Dry and wet deposition of 7Be, 210Pb and 137Cs in Monaco air during 1998–2010: Seasonal variations of deposition fluxes

Temporal variations of 7Be, 210Pb and 137Cs activity concentrations in precipitation in Monaco from 1998 to 2010 showed that maxima of 7Be and 210Pb deposition fluxes coincide with the peaks of precipitation amounts observed in different months of a year, and most of 7Be and 210Pb was washout from the atmosphere by precipitation. The seasonal variations were not uniform from year to year, and the amount of precipitation controlled the deposition fluxes of 7Be and 210Pb, which was not the case for 137Cs. The fractional deposition fluxes of 7Be and 210Pb in different seasons were in the order fall > spring > winter > summer, while the fractional amount of precipitation followed the order fall > winter > spring > summer. The fractional deposition fluxes of 137Cs were found in the order spring > fall > summer > winter. The precipitation-normalized deposition fluxes of 7Be, 210Pb and 137Cs were generally higher during summer. The highest 7Be/210Pb activity ratio was observed in 2010, and the smallest one in 2001, following the influence of the modulation of cosmic rays on the production rates of 7Be in the atmosphere by solar activity. Activity ratios of 7Be/210Pb observed in winter and fall were generally higher than during summer and spring.

► 7Be and 210Pb deposition fluxes coincide with rainfalls in different months of the year.
► Peaks in 137Cs activity concentrations were observed mostly during dried months.
► Saharan heavy dust deposition events were observed during November 23–24, 2002 and February 20, 2004.
►  Precipitation-normalized deposition fluxes of 7Be, 210Pb and 137Cs were higher during summer.