Iodine oxide in the Dead Sea Valley: Evidence for inorganic sources of boundary layer IO

Abstract

1] The importance of iodine oxide (IO) in tropospheric boundary layer chemistry has been well established in the last decade. Iodine-containing radicals have been detected in regions of high biological productivity. To date, most explanations assume biogenic precursors (e.g., emission of iodocarbons). In a 2 week field campaign at the Dead Sea, Israel, IO was found to exceed the detection limit (0.3-2 parts per trillion (ppt)) almost daily, with peak levels topping 10 ppt. Macro algae are nonexistent because of the water's high salinity. The Dead Sea's microbiology is discussed in detail, and organic sources of iodine oxide are found to be of minor importance. Thus the site can be treated as a unique place for the investigation of inorganic sources of IO. Such processes have recently been included in model studies. Our study focuses on the first direct evidence for inorganic sources of reactive boundary layer iodine. Heterogeneous iodine release induced by photolysis, liquid phase ozone reactions, or catalytic HOX interactions are discussed as well as NO x chemistry.Citation: Zingler, J., and U. Platt (2005), Iodine oxide in the Dead Sea Valley: Evidence for inorganic sources of boundary layer IO,

Modelling chemistry over the Dead Sea: bromine and ozone chemistry

“…2 in Tas et al, 2003). In addition O 3 seems to be destroyed more rapidly and more often over the Southern end of the Dead Sea than the Northern end (Tas et al, 2005;Zingler and Platt, 2005). With the Lagrangian scenario EXLIM it was possible to reproduce these measurements showing high BrO mixing ratios (>60 pmol/mol) all over the Dead Sea but an ODE only in the South.…”

Observations of iodine monoxide columns from satellite

“…Typical tropospheric abundances of iodocarbons and subsequent iodine oxides lie in the range of 0 to several pptv (Carpenter et al, 1999;Allan et al, 2000;Peters et al, 2005) and are most probably confined to the lowest layers of the atmosphere (Friess et al, 2001). In some locations the amount of IO was below the detection limit while higher values of up to 10 pptv (Peters et al, 2005;Zingler and Platt, 2005) have been measured in several locations at certain times. The currently highest amounts of up to 20 pptv (Saiz-Lopez et al, 2007a) and very recently 30 pptv (D. Heard, yet unpublished data) seem to be rather rare and transitory events.…”

Constraints on inorganic gaseous iodine in the tropical upper troposphere and stratosphere inferred from balloon-borne solar occultation observations

“…Butz et al: Inorganic iodine in the tropical UT/LS observed regularly in the form of IO radicals in the lower troposphere with concentrations of several ppt (e.g. Frieß et al, 2001;Peters et al, 2005;Zingler and Platt, 2005;SaizLopez et al, 2006SaizLopez et al, , 2007bRead et al, 2008). Only recently, space-borne observations confirmed enhanced levels of IO near coastal Antarctica (Saiz-Lopez et al, 2007a;Schönhardt et al, 2008).…”