Dynamics of the 131I specific activity in grass vegetation (a) and estimated data of the 131I specific activity in the atmosphere (b): 1 – perennial lawn grass, Warsaw Obserw Astr*; 2 – annual green, Warsaw Obserw Astr*; 3 – perennial green, Przasynski**; 4 – perennial lawn grass, County Ostrolecki**; 5 – cultivated pasture grass, County Ostrolekа**; 6- rainfall, meteo station Warsaw Obserw Astr* (* – direct data; ** – data with conversion for the minimum 137Cs fallout deposition densities in a milk producing area).