Organic carbon mineralization rate

FIGURE 2 Common sources of organic carbon and rates of mineralization of labile (LDOC) and recalcitrant (RDOC) dissolved organic carbon in lakes and streams. 

Consistent with the preceding comments on the metabolism of xenobiotics in the presence of additional carbon substrates, the result of deliberate addition of organic carbon may be quite complex and will not be addressed in detail. Two examples on rates of mineralization are given as illustration in which addition of glucose apparently elicited two different responses. It should, however, be emphasized that since the concentration of readily degradable substrates in natural aquatic systems will generally be extremely low, the environmental relevance of such observations will inevitably be restricted ... 

Cr(VI).Other remediation processes for Cr(VI) contaminated soils include H2S injection, aqueous Fe(II) injection, and the use of reduced Fe solids. Aqueous-phase Cr(VI)-Fe(II) redox reactions may be significant if Fe2+ concentrations are in equilibrium with relatively soluble, ferric hydroxide-like phases (Tokunaga et al., 2003). The overall interactions involving microbial activity, organic carbon degradation, Fe2+, and mineral surfaces control the net rates of Cr(VI) reactions in soils. 

It is assumed that of this 5000 m3/h deposited, 2000 m3/h or 40% is buried (yielding the advective flow rate in Table 1.5.1), 2000 m3/h or 40% is resuspended (as discussed later) and the remaining 20% is mineralized organic matter. The organic carbon balance is thus only approximate. 

The figure 2/3 is the dimension of the specific surfaces such as the case of the sublimation rate of mothball in the air. However, the presence of non-carbonate minerals and organic structures (kerogen matrix) which separate the carbonate mineral into isolated sites connected by channels would alter the rate so that ... 

Pentachlorophenol, a widely used wood preservative, is considered to be moderately biorefractory with a biodegradation rate constant of 3 x 1012 L/ cell/hr, a log of 5.01, and a vapor pressure of 1.1 x 10-4 mmHg at 20°C. Watts et al. (1990) carried out completely mixed batch tests by treating penta-chlorophenol-contaminated soils with Fenton s reagent. Mineralization of pentachlorophenol (PCP) was studied in commercially available silica sand and two natural soils by removal of parent compound and total organic carbon with corresponding stoichiometric recovery of chloride. The soluble iron concentration decreased over the first 3 hr of treatment, and the concentration remained relatively constant thereafter. A possible mechanism for iron precipitation was proposed as follows ... 

The formula for BCD in Eq. (2) was derived under the assumption that the bacterial growth rate was mineral nutrient limited. If the supply rate of labile organic carbon from allochthonous and autochthonous sources is insufficient to meet this demand, the pool of labile dissolved organic carbon (DOC) will eventually be depleted and the bacteria will become carbon... 

Equation (7) thus gives a theory for the ability of N-limited bacteria to consume the potentially degradable organic carbon produced as a function of the production rates for labile DOC and DON and of algal-bacterial competition for mineral forms of nitrogen. 

In the preceding discussions, we assumed labile DOC and DON to be produced at rates y/c and y/N, respectively, without discussing their sources and how the production rate and the composition of the produced material would be expected to vary with food web structure. The important differences among different models can be illustrated by some examples. One potential model is that DOC production is an overflow mechanism occurring in mineral-nutrient-limited phytoplankton not able to use the photo-synthetically produced organic carbon for biomass production due to lack... 

Figure 4.2. Carbon released as C02 from unamended soil and soils amended with pig slurry (PS), poultry manure (PM), cattle farmyard manure (FYM), aerobic sewage sludge (SS), municipal solid waste fuse compost (RC), and rye straw (RS) at a rate of lOgkg1 during incubation at 22 °C. Reprinted from Levi-Minzi, R., Riffaldi, R., and Saviozzi, A. (1990). Carbon mineralization in soil amended with different organic materials. Agric. Ecosyst. Environ. 31, 325-335, with permission from Elsevier.

Flavel,T. C., and Daniel, V. (2006). Carbon and nitrogen mineralization rates after application of organic amendments to soil. J. Environ. Qual. 35,183-193. 

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