Contribution of Saharan dust on radionuclide aerosol activity levels in Europe? The 21–22 February 2004 case study

Abstract

In February 2004, a spectacular dust event was observed in the south of France. Associated with huge particulate matter deposition, unusual 137Cs concentrations were found in samples. Using the transport model CHIMERE‐DUST, we first show that these dust aerosols came from North Africa. More precisely, the question is whether this sudden increase of measured 137Cs concentrations was due to a huge amount of dust over a large region (with an usual radionuclide content) or due to an import of more concentrated air masses over a limited area. This question is connected to the open debate about the contribution of 137Cs concentrations in Europe from “Gerboise” sites, where former French nuclear tests in the 1960s were performed. With the model in scenario mode, this study attempts to track down 137Cs concentrations recorded in the south of France. To quantify the origin and percentage of dust originating from North Africa to the south of France, three simulations are performed: (1) with the complete dust emissions inventory of Africa, (2) with only emissions in the eastern Maghreb, and (3) only considering the Gerboise sites. It is showed that the majority (80%) of the dust was coming from eastern Maghreb, but only 0.7% of the African emissions were from Gerboise, leading to 1–5% of the concentrations recorded in the south of France for the day of the peak.

Impact of surface roughness and soil texture on mineral dust emission fluxes modeling

“…The CHIMERE chemistry‐transport model may be used for urban to regional air pollution (including anthropogenic and biogenic emissions [ Bessagnet et al ., ]), for analysis and forecast [ Menut and Bessagnet , ], and for long‐range transport [ Menut et al ., ]. In this study, the model is used with only the mineral dust emissions and transport.…”

CHIMERE 2013: a model for regional atmospheric composition modelling

“…It was shown that the sum of all model uncertainties (emissions, transport, deposition) and of the spread of the forecasted meteorology induces a variability in surface concentrations still higher than the required precision for European air quality forecast. A sensitivity study was presented in Menut et al (2009b) and it was shown that a very small area in the Sahara (around the position of the former French nuclear tests site during the 60s) may explain the sporadic (but low) radionuclides concentrations measured sometimes in the South of France. Finally, the dust emissions are only calculated using a bottomup approach and future interesting developments could be to merge these calculations with satellite data to improve the calculated emitted dust flux (as in Huneeus et al, 2012 at the global scale).…”

Change of the Asian dust source region deduced from the composition of anthropogenic radionuclides in surface soil in Mongolia

“…137 Cs contamination detected in France during a Saharan dust event was suspected to be the result of leakage from past nuclear test sites in French Saharan territory (Danesi et al, 2008). Igarashi et al (2005) pointed out that close-in fallout from atmospheric nuclear explosions should have been an insignificant source of surface contamination of 90 Sr and 137 Cs around the test sites, thus negligible in aeolian dust transport; and French researchers drew similar conclusions (Menut et al, 2009;Masson et al, 2010). Only 0.7 % of the Saharan dust was ascribed to the test area, accounting for only a small percentage of the atmospheric 137 Cs peak concentrations recorded in France during the transport event (Menut et al, 2009).…”

“…Igarashi et al (2005) pointed out that close-in fallout from atmospheric nuclear explosions should have been an insignificant source of surface contamination of 90 Sr and 137 Cs around the test sites, thus negligible in aeolian dust transport; and French researchers drew similar conclusions (Menut et al, 2009;Masson et al, 2010). Only 0.7 % of the Saharan dust was ascribed to the test area, accounting for only a small percentage of the atmospheric 137 Cs peak concentrations recorded in France during the transport event (Menut et al, 2009). These results indicate that the Saharan dust episode might have a common background with the present Asian dust case -degradation of grassland where the surface serves as a reservoir for anthropogenic radionuclide fallout.…”

“…Researchers in France (Menut et al, 2009;Masson et al, 2010) needed to solve a similar problem for transported Saharan dust because it also contains a trace but detectable amount of 137 Cs and other radionuclides. 137 Cs contamination detected in France during a Saharan dust event was suspected to be the result of leakage from past nuclear test sites in French Saharan territory (Danesi et al, 2008).…”