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

[摘要] Due to their negative water budget most recent semi-/arid regions arecharacterized by vast evaporates (salt lakes and salty soils). We recentlyidentified those hyper-saline environments as additional sources for amultitude of volatile halogenated organohalogens (VOX). These compounds canaffect the ozone layer of the stratosphere and play a key role in theproduction of aerosols. A remote sensing based analysis was performed in theSouthern Aral Sea basin, providing information of major soil types as wellas their extent and spatial and temporal evolution. VOX production has beendetermined in dry and moist soil samples after 24 h. Several C1- and C2organohalogens have been found in hyper-saline topsoil profiles, includingCH₃Cl, CH₃Br, CHBr₃ and CHCl₃. The range oforganohalogens also includes trans-1,2-dichloroethene (DCE), which isreported here to be produced naturally for the first time. Using MODIS timeseries and supervised image classification a daily production rate for DCEhas been calculated for the 15 000 km² ranging research area in thesouthern Aralkum. The applied laboratory setup simulates a short-term changein climatic conditions, starting from dried-out saline soil that isinstantly humidified during rain events or flooding. It describes thegeneral VOX production potential, but allows only for a rough estimation ofresulting emission loads. VOX emissions are expected to increase in thefuture since the area of salt affected soils is expanding due to theregressing Aral Sea. Opportunities, limits and requirements of satellitebased rapid change detection and salt classification are discussed.

[学科分类] 地球化学与岩石