Organic carbon content

Because many studies have shown a direct relationship between pesticide sorption and organic carbon content of sod, attempts have been made to develop a universal sorption coefficient based on sorption of the pesticide to sod organic carbon (44). Sorption based on sod organic carbon is expressed as C, where is pesticide sorbed per unit mass sod organic carbon, and C is pesticide solution concentration after equdibration. If. is the fraction of organic carbon, can be obtained from i in the equation. Assumptions in the use of this approach include... 

S. Source rock potential of shale A relation exists between the uranium-to-potassium ratio and the organic carbon content. The source rock potential of shale can thus be evaluated. 

The BUSES model provides an estimate of the organic carbon/water partition coefficient (Koc) based on the octanol/water partition coefficient (Kow)- From these data, it is evident that the methyltins are less likely to partition onto organic carbon (in sediments, soils, biota) than are the butyl- and octyltin compormds due to then-lower partition coefficients and higher water solubilities. The 7/oc value can then be used to derive sohds/water partition coefficients in suspended matter, in sediment, and in soil using values of 10%, 5%, and 2% for organie carbon, representing typical organic carbon contents of suspended matter, sediment, and soil, respeetively. 

Volatilization of trichloroethylene from soil is slower than it is from water but more rapid than that of many other volatile organic compounds (Park et al. 1988). This study found that an average of 37% of the applied trichloroethylene was volatilized 168 hours after treatment at 12°C, and 45% was volatilized at 21°C. This study also concluded that soil t> pe had no effect on rate of volatilization, although this may simply be a reflection of the fact that the differences between soils used in the study, particularly in organic carbon content, were not very great. 

Tao, S. et al.. Use of sequential ASE extraction to evaluate the bioavailabdity of DDT and its metabolites to wheat roots in soils with various organic carbon contents, Sci. Total Environ., 320, 1, 2004. 

Most suitable for the examination of the surface is x-ray photoelectron spectroscopy, whereas the wettability determination can be established by a detailed interpretation of core flooding experiments and wettability index measurements. The results of such studies show that the organic carbon content in the surface is well correlated with the wetting behavior of the material characterized by petrophysical measurements [1467,1468]. 

Field studies in at least two paddies where the sediment has different characteristics of pH, texture and organic carbon contents are required for registration purposes. Since especially clay content and organic carbon content affect the agrochemical behavior in sediments, it is desirable that both systems have widely different characteristics with respect to these two criteria. These paddies should have cultivation history records on type of crop, variety, and agrochemical applications for at least 5 years. 

The vacuum extraction method has been effectively applied to removing VOCs with low organic carbon content from well-drained soil, although it may also be effective for finer and wetter soils, but with comparatively slower removal rates. There are generally significant differences in the air permeability of various strata, which can influence process performance. Contaminants with low vapor pressure or high water solubilities are difficult to remove. 

Sorption. Capture of neutral organics by non-living particulates depends on the organic carbon content of the solids (9). Equilibrium sorption of such "hydrophobic" compounds can be described by a carbon-normalized partition coefficient on both a whole-sediment basis and by particle size classes. The success of the whole-sediment approach derives from the fact that most natural sediment organic matter falls in the "silt" or "fine" particle size fractions. So long as dissolved concentrations do not exceed 0.01 mM, linear isotherms (partition coefficients) can be used. At higher concentrations, the sorptive capacity of the solid can be exceeded, and a nonlinear Freundlich or Langmuir isotherm must be invoked. 

The above discussion has assumed that the rank of a coal can be adequately measured by a single parameter, such as the reflectance, the volatile matter yield or the organic carbon content. This assumption is commonly made, but it has for a long time appeared a pretty improbable proposition. The discussion also was restricted to bivariate correlations, that is, plots of a single variable against another. 

Adsorbent Organic carbon content, % Polarity Index, (N+0)/C Aromatic carbon, % Koc of naphthalene (mL g-1)... 

Redding AZ, Bums SE, Upson RT, Andersen EF (2002) Organoclay sorption of benzene as a function of total organic carbon content. J Colloid Interface Sci 250 261-264... 

The atmospheric height is selected as an arbitrary 1000 m reflecting that region of the troposphere which is most affected by local air emissions. A water surface area of 10% or 10,000 km2 is used, with a water depth of 20 m. The water volume is thus 2 x 10n m3. The soil is viewed as being well mixed to a depth of 10 cm and is considered to be 2% organic carbon. It has a volume of 9 x 109 m3. The bottom sediment has the same area as the water, a depth of 1 cm and an organic carbon content of 4%. It thus has a volume of 10s m3. 

Gershey et al. [58] concluded that a continuous and automated photooxidation procedure of the type described by Collins and Williams [30], with the reported modifications, will probably satisfy most of the needs of the oceanographer concerning measurement of dissolved organic carbon. The convenience and rapidity of the method opens up a new area of research the study of the small-scale temporal and spatial variations of the dissolved organic carbon content of the oceans. 

Table 11.3 presents some typical results obtained by this procedure on seawater samples. MacKinnon [92] concluded that since the volatile organic carbon contents of normal (i.e., unpolluted) seawaters are small, the effect of complete or partial loss of volatile organic components during the determination of total organic carbon in most ocean areas (except highly reducing environments) with either the wet and direct injection methods or dry oxidation methods should be small (about 5%), and within the precision of these methods. 

From the beginning of 14C studies, bone was burdened with a marginal status as a sample type. It was missing from the list of sample materials which Libby initially recommended [10]. He and other researchers discouraged its use for the reason that the carbon content and specifically the organic carbon content, was low even in relatively recent bone and because it was a very porous structure potentially subject to chemical alteration and presumably to contamination. It was concluded that bone would systematically violate the third assumption of the 14C method as listed in Table 1. (It should be noted that "burned bone" was highly recommended. However, the sample material was the carbonized hair, skin, and other tissue rather than the bone matrix itself.)... 

Panagos P., Van Liedekerke, M., Montanarella, L., Jones, R.J.A. 2008. Soil organic carbon content indicators and web mapping applications. Environmental Modelling Software, 23, 1207-1209. 

A variety of laboratory studies conducted over the last decade have evaluated the bioavailability and toxicity of SPs in sediments. Maund et al. [25] studied the partitioning, bioavailability, and toxicity of cypermethrin to II. azteca and C. dilutus using three sediments with organic carbon contents of 1, 3, and 13%. Bioavailability was assessed by measuring the body burden in C. dilutus and results demonstrated that bioavailability decreased with increasing organic carbon content... 

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