Evaluation of the procedures for the measurement of water solubility and n-octanol/water partition coefficient of chemicals results of a ring test in Japan

A ring test by 19 labolatories in Japan was carried out in 1984 for the evaluation of the experimental manuals for the measurements of water solubility and partition coefficient (n-octanol/water). The experimental data obtained by the procedures in the manuals were collected by Environmental Agency, Japan. In the measurement of water solubility, this manual applies a modified batch method (the glass beads technique), whereas the OECD Test Guidelines suggests the use of the column elution method for chemicals having water solubility lower than 10 mg/L. Anthracene and flouranthene were used as test chemicals for the measurement of water solubility, and γ -hexachlorocyclohexane (γ -HCH) and 1,2,3-trichlorobenzene were used for partition coefficient. Good agreements were observed at a practical basis between the OECD methods and our methods for the results of mesurements of water solubility and partition coefficient. We concluded that the present ring test showed an advantage of the use of the glass beads method which requires only simple apparatus in water solubility measurement, and the HPLC method is very useful to measure partition coefficient because of the simplicity of procedure and the wide range of measurement, especially at higher values of partition coefficient.     

Enhanced transformation of lead speciation in rhizosphere soils using phosphorus amendments and phytostabilization: an x-ray absorption fine structure spectroscopy investigation

To formulate successful phytostabilization strategies in a shooting range soil, understanding how heavy metals are immobilized at the molecular level in the rhizosphere soil is critical. Lead (Pb) speciation and solubility in rhizosphere soils of five different plant species were investigated using extended X-ray absorption fine structure (EXAFS) spectroscopy and chemical extraction. The EXAFS analysis indicated that Pb occurred as PbCO (37%), Pb sorbed to organic matter (Pb-org: 15%), and Pb sorbed to pedogenic birnessite and/or ferrihydrite (Pb-ox: 36%) in the bulk soil. Comparison of the EXAFS spectra between bulk and rhizosphere soils demonstrated notable differences in fine structure, indicating that Pb species had been modified by rhizosphere processes. The estimated proportion of PbCO (25%) in the buckwheat soil was smaller than the other rhizosphere soils (35-39%). The addition of P significantly reduced Pb solubility in the bulk and rhizosphere soil except in the rhizosphere of buckwheat, for which the Pb solubility was 10-fold greater than in the other P-amended soils. This larger solubility in the buckwheat rhizosphere could not be explained by the total Pb speciation in the soil but was presumably related to the acidifying effect of buckwheat, resulting in a decrease of the soil pH by 0.4 units. The reduced Pb solubility by P amendment resulted from the transformation of preexisting PbCO (37%) into Pb(PO)Cl (26-32%) in the bulk and rhizosphere soils. In the P-amended rhizosphere soils, Pb-org species were no longer detected, and the Pb-ox pool increased (51-57%). The present study demonstrated that rhizosphere processes modify Pb solubility and speciation in P-amended soils and that some plant species, like buckwheat, may impair the efficiency of Pb immobilization by P amendments.     

Nucleophilic substitution of poly(vinyl chloride) with iminoacetic acid and n-dodecanethiol

The modification of poly(vinyl chloride) was carried out with iminodiacetic acid (IDA, C₄H₇NO₄) and iminodiacetic acid dimethylester (IDADM, C₆H₁₁NO₄), as well as with n-dodecanethiol (DT, C₁₂H₂₆S) in the presence of K₂CO₃. The reaction was carried out at different temperatures below 100 °C with dimethyl formamide (DMF) and cyclohexanone as solvents. IDA did not show any reactivity, probably due to the dipolar character of the molecule. IDADM caused the elimination of HCl, while only substitution ratios of about 3 % were observed. However, the modification of PVC with DT resulted in a substitution rate of 18 % without elimination. DT-PVC showed excellent thermal properties, comparable with those of the unmodified polymer.     

Aryl hydrocarbon receptor activities of hydroxylated polycyclic aromatic hydrocarbons in recombinant yeast cells

Hydroxylated polycyclic aromatic hydrocarbons (OH-PAH) with less than four rings are frequently found in the environment, whereas the toxicities associated with these compounds remain unclear. In this study, aryl hydrocarbon receptor (AhR)–ligand binding activities of OH-PAH were investigated by using a recombinant yeast assay system. The majority of the OH-PAH tested showed AhR–ligand binding activities, especially, when the hydroxylated derivatives of naphthalene were incubated with recombinant yeast. The structure–activity relationship between AhR activity and molecular weight or the octanol–water partition coefficient value of OH-PAH displayed significant correlations. These findings indicate that the site and number of hydroxy-groups substituted on PAH skeleton apparently influenced the AhR – ligand binding activity in the recombinant yeast assay.     

Prediction of seawater solubility of aromatic compounds

The salting-out effect by seawater constituents on the water solubilities of 11 aromatic compounds, anthracene, pyrene, phenanthrene, biphenyl, naphthalene, p-nitrotoluene, p-toluidine, o-nitrophenol, m-nitrophenol, p-nitrophenol and phenol was investigated. A best fit equation (r = 0.965) for the salting-out parameters, K, and distilled water solubilities, S_o, at 20°C was found to be K = ?0.0298 log S_o + 0.114. Seawater solubilities, S, predicted for solutions of ionic strength, I, using the equation log S = (0.0298 I + 1) log S_o ? 0.114 I were in agreement with observed values within 13 % (average 4.8 %) and there were no significant differences between values from the Pacific Ocean seawater and those from 35 o/oo NaCl solutions. It was concluded that dissolved organic matter in seawater had an insignificant effect for the test chemicals.