"Concentration standard deviation of soluble copper {soluble_Cu CAS 7440-50-8} per unit volume of the atmosphere [aerosol <1um phase] by filtration, leaching with pH 4.7 ammonium acetate buffer"@en . . "SDN:P01::AEC091SD" . "The square root of the average of the squares of deviations about the mean of a set of values of the specified measurement."@en . .