The Effect of Humidity and Particle Composition on Partitioning of Volatile Organic Compounds
Abstract
Anthropogenic chemicals can partition between many different phases in the environment, including air (gas phase and airborne particles), water, and soil. A single chemical may be present in multiple phases at once, and its division among the different phases is described quantitatively by a partition coefficient. Values of partition coefficients are required for accurate prediction of the fate and transport of chemicals in the environment. In this research and development project, we will determine partition coefficients for volatile organic compounds (VOCs) between soil, air, and airborne particles as a function of temperature, humidity, soil textural class, and particle composition. VOCs include anthropogenic chemicals that are used as fuel additives, solvents, and pesticides, to name just a few of their applications. While such information exists for semi-volatile organic compounds (SVOCs), VOCs have been largely overlooked even though there is evidence to suggest that their partitioning to airborne particles may be important. Using an environmental chamber that closely mimics the natural environment, we will develop an experimental model that can be used to validate partitioning data from theoretical modeling and reconcile them with real-world experimental data. Results from this research can be used to improve prediction of the impacts of VOCs on health and the environment. The overall goal of this project is to develop an experimental model system for measuring partitioning of VOCs as a function of temperature, humidity, soil textural class, and particle chemical composition. We will design and fabricate an environmental chamber that mimics the natural environment to measure the soil-to-gas partition coefficient Ks and gas-particle partition coefficient Kp of representative VOCs. We will evaluate the sensitivity of partition coefficients to all the variables of interest. While the effects of temperature on partitioning of VOCs in the environment are well understood, a comparable understanding of the dynamic interplay of other variables, such as humidity and particle composition, and their effects on partitioning are often neglected. This project is innovative because it links multiple environmental variables to predict the partitioning of VOCs and aims, for the first time in a single study, to determine how humidity, particle chemistry, and other variables affect partitioning in an environmentally relevant experimental model. Such a mechanistic understanding will enable more accurate prediction of partition coefficients. Implications of this research include improved abilities (1) to predict the fate and transport of VOCs in the environment and (2) to assess inhalation exposure to particle-phase VOCs. The contribution of VOCs to the toxicity of particles has been often overlooked. Modeling studies evolving from our results may be used to improve the application of partitioning theory and reduce the discrepancy between theoretical and experimental data. Development of strategies to reduce exposure to VOCs by manipulating environmental conditions may also ensue from this research.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Feb 14, 2019
- Source ID
- W911NF1610007
Entities
People
- Linsey Marr
Organizations
- Army Contracting Command
- United States Army
- Virginia Tech