Humic acids coastal

Fox, L.E. (1983) The removal of dissolved humic acid during estuarine mixing. Estuar. Coastal Shelf Sci. 16, 413 140. 

Hair, M.E. and Bassett, C.R., Dissolved and particulate humic acids in an east-coast estuary, Estuary and Coastal Mar. Sci., 1, 107, 1973. 

Finally, a variety of zooplankton have recently been shown to produce colored (chromophoric) DOM (CDOM), a fraction of which is fluorescent (FDOM) (Steinberg et al, 2004 Urban-Rich et al, 2004, 2006). Although the nitrogenous composition of CDOM/FDOM is little known, fluorescent humic-hke material (likely fulvic and humic acids) is produced during grazing, influencing the optical characteristics of coastal waters (Urban-Rich et al, 2006). A recent culture study shows that humic-N can be a source of N for coastal phytoplankton (See et al, 2006). 

Musani, Lj., Valenta, P., Nurnberg, H. W., Konrad, Z., and Branica, M. (1980). On the chelation of toxic trace metals by humic acid of marine origin. Estuarine Coastal Mar. Sci. 11, 639-649. 

Humin varies widely in composition. Sediments derived from algal/microbial biomass have humin with paraffinic structures resembling those of corresponding humic acids. Estuarine or coastal marine sediments examined in this study have humin with highly aromatic structures which resemble coal-like materials rather than modern plant residues. In these latter sediments no structural correspondence exists between humin and humic acids which appear to more nearly reflect the nature of modern plant... 

While specific compounds such as siderophores have been found in natural waters, the bulk of the dissolved organic matter (DOM) is made up of relatively refractory compounds known as humic substances. These substances exhibit complex, ill-defined structures with the actual structure depending markedly on the source of the organic material. DOM in the open ocean is almost entirely authochthonous and formed by condensation, polymerisation and partial oxidation of smaller molecules such as triglycerides, sugars and amino acids and exhibits very little aromatic character [78]. In contrast, the DOM in fresh and coastal waters is largely allochthonous and derived... 

The ratios of humic to fulvic acids in estuarine and coastal sediments range from 0.4 to 3.4, the higher values being associated with areas or sediments having a terrestrial influence (Palacas et al., 1968 Brown et al., 1972 Hue and Durand, 1973 Pelet and Debyser, 1977 MacFarlane, 1978). These values are also consistent with those from other marine and terrestrial environments (Ishiwatari, 1966 Kononova, 1975 Stuermer et al., 1978 Cronin and Morris, 1982). Other parameters measured on coastal humic substances, such as elemental composition, spectral properties, organic components, stable isotope ratios, or C ages (Pelet and Debyser, 1977 Stuermer et al., 1978 Benoit et al., 1979 Nissenbaum, 1979) are consistent with terrestrial or marine humic compounds, or a mixture of these two endmembers. 

Based on comparison of data from UV, fluorescence, and NMR spectroscopy, and from carbon isotope determination for humic substances isolated from coastal and open ocean environments, the authors have concluded the following (1) other than its metal complexation and redox functions, the only resemblance between humic substances from open ocean (marine) and terrestrial environments is that they are both colored organic acids soluble in water, and (2) marine humic substances are formed in situ and only in the coastal zone is there an admixture of terrestrially derived humic substances from rivers. However, this second conclusion has not yet been reconciled with the observations discussed by Mayer in Chapter 8 that riverine humic... 

Concentrations of 4-8 mg organic acids liter are common in surface waters and often exceed 50 mg l Mn organic-rich waters, such as those of wetlands, flood plains of river ecosystems, and interstitial waters of hydrosoils [1]. Concentrations of both CDOM and humic substances commonly decrease along the gradient of fresh-to-coastal-to-oceanic waters. 

At low pH (ca. 3-5), H2O2 can be consumed through iron cycles associated with the oxidation of fulvic acids involving the photo-Fenton reaction (reaction 8) [84]. As previously discussed, reactions (8) and (9) may be important in humic-rich natural waters at low pH such as in black-water rivers of the southeastern United States (e.g., Suwanee River, GA), but their importance in marine waters at higher pH (typically ca. pH 8.2) is unlikely except for some organic rich coastal environments (vide supra). 

The formation of soluble iron or fulvic acid chelates, represented in general as FeFA (Equation 9.8), has been shown to be responsible for soluble iron in runoff from humic-substance-rich peat bog leachate earrying iron into coastal seawater off North Scotland. ... 

---