Properties of the Yellow Organic Acids of Natural Waters1

Abstract

Gel filtration profiles obtained from a variety of naturally colored waters indicate that color producing molecules are mostly in the apparent molecular weight range of 700-10,000 relative to dextrans.One fraction seems to have a molecular weight in excess of 50,000. The apparent size of the color molecules was found to be pH dependent, increasing as pH increases.Size increases are attributed to increased functional group ionization and a decrease in the adsorbability on Sephadex. The degree of association of color molecules with iron was also found to bc pH dependent, being greater at both high and low pH than in the range of 7-8.

Interactions of ferric and ferrous irons and organic matter in water environment

“…In contrast to his opinion, GHASSEMI and CHRISTMAN (1968) explained the iron-organic association in terms of a chelation model in which COOH group played a dominant role.…”

The effect of pH, dissolved humic substances, and ionic composition on the transfer of iron and phosphate to particulate size fractions in epilimnetic lake water

“…Results from this study show that in the presence of DHS, the formation of particulate 55Fe is suppressed at higher pH. It is known that pH influences both the protonation of DHS functional groups (Schnitzer and Khan 1972) and the conformation of DHS molecules (Ghassemi and Christman 1968). Thus, the "stretched" conformation and low protonation of DHS at higher pH appear to favor colloidal and truly dissolved forms of Fe and POd3-, and this preference may be due to the formation of stabilized Fe(III) oxide colliods (Stumm and Morgan 198 1).…”

Chemical composition and molecular weight distribution of dissolved organic matter produced by bacterial degradation of green algae

“…Even though lipid fraction is highly coloured , most of yellow colour may be caused by the colour of chlorophyll degradative products and chlorophyll pigments probably bound to lipid. GHASSEMi and CHRISTMAN (1968) reported that the colour producing molecules in natural water consist , mainly of materials with apparent molecular weight from 700 to 10,000. The molecular weight distribution and the chemical and spectro scopic natures of yellow organic substances studied by SHAPIRO (1957) are similar to those of the lipid fraction of the present work.…”