Activity ratio standard deviation of polonium-210/lead-210 {210Po/210Pb} in the water body [dissolved plus reactive particulate <0.4/0.45um phase] by filtration, acidification and alpha spectroscopy Po210/Pb210_SD_water<0.4/0.45um The square root of the average of the squares of deviations about the mean of a set of values of the specified measurement. 2019-06-04 17:32:45.0 SDN:P01::APO77006 SDN:P01::APO77006 SDN:P01::APO77006 2 2 2019-06-04 17:32:45.0 accepted false