Sink strength, oxidizer

The total flux of methane into the stratosphere, 60 Tg/yr, combines with the rate of CH4 oxidation by OH to give a total sink strength of 400 Tg/yr. This agrees approximately with the global emission estimates of Table 4-7. Although methane has been observed to increase in the troposphere, the budget must be about balanced since the increase is slow. If we take a value of 400 Tg/yr as representative for ( Ch4 ch4 the tropospheric residence time for methane is... 

There are only two important sinks that serve to destroy methane. The first is the oxidation of methane by aerobic bacteria in soils whereas the second and the most important sink is reaction (oxidation) with hydroxyl radicals in the atmosphere. Biological oxidation of methane in soils is responsible for 6-10% of the global source strength. Oxidation dne to the reaction of methane with hydroxyl radicals in the atmosphere, however, accounts for the remaining 90% (Cicerone and Oremland, 1988). An estimated 500 Tg year is removed from the atmosphere each year over 95% of the annual emission is removed through these two primary sinks (Khalil et al., 1992). 

Three estimates of CH4 sink strengths also are shown in Table 4.15. The primary sink for CH4 in the atmosphere is reaction with OH-. Other sinks include microbial oxidation of CH4 in soils and photolysis of CH4 in the stratosphere. As is the case with the CO2 budget, many of the sink and source strengths of CH4 are only approximately known. 

Electro discharge (spark erosion) techniques rely heavily on the ability of EDM oil to act as an electrical insu-lant, to dissipate heat from the electrode, and to flush away erosion debris from the workpiece. EDM oils also are suitable for all die-sinking spark erosion operations. They should have low aromatic levels, good filterability, low fuming, high dielectric strength, excellent oxidation resistance and low color level. 

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