Measurement-based modeling of bromine chemistry in the boundary layer: 1. Bromine chemistry at the Dead Sea E. Tas1, M. Peleg1, D. U. Pedersen1, V. Matveev1, A. Pour Biazar2, and M. Luria1 1Institute of Earth Sciences, Hebrew University of Jerusalem, Israel 2Earth System Science Center, University of Alabama in Huntsville, Huntsvile, AL 35899, USA
Abstract. The Dead Sea is an excellent natural laboratory for the
investigation of Reactive Bromine Species (RBS) chemistry, due to the high
RBS levels observed in this area, combined with anthropogenic air pollutants
up to several ppb. The present study investigated the basic chemical
mechanism of RBS at the Dead Sea using a numerical one-dimensional chemical
model. Simulations were based on data obtained from comprehensive
measurements performed at sites along the Dead Sea. The simulations showed
that the high BrO levels measured frequently at the Dead Sea could only
partially be attributed to the highly concentrated Br− present in the
Dead Sea water. Furthermore, the RBS activity at the Dead Sea cannot solely
be explained by a pure gas phase mechanism. This paper presents a chemical
mechanism which can account for the observed chemical activity at the Dead
Sea, with the addition of only two heterogeneous processes: the "Bromine
Explosion" mechanism and the heterogeneous decomposition of BrONO2.
Ozone frequently dropped below a threshold value of ~1 to 2 ppbv at
the Dead Sea evaporation ponds, and in such cases, O3 became a limiting
factor for the production of BrOx (BrO+Br). The entrainment of O3
fluxes into the evaporation ponds was found to be essential for the
continuation of RBS activity, and to be the main reason for the jagged
diurnal pattern of BrO observed in the Dead Sea area, and for the positive
correlation observed between BrO and O3 at low O3 concentrations.
The present study has shown that the heterogeneous decomposition of
BrONO2 has a great potential to affect the RBS activity in areas
influenced by anthropogenic emissions, mainly due to the positive
correlation between the rate of this process and the levels of NO2.
Further investigation of the influence of the decomposition of BrONO2
may be especially important in understanding the RBS activity at
Citation: Tas, E., Peleg, M., Pedersen, D. U., Matveev, V., Pour Biazar, A., and Luria, M.: Measurement-based modeling of bromine chemistry in the boundary layer: 1. Bromine chemistry at the Dead Sea, Atmos. Chem. Phys., 6, 5589-5604, doi:10.5194/acp-6-5589-2006, 2006.