Coefficients with organic matter

In practical geochemical and ecologic studies the composition of natural organic matter (liquid or solid) is in most cases unknown. So, as a rule, partition coefficients of a component i for a complex natural solution of unknown composition have to be dealt with. They are called absorption partition coefficient with organic matter. This coefficient Kw,i is experimentally determined and is equal to the ratio of balanced weight concentrations component i in organic matter and in water, according to equations 1.20 in (see Tikhomirov, 2016, v.l) and (2.314), i.e.,... 

Absorption by organic matter of rock Content of organic matter C or carbon in rock, of component i in water C,. Absorption partition coefficients with organic matter - carbon - Iw - ... 

Example 3.4 Compare the rate of migration of lindane (C HgClg) and endrin (Cl HgCl O) with respect to groundwater seepage velocity in the sediments with organic matter content of 0.3%, porosity 0.3% and bulk density 1.9 g em We find the values of the partition coefficients of insecticides between the water and the carbon of organic matter of sediments K j which are 5.250 ml g for lindane and 89,100 ml-g" for endrin. 

Available Chlorine Test. The chlorine germicidal equivalent concentration test is a practical-type test. It is called a capacity test. Under practical conditions of use, a container of disinfectant might receive many soiled, contaminated instniments or other items to be disinfected. Eventually, the capacity of the disinfectant to serve its function would be overloaded due to reaction with the accumulated organic matter and organisms. The chlorine germicidal equivalent concentration test compares the load of a culture of bacteria that a concentration of a disinfectant will absorb and still kill bacteria, as compared to standard concentrations of sodium hypochlorite tested similarly. In the test, 10 successive additions of the test culture are added to each of 3 concentrations of the hypochlorite. One min after each addition a sample is transferred to the subculture medium and the next addition is made 1.5 min after the previous one. The disinfectant is then evaluated in a manner similar to the phenol coefficient test. For equivalence, the disinfectant must yield the same number of negative tubes as one of the chlorine standards. 

The Level I calculation suggests that if 100,000 kg (100 tonnes) of benzene are introduced into the 100,000 km2 environment, 99% will partition into air at a concentration of 9.9 x 10-7 g/m3 or about 1 pg/rn3. The water will contain nearly 1% at a low concentration of 4 pg/rn3 or equivalently 4 ng/L. Soils would contain 5 x 10-6 pg/g and sediments about 9.7 x 10 6 pg/g. These values would normally be undetectable as a result of the very low tendency of benzene to sorb to organic matter in these media. The fugacity is calculated to be 3.14 x 10-5 Pa. The dimensionless soil-water and sediment-water partition coefficients or ratios of Z values are 2.6 and 5.3 as a result of a Koc of about 55 and a few percent organic carbon in these media. There is little evidence of bioconcentration with a very low fish concentration of 3.0 x FT5 pg/g. The pie chart in Figure 1.7.6 clearly shows that air is the primary medium of accumulation. 

Fig. 21.3. Transport of benzene within an aerobic aquifer, as depicted in Figure 21.2, calculated assuming the species not only biodegrades, but sorbs to organic matter in the aquifer. Benzene in the simulation sorbs with a distribution coefficient of 0.16 x 10-3 mol (g sediment)-1, equivalent to a retardation factor R of 2. Fine lines show non-reactive case.

The octanol-water partition coefficient, Kow, is the most widely used descriptor of hydrophobicity in quantitative structure activity relationships (QSAR), which are used to describe sorption to organic matter, soil, and sediments [15], bioaccumulation [104], and toxicity [105 107J. Octanol is an amphiphilic bulk solvent with a molar volume of 0.12 dm3 mol when saturated with water. In the octanol-water system, octanol contains 2.3 mol dm 3 of water (one molecule of water per four molecules of octanol) and water is saturated with 4.5 x 10-3 mol dm 3 octanol. Octanol is more suitable than any other solvent system (for) mimicking biological membranes and organic matter properties, because it contains an aliphatic alkyl chain for pure van der Waals interactions plus the alcohol group, which can act as a hydrogen donor and acceptor. 

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