Ziska, Franziska (2014) Global halocarbon emissions for the recent past and future. (PhD/ Doctoral thesis), Christian-Albrechts-Universität Kiel, Kiel, Germany, 232 pp.

Preview

Text Global_Halocarbon_Emissions.pdf - Published Version Available under License German copyright act UrhG. Download (30MB) | Preview

Abstract

Very short lived substances (VSLS) as bromoform (CHBr3), dibromomethane (CH2Br2) and methyl iodide (CH3I) are formed in the ocean by biological, non-biological and anthropogenic processes. Marine CHBr3, CH2Br2 and CH3I concentrations show strong geographical variability (vertical and horizontal) determined by their oceanic sources and sinks. After emitted into the atmosphere these halogenated compounds and their degradation products are involved in several chemical cycles, i.e. tropospheric and stratospheric ozone depletion. Although bromine is much less abundant than chlorine in the atmosphere, it is known to deplete stratospheric ozone 45 to 69 times more efficiently. CHBr3 and CH2Br2 are the major carriers of organic bromine from the ocean to the atmosphere and CH3I is a dominant source of organic iodine in the troposphere. Atmospheric concentrations of the three halogenated compounds are highly variable due to their heterogeneous distribution and seasonally varying natural sources. The tropical ocean is identified to be a key region for enhanced halogenated emissions and for transporting large amount of VSLS into the stratosphere. Different calculation techniques derive sea-to-air flux estimates, including bottom-up and top-down approaches, as well as laboratory experiments. These estimates are used as input for atmospheric transport models i.e. chemical transport models (CTM). The global emission strength and distributions are highly variable as well as poorly quantified. Further, many uncertainties still exist in the production processes, dimension of sources and sinks and chemical fates of VSLS in both the ocean and the atmosphere. Due to that it is difficult to parameterize reliable global emission maps of halogenated compounds. This thesis includes seven manuscripts and aims to reduce the uncertainties of global emission estimates based on in-situ measurements of the three VSLS and of their relevance on stratospheric ozone loss for the present and future.

Actions (login required)

View Item