Humic Substances terrestrial

Stuermer, D. H. and Payne, J. R. (1976). Investigation of seawater and terrestrial humic substances with carbon-13 and proton nuclear magnetic resonance. Geochim. Cosmochim. Acta 40,1109-1114. 

Y. Chen, Organic matter reactions involving micronutrients in soils and their effect on plants. Humic Substances in Terrestrial Ecosystems (A. Piccolo, ed.), Elsevier Sciences B. V., Amsterdam, 1996, p. 507. 

Humic acids (HA) and fulvic acids (FA) are the main components of humic substances (HS), which are the most chemically and biochemically active and widely spread fractions of nonliving natural organic matter in all terrestrial and aquatic environments. They comprise a chemically and physically heterogeneous group of substances with colloidal, polydis-persed, polyelectrolyte characteristics and mixed aliphatic and aromatic nature (Senesi and Loffredo 1999). 

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

Allard, B., Humic Substances in Aquatic and Terrestrial Environment, Springer-Verlag, New York, 1989. 

The most striking characteristic of the dissolved humic substances is their chromophoric nature. As part of the DOM, they impart a yellow-brown cast to marine and freshwaters and, hence, are part of the CDOM pool. Terrestrial hiunic substances compose a significant fraction of the riverine DOM entering the ocean. In seawater, humic substances compose 5 to 15% of the HMW DOM. Differences exist in the bulk properties of marine and terrestrial humic substances. These are summarized in Table 23.6. They have been used to trace the fate of terrestrial organic matter in the ocean. 

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. 

These types of models, while incomplete, are steps toward the formulation of composite models, which depend on future availability of compositional data. Moreover, these structural models are an important aid in understanding the interactions between anthropogenic chemicals and terrestrial organic matter. However, due to the heterogeneity of humic substances in the environment, provision of an exact, general structure does not seem feasible. 

NOM is common in sediments, soils, and near ambient (<50 °C) water. The materials result from the partial decomposition of organisms. They contain a wide variety of organic compounds, including carboxylic acids, carbohydrates, phenols, amino acids, and humic substances (Drever, 1997, 107-119 Wang and Mulligan, 2006, 202). Humic substances are especially important in interacting with arsenic. They result from the partial microbial decomposition of aquatic and terrestrial plants. The major components of humic substances are humin, humic acids, and fulvic acids. By definition, humin is insoluble in water. While fulvic acids are water-soluble under all pH conditions, humic acids are only soluble in water at pH >2 (Drever, 1997, 113-114). 

Tipping (1981) showed that the adsorption of terrestrial humic substances could reverse the positive electrophoretic mobility of iron oxides. Thus, both terrestrial and marine organics are strong adsorbates, able to reverse zeta potential. 

There are also structural differences between humic substances or UDOM collected from rivers and oceans (Table I). Humic substances and UDOM from rivers are enriched in aromatic components compared with their counterparts from the ocean. Terrestrial vegetation is relatively rich in aromatic components, such as lignins and tannins, and this is reflected in the greater aromatic nature of DOM in rivers. These biopolymers are relatively resistant to microbial degradation and are important components of river DOM. Humic substances and UDOM from the ocean are enriched in carbohydrates compared with their counterparts from rivers. This is consistent with observations of higher C-normalized yields of neutral sugars in bulk DOM from the ocean compared with rivers (Table I). 

Hatcher, P. G., Breger, I. A., Dennis, L. W., and Maciel, G. E. (1983). Solid-state 13C-NMR of sedimentary humic substances New revelations on their chemical compostion. In Aquatic and Terrestrial Humic Materials, Christman, R. F., and Gjessing, E. T., eds., Ann Arbor Science, Ann Harbor, MI, pp. 37-81. 

Senesi, N., Miano, T. M., and Brunetti, G. (1996). Humic-like substances in organic amendments and effects on native soil humic substances. In Humic Substances in Terrestrial Ecosystems, Piccolo, A., ed., Elsevier, New York, pp. 531-593. 

TABLE 14.1. Marker Signals in Py-FIMS of Aquatic and Terrestrial Humic Substances, Soil Fractions, and Whole Soils... 

Schulten, H.-R. (1987). Pyrolysis and soft ionization mass spectrometry of aquatic/terrestrial humic substances and soils. J. Appl. Anal. Pyrolysis 12,149-186. 

Riise, G., and Salbu, B. (1986).The influence of aquatic humic substances on the octanol/water partition coeffficient of pesticides and trace elements at different pH values. In Humic Substances in the Aquatic and Terrestrial Environment, Grimvall, A., eds., Springer-Verlag, Linkoping, Sweden, pp. 357-365. 

Th fall of the Orgueil meteorite in 1864 enabled various scientists to confirm the previous observations once again. Cloez noted in 1864 the remarkable similarity between the elementary composition of the terrestrial humic substances and that of the carbonaceous matter in the Orgueil meteorite . 

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