IDAF/DEBITS
The Tropics were recently recognized as the most active region for
atmospheric chemistry. High concentrations of trace gas, particles, water
vapor, solar UV radiation, and deep convection combine to the highest OH
concentration worldwide. Scientific knowledge is very limited on the different
steps of the biogeochemical cycles in tropical atmosphere. DEBITS (Deposition
of Biogeochemically Important Trace Species)
has been created to serve as a " catalyst "for encouraging existing and
new activities in the final step of the biogeochemical cycle: the deposition
of the chemical species to the Earth’s surface.
The goals of DEBITS are:
. To determine the atmospheric removal rates by dry and wet
deposition of biogeochemically important trace species
. To identify factors that regulate these depositions fluxes.
The DEBITS activity started in Southeast Asia, with the first planning
workshop in August 1990 in Singapore. The scope of DEBITS has since been
expanded to Africa in 1994 and South-America in 1996.
DEBITS activities in AFRICA: the IDAF program
The IDAF (IGAC DEBITS AFRICA) program started in December 1994 at
the planning workshop of Yamoussoukro in Côte-d’Ivoire. Fifty participants
representing nineteen countries attended this meeting. Taking into account
that Africa is a continent of rapid population growth and accelerated land
use change for cultivation and industrialization, it was decided to launch
a DEBITS network to address atmospheric environmental questions. Noting
in particular for Africa, the contributions to atmospheric chemistry of
biomass burning and desertification, the objectives of IDAF are:
. To estimate, from measurements in wet and dry deposition fluxes,
important chemical species involved in the C,Nand S biogeochemical cycles
at regionally representative sites.
. To identify the relative contributions of natural and anthropogenic
sources to these deposition fluxes.
These objectives will be addressed by an initial measurement program
comprising rainwater sampling for chemical analysis, passive gas sampling
for NO2, SO2, NH3 and organic acids and bulk aerosol sampling for chemical
analysis.
The set of recommended sampling and analysis protocols, produced by
the DEBITS committee, was adopted to assure data quality.
During the second IDAF meeting, held in december1995 in Abidjan, a ten
member committee representing the various regions of Africa has selected
the sites, the chemical analysis laboratories and has proposed the creation
of a data bank.
Recent accomplishments in IDAF (October 1997)
- 10 sites representative of the great ecosystems are active
in 1997. Each site, under the responsibility of one or more African scientists,
is equipped with the same package comprising: a rainwater sampler designed
for IDAF, a set of gas passive sampler and a system to collect aerosols
on Teflon filters.
- 2 laboratories have satisfied at the WMO intercalibration campaign
in 1997 and are in charge of the chemical analysis for the10 sites.
- The French organism Medias-France has in charge the production
of the IDAF data base on CD-ROM and on a Web server. The first CD-ROM will
be available in March 1997.
- The MTV unit of the European Commission has produced monthly
fire maps at continental scale using NOAA-AVHRR imagery. For each of the10
stations, rose-diagrams of fire-frequency and fire distance are presented
in the CD-ROM.
- A third scientific meeting was held in Toulouse
in October 1997 to assess to which the plans developed had been implemented
and to promote the scientific use of the data collected.
| Jean-Pierre Lacaux Laboratoire d'aérologie, OMP, 14 avenue Edouard
Belin, 31400 Toulouse France |
| Phone: 05 61 33 27 06 - Fax: 05 61 33 27 90 - Email: [email protected] |