Three species of Pseudomonas capable of utilizing atrazine as a sole source of carbon were isolated by enrichment from soil with a long history of atrazine application. Atrazine was metabolized via N-dealkylation with preferential formation of deisopropylatrazine over deethylatrazine. Two of the species were able to carry out the dechlorination of both deisopropylatrazine and deethylatrazine following incubation in glucose-supplemented mineral salts medium. The dehalogenation of atrazine and its metabolites as a bacterial degradation process is shown.

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Uniformly UC ring-labeled atrazine was applied to a mineral soil under field conditions. Nine years after application of the herbicide soil samples were collected for analysis. The soil contained about 50% UC residues in the bound (nonextractable) form. The bound 14C residues were distributed among the various soil humic fractions. In addition to the parent herbicide a considerable proportion of these residues was comprised of the hydroxy analogues of atrazine and their dealkylated products.

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X-ray absorption spectroscopic study provided an evidence for the competitive adsorption mechanism of Pb, Cu, and Cd on peat. AbstractCombined use of batch equilibration adsorption and X-ray absorption spectroscopy (XAS) was employed to study the mechanisms of competitive adsorption of Pb, Cu, and Cd on Danish and Heilongjiang peat in single-and multi-solute systems. The adsorption capacity and initial adsorption rate on the same peat in single-solute systems followed the order Pb > Cu > Cd. Both the adsorbed amount of each metal (q 0 m ) and its initial adsorption rate were decreased in multi-solute systems. It was observed that the adsorbed amounts of metals at low-energy adsorption sites (q m,1 ) decreased pronouncedly compared to those at high-energy adsorption sites (q m,2 ), indicating that the competitive adsorption of Pb, Cu and Cd occurred mainly at the low-energy adsorption sites. XAS study revealed that both Pb and Cu were coordinated in peat predominantly to carboxylic moieties without excluding the hydroxyl groups, thereby providing an insight into the mechanism of competitive adsorption of Pb and Cu on peat.

This study was undertaken to provide an insight into the effect of heterogeneous soil organic matter (SOM) on the sorption of phenanthrene. Humic acid (HA) and humin were extracted from a peat soil. Humin was further fractionated into bound-humic acid (BHA), lipid, and insoluble residue (IR) fractions. Heterogeneous natures of these fractions were characterized by elemental analysis, ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy, and solid-state 13 C NMR. Aliphaticity of the fractions followed the order lipid >BHA > HA > IR, while the polarity order was IR > BHA> HA > lipid. Sorption of phenanthrene on these fractions fitted the Freundlich equation, suggesting that phenanthrene sorption isotherms of lipid were almost linear (N ) 0.993), while those of HA, BHA, and IR were nonlinear, with N values ranging from 0.723 to 0.910. The N values followed the order lipid > HA > BHA > IR and were significantly correlated inversely with their polarities (p < 0.05). Organic carbon-normalized sorption coefficients (K FOC ) were independent of aliphatic or aromatic contents of the SOM fractions. The results suggested that SOM, especially for the humin fractions, was highly heterogeneous in terms of elemental composition, structure, and polarity. Such heterogeneity was considered to be responsible for the nonlinear sorption of phenanthrene.

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A novel technique using on-line microfiltration and HPLC analysis has been used to study sorption kinetics and sorption equilibrium of the herbicide atrazine with the clay minerals montmorillonite, kaolinite, and illite and the clay fraction of a soil. Fast and slow labile sorption have been observed for atrazine along with a reversible but kinetically slow sorption/desorption process that is consistent with diffusion of pesticide into the interior of the clay particles. Labile sorption capacity, mole fraction site coverage, labile sorption equilibrium function, and distribution coefficient were determined for the clay minerals in aqueous slurries with atrazine. The identification and quantitative descriptions of key chemical species avoid some of the commonly reported hysteresis problems. Distribution coefficients are derived from the equilibrium constants so that comparisons may be made with the results of other workers.