Of humic substances in seawater

Stuermer, D. H. (1975). The characterization of humic substances in seawater. Ph.D. Thesis, Woods Hole Oceanographic Institution, Woods Hole, MA, 187 pp. 

In principle it is wrong to speak of humic substances in seawater. Humus is the term reserved to describe degraded soil oi anics which improve the quality of agricultural or forested ground a traditional term with an intuitive rather than chemical meaning. Although Chapter 6 of this book is devoted to humification, the term will probably be used less in the future when our knowledge of specific compounds increases. 

Kogut, M. B. and Yoelker, B. M. (2001). Strong copper-binding behaviour of terrestrial humic substances in seawater, Environ. Sci. TechnoL, 35, 1149-1156. 

The addition of humic substances to seawater generally produces an increase of the immobile zone and the formation of anionic tailing of the investigated divalent radionuclides (8,9 ). In diluted seawater, if the immobile zone does not exist, it appears when humic acid is added. 

A study of the bulk properties of seawater humic substances was carried out by Kerr and Quinn (1975), while a detailed structural analysis was undertaken by Stuermer (1975) and Stuermer jmd Harvey (1978). Stuermer discussed the structural features in terms of origin, chemical and physical properties, interaction in the sea and eventual fate. As an example of the formation of a humic substance in seawater, we will discuss Stuermer s proposed structure of seawater fulvic material (Gagosian and Stuermer, 1977), the precursor compounds to its formation, and the condensation and polymerization reactions responsible for its synthesis. Although the material isolated by Stuermer represents only a small portion of the total hiunic material, it serves as an example of a possible condensation product. 

Almgren, T., Josefsson, B., and Nyquist, G. (1975). A fluorescence method for the studies of spent sulfite liquor and humic substances in seawater. Anal. Chim. Acta., 78, 411 21. 

The basic structure of humic substances involves a backbone composed of alkyl or aromatic units crosslinked mainly by oxygen and nitrogen groups. Major functional groups attached to the backbone are carboxylic acids, phenolic hydroxyls, alcoholic hydroxyls, ketones, and quinones. The molecular structure is variable as it is dependent on the collection of DOM available in seawater to undergo the various polymerization, condensation, and oxidation reactions and reaction conditions involved in humification, as well as the ambient physicochemical reaction conditions, such as temperature and light availability. 

Since most of the riverine DOM is comprised of humic substances, considerable attention has been fiacused on its fete in seawater. Little terrestrial DOM is detectable in seawater, suggesting the existence of an efficient removal process. This is surprising given the traditional view that humic substances are relatively refractory. Marine chemists are currently investigating the redox and photochemistry of humic substances to better understand its chemical fete in the oceans. 

Hubberten, U., Lara, R.., and Katmer, G. (1994). Amino acid composition of seawater and dissolved humic substances in the Greenland Sea. Marine Chemistry 45(1—2), 121—128. 

A variety of liquids have been treated with reverse osmosis and ultrafiltration membranes ranging from seawater, to wastewater, to milk and yeast suspensions. Each liquid varies in composition and in the type and fraction of the solute(s) to be retained by the membrane. Complicating factors include the presence of substances such as oil in seawater and wastewater [12-15]. The presence of the oil normally necessitates an additional pretreatment step further complicating the fouling process. The presence of humic acids in surface water and wastewater also needs special attention [16,17]. The fouling phenomena, the preventive means (i.e., pretreatment), and the frequency and type of membrane cleaning cycle are all dependent on the type of liquid being treated. 

Further work on differentiating marine and coastal runoff humic substances was hindered by the lack of suitable isolation techniques for the marine material since concentrations in the open sea rarely exceed 0.25 mg/ L. Sorption of marine humic substances from seawater onto solid phases is now a standard technique and can be used to extract gram quantities of marine humic substances for chemical and physical studies (see Aiken, Chapter 14). Sieburth and Jensen (1968) first used rolled nylon stockings as an adsorbant but the method suffered from contamination. Kerr and Quinn (1975) used a specially treated charcoal and obtained quantitative recovery of the dissolved colored substances in seawater. Riley and Taylor (1969) introduced the use of cross-linked polystyrene resins, specifically Amberlite XAD-2. This polymer is now the most widely used for open-ocean work (Stuermer and Harvey, 1974 Bada et al., 1982 Harvey et al., 1983) and in estuaries (Mantoura and Riley, 1975). These isolation methods have made available sufficient quantities of seawater humic substances for detailed chemical studies. 

---