Fig. 2.

Asymmetric Flow Field-Flow Fractionation experiments. The FFF chromatograms show the molar mass distribution of Fe and NOM (measured as UV–Vis absorption at 254 nm) in seawater-soluble NOM fractions which have been collected after separation on a Sephadex LH-20 column. Results are shown for the three Craggie Burn fractions (CB_0, CB_1, and CB_2) and for the three Suwannee River fractions (SR_0, SR_1, and SR_2): (a) CB_0; (b) CB_1; (c) CB_2; (d) SR_0; (e) SR_1; (f) SR_2. The UV signal (solid red curved line) represents the NOM and is superimposed with the iron signal (solid blue curved line). The molar mass of the Fe-NOM can be obtained from the peak maximum of the Fe signal. The resulting molar masses are listed in Table 2.