Distribution web page - Sahelian Dust Transect
Since 2015, the "Sahelian Dust Transect" is part of the National Observation Service INDAAF (International Network to Study Deposition and Atmopsheric chemistry and AFrica) supported by the French INSU-CNRS and the IRD .
The description of the network, the data policy and the database are now available at : https://indaaf.obs-mip.fr
Stations
The four Sahelian stations M'Bour (Senegal, 14.39° N, 16.96° W), Bambey (14.70° , 16.47° W), Cinzana (Mali, 13.28° N, 5.93° W) and Banizoumbou (Niger, 13.54° N, 2.66° E) are almost aligned around 13-14° north, on the main pathway of Saharan and Sahelian dust toward the Atlantic Ocean. They are located in the semi-arid Sahel with annual mean precipitation of 496 mm in Banizoumbou, 715 mm in Cinzana and 511 mm in M'Bour for the period 2006-2010 and 458 mm in Bambey from 2013 to 2015. The station of Medenine (33,50° N; 10,64° E) is located in the arid South Tunisia (annual precipitation ~150 mm)
Measurements
PM10 concentrations : Atmospheric concentrations of Particulate Matter smaller than 10 mm (PM10) are measured using a Tapered Element Oscillating Microbalance (TEOM 1400A from Thermo Scientific) equipped with a PM10 inlet. The inlet is located at ~6.5 m ,except at M'Bour (Senegal) (~10 m). The concentrations are recorded as 5 min averages
Meteorological parameters : The wind speed and direction, air temperature, relative humidity are measured with Campbell Scientific Instruments. Wind speed and wind direction are measured at 1Hz with a 2DWindSonic, temperature and relative humidity using 50Y or HMP50 sensors and rainfall with an ARG100 tipping bucket raingauge. The data acquisition is made using data loggers CR200. The meteorological data are recorded as 5 min averages. Meteorological measurements are made at ~ 10 m height in M'Bour (Senegal), ~ 6,5 m height in Banizoumbou( Niger) and in Bambey (Senegal) and ~ 2.3 m height in Cinzana (Mali)
Aerosol Optical depth : The stations are equipped with sunphotometers from the AERONET/PHOTONS network. The data are distributed on the : AERONET website
Deposition fluxes : Wet deposition is collected using a passive MTX ARS 1010 automatic deposition sampler (MTX Italia SPA, Modane, Italy) located on the roof of the local building (at ~7.5 m except in M'Bour (~9 m)). The collector is made of two buckets (30 cm diameter) and a humidity sensor activated an aluminum lid to cover or uncover the buckets. The samples are collected after each precipitation event.
Total deposition is collected with a passive collector of an inverted "frisbee" shape (Hall and Waters, 1986; Hall and Upton, 1988), equipped with a flow deflector ring, as tested by Wiggs et al. (2002) and full with marbles to limit dust resuspension and rain splashing. The samples are collected weekly, except in the wet season where they are also collected when the wet deposition samples are collected
For both total and wet deposition samples, the collection procedure is decomposed into three main phases ((1) rinsing with a large volume of water, (2) decantation during more than 6 hours and siphoning of excess water; (3)drying in an oven) . The collected dust is finally weighted with a precision balance.
