Direct and its instrumental data on the 131I activity in lawn grass (Gr1, Gr1_1) with weather data on rainfall at the Warsaw Observ Astr weather station, the Warsaw Area (Rain1), and reconstructed “instrumental” data for pasture grass in the county Ostrolecki (Gr2, Gr2_1) with rainfall at the Myzsyniec weather station, the Ostroleka Area (Rain2): Gr1 – instrumental data; Gr1_1 – exponential interpolation Gr1; Gr2 – reconstructed “instrumental” data; Gr2_1 – nonlinear interpolation (Gr2).