Organic complexes, transport

Transport in solution or aqueous suspension is the major mechanism for metal movement from the land to the oceans and ultimately to burial in ocean sediments. In solution, the hydrated metal ion and inorganic and organic complexes can all account for major portions of the total metal load. Relatively pure metal ores exist in many places, and metals from these ores may enter an aquatic system as a result of weathering. For most metals a more common sequence is for a small amount of the ore to dissolve, for the metal ions to adsorb onto other particulate matter suspended in flowing water, and for the metal to be carried as part of the particulate load of a stream in this fashion. The very insoluble oxides of Fe, Si, and A1 (including clays), and particulate organic matter, are the most important solid adsorbents on which metals are "carried."... 

Neutral carriers are organic complexing agents which are capable of sequestering and transporting ionic species in a hydrophobic organic phase. The antibiotics, valino-mycin and nonactin were the first neutral carriers to be incorporated in an ISE These macrocyclic neutral carriers contain a polar internal cavity and an outer hydro-phobic shell. The excellent selectivity exhibited by valinomycin for potassium ions is... 

In natural waters, dissolved zinc speciates into the toxic aquo ion [Zn(H20)6]2+, other dissolved chemical species, and various inorganic and organic complexes zinc complexes are readily transported. Aquo ions and other toxic species are most harmful to aquatic life under conditions of low pH, low alkalinity, low dissolved oxygen, and elevated temperatures. Most of the zinc introduced into aquatic environments is eventually partitioned into the sediments. Zinc bioavailability from sediments is enhanced under conditions of high dissolved oxygen, low salinity, low pH, and high levels of inorganic oxides and humic substances. 

Finally, it should be noted that NAPL infiltration is accompanied by dissolution of some components into the aqueous phase, volatilization of other components into the air phase of the partially saturated zone, and possibly organic complexation with resident soil (Jury and Fluhler 1992). Mass flux of volatilized phases in the near surface can be included in transport equations, as discussed in Sect. 11.3. 

Bach et al. have successfully introduced the concept of a solid p-type semiconductor (heterojunction), with the amorphous organic hole-transport material 2,2, 7,7 -tetrakis (, V, V-di-/ -methoxyphcnyl-aminc)9,9 -spirobifluorenc [96]. This hole-conducting material allows the regeneration of the sensitizers after electron injection due to its hole-transport properties. Nevertheless, the incident photon-to-current conversion efficiencies using complex 22 as a charge-transfer sensitizer... 

This volume covers ongoing research and, thus, leaves many questions unanswered and many problems unsolved. The geochemistry of disposed radioactive wastes involves many complex issues that will require years of additional research to resolve. High-priority problems include integration of geochemical data with computer models of chemical interaction and transport, definition of environmental conditions that affect the behavior of radionuclides at specific disposal sites, evaluation of complex formation of dissolved radionuclides with inorganic and organic complexants, and determination of radionuclide solubilities in natural waters. 

Mucociliary clearance is an organized, complex process which is highly dependent upon the composition and depth of the epithelial lining fluid and the viscoelastic properties of the mucus. In many airways diseases there is hypersecretion of mucus. This may cause an overloading of the ciliary transport process, resulting in... 

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