Water dissolved organic matter

Anaerobic decomposition of organic matter in natural waters Dissolved organic matter will decompose in water under anaerobic (oxygen-free) conditions if appropriate bacteria are present. Anaerobic conditions occur naturally in stagnant water such as swamps and at the bottom of deep lakes. The bacteria operate on carbon so as to disproportionate it. In other words, some carbon is oxidized to carbon dioxide and the rest is reduced to methane (reaction (8))... 

Brinkmann, T., Horsch, P., Sartorius, D., and Frimmel, F. H., Photoformation of low-molecular-weight organic acids from brown water dissolved organic matter. Environ. Sci. Technol, 37, 4190-4198, 2003. 

In natural waters, dissolved organic matter or other solutes inhibited the reaction to some extent, probably by scavenging reactive free radicals or other potent oxidants. 

Hunchak-Kariouk K (1992) Influence of anoxic pore water dissolved organic matter on the fate and transport of hydrophobic organic pollutants. Ph.D. dissertation, Drexel University, Philadelphia, PA. 

Baker, A., Bolton, L., Newson, M., and Spencer, R.G.M. (2008). Spectrophotometric properties of surface water dissolved organic matter in an afforested upland peat catchment. Hydrol. Process., 22,2325-2336. 

Studies have appeared where photolysis in natural bodies of water under normal sunlight conditions has been examined. For example, metolachlor was slowly photodegraded by sunlight in lake water, with a half-life of 22 days in summer and 205 days in winter (28). Addition of a 5% solution of dissolved organic matter to the water extended the half-Hves two to three times longer, depending on the season (see PHOTOCHEMICAL TECHNOLOGY, photocatalysis). ... 

The bioavailability, and hence the toxicity, of metal depends on the physical and chemical form of the metal, which in turn depends on the chemical characteristics of the surrounding water. The dissolved form of the metal is generally viewed as more bioavailable and therefore more toxic than the particulate form. Particiilate matter and dissolved organic matter can bind the metal, making it less bioavailable. What is not well known or documented is the various chemical transformations that occur both within the effluent stream and when the effluent reaches and mixes with the receiving water. Metal that is not bioavailable in the effluent may become bioavailable under ambient chemical conditions. 

This removal may also include diffusion of soluble U(VI) from seawater into the sediment via pore water. Uranium-organic matter complexes are also prevalent in the marine environment. Organically bound uranium was found to make up to 20% of the dissolved U concentration in the open ocean." ° Uranium may also be enriched in estuarine colloids and in suspended organic matter within the surface ocean. " Scott" and Maeda and Windom" have suggested the possibility that humic acids can efficiently scavenge uranium in low salinity regions of some estuaries. Finally, sedimentary organic matter can also efficiently complex or adsorb uranium and other radionuclides. 

A great diversity in the concentration of dissolved organic matter also occurs in natural water. Commonly, the concentration ranges from 0.5 to 50 mg/liter. Fresh water and seawater typically have values of 0.5-1.5 mg/liter (18). 

Little is known about MeHg in phytoplankton, particnlarly freshwater phytoplankton (Becker and Bigham 1995). Concentrations of MeHg in freshwater phytoplankton are related to those in water bnt the partitioning of MeHg between water and phytoplankton is strongly affected by concentrations of dissolved organic matter (Watras et al. 1998). 

Dissolved organic matter can be thought of, for simplicity, as soluble organic matter present in soil solution. However, although some workers have measured dissolved organic matter in soil leachates or extracted soil solutions, many use the extract from a 1 2 w/v soil/water extraction... 

Chan KY, Heenan DP (1999) Microbial-induced soil aggregate stability under different crop rotations. Biol Fertil Soils 30 29-32 Chantigny MH (2003) Dissolved and water-extractable organic matter in soils a review on the influence of land use and management practices. Geoderma 113 357-380... 

Kan, A.T., Tomson, M.B. (1990) Ground water transport of hydrophobic organic compounds in the presence of dissolved organic matter. Environ. Sci. Technol. 9, 253-263. 

Mills et al. [20] carried out reversed-phase liquid chromatographic studies of dissolved organic matter and copper-organic complexes isolated from estuarine waters. 

Moore RM (1977) Trace metals dissolved organic matter and their association in natural waters. PhD Dissertation. University of Southampton... 

A variety of physical, chemical and biogeochemical processes had worked in concert to alter the organic and inorganic composition of particulate and dissolved organic matter as it was transported through the water column (Figure 5). 

A soil sample is placed in a centrifuge tube, mixed with 0.5 M HC1 for 1 hour, and centrifuged. The HC1 solution is removed and the soil washed with water to remove the acid. The soil is then extracted with 0.5 M NaOH for 18 hours with shaking, followed by centrifuging to remove dissolved organic matter from soil (adapted and condensed from Reference 21). 

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