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The measured Pb concentration in seawater after spiking with NBS-981 standard reference material. Bottle A (grey filled triangles) is the unfiltered seawater; bottle B (open triangles) is the 0.4 µm filtered seawater; and the unspiked sample is shown in a black filled triangle. The main figure shows the detail change in Pb concentration in bottle A within first 200 h and the inset figure shows the two-month-long variation of Pb concentration in both bottles A and B.
