Organohalogen emission from saline environments – spatial extrapolation using remote sensing as most promising tool

Due to their negative water budget most recent semi-/arid regions are characterized by vast evaporates (salt lakes and salty soils). We recently identified those hyper-saline environments as additional sources for a multitude of volatile halogenated organohalogens (VOX). These compounds affect the ozone layer of the stratosphere and play a key role in the production of aerosols. A remote sensing based analysis was performed in the southern Aral Sea basin, providing information of main soil types as well as their extent and spatial and temporal evolution. VOX production has determined in dry and moist soil samples for 24 h. Several C1- and C2 organohalogens, including chloromethane and bromomethane, have been found in hyper-saline topsoil profiles. The range of naturally produced organohalogens includes dichloroethene. For the 15 000 km² ranging research area in the southern Aralkum desert a daily production of up to 23 t dichloroethene has been calculated using MODIS time series and supervised image classification. The applied setup reproduces a short-term change in climatic conditions starting from dried-out saline soil, instantly humidified during rain events or flooding. VOX emission from dry fallen Aral Sea sediments will further increase since the area of salt affected soils is expected to increase in future. Opportunities, limits and requirements of satellite based rapid change detection and salt classification are discussed