Impact of Saharan dust events on radionuclide levels in Monaco air and in the water column of the northwest Mediterranean Sea.
Characterization of atmospheric aerosols collected in Monaco (2004-2008) and in sediment traps at 200 m and 1000 m water depths at the DYFAMED (Dynamics of Atmospheric Fluxes in the Mediterranean Sea) station (2004) was carried out to improve our understanding of the impact of Saharan dust on ground-level air and on the water column. Activity concentrations of natural (210Pb,210Po, uranium and radium isotopes) and anthropogenic (137Cs,239Pu,240Pu, and239+240Pu) radionuclides and their isotopic ratios confirmed a Saharan impact on the investigated samples. In association with a large particulate matter deposition event in Monaco on 20 February 2004, the137Cs (∼40 Bq kg-1) and239+240Pu (∼1 Bq kg-1) activities were almost a factor of two higher than other Saharan deposition dust events. This single-day particle flux represented 72% of the annual atmospheric deposition in Monaco. The annual deposition of Saharan dust on the sea was 232-407 mBq m-2for137Cs and 6.8-9.8 mBq m-2for239+240Pu and contributed significantly (28-37% for137Cs and 34-45% for239+240Pu) to the total annual atmospheric input to the northwest Mediterranean Sea. The137Cs/239+240Pu activity ratios in dust samples collected during different Saharan dust events confirmed their global fallout origin or mixing with local re-suspended soil particles. In the sediment trap samples the137Cs activity varied by a factor of two, while the239+240Pu activity was constant, confirming the different behaviors of Cs (dissolved) and Pu (particle reactive) in the water column. The137Cs and239+240Pu activities of sinking particles during the period of the highest mass flux collected in 20 February 2004 at the 200 m and 1000 m water depths represented about 10% and 15%, respectively, of annual deposition from Saharan dust events.
IAEA-Environment Laboratories, Monte Carlo 98000, Monaco. Electronic address: m.pham@iaea.org.
Mai Khanh
MK
Pham
Centro Nacional de Aceleradores, Universidad de Sevilla, Isla de la Cartuja, 41092 Sevilla, Spain.
Elena
E
Chamizo
Departamento de Física Aplicada I, Universidad de Sevilla, 41012 Sevilla, Spain.
José Luis
JL
Mas Balbuena
IAEA-Environment Laboratories, Monte Carlo 98000, Monaco.
Juan-Carlos
JC
Miquel
CADIC-CONICET, Bernardo Houssay 200, Ushuaia 9410, Argentina.
Jacobo
J
Martín
IAEA-Environment Laboratories, Monte Carlo 98000, Monaco.
Iolanda
I
Osvath
Faculty of Mathematics, Physics and Informatics, Comenius University, SK-84248 Bratislava, Slovakia.
Pavel P
PP
Povinec
D000352:Africa, Northern; D000396:Air Pollutants, Radioactive / Q000032:analysis*; D004391:Dust / Q000032:analysis*; D008522:Mediterranean Sea; D008984:Monaco; D011834:Radiation Monitoring; D014875:Water Pollutants, Radioactive / Q000032:analysis*
D000396:Air Pollutants, Radioactive; D004391:Dust; D014875:Water Pollutants, Radioactive
Air monitoring; DYFAMED; Northwest Mediterranean; Radionuclides; Saharan dust; Sediment trap