-chemical regression model for Arizona road dust. We also will concentrate on developing a thermodynamic predictive model for adsorptive partitioning.
Journal Articles on this Report: 3 Displayed | Download in RIS Format
| Other project views: | All 8 publications | 8 publications in selected types | All 8 journal articles |
| Type | Citation | ||
|---|---|---|---|
|
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Chandramouli B, Kamens RM. The photochemical formation and gas-particle partitioning of oxidation products of decamethyl cyclopentasiloxane and decamethyl tetrasiloxane in the atmosphere. Atmospheric Environment, Volume 35, Issue 1, 2001, Pages 87-95. |
R826771 (1999) |
not available |
|
|
Jaoui M, Kamens RM. Gas phase photolysis of pinonaldehyde in the presence of sunlight. Atmospheric Environment 2003;37(13):1835-1851. |
R826771 (1999) R826771 (Final) R828176 (Final) |
not available |
|
|
Lee S, Kamens RM. Particle nucleation from the reaction of α-pinene and O3. Atmospheric Environment 2005;39(36):6822-6832. |
R826771 (1999) R826771 (Final) R831084 (2005) R831084 (2006) R831084 (2007) |
|
gas-particle equilibrium, adsorption, adsorption activity coefficients, vapor pressure, solvation energy relationships, compound polarizability. , Toxics, Air, Scientific Discipline, RFA, Engineering, Chemistry, & Physics, Ecological Risk Assessment, air toxics, particulate matter, Environmental Chemistry, National Recommended Water Quality, VOCs, aerosol partitioning, aerosols, chemical mixtures, vapor phase, exposure and effects, semivolatile organic compounds, aerosol particles, combustion, monitoring, particulates, PM 2.5, air modeling, PAH, linear solution energy realtionships, gas/particle partitioning
Progress and Final Reports:
Original Abstract
2000 Progress Report
Final Report