 part of the solution was transferred into a 0 cm quartz cell. The RRS spectra were recorded by synchronous scanning excited wavelength *λ*~ex~ and emission wavelength *λ*~em~ (*λ*~ex~−*λ*~em~ = Δ*λ* = 0), a PMT voltage of 000 v, both excited and emission slit width of 0 nm, The RRS intensity at 000 nm (*I*~000 nm~) and the blank value (*I*~000 nm~)~0~ without Pb^0+^ were recorded. The value of Δ*I*~000 nm~ = 