The DEBITS-II Programme
DEposition of Biogeochemically Important Trace Species
Wet and dry deposition play an essential role in controlling the concentration of gases and aerosols in the troposphere. The chemical content of atmospheric deposition is the signature of several interacting physical and chemical mechanisms such as: emission and source amplitude; transport in and dynamics of the atmosphere; atmospheric chemical reactions; and removal processes. The study of deposition thus allows for tracing the temporal and spatial evolution of atmospheric chemistry and is a pertinent indicator for evaluating natural and anthropogenic influences.
In 1990 the IGAC (International Global Atmospheric Chemistry) program launched the DEBITS (DEposition of Biogeochemically Important Trace Species) project to encourage existing and initiate new activities related to the final step of biogeochemical cycles: the deposition of chemical species. The DEBITS program focuses largely on the tropical regions for several reasons:
- urbanisation, industrialisation, agricultural growth and biomass burning are increasing rapidly in these regions, producing significant emissions of trace gases and aerosol particles
- a high flux of UV radiation, high temperatures and high atmospheric water vapour content in these regions promote intense photochemistry all year around
- this area is characterized by deep convection, which provides rapid vertical transport so that surface emissions are lifted efficiently into the upper troposphere, were they have a longer lifetime and may have greater impact on the global atmosphere
Following the success of the DEBITS-I program, the new DEBITS-II task addresses one of the core objectives of the IGAC science plan. The program aims to provide a fundamental understanding of the processes that control the distributions of chemical species in the atmosphere and their impact on global change and air quality.