Abstract 210Pb measurements were carried out on the sediments cores from a small south Belgian pond. In two cores, the 210Pb activity decreases exponentially with depth. Under various assumptions described in the article, the corresponding accumulation rates would be of the order of 60–100 mg/cm 2 of dried sediment per year. The stable lead content greatly increases from the older to the more recent sediment. This increase is accompanied by a change in isotopic composition: from the bottom to the top of the cores, the lead isotopic composition becomes progressively less radiogenic, reaching at the surface values identical to that for present atmospheric lead.