During the past century extensive uranium mining took place in Portugal for radium and uranium production.Many uranium deposits were mined as open pits and after ore extraction and transportation to milling facilities,mining waste left on site were generally of no radiological concern.One uranium mining ore site,Ribeira do Boco Mine,was extracted in the 1960s and 70s and mining waste and open pits were left uncovered and non-remediated since closure of uranium mining activities.During the nineties a quarry for sand extraction was operated in the same site and water from a local stream was extensively used in sand sieving.Downstream the mine areas,agriculture soils along the water course are currently used for cattle grazing.Water from the stream,water wells,soil,pasture and lamb meat were analyzed for radionuclides of uranium natural series.The U- series radionuclide 226Ra was generally the highest in concentrations especially in soil,pasture,and in internal organs of lambs.Ra-226 concentrations were 1093+96 Bq/kg (dry weight) in soil,43+3 Bq/kg (dw) in pasture,and in muscle tissue of lambs grown there were 0.76+0.41 Bq/kg (dw).Other lamb internal organs displayed much higher 226Ra concentrations,such as the brain and kidneys with 7.7±2.3 Bq/kg (dw) and 28±29 Bq/kg (dw),respectively.Results of analyses of tissue samples from lambs grown in a comparison area were 2 t0 11 times lower,depending on the organ.Absorbed radiation doses for internal organs were computed and may exceed 20mSv/y in the case of kidneys.Although elevated,this absorbed dose seems below the threshold for observed biological effects in mammals.Nevertheless,enhanced environmental radioactive contamination mainly due to radium was observed in the area of influence of this legacy uranium mine.This was probably due to the dissolution of radium from washed sands during quarry exploitation,adding to lixiviation of 226Ra from uncovered waste piles on site,and radium transportation downstream.The need for site remediation is discussed.