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Release of gaseous bromine from the photolysis of nitrate and hydrogen peroxide in simulated sea-salt solutions [An article from: Atmospheric Environment]
Book Details
Author(s)I.J. George, C. Anastasio
PublisherElsevier
ISBN / ASINB000PC6N3Q
ISBN-13978B000PC6N35
AvailabilityAvailable for download now
Sales Rank99,999,999
MarketplaceUnited States 🇺🇸
Description
This digital document is a journal article from Atmospheric Environment, published by Elsevier in 2007. The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.
Description:
We have carried out a series of laboratory experiments to investigate the oxidation of bromide (Br^-) by hydroxyl radical (^?OH) in solutions used to mimic sea-salt particles. Aqueous halide solutions with nitrate or hydrogen peroxide (HOOH) as a photochemical source of ^?OH were illuminated with 313nm light and the resulting gaseous bromine (Br*(g)) was collected. While illumination of these solutions nearly always formed gaseous bromine (predominantly Br"2 based on modeling results), there was no evidence for the release of gaseous chlorine. The rate of Br*(g) release increased (up to a plateau value) with increasing concentrations of bromide and was enhanced at lower pH values for both nitrate and HOOH solutions. Increased ionic strength in nitrate solutions inhibited Br*(g) release and the extent of inhibition was dependent upon the salt used. In HOOH solutions, however, no ionic strength effects were observed and the presence of Cl^- strongly enhanced Br*(g) release. Overall, for conditions typical of aged, deliquesced, sea-salt particles, the efficiencies of gaseous bromine release, expressed as mole of Br*(g) released per mole of ^?OH photochemically formed, were typically 20-30%. Using these reaction efficiencies, we calculated the Br"2(g) release rate from aged, ambient sea-salt particles due to ^?OH oxidation to be approximately 0.07pptvh^-^1 with the main contributions from nitrate photolysis and partitioning of gas-phase ^?OH into the particle. While our solution conditions are simplified compared to ambient particles, this estimated rate of Br"2 release is high enough to suggest that ^?OH-mediated reactions in sea-salt particles could be a significant source of reactive bromine to the marine boundary layer.
Description:
We have carried out a series of laboratory experiments to investigate the oxidation of bromide (Br^-) by hydroxyl radical (^?OH) in solutions used to mimic sea-salt particles. Aqueous halide solutions with nitrate or hydrogen peroxide (HOOH) as a photochemical source of ^?OH were illuminated with 313nm light and the resulting gaseous bromine (Br*(g)) was collected. While illumination of these solutions nearly always formed gaseous bromine (predominantly Br"2 based on modeling results), there was no evidence for the release of gaseous chlorine. The rate of Br*(g) release increased (up to a plateau value) with increasing concentrations of bromide and was enhanced at lower pH values for both nitrate and HOOH solutions. Increased ionic strength in nitrate solutions inhibited Br*(g) release and the extent of inhibition was dependent upon the salt used. In HOOH solutions, however, no ionic strength effects were observed and the presence of Cl^- strongly enhanced Br*(g) release. Overall, for conditions typical of aged, deliquesced, sea-salt particles, the efficiencies of gaseous bromine release, expressed as mole of Br*(g) released per mole of ^?OH photochemically formed, were typically 20-30%. Using these reaction efficiencies, we calculated the Br"2(g) release rate from aged, ambient sea-salt particles due to ^?OH oxidation to be approximately 0.07pptvh^-^1 with the main contributions from nitrate photolysis and partitioning of gas-phase ^?OH into the particle. While our solution conditions are simplified compared to ambient particles, this estimated rate of Br"2 release is high enough to suggest that ^?OH-mediated reactions in sea-salt particles could be a significant source of reactive bromine to the marine boundary layer.
