C/N ratios

C N ratio The C N ratio should be about 10 1. The organic carbon in the medium provides both a... 

C and 5 N values were determined by mass spectrometry (MM 903, VG Isogas), equipped with a CN elemental analyzer (Roboprep CN, Europa Scientific). As control for sample purity, C N ratios from the elemental analyser were compared with C N ratios as calculated from the amino acid profile of the same sample. 

A number of substituted triazines are used as herbicides, and their biodegradation has been discussed in Chapter 10, Part 1. Treatment of soil contaminated with atrazine (2-chloro-4-(ethylamino)-6-isopropylamino-l,3,5-triazine) illustrated a number of significant features. Although the soil that was used had the potential for degradation, a laboratory experiment with Pseudomonas sp. strain ADP that had an established potential for atrazine degradation revealed important limitations. There was a substantial decline in the numbers of Pseudomonas sp. strain ADP and only limited mineralization. Supplementation with citrate or succinate increased the survival of the strain, and successful mineralization was dependent on the preservation of a carbon/nitrogen ratio >10 (Silva et al. 2004). The last would apply generally to substrates with a low C/N ratio such as triazines. 

E. S. Jensen, Mineralization-immobilization of nitrogen in. soil amended with low C N ratio plant residues with different particle sizes. Soil Biol. Biochem. 26 519 (1994). 

Although these studies utilizing Incorporated debris are valuable because they show the potential for allelochemlcals to be released from plant litter, they suffer from a disadvantage. The amount of debris added and Its carbon to nitrogen ratio might lead to alterations In nutrient contents In the soil as the result of proliferation or shifts In populations of micro-organisms. Thus, a control In which a material of similar C/N ratio but lacking allelochemlcals needs to be Included for such studies to be conclusive. The above studies did not Include such controls and thus are not definitive. 

The theoretical formaldehyde requirements for denitrifying nitrite or nitrate, if biomass production is not considered, are 0.64 and 1.07 kg C/kg N-NO , respectively. Garrido and colleagues3 found C/N ratios of 0.8 and 1.3 kg C/kg N-NO for denitrification of nitrite and nitrate, respectively, these values being 20% higher than the theoretical ones. 

When the system was operated at a high inlet C/N ratio, part of the formaldehyde was not removed in the anoxic reactor and entered the nitrification reactor. This led to a heterotrophic layer... 

Fig. 4. Run of [N/Fe] as a function of the sum [(C+N+0)/Fe] (left panel) and run of the [C/N] ratio vs [O/N] ratio (right panel) for unevolved stars in NGC 6397, NGC 6752 and 47 Tuc. Symbols are as in left panel of previous figure. Right panel superimposed to the data are models for dilution with matter processed by complete CNO cycle (solid line), contamination from N-poor RGB stars (dashed line) and contamination from N-rich upper-RGB stars experiencing very deep-mixing (dotted line).

Theoretical models for nucleosynthesis in asymptotic giant branch stars predict a large contribution to the cosmic nitrogen abundance from intermediate-mass stars [1], In particular, hot-bottom-burning in stars above a certain mass produces [C/N] —1 [2]. However, observations of C and N abundances in C-rich, metal-poor stars, usually using the CH and CN bands, show [C/N] values that vary between —0.5 and 1.5. (Fig. 1). If any of these stars have been polluted by intermediate mass AGB stars, then they should have lower [C/N] ratios. However, most of the CH stars with detailed abundances have [C/Fe] > 1.0, and it is more likely than stars mildly enhanced in C have been polluted by N-rich stars. 

We do not find any stars with low [C/N] ratios and the range of [C/N] we find is much more restricted than predicted. If a standard initial mass function is used, we would expect about one in five AGB stars to undergo hot-bottom-burning, a ratio not seen in Fig. 1. It is possible that some of the C-rich stars in our sample were polluted by nucleosynthesis sources other than AGB stars, and we are currently observing a larger sample of stars. There are also many assumptions which need to re-evaluated, such as mass loss being unaffected by... 

Table 12.1 C/N ratio of some raw compost materials (in Periurban Vegetable Project http //puvep.xu.edu.ph/composting.htm)...

Nitrogen-rich waste C/N ratio Carbon-rich waste C/N ratio... 

Compost quality parameters, such as C/N ratio, degradable amounts of C and N fractions... 

As carbon is broken down through composting the C/N ratio drops. (C/N ratio starts ideally at 30, but can be higher) Microbes require oxygen, so a drop in the 02 required signals a slowing of microbial activity. 

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