Exposure to sulfosulfuron in agricultural drainage ditches: field monitoring and scenario-based modelling.

Field monitoring and scenario-based modelling were used to assess exposure of small ditches in the UK to the herbicide sulfosulfuron following transport via field drains. A site in central England on a high pH, clay soil was treated with sulfosulfuron, and concentrations were monitored in the single drain outfall and in the receiving ditch 1 km downstream. Drainflow in the nine months following application totalled 283 mm. Pesticide lost in the first 12.5 mm of flow was 99% of the total loading to drains (0.5% of applied). Significant dilution was observed in the receiving ditch and quantifiable residues were only detected in one sample (0.06 microg litre(-1)). The MACRO model was evaluated against the field data with minimal calibration. The parameterisation over-estimated the importance of macropore flow at the site. As a consequence, the maximum concentration in drainflow (2.3 microg litre(-1)) and the total loading to drains (0.76 g) were over-estimated by factors of 2.4 and 5, respectively. MACRO was then used to simulate long-term fate of the herbicide for each of 20 environmental scenarios. Resulting estimates for concentrations of sulfosulfuron in a receiving ditch were weighted according to the prevalence of each scenario to produce a probability distribution of daily exposure.

Dibarium zirconium tetraoxalate trihydrate.

A new mixed barium zirconium oxalate, triaquatetra-mu-oxalato-dibarium(II)zirconium(IV), Ba(2)Zr(C(2)O(4))(4).3H(2)O or [Ba(2)Zr(C(2)O(4))(4)(H(2)O)(3)](n), has been synthesized. The complex is built from eightfold-coordinated Zr atoms and eleven- and sixfold-coordinated Ba atoms, linked by oxalate groups. The Zr atom, the two Ba atoms and one water O atom lie on crystallographic twofold axes, so that each coordination polyhedron has imposed C2 symmetry. Packing in the crystal is also assumed through hydrogen bonds.

Modification of calix[4]arenes with CMPO-functions at the wide rim. Synthesis, solution behavior, and separation of actinides from lanthanides.

Two calix[4]arene tetraethers (Y = C5H11, C14H29) bearing on their wide rim four -N(Me)-CO-CH2-P(O)Ph2 residues were synthesized for the first time. Their ability to extract lanthanides and actinides from an acidic aqueous phase to organic phases (CH2Cl2, NPHE) was studied. In comparison to the corresponding -NH-analogs, they are less efficient extractants, the selectivity for the light over the heavy lanthanides is less pronounced, while there is still an interesting selectivity of Am3+ over Eu3+. Stability constants for selected lanthanide salts were determined also in homogenous phase (methanol, acetonitrile) but do not account for the different extraction results. The complexation of Gd3+ was also followed by relaxivity (NM RD) measurements, which suggest an even stronger aggregation for the N-methyl compound while the 1:1 complex is reached for a smaller ratio [L]/[Gd3+] compared to the NH analog. The formation of aggregates is also supported by dynamic light scattering measurements. A single crystal X-ray structure of the pentyl ether reveals a C2-symmetrical pinched cone conformation for the free ligand.

KZn(HP(2)O(7)) x 2H(2)O and KMn(HP(2)O(7)) x -2H(2)O: acidpyrophosphate metallates(II) with layer structures.

The crystal structures of the isomorphous title compounds, namely potassium zinc hydrogen pyrophosphate dihydrate and potassium manganese hydrogen pyrophosphate dihydrate, consist of acidic pyrophosphate-metallate(II) layers joined by K(+) ions and hydrogen-bridging bonds. The Zn(2+)/Mn(2+) ions are octahedrally surrounded by four pyrophosphate O atoms and by two water molecules. The (HP(2)O(7))(3-) anions exhibit eclipsed conformations. The metal ions and water O atoms lie on mirror planes, as does the central O atom of the (HP(2)O(7))(3-) anion.