Deep mixing time

In the Pacific Ocean, most of the waters at 2500 m have a prefiormed phosphate concentration intermediate between NADW and AABW. Because preformed phosphate is a conservative tracer, it can be used to estimate the proportions of NADW and AABW present in the deep zones of the ocean basins. The average deep-water preformed phosphate concentration is 1.4 (jlM. This concentration would result from an equal-volume admixture of NADW and AABW. This conservative mixing estimate is based on the assumption that the preformed phosphate concentrations of the end-member water masses have remained constant over time scales at least as long as the mixing time of the ocean. 

A lake mixes on some time scale so it might be modeled as a stirred reactor for times longer than the mixing time, and it is a tubular reactor for shorter times. Most lakes turn over seasonally because of the density rrtirtimum of water at 4°C so they are mixed on at least a 1 year time scale. Small lakes are mixed effectively by wind on shorter time scales. Deep lakes exhibit an upper layer that turns over and mixes and a lower layer that does not. The inlets to a lake are aU the rivers that flow into it and also water coming from rainfall, and the outlets are aU the rivers that flow out of it and evaporatiorr... 

The straight-chain 1- and 2-butenes are preheated to 600°C in a furnace, mixed with steam as a diluent to minimize carbon formation, and passed through a 5-m-diameter reactor with a bed of iron oxide pellets (or calcium nickel phosphate) 90 to 120 cm deep (contact time 0.2 second) at 620 to 750°C. The material is cooled and purified by fractional distillation and extraction with solvents such as furfural, acetonitrile, dimethylformamide (DMF), and N-mcthyIpyro11idonc (NMP) (Fig. 2). 

Trace metals with scavenged-type distributions have strong interactions with particles and short oceanic residence times (—100-1,000 yr), residence times that are less than the ventilation or mixing time of the oceans. Their concentrations tend to be maximal near major sources such as rivers, atmospheric dust, bottom sediments, and hydrothermal vents. Concentrations decrease with distance from the sources and, in general, the concentrations of the scavenged metals tend to decrease along the flow path of deep water due to continual particle scavenging. 

Since we assume the atmosphere and ocean are in chemical equilibrium, and the input from rivers and burial in the sediments are small compared to the other fluxes, the entire dynamics of the model is reduced to the rate of surface-deep mixing and the sinldng of particles. (For simplicity, DOC transport is not considered in this simple model.) One can see that for a steady state to be achieved the flux of carbon to the surface ocean must equal the sinking flux of particles. The mean residence time for deep water is that determined by natural measurements (see Chapter 6) 500-1000 y. 

All three methods can use the same grouts, but deep mixing will be more effective with very viscous materials. The selection of grout is critical, since it must be resistant to degradation by the contaminant. If grouting is used, those materials with low viscosity are preferable, since they can be used at very short gel times to increase uniformity of penetration in stratified deposits (see section 13.7). Research for new grouts continues, as reported in... 

In most high latitude intermediate and deep-water source regions the age clock is not reset to zero due to lack of time to equilibrate deep mixed layers with the atmosphere. Thus, water masses will start out with an age of a few years (rather than zero), that is, they are not completely renewed during formation. This additional age is called a relic age which can be estimated from observations of the tracers at the water mass formation regions. The relic age can then be subtracted from the tracer ages calculated downstream from the water mass formation regions. 

The dispersed mode will occur at high stirring speeds and certainly when deep vortex formation occurs. T ical characteristic mixing times for both phases can be anticipated to be will be of the order of 1 min. The overall liquid-liquid mass-transfer coefficient will probably be comparable to that of well-designed agitated tanks. 

Ltebermann Reaction To 1 minute crystal of sodium nitrite in a clean dry test-tube add 0 5 g. of phenol and heat very gently for about 20 seconds allow to cool and add twice the volume of cone. H2S04. On rotating the tube slowly in order to mix the contents, a deep green or deep blue coloration develops (some times only after i 2 minutes). Dilute cautiously with water the solution turns red. Now add an excess of NaOH solution the green or blue coloration reappears. 

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