Inorganic chlorine and bromine in coastal New England air during summer

Abstract

[1] During summer 2004, a comprehensive suite of reactive trace gases (including halogen radicals and precursors, ozone, reactive N, soluble acids, and hydrocarbons), the chemical and physical characteristics of size-resolved aerosols, actinic flux, and related physical conditions were measured at Appledore Island, Maine, as part of the International Consortium for Atmospheric Research on Transport and Transformation (ICARTT). Sea-salt mass averaged 4 to 8 times lower than that over the open North Atlantic Ocean. Production in association with sea salt was the primary source for inorganic Cl and Br. Acid displacement of sea-salt Cl À primarily by HNO 3 sustained high HCl mixing ratios (often >2000 pptv) during daytime. Median pHs for the larger sea-salt size fractions (geometric mean diameters, GMDs ! 2.9 mm) ranged from 3.1 to 3.4; median pHs for sub-mm size fractions were 1.6. Cl* (including HOCl and Cl 2 ) ranged from <20 to 421 pptv Cl but was less than the detection limit (DL) during most sampling intervals. Periods during which Cl* was consistently detectable corresponded to relatively clean conditions, multiday transport over water, and relatively low actinic flux. At high HCl mixing ratios (>1000 pptv), HCl + OH sustained steady state Cl-atom concentrations in the range of 10 4 cm À3 . When detectable, photolysis of Cl* was generally the dominant source of atomic Cl; steady state concentrations of Cl atoms were frequently in the range of 10 4 to 10 5 cm À3 . At these concentrations, Cl played an important role in the chemical evolution of polluted coastal air. Br radical chemistry was relatively unimportant.

Reactive chlorine in the marine boundary layer in the outflow of polluted continental air: A model study

“…This is in reasonable agreement with conclusions of Keene et al [2007] and Pszenny et al [2007], who inferred Cl atom concentrations from measurements at Appledore Island.…”

“…They estimated that Cl reactions increase the reactivity of VOCs by 16 -30% (depending on source region) over that due to OH alone. Using a different technique, Keene et al [2007] derived similar Cl concentrations for these conditions. In the present model study, we investigate reactive chlorine chemistry for conditions representative for the same campaign.…”

Concentration-weighted trajectory approach to identifying potential sources of speciated atmospheric mercury at an urban coastal site in Nova Scotia, Canada

“…The GOM source areas that were located in the Atlantic Ocean between Maine and Nova Scotia and in the Gulf of St. Lawrence near New Brunswick could be the result of the oxidation of GEM by Br. These areas often experience large tidal waves that generate the strong turbulence needed to form sea-salt aerosols and Br (Keene et al, 2007). The ocean is likely not a source of PBM (≤ 2.5 µm) because there are no emission sources from the ocean.…”

Evolving research directions in Surface Ocean - Lower Atmosphere (SOLAS) science

“…[75] Advances have also been made in our understanding of the effect of ocean-derived aerosols on climate, particularly with respect to the effects of OM on CCN production, [76][77][78] and on boundary layer chemistry. [79][80][81] There has also been recent recognition that particles of ,1 mm may be a significant source of CCN in marine regions, [70] that is potentially more important than the contribution from the oxidation of DMS. [61,82,83] Emissions and chemical processing of primary ocean-derived particulate OM are now being integrated into ocean-derived aerosol source functions, [84,85] and the effects of sea surface temperature [86] and wind-speed dependent size-resolved OM production [87,88] incorporated into global models.…”