Fulvic acids isolation

Table 1 Range of Di.stribution of Oxygen-Containing Functional Groups in Humic and Fulvic Acids Isolated from Soils of Widely Different Climatic Zones (in mEq/lOO g)...

Fig. 8. N Is XANES spectra of (a) fulvic acid isolated from a glucose-glycine-S-Mn02 system and (b) the lyophilized solid phase (Jokic et al. 2004b). The peaks are assigned to pyridinic (398.6 eV), pyridone (400.7 eV), amide (401.3 eV) and pyrrolic (402.0 eV) moieties.

The 14C age determination of the fulvic acid isolated rom water near the lake surface was 2300 years before the present, whereas the 14C age was 4900 years before the present for the fulvic acid isolated from water below the chemocline. These old ages for both fulvic acids from Big Soda Lake are in marked contrast to that reported for fulvic acid from the Suwannee River, less than 30 years before the present (11). The refractory nature of this type of fulvic acid derived from phytoplankton and photosynthetic bacteria is significant for carbon-cycling studies. 

Fulvic acid isolated from Island Lake provided direct spectral evidence of protons attached to aliphatic alicyclic rings. The H NMR spectrum of this sample (Figure 3) has a broad medium-intensity peak near 1.8 ppm. The chemical shifts of protons on aliphatic alicyclic rings are commonly split into two broad peaks centered at 1.1 and 1.8 ppm because of their variable boat and chair configurations (23). 

Note Ultrafiltration was used to fractionate the DOM prior to fulvic acid isolation, and the size was determined by high-pressure size exclusion chromatography. The middle and large size fractions had molecular weights corresponding to a range of 1260 to 1470 amu (atomic mass units), and those in the small size fraction had molecular weights of about 1000 amu. 

Humic acid is composed of aromatic, aliphatic and carbohydrate carbon compounds. An average humic acid s elemental composition is 55.1% C, 5.0% H, 3.5% N, 35.6% O, and 1.8% S (Rice and MacCarthy, 1991). Its molecular weight distribution is typically broad, and it is a relatively high-molecular-weight material relative to the fulvic acid isolated from the same soil or sediment. It s predominantly functionalized by carboxylic acid and phenolic groups. At least some components of humic acid are surface-active, and these components have been shown to form micelles in concentrated, alkaline aqueous solutions (Piret et al., 1960 Visser, 1964 Wershaw et al., 1969 Tschapek and Wasowski, 1976 Chen et al., 1978 Rochus and Sipos, 1978 Hayano et al., 1982 Hayase and Tsubota, 1984 Guetzloff and Rice, 1994). 

Guetzloff,T. F., and Rice, J. A. (1996). Micellar nature of humic colloids. In Humic and Fulvic Acids Isolation, Structure, and Environmental Role, Gaffney, S., Marley, A., and Clark, S. B., eds., ACS Symposium Series, No. 651, American Chemical Society, Washington, D.C., pp. 18-25. 

The photodegradation of an aqueous solution of terbuthylazine was not only accelerated, but was also more extensive in the presence of humic acids isolated from soil (Mansour et al., 1997). In the absence of humic acids, only hydroxyterbuthylazine (OBET) was formed (Sanlaville et al., 1996), whereas in the presence of humic acids, dealkylated products (CBAT, CBDT, CEAT, CAAT, OAAT) were formed (Table 23.2) (Sanlaville et al., 1996 Mansour et al., 1997). In contrast, fulvic acids isolated from stream water slowed the photolysis of terbuthylazine, most likely reflecting differences in structure between the soil- and stream-derived materials. The photodegradation of atrazine and its initial photoproduct OEIT (Table 23.2) in artificial sea water containing humic acids was also accelerated compared to photolysis in distilled water (Durand et al., 1990,1991). 

Gaffney JS, Marley NA, Clark SB, (eds) (1996) Humic and fulvic acids - isolation, structure, and environmental role. ACS Symp Ser, vol. 651... 

Several alternatives are used to reduce ammonia elimination. Applied in relatively small quantities, urease inhibitors such as A-(n-butyl) thiophosphoric acid triamide reduce the rate of microbial hydrolysis of urea and increase its efficiency as a fertilizer (Manahan, 2005). Ammonia volatilization could also be reduced using a mixture of urea with tropical peat soil or free humic substances, such as humic and fulvic acids, isolated from peat soils (Bernard et al., 2009). Another application of green technologies is the use of thermal polyaspartate, a product formed by the condensation and base treatment of a natural compound, aspartic acid. This has been found to be effective in stimulating plant uptake of fertilizer thus reducing the amount of fertilizer required (Manahan, 2005). 

Table I. Main thermal degradative products identified in the pyrolysates of the fulvic acids isolated from a water-logged peatland Reproduced with permission from reference 9. Copyright 1994 Elsevier Science—Netherlands.

Elemental Analysis. Carbon, hydrogen, nitrogen, oxygen, sulfur, phosphorous, and ash determinations were made on freeze-dried samples of raw foam, and humic and fulvic acids isolated from Como Creek and Suwannee River foam and water samples by Huffman Laboratories (Golden, CO). Trace-metal analysis was performed on freeze-dried Como Creek foam by Huffman Laboratories (Golden, CO). 

FIGURE 4. Titration curves for stream humic and fulvic acids isolated from the Ogeechee River near Louisville, Georgia during December 1981. 

FIGURE 5. Infrared spectra of (A) a natural marine fulvic acid isolated from the Gulf of lexico and (B) a synthetic fulvic prepared by the autoxidation of trilinolein. 

FIGURE 6. Proton NMR spectra of a synthetic fulvic acid (lop), a natural fulvic acid isolated from open-ocean seawater (middle), and the starting glyceride (bottom). 

Ruggiero et al. (1978, 1981) have also examined the H NMR spectra of different molecular weight fractions of humic and fulvic acids isolated by adsorption and gel permeation chromatography. They found that there are differences in the aliphatic and aromatic regions of the spectrum between the different fractions. Their data are fragmentary and substantially more work... 

One must be cautious in interpreting data on carbohydrates, hydroxyl acids, and uronic acids in humic substances. As Thurman and Malcolm 11983) have pointed out, the amount of these materials in a fulvic acid is a function of the way that it was isolated. They have shown that nonassociated carbohydrates, uronic acids, and hydroxyl acids may be separated from fulvic acid by adsorption chromatography on XAD resins. For example, a prairie soil fulvic acid contained 20% carbohydrate before XAD adsorption chromatography and only 5% after chromatography. In the fulvic acid isolated by Sposito et al. (1978) adsorption chromatography was not used in the purification process and therefore some of the carbohydrate that they report may not be an integral part of the fulvic acid structure. 

Ewald, M., Belin, C., Berger, P., and Weber, J. H. (1983). Corrected fluorescence spectra of fulvic acids isolated from soil and water. Environ. Sci. Technol. 17, 501-504. 

Saito, Y. and Hayano, S. (1981). Characterization of humic and fulvic acids isolated from marine sediments of Sagami and Suruga Bays with C and proton nuclear magnetic resonance. J. Oceanogr. Soc. Japan 36, No. 6, 286-292. 

Wilson, S. A. and Weber, J. H. (1977). A comparative study of number-average dissociation-corrected molecular weights of fulvic acids isolated from water and soil. Chem. Geol. 19, 285-293. 

Fulvic acids. Marine sedimentary humic substances soluble in base and acid (fulvic acids) have previously been examined by and NMR (12). The dominant structural components were postulated to be polysaccharide - like substances, probably polyuronic acids. Solid-state NMR spectra of fulvic acids isolated from a number of marine and estuarine sediments are shown in Figure 1. Major peaks at 72 and 106 ppm betray the overwhelming presence of polysaccharide -like substances, and, as shown by Hatcher and others (12.), the moderate peak for carboxyl or amide carbon at 175 ppm suggests that these polysaccharides are more like polyuronides. Aromatic carbons (110 to 160 ppm) are decidedly minor components. Aliphatic carbons (0-50 ppm) are also minor components. H NMR spectra shown by Hatcher and others (12) indicate that these aliphatic structures are highly branched. 

Krajnc, M., Stupar, J., and Milicev, S. (1995). Characterization of chromium and copper complexes with fulvic acids isolated from soils in Slovenia. Sci. Total Environ. 159, 23-31. 

Prasad, B., Dkhar, G. D. and Singh, A. P. (1987). Cobalt(II), iron(in) and zinc(ll) complexation by fulvic acids isolated from north-eastern Himalayan forest and cultivated soils. J. Indian Soc. Soil Sci. 35, 194-197. 

Fulvic Acid Isolated from Surface Water... 

---