Project at a Glance
Title: Chlorine emissions from activated sea-salt aerosols and their potential impact on ozone.
Principal Investigator / Author(s): Dabdub, Donald
Contractor: UC Irvine
Contract Number: 00-324
Research Program Area: Atmospheric Processes
Topic Areas: Modeling
A photochemical modeling study is performed to determine whether urban photochemical models simulating sea-salt particle chemistry can predict observed chlorine levels and how such chlorine levels affect ozone formation. A host urban airshed model, employing a rich chemical mechanism and simulating aerosol dynamics, is augmented with current sea-spray generation functions, a comprehensive gas-phase chlorine chemistry mechanism and several heterogeneous/multiphase chemical reactions considered key processes leading to reactive chlorine formation. Modeling results adequately reproduce regional sea-salt particle concentrations. These particular heterogeneous / multiphase chemical reactions do not affect the rate of hydrochloric acid displacement nor do they enhance aerosol nitrate formation. Chlorine levels in the model are predicted an order of magnitude below observed values, albeit 30 times better than previous studies. The results suggest that inclusion of sea-salt derived chlorine chemistry may increase morning ozone predictions by as much as ~12 ppb in coastal regions and by ~4 ppb to the peak domain ozone in the afternoon. Peak ozone concentrations at most monitoring sites increase by 2 Ė 4 ppb and even higher ozone increases, up to 7 ppb, are predicted at other times not coinciding with the peak. An emissions inventory of anthropogenic sources of chlorine is recommended as these may enhance ozone formation even further by emitting chlorine gases directly into polluted regions.
For questions regarding research reports, contact: Heather Choi at (916) 322-3893
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