OHS competencies

This reaction is primarily a daytime reaction because most OH sources are photolytic in nature. As a result, the N02 reaction with OH competes with N02 photolysis, reaction (4). As discussed in Chapter 3, a typical value of the photolysis rate constant for N02 would be kp = k4 = 7 X 10 3 s-1 at a solar zenith angle of 50° (e.g., see Fig. 3.31). Thus, the reaction with OH is not usually a dominant loss process for N02, but it is still sufficiently fast to form significant amounts of HNO, during the day, particularly in polluted regions with relatively large N02 concentrations. 

Hydroxyl ion (OH-) competes with humic substances for the cationic metal-ion... 

Figure 6.10 illustrates that [H" ] and [OH ] influence markedly the degree of complexation. At low pH, H competes successfully with the metal ions for the ligand. At high pH, OH competes successfully with the ligand for the coordinative positions on the metal ion. Furthermore, at low and high pH,... 

The magnitude of k is determined by the adsorption strength or chemical affinity between the substrate and sorbate. The value of Ng is often affected by the solution pH, since H+ and OH compete with species i for adsorption sites when this happens, the number of sites available for the adsorption of i is reduced. The term C, may also be affected by the solution pH or complexing agents a complexed species may be favored over an uncomplexed one, or vice versa, dins is seen for the adsorption of metallic species on clays, where hydroxycomplexes of the metal ion are favored. 

The formation of metal-ligand complexes, because protons compete with metal ions to bond with weak-acid anions, and OH" competes with other ligands that would form complexes. 

There is competition for the free electrons between the positrons and the holes (OH radicals in the case of water media). When OH competes for these free electrons the addition of OH scavengers is predicted to cause an increase in the yield of o-Ps, a phenomenon called enhancement . On the other hand, addition of electron scavengers will reduce the yield of o-Ps, an effect known as inhibition . The yield of o-Ps is usually denoted by I3 (where and I2 are the yields of free positrons and />-Ps, respectively, having a much shorter half-life than o-Ps). Duplatre and coworkers - found that the yield of o-Ps in aqueous solution in the presence of concentration C of allylamine is given by equation 10. The enhancement factor 1 -h )SC is due to the reaction of allylamine with OH radicals, while the 1 + C inhibition factor is due to the reaction with aqueous or free electrons. The enhancement by amines is one of the main pieces of evidence for the existence of the spur mechanism . Yet, it should be emphasized that it does not rule out the simultaneous existence of both mechanisms . Duplatre and coworkers found that the inhibition by a strong inhibitor such as NO3 is the same in the presence or absence of allylamine. 

The pH can affect stability of the complex (i.e., K ) by affecting not only the form of the EDTA but also that of the metal ion. For example, hydroxy species may form (M2+ -I- OH- MOH" "). That is, OH- competes for the metal ion just as H" " competes for the Y ". Figure 9.2 (prepared from a spreadsheet—see Problem 20) shows how Kf changes with pH for three metal-EDTA chelates with moderate (Ca) to strong (Hg) formation constants. The calcium chelate is obviously too weak to be titrated in acid solution K < 1), while the mercury chelate is strong enough... 

In countries such as Australia you will also find assistance in materials which have been produced under the national training agenda. These include OHS competencies for specific occupational areas and levels of responsibility. In the UK the New Vocational Qualifications relating to safety are of assistance. 

Worksafe Australia. (1992). National Guidelines for OHS Competency Standards for the Operation of Loadshiftine Equipment and Other Types of Specified Equipment. (NOHSC 7019). Canberra AGPS. 

Appendix 13.1 - OHS competencies and performance criteria for key workplace parties... 

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