Hidrológiai Közlöny 1967 (47. évfolyam)

7. szám - A „Szervesanyag meghatározási problémák édesvizekben” című 1966. szeptember 25–28. között Tihanyben rendezett Szimpózium előadásai - Shapiro, Joseph: Különböző tavakból száramzó szervesnyagok összehasonlítása

Shapiro, J.: Különböző tavakból származó szervesanyagok Hidrológiai Közlöny 1967. 7. sz. 293 and very similar chemicallv fali into different types, whereas other lakes geographically distant and chemicallv different fali into the same type. Thus as the data in Table 2 illustrate, Green Laké and Spectacle Laké, although less than a kilometer apart, and very similar chemically, belong to different types. Similarly Lac Qui Parle and Big Kandivohi Laké, belong to different types although their chemistry is similar. Finally Green Laké and Lac Qui Parle, very different from each other chemically, belong to the same type. lron Holding Capacity as Related to Type It has been speculated that differences previously found iniron holding capacity of different extracts might have been related to differences in constitution of the colored materials. The data in Figure 10 strongly substantiate this suspicion. The iron holding capacity clearly is a function of the laké type as here defined. Type I extracts are capable of holding about twice as much iron/mg as are Type IV extracts, and Type II and III are intermediate in capacity. As Tvpe I extracts contain the highest proportion of high 'molecular weight constituents, and the other types fali into descending order in this regard, the results suggest that the high molecular weight components are more effective than the low in peptizing iron. Further evidence for this speculation comes from the data in Figures 11 and 12 and Table 3. The extracts referred to as pH 4.3, pH 3.0, and pH 1.0, were obtained by sequentialty lowering the pH of a laké water concentrate, beginning with pH 4.3, and extracting exhaustively with butanol at each step. The curves in Figure 11 Fig. 10. Iron holding capacity of the different laké types as a function of pH < > med. high mol wt. / tpH 1.0 extraet high mol. wt. / ipH 3.0 extraet 'pH 4.3 extrád 'med.low mol.wt^^ J ' // i / itow mol. wt. 6 7 $ 7 pH Fig. 11. Iron holding capacity cf the acids extracted from, a single portion of laké water concentrate at three pH values. The circles referred to in terms of molecular weight show the iron holding capacity of franctions cut during elution of an extraet from Sephadex (see text) Table 3. Molecular weight distributions o! fractions sequentially extracted from a laké water concentrate at different pH values Sample Planimeter reading of fraction as % of the totál Sample A B C D high mol. wt. low mol. wt. pH 4.3 extraet .... pH 3.0 extraet .... pH 1.0 extraet .... 22.8 46.5 63.7 23.6 23.9 18.3 26.9 19.2 13.4 26.7 10.3 4.7 show that the pH 1.0 extraet liolds more iron than does the pH 3.0 extraet, which in turn holds more than does the pH 4.3 extraet. The curves in Figure 12 and the data in Table 3 demonstrate that this rank order of iron holding capacity is the same as that showing the proportions of high molecular weight components in the extracts. Thus, a shift in relative proportions of different molecular weight components, even by extraction of a single laké water sample at different pH values, is able to influence the iron holding capacity. The most convincing proof that the high molecular weight components are the most effective in peptizing iorn is shown in the four circles in Figure 11. The fractions indicated were obtained by cutting fractions of the effluent from a Sephadex column of a sample of Green Laké extraet. Note that the series is not perfect, the médium high molecular weight being able to peptize more iron than the high molecular weight. However the médium high component is more than 10 times as effective as the low molecular weight component.