Collaborative Research: Halogen Activation and Multiphase Chemical Processing in the Continental Boundary Layer

University Of New Hampshire, Durham NH

Investigators

Abstract

The multiphasic chemistry of halogens is known to be involved in a range of chemical interactions in the atmosphere ranging from the O3 cycle, oxidation of hydrocarbons and reduced sulphur compounds, the odd nitrogen and oxygen (HOx and NOx) cycles, as well as involvement in aerosol nucleation, growth and heterogeneous chemical paths. Active halogen reactivity is frequently associated with coastal or marine zones, reflecting the abundance of oceanic halide sources found there. Recent nocturnal observations of the reactivity of a chlorine atom precursor, nitryl chloride (ClNO2) has seemed to predict a surprising continental presence of this pathway, which potentially has implications to our understanding of the global impact of halogens on several of the above species in non-marine settings. Nocturnal ClNO2 arises from the reactivity of N2O5 on particulate chloride, which brings into question how well continental chloride sources including industrial activity, biomass burning, and the transport of wind blown mineral dust are really known. Several aspects of the above suspected chlorine activation pathways remain to be investigated. This investigation involves a number of university researchers joining with NOAA (ESRL) colleagues on additional characterization of halogen reactivity pathways in continental air masses. Overarching issues to be investigated include: i) quantitative evaluation of halogen photochemical processes in continental air, ii) mechanistic study of the generation and recycling of active halogen chemistry in nocturnal continental air. This research has implications for air quality, the natural cycle of halogens in the atmsphere and the oxidative capacity of the air we breathe.