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

Abstract

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 NOx chemistry.