Total organic carbon humic acids

Fig. 11. Diagram showing the efficiency of an organoclay in removing dissolved humic acid from a Florida ground water in comparison with activated carbon. The total organic carbon concentration was 5.6 ppm. See Fig. 8 for the meaning of C/C0. After Beall (2003).

Note Humic substances (HS) are operationally defined as DOC that is retained on XAD-2 or XAD-8 resins. UDOM is operationally defined as DOC that is retained by a membrane with a 1 nm pore size and 1000 Da molecular weight cutoff. 13C-NMR spectroscopy was used for analysis of carbon functional groups, which are presented as a percentage of the total organic carbon in the sample. THNS, total hydrolyzable neutral sugars THAA, total hydrolyzable amino acids. 

Dissolved organic matter, expressed as chemical oxygen demand (COD) or total organic carbon (TOC), including methane, volatile fatty acids (in particular in the acid phase of the waste stabilization Christensen and Kjeldsen (1989), and more refractory compounds, e.g., fulvic-like and humic-like compounds. 

The type of activated carbon used for the treatment of groundwater depends upon the other organic compounds present. For example, humic acids will often compete with other contaminants for adsorption sites. Hence, for each situation, isotherms should be determined, and the efficiency of contaminant removal should be evaluated on a TOC basis (total organic carbon). As noted, the compounds most prevalent in groundwaters are chlorinated organics. Their removal by adsorption on GAC is the most effective treatment in liquid or gas phase processes [66]. 

This paper will consider the efficacy or horse-radish peroxidase (HPR) for the removal of 2-chlorophenol — a taste and odor compound, and pentachlorophenol — a wood preservative sometimes found as a contaminant in drinking-water. These compounds were evaluated at low as well as high concentrations, and in the presence of potential competing compounds. Competing compounds may be innocuous aromatic compounds or other specific micro pollutants. Humic substances are organic compounds composed mainly of aromatic structures [ 14 ] which account for up to 90% of the background total organic carbon (TOC) in natural waters [15 ]. Recent studies have indicated th t the presence of humic acids may deactivate horse-radish peroxidase [16 ]. 

In natural water, dissolved OM comprises several families of compounds, e.g. humic acids, carboxylic acids and carbohydrates. It is characterized as a general rule by permanganate oxidizability or total organic carbon (TOC). 

The weight of ash-free humic acid was derived from 10 g air-dry soil, therefore should be multiplied by 10 to convert to percent air-dry soil and further converted to percentage oven-dry soil. The fulvic and humic acid content may be expressed as a percentage of total soil organic matter, which is quantified as soil organic carbon (SOC). SOC is conveniently determined from the loss on ignition, where the correlation is ... 

Summary of Biomarker Analyses. The combination of phospholipid fatty acids, steroids, and lignin phenols indicates that the chemical makeup of raw foam includes input from bacterial, algal, diatoms, fungal, and higher plant sources. The total of these compounds account for less than 5% of the organic carbon present in raw foam, and it is not possible, therefore, to assess which is the largest source. These compounds however, do reveal interesting compositional trends between the raw foam and the stream and foam humic substances. The compositional complexity of humic substances increases from stream, to foam, to foam extract and from fulvic acids to humic acids. 

To this purpose, isotopic data presented in this paper were obtained from several selected Gorleben groundwaters as part of the colloid characterisation programme. The contents of major and minor ions, light isotopes ( H, H, and and the U/Th isotopes were measured. Radiocarbon and were measured in dissolved inorganic carbon (DIG), ion the humic acid (HA-colloids) and fulvic acid (FA-solution) fractions of dissolved organic caibon (DOC). The and were also determined in dissolved sulphate phase. The U/Th isotope measurements were carried out on total and surface solid phases, colloid fraction (1-1000 nm particle size, HA) and solution (<1.5 nm, FA). 

Dissolved humic and fulvic acids can be isolated from the total DOC pool by adsorption onto resins as discussed by Aiken in Chapter 14 of this book. Muenster (1982) found that 77-86% of the DOC (measured by UV absorbance and organic carbon) adsorbed onto XAD resin at pH values of 2.0-3.0. Adsorption onto PVP resin was slightly less effective (70-76% at pH values of 2.0-3.0). These differences in adsorption efficiency may be explained by organic material other than humic substances being retained on these resins. 

Nevertheless, it seems reasonable to infer that aquatic humic substance concentrations in estuaries are intermediate between those of rivers and those of the open ocean, as would be expected from a mixture of river water and seawater. The concentrations of humic acids at intermediate salinities do not correspond, in a linear fashion, to the relative proportions of river water and seawater (Fig. 2), primarily because of a removal from solution of a portion of the riverine contribution. This behavior is in contrast to that of total dissolved organic carbon (DOC) which generally does show linear mixing lines when plotted versus salinity (Sholkovitz et al., 1978 Moore et al., 1979 Laane, 1980 Fox, 1983a Mantoura and Woodward, 1983). 

FIGURE 2. Schematic plot of typical distributions of total dissolved organic carbon (DOC) and humic acid carbon versus salinity. 

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