Aerosols Deposition Loss Observed during Desert Dust Events of 2018 in French Guiana

The Sahara Desert is the main source of mineral dust reaching northern part of South America where desert dust play an important role by feeding in phosphor the rain forest. The dust deposition rate obtained by remote sensing model must be refined by ground measurements. During the dust season of 2018, a measurement campaign has been performed, in order to observe the behavior of desert dust plume during it cross from the coast to inland rain forest. We used four TEOMs to determine the PM10 concentrations. Three were located along the French Guyana coastline (Cayenne, Kourou, Awala-Yalimapo) and one inland in Apatou town.
First, the background PM10 level of each site have been calculated by using the 20% of the smallest measured values. The values of the integral on PM10 - background for all the event duration, is called Desert Dust Activity (DDA). If we consider the PM10 deposition speed as constant, we have a DDA proportional to PM10 deposition rate.
We observed a good correlation between DDA of Kourou and Cayenne with Apatou (R > 0.96) and a lower one with Awala-Yalimapo (R=0.88).
The dust deposition rate inland (200 km to the coast) represents 65% of the dust deposition observed over the sites along the coast (Kouroun, Awala-Yalimapo). A deposition loss of 55% is obtained between Cayenne and Apatou, suggesting that wind direction have an important impact on the DDA.
In conclusion, this first deposition loss performed for French Guiana rain forest have to be compared to variation observed through remote sensing data.