Al-organic complexes

The ultrasonic field considerably accelerates processes and increases yields of Al-organic complexes with low-active alkyl halides, complexes of sodium, naphthaline, benzoquinoline, and other aromatic compounds [742], Use of US treatment in Ulmann condensation [742] in the presence of copper powder (3.285) allows acceleration of the reaction rate 50 times and a yield of 81% in comparison with <1.5% without US ... 

Comparison of UV-Resonance Raman and Calculated Vibrational Frequencies (cm1) of Aqueous Al-Organic Complexes... 

Organic Matter Complexation ModeL Soil humus contains a variety of acidic functional groups, some of which have high specificity for Al complexation or chelation (see section 4.3b). Al-organic complex formation requires that the acidic group, RH , dissociate ... 

Overall, the soils referred to in Table 5.2 are net exporters of Al, mostly in the form of soluble Al-organic complexes. If the lower mineral horizons are considered separately from the surface organic litter layer, these B horizons are a net accumulator (sink) of Al-organic complexes and a net generator (source) of inorganic Al. 

Finally a note should be made about Al. The dissolved Al concentrations appear to be easily explained by sinqile inorganic complexation reactions (i.e., A1(0H)4 ). However, the dissolved Al concentration is quite high, and it is still possible that small concentrations of Al-organic complexes could form that could compete with Sr for conqtlexation with the chelates. Therefore, conq>etition studies are planned to examine the influence of dissolved Al on die solubility of SrC03(c) at high base and carbonate concentration. 

J. Gerke, Orthophosphate and organic phosphate in the soil solution of four sandy soils—evidence for humic-Fe(Al) phosphate complexes. Commim. Soil Sci. Plant Anal. 25 601 (1992). 

Ra. Exceptions to this are environments where Rn is lost from the system by degassing (e.g., see Condomines et al. 2003), or aqueous systems where the insoluble nature of °Pb leads to its preferential removal. The speciation of Pb in natural waters is rather complex and heavily depends on the availability of organic complexing agents for which Pb has the highest affinity. In the oceans, Pb has a very short residence (30-150 yrs) and is rapidly scavenged by particles. 

MacNeil, D.J., Occi, J.L., Gewain, K.M. et al. (1992) Complex organization of the Streptomyces avermetilis genes encoding the avermectin polyketide synthase. Gene, 115, 119-125. 

Organic complexed Cd is not important in arid soil solution. Hirsh and Banin (1990) observed 5-10% of Cd bound to organic ligands in Israeli arid soil solution. Emmerich et al. (1982) found that organic-Cd complexes constituted 1-4% of Cd in California arid soil solution. However, Villarroel et al. (1993) reported that in a California sludge-treated soil, Cd was mainly present in both free ion and organic complex forms (each accounted for 32-40% and 30-45% of total Cd in soil solution, respectively), followed by the chloride complexes (8-20%), S04-complex (3-10%), and P04-Cd complex (1.5-7.7%). The nitrate Cd complexes were the lowest. Cadmium activities and speciation is not significantly affected by P and N treatments. 

Hirsh and Banin (1990) reported that an increase in Cl concentration decreased Cd sorption due to formation of the CdCl+ ion pair. Enhanced sorption in the presence of HC03 was observed due to the formation of the CdHC03+ ion pair. Mahler et al. (1980) found that in calcareous soils treated with sewage sludge spiked with CdS04, Cd complexes were mainly Cd sulfate and carbonate complexes, and the formation of Cd-Cl complexes increased in both soils as total Cd increased. In sludge-amended California soils with pH 7-8, both Cd and Zn organic complexes and Cd phosphate complexes increase with P levels, but free Cd2+ and Zn2+ decrease with P levels (Fig. 3.4) (Villarroel et al., 1993). 

Soil solution to soil ratios also strongly affect distribution of some trace elements such as Zn speciation in arid and semi-arid soils. Fotovat et al. (1997) reported that the proportion of free hydrated Zn2+ to total Zn ranged from 20-65% at field capacity soil water content and decreased with increases in solution to soil ratios, while the proportion of Zn complexed with organic ligands increased dramatically in soils. However, solution to soil ratios do not strongly affect the distribution of Cu speciation in soil solution since Cu primarily occurs as organic complexes in these soil solutions. 

Previous studies carried out with clay based catalysts pillared by Fe hydroxo complexes [13] or mixed (Al-Cu or Al-Fe) complexes, have shown that the mixed PILCs lead to the most promising results for organic compounds total oxidation in water, by using hydrogen peroxide as oxidant [14-16],... 

Mills et al. [20] carried out reversed-phase liquid chromatographic studies of dissolved organic matter and copper-organic complexes isolated from estuarine waters. 

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